Glossary

A blocky, stubby, rubble-like lava.

Quantitative method of dating a geologic substance or event to a specific time in the past.

Relating to the bottom of the ocean.

Relatively flat ocean floor that accumulates very fine-grained detrital and chemical sediments.

Mix of sediments that form as a subducting plate descends, the overriding plate scrapes material, and material is added.

Toxic waters rich in heavy metals and often of low pH that come from unregulated mining districts.

A convergent boundary between continental and oceanic plates.

A system using mechanical and electrical equipment to collect, store, or distribute solar energy for various uses.

Unchanged materials preserved in the fossil record, which are rare and exceedingly less likely with soft materials and older materials.

The process by which individuals, communities, and societies adjust to new conditions or changes in their environment to maintain or improve their living standards and well-being.

Forces that cause one substance to stick to another.

Deposition with wind-blown sediment.

Earthquakes that occur after the mainshock, usually decreasing in amount and magnitude over time.

The amount of light that is reflected off of an object, measured on a scale of 0 (absorbs all light) to 1 (reflects all light).

Depositional environments that are associated with running water.

Loose sediment deposited from running water.

Radioactive decay in which two protons and two neutrons leave the isotope.

A glacier that forms on a mountain.

An instrument used to measure the altitude of an object above a fixed level.

A group of chain silicate minerals that form needlelike or prismatic crystals; can be many colors, but the most common form, hornblende, is dark brown to black; has oblique cleavages at 54° and 126°; common in many igneous rocks and some metamorphic rocks.

Height or depth of a wave from the middle point.

General name of an intermediate igneous rock that is extrusive, usually with a gray groundmass.

Angle between a light ray that hits the ground and a line perpendicular at the point of contact with the ground. If the sun is directly above a point and light rays are hitting the ground directly, then the angle of incidence is 0.

Slope angle where shear forces and normal forces are equal.

Angular discordance between two sets of rock layers; caused when sedimentary strata are tilted and eroded, followed by new deposition of horizontal strata above.

A mineral that shows no crystal habit, either because it is not prone to having a habit or because it was confined and could not grow with its normal habit.

A negatively charged ion. In geology, this commonly includes elements and molecules like SiO4-4, S-2, SO4-4, and O-2.

Data that is out of the ordinary and does not fit previous trends.

A newly proposed time segment (an epoch) that would be representative of the time since humans began changing (and leaving evidence within) the geologic record.

Made or influenced by humans.

Climate change caused by human activity, namely the burning of fossil fuels.

Downward-facing fold that has older rock in its core.

Similar to dunes in that they are ridges of sand that form perpendicular to flow, but internally, the sediments dip upstream; they form in the upper part of the upper flow regime.

Microscopic crystals within an igneous rock that are invisible to the naked eye; common in extrusive rocks.

A layer with so little porosity and/or permeability that fluids essentially cannot flow through it and only flow around it.

A rock or sediment that has good permeability and porosity, which allows water to move easily, making the water accessible for human use.

A layer with lower porosity and/or permeability, which allows only minimal and/or slow fluid flow.

A chain of volcanic activity, typically in a curved pattern, rising from a subduction zone; located on the overriding plate, typically a few hundred kilometers from the trench, parallel to the trench.

Eon defined as the time between 4 billion years ago to 2.5 billion years ago, when most of the oldest rocks on Earth formed, including large portions of the continents.

A ridge that is carved between two glacial valleys.

A sandstone rich in feldspar.

Dry riverbed in an arid region.

A well that allows pressurized water to reach the surface.

Fault, or movement along a fault, that does not have earthquake activity.

Volcanic tephra that is less than 2 mm in diameter.

Bedrock around the magma chamber being incorporated into the magma, sometimes changing the composition of the magma.

A small rocky body orbiting the sun.

A ductile physical layer of the Earth, below the lithosphere. Movement within the asthenosphere is the main driver of plate motion, pushing the overriding lithosphere.

The scientific study of life in the universe, including its origins, evolution, and potential existence beyond Earth.

The average distance from the Earth to the Sun.

The branch of science that deals with celestial objects, space, and the physical universe as a whole.

Driest nonpolar desert on Earth, located in west-central South America.

The gases that are part of the Earth, which are mainly nitrogen and oxygen.

Strong crystals that do not deform as easily under ductile deformation and that form lens-shaped porphyroblasts.

A depression that occurs in an area that was subject to earlier rifting.

A zone of contact metamorphism that surrounds an intrusion. Since intrusions are typically somewhat round in cross section, the pattern of metamorphism is concentric about the intrusion.

Specialized mineralization around organic material, which produces highly precise molds and casts.

A two-dimensional line that divides the two sides of a fold.

Area behind an arc, which can be subject to compressional forces (causing thrusted mountain belts) or extensional forces (causing back-arc basins).

Depression formed by extension behind an arc, typically with seafloor spreading.

Area of the shoreline that is always entirely above normal wave action.

A group of several alluvial fans that have come together and formed a single surface.

A sedimentary rock that formed long ago when free oxygen changed the solubility of iron, causing layers of iron-rich and iron-poor sediments to form in thin layers, or bands.

A separation of light (felsic) and dark (mafic) minerals in higher-grade metamorphic rocks like gneiss.

Largest amount of flow a river can hold before flooding.

Crescent-shaped dune formed by consistent wind and limited sediment.

Ridges of sand that are made from former beach sediments and form parallel to the shoreline.

General name of a mafic rock that is extrusive, usually with a black groundmass.

Elevation of the mouth of a river.

A down-warped feature in the crust.

The extensional tectonic province that extends east from California's Sierra Nevada Mountains to Utah's Wasatch Mountains, and south from Idaho and southern Oregon to northern Mexico; known as a wide rift, each graben (basin) is bounded by horsts (ranges).

Used to describe a large mass or chain of many plutons and intrusive rocks.

The measurement of depth of water in oceans, seas, or lakes.

A highly weathered soil deposit that consists of aluminum ores.

A bar formed when a spit extends outward and covers a bay.

Active area of crashing waves.

A specific layer of rock with identifiable properties.

Discernible layers of rock, typically from a sedimentary rock.

A specific type of sedimentary structure (ripples, plane beds, etc.) linked to a specific flow regime.

Large, dense sediment that typically sits on the bottom of stream channels and is only moved with higher-speed flows.

The underlying lithified rocks that make up the geologic record in an area. This term can sometimes refer to only the deeper, crystalline (nonlayered) rocks.

Ridge of sand built above the beach face.

A radioactive decay process where a neutron changes into a proton, releasing an electron.

The theory that the universe started with a expansive explosion, followed by the creation of elements (mostly hydrogen) and the formation of galaxies.

Chemical sedimentary rocks that have a biologic component to their origin. Many limestones are biochemical.

The branch of science that explores the chemical processes and substances that occur within living organisms.

Liquid fuels produced from renewable biological sources, including plants and algae.

The scientific study of living organisms and their interactions with each other and their environments.

A detectable substance or characteristic in an astronomical body's atmosphere or surface that indicates the potential presence of life.

Matter from recently living organisms, which is used for bioenergy production.

One of Earth's interacting spheres; it is composed of all living organisms and the nonliving parts with which they interact.

A type of stratigraphic correlation in which fossils are used to match different rock layers.

The disturbance of sedimentary layering by the movement of organisms.

Mineral chimneys that form at hydrothermal vents.

A depression in dune sediment formed because of a lack of anchoring vegetation.

A metamorphic facies of low-temperature, high-pressure rocks, typified by blueschist, a metamorphic rock containing a blue amphibole called glaucophane.

Seismic waves that travel through the Earth, mainly P waves and S waves.

A large extraterrestrial object, such as a meteor or asteroid, that hits the surface of the Earth.

Large volcanic tephra greater than 64 mm in diameter.

Two or more atoms or ions that are connected chemically.

Predictable sequence of fining upward sediments, caused by turbidity flows.

A series of mineral formation temperatures that can explain the minerals that form in specific igneous rocks. For example, pyroxene will form with olivine and amphibole but not quartz.

Water that is a mixture of sea water and fresh water.

Channel type with many switching channels, common with large sediment volumes.

Durable offshore structure designed to lessen wave action and reduce longshore drift.

A property of solids in which a force applied to an object causes the object to fracture, break, or snap. Most rocks are brittle at low temperatures.

A style of strain in which an object suddenly breaks, fractures, or otherwise fails in a way different from ductile deformation.

Metamorphism that is caused by confining pressure and heat, both of which increase with depth.

A mineral also known as CaCO3 that is clear in its pure form but can take on many different colors with impurities; it is soft, fizzes in acid, and has three cleavages that are not at 90°.

The point in the depths of the ocean where calcite starts to dissolve, leaving only siliceous ooze behind.

Hole left behind after a large volume of material erupts out of a volcano, which often turns into a valley or lake after the eruption is over.

A process where ice from the ends of glaciers falls into the ocean.

The first period of the Paleozoic, 541 million years ago to 485 million years ago.

A period of time in the early Cambrian (about 541–516 million years ago) in which a large diversification of life forms appeared in the fossil record. Many of the modern phyla of organisms evolved in this time span.

A deep, narrow valley with steep sides.

Mineral group in which the carbonate ion (CO3-2) is the building block. This can also refer to the rocks that are made from these minerals, namely limestone and dolomite (dolostone).

An igneous composition or rock containing more than 50% carbonate minerals (e.g., calcite). Magma of this composition is very low temperature (500–600°C) relative to other magmas.

An acid that forms from carbon dioxide and water; a large contributor to chemical weathering.

The fifth (second-to-last) period in the Paleozoic, 359–299 million years ago. In North America, the Carboniferous is split into two different periods, the Mississippian (359–323 million years ago) and the Pennsylvanian (323–299 million years ago).

A type of fossilization where only a carbon-rich film is preserved, common in plants.

Material filling in a cavity left by a organism that has dissolved away.

A type of breccia that forms in a brittle way within fault zones.

The idea that large, damaging occurrences are the cause of most geologic events.

A positively charged ion. In geology, this commonly includes ions of the elements Ca+2, Na+1, K+1, Fe+2,+3, Al+3, and Mg+2.

Sediment becoming "glued" together via mineralization, typically calcite and quartz from groundwater fluids.

The last (and current) era of the Phanerozoic Eon, starting 66 million years ago and spanning through the present.

A limestone made of the shells of coccolithophore, a type of single-celled algae.

A form of potential energy stored in the bonds of chemical compounds and released during a chemical reaction.

Sedimentary rocks that form through precipitation, from solution.

Breaking down of mineral material via chemical methods, like dissolution and oxidation.

A biologic process of gaining energy from chemicals from within the Earth, similar to using the energy of the sun in photosynthesis.

A fine-grained version of silica deposited with or without microfossils.

A 180-kilometer (110-mile) crater that exists near Chicxulub, Mexico, on the Yucatan Peninsula. Widely accepted to be the result of the asteroid that caused the K-T extinction.

Organisms that possess vertebrae or some form of a spinal column, including humans.

A type of stratigraphic correlation that is based on similar ages.

A type of tephra that forms as blobs of magma splatter out of a volcanic vent (e.g., cinder cone) and cool and harden quickly.

Volcano formed from piles of cinders and tephra, containing low-viscosity lava with high-volatile content.

Glacially-carved, bowl-shaped valley.

Sedimentary rocks that are made of weathered pieces of bedrock.

A rock made primarily of clay.

A weakness (or weaknesses) within the atomic structure of a mineral, which allows the mineral to break more easily along that plane. Cleavage can also refer to the alignment of features within metamorphic rocks., though this usage is unrelated.

Long-term averages and variations within the conditions of the atmosphere.

An internally draining watershed whose waters do not flow to the ocean.

Former swamp-derived (plant) material that is part of the rock record.

The entire area related to land-sea interactions.

Forces that hold a substance together.

When two continents crash with no subduction (and thus little to no volcanism) since each continent is too buoyant. Many of the largest mountain ranges and broadest zones of seismic activity come from collisions.

A celestial object consisting of a nucleus of ice and dust and, when near the Sun, a “tail” of gas and dust particles pointing away from the Sun.

Sediment being squeezed together into a coherent mass.

The mineral makeup of a rock (i.e., which minerals are found within a rock).

Stresses that push objects together into a smaller surface area or volume; contracting forces.

A mechanical process that takes ore and separates it from gangue material.

Fractures that have a circular appearance.

Pipe that connects the magma chamber to the volcanic vent.

Area with a lower water table due to water pumping from a well.

Nondirectional pressure resulting from burial.

A layer that has low permeability and porosity and does not allow fluid flow as easily.

A sedimentary rock with larger, rounded (≥ 2 mm) clasts.

Original water trapped inside a forming rock.

Metamorphism that occurs when rocks are next to a hot intrusion of magma.

The layers of igneous, sedimentary, and metamorphic rocks that form the continents; much thicker than oceanic crust; contains higher concentrations of very light elements like K, Na, and Ca, and is the lowest density rocky layer of Earth, with an average composition similar to granite.

A body of ice covering large stretches of land over a continent (mainly found in Antarctica).

The transition from land to the deep ocean, where continental crust gives way to oceanic crust.

Submerged part of the continental mass, with a gentle slope.

Steep part of an ocean basin located at the transition between the continental mass and the ocean floor.

The property of unevenly-heated (heated from one direction) fluids (like water, air, ductile solids) in which warmer, less dense parts within the fluid rise and cooler, denser parts sink. This typically creates convection cells: round loops of rising and sinking material.

Place where two plates come together, causing subduction or collision.

The Copernican principle posits that the Earth is not in a central, specially favored position in the universe.

Limestone made of shell fragments cemented together.

The innermost chemical layer of the Earth, made chiefly of iron and nickel, with both liquid and solid components.

Matching rocks of similar ages, types, etc.

Radiation left over from the early stage in the development of the universe, when protons and neutrons were recombining to form atoms.

A bowl-shaped depression, or hollowed-out area, produced by the impact of a meteorite, volcanic activity, or an explosion.

The stable interior part of a continent, typically more than a billion years old and sometimes as much as 2.5–3 billion years old; called a shield when exposed on the surface.

A slow and steady movement that can occur as part of faults, mass wasting, and grain movement.

The last period of the Mesozoic, 145–66 million years ago.

A waterway that existed in North America around 100 million years ago, separating western and eastern North America.

A crack that forms with glacial movement in the upper, brittle part of the glacier.

Sediment that breaks through a levée and deposits in a floodplain during a flood event.

A sedimentary structure that forms in the lower flow regime, where ridges of sediment form perpendicular to flow direction, while within the ridges, sediment layers and dips toward flow direction; found in ripples and dunes; can be tabular, sinuous, or trough-shaped.

A sedimentary structure that has inclined layers within an overall layer; forming commonly in dunes, it is larger in eolian dunes.

The outermost chemical layer of the Earth, defined by its low density and higher concentrations of lighter elements. The crust has two types: continental, which is thicker, more ductile, and has lower density, and oceanic, which is thinner, more brittle, and has greater density.

The part of the hydrosphere (water) that is frozen, found mainly at the poles.

The typical form or forms a crystal takes when it grows.

The process of liquid rock solidifying into solid rock. Because liquid rock is made of many components, the process is complex, with different components solidifying at different temperatures.

Erosional part of a meandering channel.

A barrier that stops or restricts the flow of surface water or underground streams.

The atom that is made after a radioactive decay.

A mixture of coarse material and water channeled and flowing downhill rapidly.

A series of several radioactive decays that eventually leads to a stable isotope.

Large flood basalt province in India that occurred around the same time as the K-T extinction, 66 million years ago.

Melting that occurs as material is moved upward and pressure is released, typically found at divergent plate boundaries or hotspots.

Using known truths to develop new truths.

A strain that occurs in a substance in which the item changes shape due to a stress.

Place where rivers enter a large body of water, forming a triangular shape as the river deposits sediment and switches course.

A common branching style of drainage pattern that resembles tree roots.

The mass of a substance per unit volume. Density is given in units where the density of water is 1 g/cm cubed; to get densities in units of kg/m cubed, multiply the given value by 1,000.

Sediment gathering together, typically in a topographic low point.

An interpretation of the rock record that describes the cause of sedimentation (ancient beach, river, swamp, etc.).

Drainages that are erratic and disappearing, typically in karst environments.

The process of removing salt and other impurities from seawater or brackish water to make it suitable for drinking, irrigation, or other uses.

Dark mineralization that forms on rocks in desert environments.

The process that turns nondesert land into desert.

A style of low-angle, high-extension normal faulting.

Sedimentary rocks made of mineral grains weathered as mechanical detritus of previous rocks (sand, gravel, etc.).

Known as the "Age of Fishes," the fourth period of the Paleozoic, about 419–359 million years ago.

Movement in a transform or strike-slip setting toward the right as viewed across the fault.

Changes in sedimentary rocks due to increased temperatures (though still low compared to metamorphism) and pressures. This can include deposition of new minerals (e.g., limestone converting to dolomite) or dissolution of existing minerals.

A straight line passing from side to side through the center of a body or figure, especially a circle or sphere.

A sedimentary rock containing two distinct grain sizes, typically cobbles (or larger) mixed with mud.

A ductile material that moves toward the surface of Earth. Can be used to describe salt domes and intrusions.

In planetary science, the process of separating the different components within a planetary body as a consequence of their physical or chemical behavior (e.g., density and chemical affinities).

A narrow igneous intrusion that cuts through existing rock, not along bedding planes.

General name of intermediate rock that is intrusive and has about the same amount of felsic minerals and mafic minerals.

A measure of a plane's maximum angle with respect to horizontal, where a perfectly horizontal plane has a dip of zero and a vertical plane has a dip of 90°.

Faulting that occurs with a vertical motion.

Stress that has a strong (unequal) directional component, typically creating elongated or flattened features.

Amount of water that leaves a system such as a river or aquifer.

Exists when there is an erosional surface between two layered rocks that may otherwise seem conformable.

The process in which solids (like minerals) are disassociated and the ionic components are dispersed in a liquid (usually water).

Amount of material dissolved in stream water.

Areas that have one clear high tide and one clear low tide each tidal day.

Place where two plates are moving apart, creating either a rift (continental lithosphere) or a mid-ocean ridge (oceanic lithosphere).

A rock upwarping made up of symmetrical anticlines.

A change in wavelength and frequency of a wave due to its source's movement relative to the observer of a wave.

The area within a topographic basin or drainage divide in which water collects.

Topographic prominence that separates drainage basins, or watersheds.

The shape or form of a river and/or tributary drainage system.

Ridge of sediment that forms under a glacier with steep uphill and gentle downhill sides in respect to the glacier.

A property of a solid, such that when a force is applied, the solid flows, stretches, or bends along with the force instead of cracking or breaking. For example, many plastics are ductile.

A bending, squishing, or stretching style of deformation where an object changes shape smoothly.

A large pile of sediment deposited perpendicular to flow, with internal bedding dipping toward flow direction (i.e., cross-bedding). Formed in the upper part of the lower flow regime.

A small planetary-mass object that is in direct orbit of the Sun; smaller than any of the eight classical planets, but still a world in its own right.

A fine-grained type of plastic flow.

The study of the interaction of the spheres within the system that is the Earth, mainly the study of the hydrosphere, atmosphere, geosphere (lithosphere), and biosphere.

The measure of the circular or elliptical nature of the Earth's orbit.

A system that applies sonar technology to measure the depth of water.

A metamorphic rock that forms in the upper mantle as a result of high-pressure metamorphism, composed of red garnet hosted in a matrix of green pyroxene.

A group of relatively complex organisms that existed at the end of the Proterozoic.

A type of deformation that reverses when the stress is removed.

A theory concerning built-up energy that is released during an earthquake.

The energy emitted and propagated through space in the form of electromagnetic waves.

Visible light and its related energetic waves, including X-rays, UV rays, and radio waves.

Waves of electric and magnetic fields that propagate through space at the speed of light, encompassing a broad spectrum that includes radio waves, microwaves, infrared, visible light, ultraviolet, X-rays, and gamma rays.

A stable subatomic particle with a charge of negative electricity, found in all atoms and acts as the primary carrier of electricity in solids.

A type of radioactive decay where an electron combines with a proton, making a neutron.

A group of all atoms with a specific number of protons, having specific, universal, and unique properties.

An exposed coastline where relative sea level is falling.

A measure of the energy efficiency of a nation's economy. It is calculated as the amount of energy consumed per unit of gross domestic product (GDP), with lower energy intensity indicating a more efficient use of energy in producing economic output.

A channel that carves into existing bedrock, preserving its original shape and character.

The largest span of time recognized by geologists, larger than an era. We are currently in the Phanerozoic Eon.

A stream or river that can be wet or dry depending on the season.

The surface directly above the focus of an earthquake, typically associated with strong damage.

A unit of geological time recognized by geologists; smaller than a period. We are currently in the Holocene epoch.

Stubby, not longer in any direction.

The second-largest span of time recognized by geologists; smaller than an eon, larger than a period. We are currently in the Cenozoic Era.

A vast stretch of sand dunes.

The transport and movement of weathered sediments.

Ridge of sediment that forms under a glacier by meltwater that has formed a river.

Lagoon with brackish water, typically with abundant biologic factors.

A mineral that perfectly shows its true crystal habit.

A type of organism in with a cell or cells that contains a nucleus.

Referring to overall global sea level change, either due to climate or seafloor spreading rate.

Turn from liquid into vapor.

A chemical sedimentary rock that forms as water evaporates.

A combination of evaporation and transpiration from plants, serving as a measure of water entering the atmosphere.

A type of mechanical weathering in which outer layers of rock fracture off, occurring approximately parallel to the surface.

Any planet beyond our Solar System.

A test of an idea in which new information can be gathered to either accept or reject a hypothesis.

When a species no longer exists.

Anything originating, existing, or occurring outside the Earth and its atmosphere.

Relating to igneous rock that has formed by cooling outside of the Earth (i.e., on the surface).

A specific set of features that are shared by an interpretive group of rocks. Facies can be based on mineralogy, biologic factors, fossils, rock types, etc.

A section of a rift that starts to develop without fully forming. This typically occurs at 120° angles to the active rift.

The depth reached by normal, nonstorm waves.

The idea that claim in science can be proved wrong with proper evidence.

Planar feature where two blocks of bedrock move past each other via earthquakes.

Place where fault movement cuts the surface of the Earth.

Group of minerals consisting of three end members: potassium feldspar (K-spar, KAlSi3O8), plagioclase with calcium (anorthite, CaAl2Si2O8), and plagioclase with sodium (albite, NaAlSi3O8). Commonly blocky, with two cleavages at ~90°. Plagioclase is typically dull white and gray, and K-spar is more vibrant white, orange, or red.

Can refer to a volcanic rock with higher silica composition or to the minerals that make up those rocks, namely quartz, feldspar, and muscovite mica. Felsic rocks are lighter in color and contain more minerals that are light in color. Primary felsic rocks are rhyolite (extrusive) and granite (intrusive).

The Fermi paradox highlights the contradiction between the high probability of the existence of extraterrestrial civilizations and the lack of evidence or contact with such civilizations.

Distance wind has been building a wave.

Lake that fills a glacial valley.

Snow that has been compressed and is starting to turn into ice.

Easily split along bedding planes, a characteristic of shale.

Glacial valley filled by ocean water.

Dangerous flooding that occurs in arid regions.

The result of a rare, low-viscosity eruption that covers vast areas. None have been observed in human history.

Flat area around a river channel that is filled with water during flooding events.

A qualitative measure of the speed of a fluid flow that considers how different flows are affected by different sedimentary structures, called bedforms. Typically, it is split into upper and lower flow regimes, with upper being a more rapid flow.

A small area along a strike-slip or transform fault with branching structures of transpression/transtension, that cause local hills or valleys.

Deposition that has to do with rivers.

The process in which volatiles enter the mantle wedge and the volatiles lower the melting temperature, causing volcanism.

Initiation point of an earthquake or fault movement.

A rock layer that has been bent in a ductile way instead of breaking (as with faulting).

A planar alignment of minerals and textures within a rock.

On a dipping fault, the part of the block that is below the fault; moves down in normal faulting, up in reverse faulting.

Area in front of the arc, between the arc and the trench. Often marked by an accretionary wedge or a forearc basin.

Any depression formed between the arc and the trench, commonly between the arc and the accretionary wedge.

An earthquake that sometimes occurs before the larger mainshock.

Area between high tide and low tide.

An extensive, distinct, and mapped set of geologic layers.

Any evidence of ancient life.

Energy resources (typically hydrocarbons) derived from ancient chemical energy preserved in the geologic record. Includes coal, oil, and natural gas.

Adjective for a rock filled with fossils, most commonly with limestones.

A process of injecting pressurized fluids into the ground to aid in hydrocarbon migration.

A break within a rock that has no relative movement between the sides; there are various causes, including cooling, pressure release, and tectonic forces.

Faults along mid-ocean ridges that have a transform motion but do not produce earthquakes. These faults accommodate different amounts of movement along the mid-ocean ridge.

The force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other.

A process in which water freezes inside cracks in rocks, causing expansion and mechanical weathering.

A process inside stars in which smaller atoms combine and form larger atoms.

General name of a mafic rock that is intrusive.

A gravitationally bound system of stars and interstellar matter.

A penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. Its electronic waves have the shortest wavelengths, typically shorter than those of X-rays.

Material found around ore that is less valuable and needs to be removed in order to obtain the ore.

A feature in a rock that allows the observer to determine which direction was up in the past.

The solid, rocky parts of the Earth, including the crust, mantle, and core. Also referred to as the lithosphere.

Heat that is generated within the Earth.

The average change in temperature experienced as material moves into the Earth. Near the surface, this rate is about 25°C/km.

Idea that a large body struck the Earth, spraying material into space that eventually collected to form the Moon.

Deposition and erosion tied to glacier movement.

The net gain or loss of ice within a glacier.

Large sediment (e.g., boulder) carried and then dropped by a glacier.

Smooth surface carved in hard rocks by glacial action.

Grooves scratched in rock by glacial action.

A period of cooler temperatures on Earth in which ice sheets can grow on continents.

A body of ice that moves downhill under its own mass.

A metamorphic rock higher in grade than schist, with separate light and dark minerals.

Working opposite of Bowen's reaction series, it states that minerals that are formed at conditions more dissimilar to the surface are more quickly prone to chemical weathering.

A valley formed by normal faulting.

A qualitative measure of the amount of metamorphism that has occurred or the amount of a resource present in an ore.

Slope of a stream channel.

A sequence of layers in which the sediment changes linearly in size, getting either coarser or finer.

The average diameter of a grain of sediment, ranging from small, fine-grained (e.g., clay, silt) to large, coarse-grained (e.g., boulder).

General name of a felsic rock that is intrusive.

Desert area stretching east from California to Utah and north to Idaho/Oregon; formed due to both latitude and rain shadow.

A period of the early Proterozoic (around 2.5–2 billion years ago) where atmospheric oxygen levels dramatically increased, killing many non-oxygen-breathing organisms and allowing oxygen-breathing organisms to thrive.

A reddish-colored cyclonic storm that circulates counterclockwise in the southern hemisphere of Jupiter's atmosphere. Continuously observed since the seventeenth century, the storm is so large that it could fit multiple Earths within its boundaries.

The ability for the atmosphere to absorb heat that is emitted by a planet's surface.

A sandstone with either a significant mud component or a significant lithic fragment component.

A hard stabilization structure built perpendicular to the shoreline to help control longshore drift.

The total value of all goods and services produced within a country over a specific period, usually a year.

An accumulation of sediment that forms beneath a glacier.

General term for the fine-grained, non-discernible part of a rock. In igneous rocks, this is the part of the rock that is not phenocrysts and can help in determining the composition of extrusive rocks. In sedimentary rocks, it typically refers to the fine-grained components, namely mud. In metamorphic rocks, it usually refers to material between porphyroblasts or a low-grade rock with only microscopic mineralization.

Water that is below the surface.

When discharge exceeds recharge and the groundwater is withdrawn at a rate that depletes groundwater storage.

A typically clear or white evaporite mineral, CaSo4•2H2O; has one cleavage and a hardness of 2.

Large, circular ocean currents formed by global atmospheric circulation patters.

The region around a star where conditions are suitable for liquid water to exist on a planet's surface, potentially allowing for life as we know it.

A dust storm that occurs in desert areas.

Eon that represents the time from Earth's formation to four billion years ago. Noted for high levels of volcanism, impacts, and very low preservation.

A part of the global circulation system that rises at the equator and sinks at 30°.

A valley formed by normal faulting on just one side.

The calculated amount of time that half of the mass of an original (parent) radioactive isotope breaks down into a new (daughter) isotope.

Minerals based on bonds to column 17 halogens, such as chlorine and fluorine.

A typically clear or white mineral also known as rock salt or table salt; has 3 cleavages at 90°, a cubic crystal habit, and a hardness of 3.

A feature formed by a tributary glacier moving into a main glacier, forming a tributary valley floor higher in elevation than the main valley floor.

On a dipping fault, the side that is on top of the fault plane; moves down in normal faulting, up in reverse faulting.

The ease or difficulty in scratching a mineral, measured by the qualitative Mohs hardness scale, which ranges from soft talc (1 on the scale) to hard diamond (10 on the scale).

The source or beginning of a river.

A former Pearl-class corvette of the Royal Navy that was picked to undertake the first global marine research expedition: the Challenger expedition.

The most recent epoch of geologic time, from 11,700 years ago to present.

Evaporites (like salt) that form cavities within rocks, mimicking the shape of the crystal.

Steep spire carved by several glaciers.

A hard, dense metamorphic rock, typically derived from contact metamorphism.

Uplifted mountain block caused by normal faulting.

Rising stationary magma, forming a succession of volcanism and appearing as islands on oceanic plates and as volcanic mountains or craters on land.

A special type of cross-bedding that forms when strong storms produce mounds and divots of cross-bedded sand in deeper water.

Rich organic material found in soil.

Relating to movement brought about by water.

The measure of how well a fluid flows through an object.

A renewable energy source that uses the kinetic energy of moving water to generate electricity.

A weak chemical bond that attracts hydrogen to a negative part of a molecule. Many of water's properties are due to hydrogen bonds.

Water breaking into ions and replacing ions in minerals; a major type of chemical weathering in silicates.

A renewable energy source that uses the kinetic energy of moving water to generate electricity.

The part of the Earth composed of water, as a solid, liquid, or gas.

Metamorphism that occurs when hot fluids flow into rocks, altering and changing the rocks.

A proposed explanation for an observation that can be tested.

Thick glaciers that cover continents, particularly during ice ages.

Relating to molten rock.

Rock formed by liquid rock from volcanic processes.

Cobbles stacked in the direction of flow.

Referring to a material or surface that does not allow fluids, such as water, to pass through it.

A piece of a rock that is contained inside of another rock.

A fossil with a wide geographic reach but originating from a short geologic time span; used to match rock layers to a specific time period.

Minerals that form at a specific range of temperatures and pressures. Studying a collection of index materials helps identify the conditions of a rock's formation.

Earthquakes that occur due to human activity.

Establishing evidence (including new observations) to infer a possible truth.

The process by which water works its way down into the subsurface.

The innermost physical layer of the Earth, which is solid.

Isolated piece of bedrock that protrudes from an alluvial surface.

Period of warming within a glacial or ice age cycle.

A classification of volcanic rock with medium silica composition, equally rich in felsic minerals (e.g., feldspar) and mafic minerals (e.g., amphibole, biotite, pyroxene); grey in color, containing somewhat equal amounts of minerals that are light and dark in color. Primary intermediate rocks are andesite (extrusive) and diorite (intrusive).

Activity that occurs at the boundaries between plates.

A very brief period of warming within a glacial or ice age cycle, even warmer than an interglacial.

Occurring or situated between stars.

Activity that occurs within plates, away from plate boundaries.

Relating to igneous rock that has formed by cooling inside of the Earth (i.e., under the surface).

An atom or molecule that has a charge (positive or negative) due to the loss or gain of electrons.

Place where oceanic-oceanic subduction causes volcanoes to form on an overriding oceanic plate, making a chain of active volcanoes.

Relative balance of an object based on how it floats.

An upward movement of the lithosphere when weight is removed, such as water or ice.

An atom that has different number of neutrons but the same number of protons. While most properties are based on the number of protons in an element, there can be subtle differences in isotopes, including temperature fractionation and radioactivity.

Artificial device (typically a wall of concrete or rocks) placed to stop or slow longshore drift.

The middle period of the Mesozoic Era, 201–145 million years ago.

The most recent mass extinction, which killed the non-avian dinosaurs and paved the way for the diversification of mammals; occurred when a bolide hit near Chicxulub, Mexico, 66 million years ago.

A landscape created when carbonate rocks dissolve, leaving behind caverns and holes.

Depression formed by ice resting in sediment, then preserved after the ice melts and the sediment lithifies.

An ultramafic rock from deep volcanic vents that can contain diamonds.

The energy an object possesses due to its motion.

A circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun.

An international agreement established in 1997 in which participating industrialized countries committed to reducing their greenhouse gas emissions to help combat climate change. It set legally binding emission reduction targets for developed countries.

Large igneous intrusion that is wedged between sedimentary layers, bulging upwards.

Deposition in and around lakes.

An exceptionally well-preserved fossil locality, often including soft tissues.

Interior body of ocean water, at least partially cut off from the main ocean water.

A type of volcanic mudslide in which rain or snowmelt accumulates volcanic ash on the slopes of steep volcanoes or other mountains and then wash downhill, causing damaging flooding.

Beds of rock that are thinner than 1 cm.

General term for material suddenly falling (sliding) down a slope due to gravity.

Volcanic tephra that has a diameter between 2 mm and 64 mm. Many cinders are categorized as lapilli.

A hypothesis that states that movement of Jupiter and Saturn about four billion years ago caused a destabilization of orbits in the Asteroid and Kuiper Belts, which then caused a spike in impacts throughout our Solar System.

Moraines that form at the sides of glaciers.

The measure of degrees north or south from the equator, which has a latitude of 0 degrees. The Earth's north and south poles have latitudes of 90 degrees north and south, respectively.

Geologic name for the craton that makes up North America.

Liquid rock on the surface of the Earth.

Volcanic feature with very steep sides formed by higher viscosity, higher-silica lava.

Metallic mineral deposit consisting of mafic plutonic rocks, typically containing platinum-group elements, chromium, copper and nickel.

The distance that light can travel through space in a year. One light year is 9.4607 × 10^12 km.

A chemical or biochemical rock made of mainly calcite.

Dunes that are much longer than they are wide, forming from wind blowing in two opposite directions.

Linear alignment of minerals within a rock.

Process of saturated sediments becoming internally weak (like quicksand) and destabilizing foundations.

The process of turning sediment into sedimentary rock, including deposition, compaction, and cementation.

The outermost physical layer of the Earth, made of the entire crust and upper mantle. It is brittle and broken into a series of plates, which move in various ways (relative to one another), causing the features described by the theory of plate tectonics.

A type of stratigraphic correlation in which the physical characteristics of rocks are used to correlate.

Referring to the beach zone, also known as the shoreline, where waves crash into land.

Wind-blown silt, mainly formed from glacial processes.

An illustrated topography of the base of a stream, showing zones of sediment production, transport, and deposition.

A net movement that occurs when waves intersect the shoreline at nonperpendicular angles.

Sediment that moves via a longshore current.

Large igneous intrusion that is wedged between sedimentary layers, bulging downwards.

Surface waves that have a side-to-side motion.

The shine created from light reflecting off of a mineral. This is typically divided into two main categories: metallic (metal-like shine) and nonmetallic.

Can refer to a volcanic rock with lower silica composition or to the minerals that make up those rocks, namely olivine, pyroxene, amphibole, and biotite. Mafic rocks are darker in color and contain more minerals that are dark in color, but can contain some plagioclase feldspar. Primary mafic rocks are basalt (extrusive) and gabbro (intrusive).

Liquid rock within the Earth.

A reservoir of magma below a volcano.

The process of changing a magma's composition, usually through assimilation or fractionation.

Symmetric patterns of magnetism occurring around an ocean ridge; created by ocean floor rocks recording changes in Earth's magnetic field.

A measure of earthquake strength. Scales include Richter and moment.

Largest earthquake in an earthquake sequence.

Middle chemical layer of the Earth, made of mainly iron and magnesium silicates. It is generally denser than the crust (except for older oceanic crust) and less dense than the core.

Rising material and heat derived from the mantle. These may be responsible for hotspots.

The area of the mantle where volatiles rise from the slab, causing flux melting and volcanism.

A metamorphosed limestone.

Referring to locations that are under ocean water at all times.

A pronounced increase in the extinction rate, typically caused by significant environmental change. There have been five mass extinctions in geologic history, with a sixth suggested to be currently occurring.

A device that can determine the amounts of different isotopes in a substance.

Any downhill movement of material caused by gravity.

Referring to a geological feature with no internal structure, habit, or layering.

Silted-in oxbow that still has a topographic expression.

Low-gradient channel where rivers sweep across broad flood plains.

The physical breakdown (weathering) of bedrock by processes such as pressure or ice expansion.

Formed by two or more glaciers merging, with lateral moraines combining to form a moraine within the glacier.

Referring to high-magnitude faulting that occurs in subduction.

A solid, more brittle physical layer of the Earth, located below the asthenosphere; also called the lower mantle.

Meaning "middle life," it is the middle era of the Phanerozoic, starting 252 million years ago and ending 66 million years ago. Known as the Age of Reptiles.

A solid material that is typically hard, shiny, malleable, fusible, and ductile, with good electrical and thermal conductivity.

Referring to minerals that contain metals, giving them lusters similar to metals. Valuable elements like lead, zinc, copper, and tin are metallic.

Referring to rocks and minerals that are changed by heat and pressure within the Earth (a process known as metamorphism).

A specific set of index minerals tied to specific styles of metamorphism. The presence of these minerals allows a history of metamorphism to be determined.

Rocks formed via heat and/or pressure changing the minerals within the rock.

A small body of matter from outer space that enters the Earth's atmosphere, becoming incandescent as a result of friction and appearing as a streak of light.

A stony and/or metallic object from our solar system that was never incorporated into a planet and has fallen onto Earth. The term "meteorite" is used to describe the rock on Earth, "meteoroid" for the object in space, and "meteor" as the object travels in the Earth's atmosphere.

A small rocky (or metallic) body in outer space.

The science concerned with the Earth's atmosphere and its physical processes.

X1A2-3Z4O10(OH, F)2, where commonly X=K, Na, Ca; A=Al, Mg, Fe; and Z=Si, Al. A shiny silicate mineral usually occurring as a light-colored (translucent and pearly tan) muscovite or a dark-colored biotite; has one strong cleavage and is typically seen as sheets in stacks or "books"; commonly found in many igneous and metamorphic rocks; structured in two-dimensional sheets of silica tetrahedra in a hexagonal network.

Limestone made of primarily fine-grained calcite mud. Microscopic fossils are commonly present.

Relating to or involving microorganisms, such as bacteria, viruses, fungi, and other microscopic life forms.

A form of electromagnetic radiation with wavelengths shorter than other radio waves but longer than infrared waves, ranging from about one millimeter to about one meter.

A divergent boundary within an oceanic plate where new lithosphere and crust is created as the two plates spread apart. "Mid-ocean ridge" and "spreading center" are synonyms.

A rock in transition between metamorphic and igneous rock, i.e., rocks so metamorphosed that they begin the process of melting.

A series of changes in the Earth's orbit/position in relation to the Sun, which can cause climates to fluctuate over periodicities.

Place where material is extracted from the Earth for human use.

A natural substance that is typically solid and formed by inorganic processes, with a crystalline structure. Minerals are the building blocks of most rocks.

A mineral-like substance that does not meet all the criteria of a true mineral. Examples include glass, coal, opal, and obsidian.

Metallic mineral deposit of mainly lead and zinc from groundwater movements within sedimentary rocks.

The action of reducing the severity, seriousness, or harmful effects of something, in a general context, it involves taking steps to minimize negative impacts and manage potential risks.

Areas with an irregular sequence of tides over the course of a month.

A qualitative earthquake scale of the degree of shaking in an earthquake, ranging from I to XII.

Short for Mohorovičić discontinuity, it is the seismically-recognized layer within the Earth in which the crust ends and the mantle begins. The moho is easy to find since the crust is very different in composition to the mantle, with seismic waves traveling differently through the two materials.

Organic material making a preserved impression in a rock.

A magnitude scale based on calculation of the energy released in an earthquake.

A one-sided, fold-like structure in which layers of rock warp upwards or downwards.

An object that orbits a planet or something else that is not a star (e.g., dwarf planets or large asteroids).

Accumulation of sediment at the margins of glaciers, including the base, sides, and end.

A landform that rises above its surrounding area.

A form of surface mining that involves removing the top of a mountain to expose a desired resource underneath.

The end of a river.

Pieces of mudcracks that are incorporated into a sedimentary rock.

Polygonal cracking that occurs with shrinking clays. Indicative of mud submerged underwater and then exposed to air.

A rock made of primarily mud, i.e., particles smaller than sand (≤ 0.064 mm).

Fault-formed rock created through ductile deformation deeper within the Earth.

Minerals made from just a single element bonded to itself. Examples include gold, silver, copper, and diamond, which is a native version of carbon.

Gaseous fossil fuel derived from petroleum, mostly made of methane.

A significant and dangerous event that is part of a natural process.

Built-up area around a river channel that can hold river flow within a channel.

Items that are found within Earth that are valuable and limited. Examples include coal, water, and gold.

Lowest low tide of the month.

Shore area between low tide and storm wave base, with the upper part dominated by fair-weather wave base and the lower dominated by storm wave base.

A cloud of gas and dust in space that can form a new star/solar system if it collapses.

A system that reverts back to a baseline when it deviates.

A subatomic particle without an electric charge, present in all atomic nuclei (except hydrogen).

Layered rocks on top of a nonlayered rock, such as crystalline basement.

Referring to metamorphic textures whose minerals lack a directional component.

Minerals that have a luster that is not similar to metal. Divided into subtypes based on the way light reflects (or doesn't), including glassy/vitreous, greasy, pearly, dull, etc.

Pollution that does not come from one specific, known place but instead comes from a broad zone.

A resource that is not able to be replaced on a human timescale.

A dip-slip fault in which the hanging wall drops relative to the footwall, caused by extensional forces.

Component of the gravitational force that holds material on a slope.

Process in which a continental plate causes oceanic plate to rise, frequently occurring in collision zones.

Referring to an observation that is completely free of bias (i.e., anyone would make the same observation).

The angle of the Earth's axis with respect to the plane of rotation.

The act of gathering new information from the senses or from a scientific instrument.

Dark-colored volcanic glass with extremely small microscopic crystals or no crystals, typically forming from felsic volcanism.

The thin, outer layer of the Earth that makes up the rocky bottom of ocean basins; much thinner (but denser) than continental crust; made of rocks similar to basalt, and as it cools, it becomes more dense.

A large, elevated, flat area on the ocean floor with steep edges, formed by extensive outpourings of basaltic lava.

Process in which an ocean plate subducts beneath a continental plate, causing a volcanic arc to form.

Process in which a dense oceanic plate subducts beneath a less dense oceanic plate, causing an island arc to form on the overriding plate.

The scientific study of oceans.

A rule that says the outer valence shell of electrons is complete when it contains eight electrons.

Amount of movement during a faulting event.

Referring to the part of the coastline below any wave base action.

A dark liquid fossil fuel derived from petroleum.

Oil found in low-permeability, high-porosity rocks such as shale.

(Fe,Mg)2SiO4. A mineral that is typically translucent olive green and equant, with no cleavage; common in mafic igneous rocks and in the mantle, but easily weathered in surface conditions; structured as isolated silica tetrahedra; known as peridot when a gem.

Spheres of calcite that form in saline waters with slight wave agitation. A rock with these spheres is known as an oolite.

A spherical layer of icy objects surrounding the Sun; likely occupies space at a distance between about 2,000 and 100,000 AU from the Sun.

Large surface mine with opening carved into the ground.

Rocks of the ocean floor, such as mid-ocean ridge rocks, that are brought to the surface.

The second period of the Paleozoic Era, 485–444 million years ago.

Valuable material in the Earth, typically used for metallic mineral resources.

A proven commodity of profitable material that could be mined.

Material that is potentially (but not proven to be) extractable and valuable.

The branch of chemistry that studies the structure, properties, composition, reactions, and synthesis of carbon-containing compounds.

A molecule that contains carbon atoms bonded together, often with hydrogen, oxygen, nitrogen, and other elements, forming the basis of life on Earth.

The process of uplifting mountains and creating mountain belts, primarily via tectonic movement. Orogenic belts are the mountain belts that result from these movements, and orogenesis is the name for the process of forming mountain belts.

The liquid outer physical layer of the core. Movement within the outer core is believed to be responsible for Earth's magnetic field and flips of the magnetic field.

Accumulation of fine-grained sediment formed downhill of the terminal moraine.

A slope, that by natural or human activity, becomes steeper than the angle of repose.

Abandoned meanders that are cut off from the main channel.

A process in which certain metallic elements (like iron) take in oxygen, causing reactions like rust.

Minerals in which ions are bonded to oxygen, such as hematite (Fe2O3).

The fastest seismic wave that occurs after an earthquake, compressional in nature.

Rope-like, flowing basaltic lava.

The warmest climate spike in recent geologic past, occurring about 55.5 million years ago. Commonly abbreviated as the PETM.

Direction of flow preserved in the rock record.

As a rock cools, the iron minerals within the rock align with the current magnetic field. Since the magnetic field changes (by where you are on Earth, by flips in which "north" and "south" switch, and by migration of the magnetic north pole), scientists use the magnetic alignment within rocks to determine past movement or the magnetic field itself, along with the movement of rocks and plates via plate tectonics.

Meaning "ancient life," the era that started 541 million years ago and ended 252 million years ago. Vertebrates (including fish, amphibians, and reptiles) and arthropods (including insects) evolved and diversified throughout the Paleozoic. Pangea formed near the era's end.

Referring to deposition that occurs in swamps.

The most recent supercontinent, which formed over 300 million years ago and started breaking apart less than 200 million years ago. Africa and South America, as well as Europe and North America, bordered each other.

Dunes that form semicircular shapes due to anchoring vegetation.

Small side vent of a stratovolcano where secondary eruption can occur.

A radioactive atom that can and will decay.

An international accord adopted in 2015 that aims to limit global warming to well below 2°C above pre-industrial levels, with efforts to limit the increase to 1.5°C. It involves voluntary emission reduction targets from participating countries, along with financial and technological support to help them achieve their climate goals.

The process of some material being derived from a heterogenous mixture when melting (e.g., rocks). Because all rocks are made of many different components, they have many different melting points; as they are heated, certain easy-to-melt components will be melted first.

Subtle ridges formed in the upper flow regime on top of plane beds in the direction of flow.

A boundary between continental and oceanic plates that has no relative movement; despite being a place where an oceanic plate is connected to a continental plate, it is not a plate boundary.

An energy system that uses a building's design, materials, and placement to capture solar energy to heat and cool living spaces without relying on mechanical or electrical devices.

A series of lakes between moraines within an alpine glacier basin, typically a cirque.

A process where experts in a field review and comment on a newly introduced work, typically a part of publication.

A rock (or texture within a rock) with unusually large crystals, minerals with rare trace element concentrations, and/or unusual minerals, typically forming in veins as the last dredges of magma crystallize.

An intrusive ultramafic rock that is the main component of the mantle. The minerals in peridotite are typically olivine with some pyroxene.

A unit of the geologic timescale; smaller than an era, larger than an epoch. We are currently in the Quaternary Period.

Soil and rock with temperatures below freezing for long periods of time.

The ability for a fluid to travel between pores, or a description of how connected the pores are within a rock or sediment.

Having interconnected spaces (pores) that allow liquids or gases to pass through.

The last period of the Paleozoic, 299–252 million years ago.

The largest mass extinction in history, in which an estimated 83% of genera went extinct. The Siberian Traps are potentially related to the event causing the extinction.

Style of fossilization in which materials are replaced by minerals in groundwater fluids.

A liquid fossil fuel derived from shallow marine rocks; also known as crude oil.

The study of rocks, either macroscopically or microscopically; specializations within the study are typically based on the three rock types (e.g., igneous petrology).

A logarithmic scale that measures the acidity or alkalinity of an aqueous solution. It ranges from 0 to 14, with 7 being neutral.

Referring to igneous rocks with large, easy-to-see crystals. This is common in intrusive rocks.

Meaning "visible life," the most recent eon in Earth's history, starting at 541 million years ago and extending through the present. Known for the diversification and evolution of life, along with the formation of Pangea.

Chart that shows the stability of different phases of a substance at different conditions.

A large crystal within an igneous rock; specifically phaneritic and porphyritic rocks.

Minerals that are bonded with the phosphate anion, PO43-.

An electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect.

A rock more metamorphosed than slate, to the point that microscopic (but larger) mica gives the rock a glow called a sheen. Crenulation, or small bends/folds in the foliation, can be present.

An object that is cut by a fault, which allows the amount of movement to be determined. This is useful for studying all faults but is more commonly used in strike-slip faults.

Deposit of heavy ores in stream or beach sediments.

A specific layer of rock formed by flowing fluid, either in the lowest part of the lower flow regime or lower part of the upper flow regime.

A large astronomical body that is neither a star nor a stellar remnant.

The generic term for a group of planets and other bodies circling a star.

A body that could or did come together with many others under gravitation to form a planet.

A solid part of the lithosphere that moves as a unit, i.e., the entire plate generally moves the same direction at the same speed.

Location where two plates are in contact, allowing relative motion between the two plates. Most earthquakes and volcanoes occur at plate boundaries.

The theory that the outer layer of the Earth (the lithosphere) is broken into several plates that move relative to one another, causing the major topographic features of Earth (e.g., mountains, oceans) as well as most earthquakes and volcanoes.

Part of a craton that is covered by mostly sedimentary rocks.

A dry lake bed in a desert valley.

A coherent body of intrusive rock that formed underground and is now at (or near) the surface.

Lakes that form via increased precipitation from glacial climate shifts.

Depositional portion of a meandering channel.

Pollution that comes from one known source.

Part of the global circulation pattern in which air sinks at the poles (90° latitude) and rises at 60° latitude.

Deserts formed by descending air at the poles.

A molecule (like water) that has a positive side and a negative side.

Minerals with matching compositions but different crystal structures. Quartz has several different polymorphs, including coesite, tridimite, and stishovite.

A trait in which a specific chemical composition can form different minerals at different temperatures and pressures.

Empty space in a geologic material, either within sediments or within rocks. Can be filled by air, water, or hydrocarbons.

Amount of empty space within a rock or sediment, including space between grains, fractures, or voids.

Having spaces or holes through which liquid or air may pass, depending on the spaces' connectivity (permeability).

An igneous rock with two distinctive crystal sizes.

Large metallic mineral deposit that forms near magma bodies like plutons. Commonly contains copper, lead, zinc, molybdenum, and gold.

A process that exacerbates the effects of an input, amplifying the output, i.e., a one-directional loop that self-reinforces change.

The energy stored within an object or system that has the potential to do work based on its position, configuration, or state.

The height of the water table if no confining layers or other hindrances present.

A term for the collective time before the Phanerozoic (pre-541 million years ago), including the Hadean, Archean, and Proterozoic. Known for a lack of easy-to-find fossils.

Wobbles in the Earth's axis.

The act of a solid coming out of solution, typically resulting from a drop in temperature or a decrease in the dissolving material.

The force applied perpendicular to the surface of an object per unit area over which that force is distributed.

A geologic object cannot be altered until it exists, meaning that the change to the object must be younger than the object itself.

The fossils originating from specific times are unique, and the fossils in layers of different ages have progressed and changed as time has moved forward; fossils found in newer layers have organisms that more resemble organisms that are alive today.

Layered rocks can be assumed to continue if interrupted within their area of deposition.

Layered rocks generally lay down flat at their formation.

In an undisturbed sequence of strata, the rocks on the bottom are older than the rocks on the top.

Idea championed by James Hutton that the present is the key to the past, meaning the physical laws and processes that existed and operated in the past still exist and operate today.

Lake that forms next to a glacier because of crustal loading.

A type of single-celled organism with no nucleus.

Meaning "earlier life," the Proterozoic is the third eon of Earth's history, starting 2.5 billion years ago and ending 541 million years ago. Marked by increasing atmospheric oxygen and the supercontinent Rodinia.

The rock that existed before changes that formed a metamorphic rock, i.e., the rock that would exist if the metamorphism was reversed.

A subatomic particle with a charge of positive electricity.

The study of the components of a rock, mainly sedimentary rocks, and the information that can be obtained by understanding the origins of the components.

A measurement from one system that can specify a change in another system. For example, changes in climate can change the amount of certain isotopes of oxygen and carbon in sea creatures.

A method of investigation that claims to be scientific but does not hold up to full scientific scrutiny. Examples include astrology, paranormal studies, young-Earth creationism, and cryptozoology (i.e., the study of creatures like Bigfoot and the Loch Ness Monster).

A low-density, highly vesiculated volcanic rock, usually white-to-tan in color and typically arising from felsic volcanism.

A layer in a body of water where the water density increases more rapidly with depth compared to the layers above and below.

Rocks (or rock textures) that are formed from explosive volcanism.

A mixture of rock, gas, and ash that travels down at very hot temperatures and very fast speeds, resulting from parts of the eruption column collapsing. They are the most dangerous immediate volcanic hazard.

XY(Al,Si)2O6, in which commonly X = Na, Ca, Mg, or Fe; Y = Mg, Fe, or Al. A mineral that is typically black to dark green, blocky, with two cleavages at ~90°; common in mafic igneous rocks and some metamorphic rocks; structured as a single chain of silica tetrahedra.

An observation based on non-numerical data. While these types of observations are not preferred, they can still be useful.

An observation based on numerical data. These observations are preferred because they can be used in calculations.

SiO2. A mineral that is transparent but can be any color imaginable with impurities; has no cleavage, is hard, and commonly forms equant masses; perfect crystals are hexagonal prisms topped with pyramidal shapes; structured as a three-dimensional network of silica tetrahedra, connected to each other as much as possible. One of the most common minerals, quartz is found in many different geologic settings, including the dominant component of sand on the surface of Earth.

A metamorphosed sandstone.

The most recent, and current, period within the Cenozoic Era, starting 2.58 million years ago.

A system for detecting the presence, direction, distance, and speed of aircraft, ships, and other objects by sending out pulses of high-frequency electromagnetic waves that are reflected off the object back to the source. It is an acronym for "radio detection and ranging."

Drainage pattern emanating from a high point.

The difference between the incoming solar energy absorbed by the Earth and the energy radiated back to space. It is a measure of the influence that factors like greenhouse gases and aerosols have on the Earth's energy balance, typically leading to warming (positive forcing) or cooling (negative forcing) of the climate system.

The process of atoms breaking down randomly and spontaneously.

Deserts that form as air loses moisture traveling over mountains.

Small circular pits formed by raindrops impacting soft sediments.

The collection and storage of rainwater from rooftops, surfaces, or other catchment areas for later use in irrigation, drinking water, or other purposes.

Surface waves that have an up and down motion.

A terminal moraine that forms as a glacier melts.

Area where water infiltrates the ground and adds to the overall groundwater.

The process of changing a mineral without melting.

Drainage pattern in an area of low topography dominated by bedding planes, joints, and fracture patterns.

Average time between earthquakes, calculated based on past earthquake records.

Increase in the wavelength of light resulting from the light source moving away from the observer.

Reactions that are related to the availability of oxygen. Many minerals or ions change their solubility based on redox conditions.

A half-reaction in which a chemical species decreases its oxidation number, usually by gaining electrons.

A topographic high found away from the beach in deeper water but still on the continental shelf, typically formed in tropical areas by organisms such as corals.

Removing trace elements from desired elements.

Waves bouncing off of a boundary between mediums of different properties.

Waves changing direction due to changing speeds, typically caused by a change in density of the medium.

Metamorphism that occurs with large-scale tectonic processes, like collision zones.

Loose material that is a mixture of soil components and weathered bedrock sediments.

The decrease in sea level over time.

Determining a qualitative age of a geologic item in relation to another geologic item.

The process of cleaning up a polluted site.

A resource that is replaced on a human timescale.

A rock that allows petroleum resources to collect or move inside it.

A body of water behind a dam, usually built to store fresh water, often doubling for hydroelectric power generation.

An amplification of earthquake waves due to buildings or other structures.

A dip-slip fault in which the hanging wall rises with respect to the foot wall.

To move in a circular or curving course or orbit. Not to be confused with rotate (to spin on an axis).

A root system preserved in rock.

General name of a felsic rock that is extrusive; its groundmass is usually white, tan, or pink in color.

A magnitude scale based on the amplitude of shaking, measured via a seismograph.

Area formed when the continental lithosphere extends, forming a depression. Rifts can be narrow (focused in one place) or broad (spread out over a large area with many faults).

Currents that push seaward.

Ridges of sediment that form perpendicular to flow in the lower part of the lower flow regime.

Channels of water that flow downhill due to gravity.

The concept that any rock type (igneous, sedimentary, or metamorphic) can change into another rock type under the right conditions over geologic time.

Detached rocks free-falling from very steep slopes.

The supercontinent that existed before Pangea, about one billion years ago. North America was positioned in the center of the landmass.

A wave that is large, unexpected, and dangerous.

A process in which plants and their roots wedge into cracks in bedrock, widening them.

To spin on an axis. Not to be confused with revolve (to move in a circular or curving course or orbit).

Movement of regolith along a curved slip plane.

The smoothness or roughness of the edges within a sediment.

Water that flows over the surface.

Second-fastest seismic wave, which has a shear motion.

Rocks that move along thin ice sheets with high winds.

Silt and sand that is lifted from the bed and transported short distances.

A rock primarily made of sand.

The point at which a solution has the maximum possible amount of the dissolved component and is unable to dissolve more.

Rock more metamorphosed than phyllite, to the point that mica grains are visible. Larger porphyroblasts are sometimes present.

Visible, coarse-grained, platy minerals in a planar fabric, typical of schists.

The act of purposely ignoring or dissenting from science for political or cultural gains.

The idea in science that phenomena and ideas need to be scrutinized through hypothesizing, experimentation, and analysis. This can eventually result in a consensus or scientific theory.

Series of ridges that result from the continuous lateral migration of a meander, showing the former locations of the river channel.

A conical submarine mountain formed from an extinct volcano that rises abruptly from the ocean floor but typically does not reach the water's surface. Over geologic time, the largest seamounts may reach the sea surface, where wave action erodes the summit to form a flat surface.

Pieces of rock that have been weathered and possibly eroded.

Diagenetic copper deposit within sedimentary rocks.

Broad, low-grade deposits of microscopic gold found in sedimentary rocks with diagenetic alteration.

Relating to pieces of rock that have been weathered (i.e., sediment).

A local or regional depression that allows sediments to accumulate.

Rocks that are formed by sedimentary processes, such as sediment lithification and precipitation from solution.

Areas that have an unpredicted change in seismic data, indicating a change in properties.

Length of fault without earthquake activity, occurring due to a locked segment in the fault.

Energy that radiates from fault movement via earthquakes.

Instrument used to measure seismic energy.

Location with two unequal tide cycles per tidal day.

The study of changes in the rock record caused by changing sea level over time.

Rock formed from hydrothermal alteration of basalt, made of serpentine.

SETI, or the Search for Extraterrestrial Intelligence, is a scientific effort aimed at detecting signals or evidence of intelligent life beyond Earth.

A very fine-grained rock with very thin layering, making it fissile.

Stress within an object that causes side-to-side movement within an internal fabric or weakness.

Component of gravitational force that pushes material downslope.

The relationship between shear force and normal force in a block of material on a slope. When shear force is greater than normal force, mass wasting can occur.

Planar flow of water over land surfaces.

A craton that is exposed at the surface.

Volcano with a gentle slope, formed from low-viscosity, low-volatility, mafic, basaltic lava.

Metamorphism caused by bolide impacts.

Part of the coastal depositional environment, located near the tidal zone but below. Lower shoreface is the part of the coastline which is only disturbed by storm waves; upper shoreface is disturbed by typical daily wave action.

The part of the coastline that is directly related to water-land interaction, specifically the tidal zone and the range of the wave base.

One of the largest volcanic eruptions on Earth, when over three million cubic kilometers of lava erupted, based on evidence found in Siberia.

Mineral group in which the silica tetrahedra, SiO44-, is the building block.

Anion structure of one silicon bonded to four oxygens in the shape of a tetrahedron, with the silicon in the center and four oxygens at the corners of the structure. It has a net charge of -4 and can bond to cations to form silicate minerals.

A sheet-like igneous intrusion that has intruded parallel to bedding planes within the bedrock.

A rock made of primarily silt.

The third period of the Paleozoic, 444–420 million years ago.

A strike-slip or transform motion in which the relative motion is to the left as viewed across the fault.

Carbonate rock that reacts with hot magmatic fluids, creating concentrated ore deposits, which can include copper, iron, zinc, and gold.

Name given to the subducting plate, from which volatiles are driven out at depth, causing volcanism.

Metamorphic rock with a strong foliation but no visible minerals, derived from mudstones or shales.

Microscopic foliation in slate, in which flat slabs and planes of rock develop.

A rock surface that has been polished by fault movement, covered with grooves.

A process that chemically separates desired element(s) from ore minerals.

The hypothesis that the entire ocean froze and continental glaciation covered the planet about 700 million years ago.

The line between the zone of accumulation and the zone of ablation.

Weak, typically saturated sediments that deform and contort before lithification.

A type of non-eroded sediment mixed with organic matter, used by plants. Many essential elements for life, like nitrogen, are delivered to organisms via the soil.

Very slow movement of soil downhill.

Specific layers within a soil profile, featuring specific properties.

A hypothetical or real section cut from soil, showing the different layers (horizons) that exist within it.

Radiation from the Sun that is capable of producing heat, causing chemical reactions, or generating electricity.

Rotating, flattened disk of gas and dust from which the Solar System originated.

While the generic term for a group of planets and other bodies circling a star is planetary system, our planetary system is the only one officially called “Solar System,” because our Sun is sometimes called Sol.

A series of sedimentary structures that form at the base of a flow and erode into underlying sediment. Examples include scour marks, flute casts, groove casts, and tool marks.

Two or more elements that can easily substitute for each other due to similarities in ionic size and charge.

The process of a solid dissolving into a liquid. This commonly occurs with salts and other minerals in water.

An acronym for "sound navigation and ranging," sonar uses sound waves to navigate and map surfaces. Sound waves created by an observer reflect off of surfaces and return to the observer; the amount of time it takes for the sound to return is a function of the distance the surface is from the observer. Bats use sonar to navigate through the dark, and ships use sonar to map the ocean floor.

The range of sediment sizes within a sediment or sediment within sedimentary rocks. "Well sorted" means the sediment has the same sizes, while "poorly sorted" means many different sizes are present.

A rock containing material that can be turned into petroleum resources. Organic-rich muds form good source rocks.

Related to density, specific gravity is the ratio of the weight of a mineral vs. the weight of an equal volume of water.

The study of the details of light, which can tell you the chemical makeup of light and even the movement of a light source.

The constant velocity at which light travels in a vacuum, approximately 299,792 kilometers per second (186,282 miles per second).

A type of exfoliation where homogenous rocks weather into round shapes.

A ridge of sediment that extends out into a body of water, formed via longshore currents.

A place where pressurized groundwater flows onto the surface.

Highest high tide of the month.

An offshore rock spire that is a remnant of a rock layer.

Dunes that form from wind of many different directions.

The process of surrounding bedrock being broken up and moved upward by magma.

The depth that waves can reach in large storms, such as hurricanes.

Channels that form straight, typically near headwaters.

The deformation that results from application of a stress.

Finding matches between disconnected rock strata across long distances.

The study of rock layers and their relationships to each other within a specific area.

Volcano with steep sides, formed due to a combination of many types of eruption styles and from low-viscosity mafic magma, higher-viscosity felsic lava, but most commonly, intermediate andesite lava.

The color(s) that a mineral produces when powdered or rubbed against a hard surface, usually a porcelain tile.

A channelled body of water.

Force applied to an object, typically in relation to forces within the Earth.

A measure of a geologic plane's orientation in 3-D space. Used to measure beds of rocks, faults, foldhinges, and more. Using the right-hand rule, dip is perpendicular and to the right 90° of the strike.

Faulting that occurs with shear forces, typically on vertical fault planes as two fault blocks slide past each other.

A surface mining technique that involves removing large strips of soil and rock to access underlying mineral deposits.

A fossil that forms as algal mats grow and capture sediment in mounds.

A basin formed structurally by symmetrical synclines.

Large and mysterious landslides that travel long distances.

A process where an oceanic plate descends below a less dense plate, causing the removal of the plate from the surface. Subduction causes the largest earthquakes, as the subducting plate can lock as it descends. Volcanism also occurs as the plate releases volatiles into the mantle, causing melting.

Metamorphism that occurs in subduction zones, typically at a lower temperature and higher pressure.

A mineral that only shows some characteristics of its true crystal habit and is not perfectly grown.

An observation influenced by the observer's personal bias.

Canyon carved into a continental shelf.

Broad cone of coarse sediment deposited from a submarine flow or turbidity flow.

Area of coast where relative sea level is rising.

The act of the land surface downwarping, typically referred to when discussing sedimentation or rapid groundwater removal.

Lower layer of the soil (B), which is a mixture of weathered bedrock, leeched materials, and organic material. Has two sublayers: the upper part, or regolith (with more organic materials), and the lower part, saprolite, which is only slightly weathered bedrock.

Lowest layer of the soil (C), which is mechanically weathered (not chemically weathered) bedrock.

Minerals bonded via a sulfate ion, SO42-.

Minerals bonded via a sulfur (S2-) atom.

Lower, seaward berm that forms with lower wave energy in summer months.

An arrangement of many continental masses that have collided together into one larger mass. According to the Wilson cycle, this occurs every half-billion years or so.

A federally supported pollution clean-up effort.

Oxidation occurring in sulfide deposits that can concentrate valuable elements like copper.

Large explosion when the largest stars end fusion; responsible for the formation of heavy elements in the universe, like gold and uranium.

Shoreline area of breaking waves.

Mining that occurs near the Earth's surface.

Seismic waves that only move along the surface, mainly R waves and L waves.

Bedload sediments that can be carried by higher-velocity flows.

A U-shaped, upward-facing fold with younger rocks in its core.

An interconnected set of parts that combine to make up a whole.

Rounded cavities within rocks that form in various ways, including the growth of minerals (mainly salt).

Loose blocks of rock that fall from steep surfaces and cover slopes.

Sands or sandstones that contain high-viscosity petroleum.

Relating to the movement of plates of lithosphere.

The measure of the vibrational (kinetic) energy of a substance.

Stress that pulls objects apart, giving them a larger surface area or volume; stretching forces.

General term for solid but fragmented material that erupts from a volcano; divided into three subcomponents: ash (<2 mm), lapilli (2–64 mm), blocks and bombs (>64 mm).

Moraine that forms at the end of a glacier.

An elevated erosional surface caused by glacial or fluvial action.

A geological province added (accreted) to a continental mass via subduction and collision.

Referring to depositional environments that are on land.

Arrangement of minerals within a rock.

Deepest part of a meandering channel.

An accepted scientific idea that explains a process using the best available information.

A distinct layer in a body of water where the temperature changes more rapidly with depth than it does in the layers above or below.

A connected global ocean circulation pattern that distributes water and heat around the globe.

Faulting located deep in the crust, typically involving crystalline basement rocks.

Faulting that is not located deep in the crust and that typically only involves sedimentary cover, not basement rocks.

Complex organic compounds formed by the irradiation of simple carbon-containing molecules, often found on the surfaces of icy bodies in the outer Solar System.

A low-angle reverse fault, common in mountain building.

The process by which the Earth's rotation is slowed down by the friction of ocean tides.

The amount of time the Moon takes to reappear over the same location of Earth, slightly more than 24 hours.

Wide and flat area of land covered by ocean water during high tide but exposed to air by low tide.

A gravitational effect that stretches a body along the line toward and away from the center of mass of another body due to spatial variations in gravitational field strength from the other body.

Movement of water (rising and falling) due to the gravity of the Moon and Sun; most often seen in marine settings.

General term for very poorly sorted sediment that is of glacial origin.

A rock made definitively of glacial till.

Sand bar that connects a stack and the shore.

A process using 3-D seismic arrays to get subsurface images.

Upper layer of soil, made mainly out of organic material.

Evidence of biologic activity that is preserved in the fossil record but not the organism itself. Examples include footprints and burrows. Ichnology is the study of trace fossils.

Desert that forms near 30° latitude due to atmospheric circulation.

Wind patterns that move from east to west near the equator due to global circulation patterns.

Place where two plates slide past each other, creating strike-slip faults.

Geological event in which sea level rises over time.

A landslide that moves along an internal plane of weakness.

A segment along a transform or strike-slip fault that has a compressional component, sometimes resulting in thrust faulting and mountains.

A place along a transform or strike-slip fault with an extensional component; sometimes includes normal faulting, basin formation, and volcanism.

A geologic circumstance (such as a fold, fault, or change in lithology) that allows petroleum resources to collect.

Porous, concentric, or layered variety of carbonate that forms with often-heated water in springs and/or caves.

A drainage pattern that forms between ridge lines in deformed (typically sedimentary) rocks.

Deepest part of the ocean, located where a subducting plate dives below the overriding plate.

The first period of the Mesozoic Era, from 252–201 million years ago.

A natural stream that flows into a larger river or other body of water.

An event that causes a landslide. Water is a common trigger.

Place where three plate boundaries (typically divergent) extend from a single point at 120° angles.

An eroded arête that forms a triangular shape.

A series of waves produced from a sudden movement of the floor of a ocean basin (or large lake), caused by events such as earthquakes, volcanic eruptions, landslides, and bolide impacts.

Porous variety of carbonate that forms in relatively unheated water, sometimes in the shape of towers and spires.

Rock made from pyroclastic tephra: either ash, lapilli, and/or bombs. It can be described by its tephra type (e.g., ash-fall tuff). If deposited hot, where material can fuse together while hot, the rock is then called a welded tuff.

Rock that forms from a turbidity flow, a relatively coarse and dense sediment transported to the abyssal plain.

Dense flow of sediment through submarine canyons that forms submarine fans and turbidites.

A rotary mechanical device that converts the kinetic energy of fluids, such as water, steam, or air, into mechanical energy or electricity by rotating a series of blades.

An igneous rock with extremely low silica composition, made of almost entirely olivine and pyroxene; commonly found in the mantle. Primary ultramafic rocks are komatiite (extrusive) and peridotite (intrusive).

Missing time in the rock record, either because of a lack of deposition and/or erosion.

Mining that occurs within tunnels and shafts inside the Earth.

A chemical that can dissolve a wide range of other chemicals.

All of space and time and their contents, including planets, stars, galaxies, and all other forms of matter and energy.

Level in which pores are filled with some water and some air, located above the water table.

An alpine glacier that fills a mountain valley.

A type of lamination that is cyclical, perhaps seasonal or diurnal.

Opening of a volcano from which lava can erupt.

Rock with abraded surfaces formed in deserts.

An animal that possesses a spinal column or backbone.

An extrusive rock filled with small bubble structures created by gases escaping from the cooling lava.

The resistance of a fluid to flow, in which a high value means a fluid does not like to flow (like toothpaste) and a low value means a fluid flows easily (like water).

Components of magma that dissolve until it reaches the surface, where they expand. Examples include water and carbon dioxide. Volatiles also cause flux melting in the mantle, resulting in volcanism.

A chain of mountain volcanism on a continent, formed by oceanic-continental subduction.

The solidified remains of a volcano's conduit and plumbing system that remains after the rest of the volcano has eroded away.

Place where lava erupts at the surface.

Metallic mineral deposit that forms near mid-ocean ridges.

A zone of earthquakes that descend into the Earth with subducting slabs. This is commonly used as evidence for plate tectonics.

A purchase or claim obtained through the state government for the legal allotment of a water source such as a spring, stream, well, or lake.

The depth of the groundwater system below which its pore space is 100% filled with water.

The depth in which the movement of waves can be felt, specifically by sediments. This is approximately equal to half the wavelength. Wave bases can change based on weather (e.g., fair vs. stormy).

Top of a wave.

The distance between the crest and trough of a wave; equal to twice the amplitude.

Erosional notch in bedrock cut by waves.

The time between similar parts of a wave passing a fixed point.

A series of waves that form and move as a group.

Bottommost part of a wave.

Speed at which a wave travels past a fixed point.

Flat erosional surface cut by wave action.

The distance between any two repeating portions of a wave (e.g., two successive wave crests).

Current conditions within the atmosphere.

Breaking rocks into small pieces by chemical or mechanical means.

Winds that move from west to east between 30° and 60° latitude due to global circulation patterns.

The cycle of opening ocean basins with rifting and seafloor spreading then closing the basin via subduction and collision, creating a supercontinent.

A form of renewable energy that harnesses the power of the wind to generate electricity.

Higher, landward berm that forms with higher-wave energy in winter months.

A piece of foreign rock that has been incorporated into a magma body, either as a different type of magma or a mantle xenolith, a rock from the mantle brought up near the surface.

Erosional rock face caused by sand abrasion.

A tributary that runs parallel to a main stream within the floodplain.

The point at which the amount of strain on a substance has caused the maximum amount of elastic deformation and switches to ductile deformation.

ZrSiO4. A relatively chemically inert mineral with a hardness of 8.5. Common accessory mineral in igneous and metamorphic rocks, as well as detrital sediments. Uranium can substitute for zirconium, making zircon a valuable mineral in radiometric dating.

Part of a glacier that has shown a net gain of material over the course of a year.