A blocky, stubby, rubble-like lava.

absolute dating

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


The deep, flat part of the ocean. Also known as the ocean floor.

abyssal plain

Relatively flat ocean floor, which accumulates very fine grained detrital and chemical sediments.

accretionary wedge

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

acid rock drainage

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

active margin

A convergent boundary between continental and oceanic plates.

actual preservation

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


Forces that cause one substance to stick to another.


Deposition with wind-blown sediment.


Earthquake(s) that occur after the mainshock, usually decreasing in amount and magnitude over time.


The amount of light that is reflected off of an object. It is 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.

alpha decay

Radioactive decay where two protons and two neutrons leave the isotope.

alpine glacier

A glacier that forms on a mountain.


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.


Possesses properties of both acid and base.


Height or depth of a wave from the middle point.


General name of an intermediate igneous rock that is extrusive. Generally has a gray groundmass color.

angle of incidence

Angle from perpendicular to the ground surface at which light rays hit 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.

angle of repose

Slope angle where shear forces and normal forces are equal.

angular unconformity

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 have a habit, or because it grew in a way that it was confined so it 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 which is out of the ordinary and does not fit previous trends.


A newly-proposed time segment (an epoch) that would be representative of time since humans have changed (and left evidence behind within) the geologic record.


Made or influenced by humans.

anthropogenic climate change

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 up stream. Forms in the upper part of the upper flow regime.


Small, microscopic, hard-to-see crystals (i.e. no visible crystals) within an igneous rock. This is common in extrusive rocks.


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


A rock or sediment that has good permeability and porosity, and allows water to move easily, making it possible to get water 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. The arc is on the overriding plate, typically a few hundred kilometers from the trench, but parallel to the trench.


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


A ridge that is carved between two glacial valleys.


A sandstone rich in feldspar.


Dry riverbed in an arid region.

artesian well

A well which 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, as the overriding lithosphere is pushed by this.


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

Atacama Desert

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.

atmosphere (astronomy definition)

The layers of gases surrounding a planet or other celestial body.


An AU (or astronomical unit) is the average distance from Earth to the Sun.


Strong crystals that do not deform as easily under ductile deformation, and 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.

authigenic mineralization

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

axial plane

Dividing two-dimensional line between the two sides of a fold.


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

back-arc basin

Depression formed behind an arc, where extension has caused a basin, 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.

banded iron formation

A sedimentary rock that formed long ago as 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.

bankfull stage

Largest amount of flow a river can hold before flooding.

barchan dune

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

barrier island

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


General name of a mafic rock that is extrusive. Generally has a black groundmass color.

base level

Elevation of the mouth of a river.


A down-warped feature in the crust.

basin and range

Term for the extensional tectonic province that extends from California’s Sierra Nevada Mountains in the west, to Utah’s Wasatch Mountains to the east, to southern Oregon and Idaho to the north, to northern Mexico to the south. 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.


A highly weathered soil deposit that consists of aluminum ores.

baymouth bar

A place where a spit extends out and covers a bay.

beach face

Active area of crashing waves.

beach replenishment

Adding sediment to a beach system in order to replace lost sediment due to longshore drift.


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.


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


Term for the underlying lithified rocks that make up the geologic record in an area. This term can sometimes refer to only the deeper, crystalline (non-layered) rocks.


Ridge of sand built above the beach face.

beta decay

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

Big Bang Theory

The theory that the Universe started with a expansive explosion. Shortly after, elements were created (mostly hydrogen) and galaxies started to form.


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


The living things that inhabit the Earth.

biostratigraphic correlation

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


Sedimentary layering disturbed by movement of organisms.

black smoker

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 the rock blueschist, a metamorphic rock containing a blue amphibole called glaucophane.

body wave

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.

Bouma sequence

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

Bowen’s Reaction Series

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.

braided channel

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


Offshore durable 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, at low temperatures, are brittle.

brittle deformation

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

burial metamorphism

Metamorphism that is caused by confining pressure and heat, both increasing with depth.


CaCO3. Pure form is clear, but can take on many different colors with impurities. It is soft, fizzes in acid, and has three cleavages that are not at 90°.

calcite compensation depth

Also known as the CCD, it is the point in the depths of the ocean where calcite start to dissolve, leaving only siliceous ooze behind.


Hole left behind after a large volume of material erupts out of a volcano. This depression is often turned into a valley or lake after the eruption is over.


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


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

Cambrian Explosion

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


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.

carbonic acid

An acid that forms from carbon dioxide and water. It is 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 events 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 being "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 coccolithophore shells, a type of single-celled algae.

chemical sedimentary

Sedimentary rocks that are precipitated, from solution.

chemical weathering

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 very fine grained version of silica deposited with or without microfossils.

Chicxulub Crater

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


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

chronostratigraphic correlation

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


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

cinder cone

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


Glacially-carved, bowl-shaped valley.


Sedimentary rocks that are made of sediment, weathered pieces of bedrock.


A rock made primarily of clay.


A weakness within the atomic structure of a mineral, which allows the mineral to break more easily along that plane. Minerals can have one, two, three, or more cleavages. Cleavage can also refer to the alignment of features within metamorphic rocks., though they are unrelated.


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

closed basin

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 which is related to land-sea interactions.


Forces that hold a substance together.


Low point within an arête.


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 which takes ore and separates it from gangue material.


Fractures that have a circular appearance.


Pipe that connects the magma chamber to the volcanic vent.

cone of depression

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


Non-directional pressure resulting from burial.

confining layer

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


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

connate water

Original water trapped inside a forming rock.

contact metamorphism

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

continental crust

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

continental glacier

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

continental shelf

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

continental slope

Steep part of an ocean basin that is 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 while cooler, denser parts sink. This typically creates convection cells: round loops of rising and sinking material.


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


Limestone made of shell fragments cemented together.


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


Matching rocks of similar ages, types, etc.

cosmic microwave background

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

cosmic microwave background radiation

Trace amounts of energy found throughout the Universe.


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 old as  2.5-3 billion years. When exposed on the surface, a craton is called a shield.


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


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

Cretaceous Interior Seaway

A waterway that existed in North America around 100 million years ago. Western North America was separated from eastern North America.


Cracks that form with glacial movement in the upper, brittle part of the glacier.

crevasse splay

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

cross bed

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

cross bedding

A sedimentary structure that has inclined layers within an overall layer. Forms commonly in dunes, 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 the thick, more ductile, and lowest density, and oceanic, which is higher density, more brittle, and thinner.


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

crystal habit

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 as different components solidify at different temperatures.

cut bank

Erosional part of a meandering channel.

daughter isotope

The atom that is made after a radioactive decay.

debris flow

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

decay chain

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

Deccan Trapps

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

Decompression melting

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

deductive reasoning

Taking known truths in order 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.

dendritic drainage

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


We give densities in units where the density of water is 1 g/cm3. To get densities in units of kg/m3, multiply the given value by 1000.


Sediment gathering together and collecting, typically in a topographic low point.

depositional environment

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

deranged pattern

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

desert varnish

Dark mineralization that forms on rocks in desert environments.


The process that turns non-desert land into desert.

detachment fault

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


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


Known as the "Age of Fishes," the 4th period of the Paleozoic, about 419-359 million years ago.


Movement in a transform or strike-slip setting which is toward the right across the fault. As viewed across the fault, objects will move to the right.


Changes in sedimentary rocks due to increased (but low when compared to metamorphism) temperatures 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, differentiation is the process of separating out 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 an intermediate rock that is intrusive. 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°.

dip slip

Faulting that occurs with a vertical motion.

directed stress

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


Increased intensity due to being along the path of fault propagation.


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


Two layered rocks that may seem conformable, but an erosional surface exists between them.


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

dissolved load

Amount of material dissolved in stream water.

diurnal tide

Areas that have two clear high and low tides per tidal day.


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


A rock up-warping of symmetrical anticlines.

Doppler Effect

A change in wavelength and frequency of a wave due to the source of a wave moving relative to the observer of a wave.

drainage basin

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

drainage divide

Topographic prominence which sheds water into a specific drainage basin.

drainage pattern

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


Ridge of sediment that forms under a glacier, with a steep uphill (with respect to the glacier) side and gentle downhill side.


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.

ductile deformation

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


A large pile of sediment, deposited perpendicular to flow. Internal bedding in dunes dips toward flow direction (i.e. cross bedding). Formed in the upper part of the lower flow regime.

dwarf planet

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

Earth System Science

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.


Plastic moving, fine-grained type of flow.


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

Ediacaran fauna

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

elastic deformation

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

elastic rebound

A theory of building energy that is released during an earthquake.

electromagnetic spectrum

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


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

electron capture

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.

emergent coastline

Features of a coastline where relative sea level is falling.

entrenched channel

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. Rocks of a specific eon are called eonotherms.

ephemeral stream

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


The location at 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 long 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 which forms 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.


An 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, which is a measure of water entering the atmosphere.


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


Any planet beyond our solar system.


Of or pertaining to an exoplanet, a planet outside the 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.


Originating or existing outside the solar system.


Igneous rock cooling, and thus forming, outside of the Earth, i.e. on the surface.


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

failed rift arm

A section of a rift that starts but does not complete. This typically occurs at 120° angles to the active rift.

fair weather wave base

The depth normal, non-storm waves reach.


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


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

fault scarp

Place where fault movement cuts the surface of the Earth.


Consisting of three end members: potassium feldspar (K-spar, KAlSi3O8), plagioclase with calcium (CaAl2Si2O8, called anorthite), and plagioclase with sodium (NaAlSi3O8, called albite). Commonly blocky, with two cleavages at ~90°. Plagioclase is typically more 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 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).


Distance wind has been building a wave.

finger lake

Lake that fills a glacial valley.


Snow which 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.

flash flood

Dangerous flooding that occurs in arid regions.

flood basalt

Rare very 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.

flow regime

A qualitative measure of the speed of a fluid flow, with different amounts of flow corresponding to different sedimentary structures, called bedforms. Typically, it is split into upper and lower flow regimes, with upper being a more rapid flow.

flower structure

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


Deposition that has to do with rivers.

flux melting

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.

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.

fossil fuel

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.


The process of a magma changing from mafic to felsic via cooling. As the magma cools, higher temperature, mafic minerals crystalize, and a more felsic magma is left.


A break within a rock that has no relative movement between the sides. Caused by cooling, pressure release, tectonic forces, etc.

fracture zone

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.

frost wedging

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


Gas expulsions from the subsurface, usually related to volcanic activity.


A process inside stars where smaller atoms combine and form larger atoms.


General name of a mafic rock that is intrusive. Has more mafic minerals than felsic minerals.


A gravitationally-bound system of stars and interstellar matter.

gamma ray

A penetrating form of electromagnetic radiation arising from the radioactive decay of atomic nuclei. It consists of the shortest wavelength electromagnetic waves, typically shorter than those of X-rays.


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

geopetal structure

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.

geothermal gradient

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

Giant Impact Hypothesis

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


Deposition and erosion tied to glacier movement.

glacial budget

The net gain or loss of ice within a glacier.

glacial erratic

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

glacial polish

Smooth surface carved in harder rocks by glacial action.

glacial striation

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 body of ice that moves downhill under its own mass.




A very high grade metamorphic rock, higher grade than schist, with a separation of light and dark minerals.

Goldich Dissolution Series

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, either getting coarser or finer.

grain size

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


General name of a felsic rock that is intrusive. Has more felsic minerals than mafic minerals.

Great Basin Desert

Desert area stretching from California to the west, Utah to the east, and Idaho/Oregon to the north. Partially caused by latitude, partially caused by rain shadow.

Great Oxygenation Event

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.

greenhouse effect

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


A sandstone with a significant mud component OR a sandstone with a significant lithic fragment component.


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

ground moraine

Moraine that forms beneath a glacier.


General term for the fine-grained, not 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 is usually referring to material between porphyroblasts or a low-grade rock with only microscopic mineralization.


Water that is below the surface.

Groundwater mining

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


An evaporite mineral, CaSo4•2H2O. Has one cleavage, hardness of 2. Typically clear or white.


Large circular ocean currents formed by global atmospheric circulation patters.


Dust storms that occur in desert areas.


Eon that represents the time from Earth's formation to 4 billion years ago. Noted for high levels of volcanism, impacts, and very low preservation.

Hadley Cell

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

half graben

A valley formed by normal faulting on just one side.

half life

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.


Also known as rock salt, or table salt. 3 cleavages at 90°, cubic crystal habit. Typically clear or white, hardness of 3.

hanging valley

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

hanging wall

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.


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

hopper crystal

Evaporites (like salt) which form cavities within rocks, which mimic the shape of the crystal.


Steep spire carved by several glaciers.


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


Uplifted mountain block caused by normal faulting.

hot spot

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

hummocky cross stratification

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


Organic rich material found in soil.


Relating to movement brought about by water.

hydraulic conductivity

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

hydrogen bond

A weak chemical bond which 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.


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


Metamorphism which occurs with hot fluids going within rocks, altering and changing the rocks.


Proposed explanations for an observation that can be tested.


A proposed explanation for an observation that can be tested.

ice sheet

Thick glaciers that cover continents during ice ages.


Relating to molten rock.

Igneous rocks

Rocks that are formed from liquid rock, i.e. from volcanic processes.


Stacked cobbles in the direction of flow.


A piece of a rock that is caught up inside of another rock.

index fossil

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

index mineral

Minerals that form at a specific range of temperatures and pressures. Using a collection of index minerals narrows down the conditions of rock formation.

induced seismicity

Earthquakes that occur due to human activity.

inductive reasoning

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


Water that works its way down into the subsurface.

inner core

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


Isolated piece of bedrock which sticks above an alluvial surface.


Period of warming within a glacial or ice age cycle.


A volcanic rock with medium silica composition, equally rich in felsic minerals (feldspar) and mafic minerals (amphibole, biotite, pyroxene). Intermediate rocks are grey in color and contain 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, even warmer than a interglacial, within a glacial or ice age cycle.


Activities that occur within plates, away from plate boundaries.


Igneous rock cooling, and thus forming, 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.

island arc

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.

isostatic rebound

An upwards 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, isotopes can have subtle changes between them, 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 kelvin, symbol K, is the SI base unit of temperature. Absolute zero is 0 K, the equivalent of −273.15°C.

K-T Extinction

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.


Carbonate rocks which dissolve, leaving behind caverns and holes which affect the landscape.


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

kettle lake

Lake that forms in a kettle.


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

Kuiper belt

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.


Large igneous intrusion that is wedged between sedimentary layers, bulging upwards. Called a lopolith if bulging downward.


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 of the slopes of steep volcanoes or other mountains and then wash downhill, causing damaging flooding.


Thin (less than 1 cm) beds of rock.


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


Volcanic tephra that has a diameter between 2 mm and 64 mm. Many cinders are within the category of lapilli.

late heavy bombardment

A hypothesis that states that movement of Jupiter and Saturn about 4 billion years ago caused a destabilization of orbits in the Asteroid and Kuiper Belts, which then caused a spike in impacts throughout of solar system.

lateral moraine

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.

Lava dome

Very steep sided volcanic feature formed by higher viscosity, higher-silica lava.

layered intrusion

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

light years

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.

linear dune

Dunes that are much longer than wide, forming from wind that varies 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, and these plates move in various ways (relative to one another), causing the features of the theory of plate tectonics.

lithostratigraphic correlation

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


The beach (shoreline) zone, where waves are crashing.


Wind-blown silt, mainly formed from glacial processes.

longitudinal profile

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

longshore current

A net movement that occurs as waves intersect the shoreline at non-perpendicular angles.

longshore drift

Sediment that moves via a longshore current.

Love wave

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


The shine a mineral takes on, based on the way light reflects off of a mineral. This is typically divided into two main categories: metallic (metal-like shine) and nonmetallic (non metal-like shine).


Can refer to a volcanic rock with lower silica composition, or 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.

magma chamber

A reservoir of magma below a volcano.

magmatic differentiation

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

magnetic striping

Symmetric (about the ridge) patterns of magnetism 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.

mantle plume

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

mantle wedge

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


A metamorphosed limestone.


Places that are under ocean water at all times.

mass extinction

A pronounced increase in the extinction rate, typically caused by significant environmental change. There have been 5 mass extinctions in geologic history, and a sixth that has been suggested to be currently occurring.

mass spectrometer

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

mass wasting

Any downhill movement of material, caused by gravity.


A feature with no internal structure, habit, or layering.

meander scar

Silted-in oxbow which still has a topographic expression.

meandering channel

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

mechanical weathering

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

medial moraine

A place where two or more glaciers combine, and the lateral moraines combine to form a moraine within the glacier.


Term for faulting that occurs in subduction.


Also called lower mantle, a solid, more brittle physical layer of the Earth, below the asthenosphere.


Meaning "middle life," it is the middle era of the Phanerozoic, starting at 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.


Minerals with a luster similar to metal and contain metals, including valuable elements like lead, zinc, copper, tin, etc.


Rocks and minerals that change within the Earth are called metamorphic, changed by heat and pressure. Metamorphism is the name of the process.

metamorphic facies

A specific set of index minerals tied to specific styles of metamorphism. When these minerals are present, it allows a history of metamorphism to be determined.

metamorphic rock

Rocks formed via heat and/or pressure which change 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 stoney and/or metallic object from our solar system which was never incorporated into a planet and has fallen onto Earth. Meteorite is used for the rock on Earth, meteoroid for the object in space, and meteor as the object travels in Earth's atmosphere.


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


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

mid-ocean ridge

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

Milankovitch Cycles

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


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


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


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


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

Mississippi Valley-type

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

mixed tide

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

Modified Mercalli Intensity Scale

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


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


Organic material making a preserved impression in a rock.

Moment magnitude

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. Besides planets, moons can circle dwarf planets, large asteroids, and other bodies.


An object that orbits a planet or something else that is not a star. Besides planets, moons can circle dwarf planets, large asteroids, and other bodies.


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


A landform that rises above its surrounding area.


The end of a river.

mud chip

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 via ductile deformation, deeper within the Earth.

native element minerals

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

natural gas

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

natural hazard

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

natural levée

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

natural resources

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

neap tide

Lowest low tide of the month.


Shore area between low tide and storm wave base. Upper part is dominated by fair weather wave base, lower part is dominated by storm wave base.


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

nebular hypothesis

The idea that a nebula can collapse and form a star with planets.

negative feedback

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


Metamorphic textures that do not have a directional component of its minerals.


Layered rocks on top of a non-layered rock, such as crystalline basement.


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.

nonpoint source

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


A resource that is not able to be replaced on human time scales.

normal fault

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

normal force

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


Process which allows a continental plate to bring up oceanic plate, frequently occurring in collision zones.


An observation that is completely free of bias, i.e. anyone and everyone 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 form from felsic volcanism.

oceanic crust

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

oceanic-continental subduction

Where an ocean plate subducts beneath a continental plate, causing a volcanic arc to form.

oceanic-oceanic subduction

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

octet rule

A rule that says the outer valence shell of electrons is complete when it contains 8 electrons.


Amount of movement during a faulting event.


The part of the coastline which is below any wave base action.


A dark liquid fossil fuel derived from petroleum.

oil shale

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


(Fe,Mg)2SiO4. Typically translucent olive green and equant, with no cleavage. Common in mafic igneous rocks and in the mantle, but easily weathered in surface conditions. Structure is isolated silica tetrahedra. Known as peridot when a gem.


Spheres of calcite that form in saline waters with slight wave agitation. Ooid refers to the sphere, oolite the rock with the spheres.

Oort cloud

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

open pit mine

Large surface mine with opening carved into the ground.


Rocks of the ocean floor, such as mid-ocean ridge rocks, which 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.

ore mineral reserve

A proven commodity of profitable material that could be mined.

ore mineral resource

Potentially extractible and valuable material, but unproven.


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.

outer core

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

outwash plain

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.


Certain metallic elements (like iron) take in oxygen, causing reactions like rust.


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


Oxidation is the loss of electrons or an increase in the oxidation state of a chemical or atoms within it.

p wave

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


Rope-like, flowing basaltic lava.

Paleocene-Eocene Thermal Maximum

A warm climate spike, the warmest in the 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 where "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 ending 252 million years ago. Vertebrates (including fish, amphibians, and reptiles) and arthropods (including insects) evolved and diversified throughout the Paleozoic. Pangea formed toward the end of the Paleozoic.


Deposition 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.

parabolic dune

Dunes that form semicircular shapes due to anchoring vegetation.

parasitic cone

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

parent isotope

A radioactive atom that can and will decay.

partial melt

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.

parting lineation

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

passive margin

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

paternoster lake

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

peer review

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, which is the main component of the mantle. The minerals in peridotite are typically olivine with some pyroxene.


A unit of the geologic time scale; smaller than an era, larger than an epoch. We are currently in the Quaternary period.


Soil and rock which is below freezing for long periods of time.


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


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

Permian Mass Extinction

The largest mass extinction in history, where an estimated 83% of genera went extinct. Linked to the Siberian Trapps as a cause.


Style of fossilization where 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. This study is typically divided into one of the three rock types (e.g. igneous petrology).


Large, easy-to-see crystals within an igneous rock. 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.

phase diagram

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


A large crystal within an igneous rock. These can be seen within phaneritic and porphyritic rocks.


Minerals that are bonded with the phosphate anion, PO4+3.


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.

piercing point

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


Deposit of heavy ores in stream or beach sediments.

plane bed

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.

planetary system

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 which moves as a unit, i.e. the entire plate generally moves the same direction at the same speed.

plate boundary

Location where two plates are in contact, allowing a relative motion between the two plates. These are the locations where most earthquakes and volcanoes are found.

Plate tectonics

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


Part of a craton that is covered, mainly by sedimentary rocks.


A dry lake bed in a desert valley.


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

pluvial lake

Lakes that form via increased precipitation with glacial climate shifts.

point bar

Depositional portion of a meandering channel.

point source

Pollution that comes from one known source.

Polar Cell

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

polar desert

Deserts formed by descending air at the poles.


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


Minerals with the same composition and different crystal structures.


A specific chemical composition that forms different minerals and different temperatures and pressures. Quartz has several different polymorphs, including coesite, tridimite, and stishovite.


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.


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.

positive feedback

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

potentiometric surface

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 of the dissolving material.

Principle of Cross-Cutting Relationships

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

Principle of Faunal Succession

The fossils found at any time are unique, and the fossils in layers of different ages have progressed and changed as time has moved forward. Fossils found in layers that are not as old have organisms that more resemble organisms that are alive today.

Principle of Lateral Continuity

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

Principle of Original Horizontality

Layered rocks are generally laid down flat at their formation.

Principle of Superposition

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

Principle of Uniformitarianism

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.

proglacial lake

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


A type of single-celled organism with no nucleus.


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


The rocks that existed before the changes that lead to a metamorphic rock, i.e. what rock would exist if the metamorphism was reversed.


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

proxy indicator

A measurement which 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).


Low density, highly vesiculated, usually white to tan volcanic rock. Typically arises from felsic volcanism.


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

pyroclastic flow

A collapsed part of the eruption column that travels down at very hot temperatures and very fast speeds. They are the most dangerous immediate volcanic hazard.


XY(Al,Si)2O6, in which X typically equals Na, Ca, Mg, or Fe and Y typically equals Mg, Fe, or Al. Typically black to dark green, blocky, with two cleavages at ~90°. Common in mafic igneous rocks and some metamorphic rocks. Structure is a single chain of silica tetrahedra.


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


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


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


A metamorphosed sandstone.


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

radial drainage

Drainage pattern emanating from a high point.


The process of atoms breaking down randomly and spontaneously.

rain shadow desert

Deserts that form as air loses moisture traveling over mountains.

raindrop impression

Small circular pits formed by raindrops impacting soft sediments.

Rayleigh wave

Surface waves that have an up and down motion.

recessional moraine

A terminal moraine that forms as a glacier melts.


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


The process of changing a mineral without melting.

rectangular drainage

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.

red shift

The increase in wavelength of light resulting from the fact that the source of the light is 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 change in starlight that occurs as light moves away from a source.


Reduction involves 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, these are formed in tropical areas by organisms such as corals.


Removing trace elements from desired elements.


Waves that bounce off of a boundary between mediums of different properties.


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

regional metamorphism

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


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


Sea level fall over time.

relative dating

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


The process of cleaning up a polluted site.


A resource which is replaced on human time scales.


Rocks which allow petroleum resources to collect or move.


An amplification of earthquake waves due to a structure of buildings or structures.

reverse fault

A dip-slip fault that has the hanging wall moving up with respect to the foot wall.


To move in a circular or curving course or orbit. Not to be confused with rotate, when something spins on an axis.


Root systems preserved in rocks.


General name of a felsic rock that is extrusive. Generally has a white, tan, or pink groundmass color.

Richter scale

A magnitude scale using the amplitude of shaking via a seismograph.


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

rip current

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.

rock cycle

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

rock fall

Detached, free-falling rocks from very steep slopes.


The supercontinent that existed before Pangea, about 1 billion years ago. North America was positioned in the center of the land mass.

root wedging

A process where plants and their roots wedge into cracks in bedrock, and widen them.


To spin on an axis. Not to be confused with revolve, when something moves in a circular or curving course or orbit.

rotational slide

Movement of regolith along a curved slip plane.


How smooth or rough the edges are within a sediment.


Water that flows over the surface.

s wave

Second-fastest seismic wave that has a shear motion.


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


A rock primarily made of sand.


A solution that has the maximum allowed 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.


Term for coarse grained, visible, platy minerals in a planar fabric, typical of schists.

science denial

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

scientific method

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


An eroded island. Since wave and weather action does not extend deep into the ocean, the root of the island is preserved as a seamount. Reefs can grow around seamounts.


Pieces of rock that have been weathered and possibly eroded.

sediment-hosted copper

Diagenetic copper deposit within sedimentary rocks.

sediment-hosted disseminated gold

Low grade, broad deposits of microscopic gold found in sedimentary rocks with diagenetic alteration.


Relating to sediment, pieces of rock that have been weathered.

sedimentary basin

A local or regional depression which allows sediments to accumulate.

sedimentary rock

Rocks that are formed by sedimentary processes, including sediments lithifying and precipitation from solution.


Pieces of rock that have been weathered and possibly eroded.

seismic anomoly

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

seismic gap

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

seismic wave

Energy that radiates from fault movement via earthquakes.


Instrument used to measure seismic energy.

semidiurnal tide

Location with two unequal tide cycles per tidal day.

sequence stratigraphy

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.


A very fine-grained rock with very thin layering (fissile).


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

shear force

Component of the gravitational force which pushes material downslope.

shear strength

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.


An exposed part of a craton.

shield volcano

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

shock metamorphism

Metamorphism caused by bolide impacts.


Part of the coastal depositional environment, 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 which is directly related to water-land interaction, specifically the tidal zone and the range of wave base.

Siberian Trapps

One of the largest volcanic eruptions on Earth, with over 3 million cubic kilometers of lava erupted, based on evidence found in Siberia.


Mineral group in which the silica tetrahedra, SiO4-4, is the building block.

silicon-oxygen tetrahedra

A 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, objects will move to the left.


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


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


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

slaty cleavage

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


A polished surface of rock from fault movement, covered with grooves.

sliding stone

Rocks that move along thin ice sheets with high winds.


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

Snowball Earth hypothesis

A hypothesis which states 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.

soft sediment deformation

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.

soil creep

Very slow movement of the soil downhill.

soil horizon

Specific layers within a soil profile with specific properties.

soil profile

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

solar nebula

Rotating, flattened disk of gas and dust from which the solar system originated.

solar system

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.

sole mark

A series of sedimentary structures formed on the base of a flow, eroding into underlying sediment. Examples include scour marks, flute casts, groove casts, and tool marks.

solid solution

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


The act of taking a solid and dissolving it 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. 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, poorly sorted means many different sizes are present.

source rock

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

specific gravity

Related to density; 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.

spheroidal weathering

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


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


A place where pressurized groundwater flows onto the surface.

spring tide

Highest high tide of the month.


Rock spire that is offshore and a remnant of a rock layer.

star dune

Dunes that form from many different wind directions.


The process of surrounding bedrock being broken off and passed through a magma.

storm wave base

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

straight channel

Channels that form straight, typically near the headwaters.


The deformation that results from application of a stress.

stratigraphic correlation

Matching disconnected rock strata over large distances.


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


Volcano with steep sides, made of a composite of many types of eruption styles, 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.


A channelled body of water.


Force applied to an object, typically dealing with forces within the Earth.


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

strike slip

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

strip mine

Mining that occurs as entire layers of ore and gangue are removed.


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

structural basin

A basin formed structurally by symmetrical synclines.


Large and mysterious landslides that travel for long distances.


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

subduction zone metamorphism

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


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


An observation which is influenced by the observer's personal bias.

submarine canyon

Canyon carved into a continental shelf.

submarine fan

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

submergent coastline

Features of a coastline where relative sea level is rising.


The act of the land surface down-warping, typically referred to when discussing sedimentation or with 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, SO4-2.


Minerals bonded via a sulfur (S-2) atom.

summer berm

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


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

superfund site

A federally-supported pollution clean-up effort.

supergene enrichment

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


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

surf zone

Shoreline area of breaking waves.

surface mine

Mining that occurs near the Earth's surface.

surface wave

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

suspended load

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 and make up a whole.


Rounded cavities within rocks that form in various ways, including mineral growth, mainly salt.


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

tar sand

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.


Stresses that pull objects apart into a larger surface area or volume; stretching forces.


General term for solid, but fragmented, material erupted from a volcano. Has three subcomponents: ash (<2mm), lapilli (2-64 mm), blocks and bombs (>64mm).

terminal moraine

Moraine that forms at the end of a glacier.


An elevated erosional surface caused by glacial or fluvial action.


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


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.

thermohaline circulation

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


Faulting that is deep into the crust, and typically involves crystalline basement rocks.


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

thrust fault

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

tidal day

The amount of time that the moon takes to appear over the same location of Earth, slightly more than 24 hours.

tidal flat

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


Movements of water (rising and falling) due to the gravity of the moon and sun. This is most often seen in marine settings.


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


Term for a rock made definitively of glacial till.


Sand bar that connects a stack and the shore.


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


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

trace fossil

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

trade wind desert

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

trade winds

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.


Sea level rise over time.

translational slide

A landslide that moves along an internal plane of weakness.


A segment along a transform or strike-slip fault which has a compressional component, sometimes creating related thrust faulting and mountains.


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


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


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

trellis drainage

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


Deepest part of the ocean 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 event. Water is a common trigger.

triple junction

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

truncated spur

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 form in relatively unheated water, sometimes as towers and spires.


Rocks made from pyroclastic tephra: either ash, lapilli, and/or bombs. Tephra type can be used as an adjective, i.e. ash-fall tuff. If deposited hot, where material can fuse together while hot, the rock is then called a welded tuff.


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

turbidity current

Dense flow of sediment that goes down submarine canyons, forming submarine fans and turbidites.


An igneous rock with extremely low silica composition, being made of almost all olivine and pyroxene. Ultramafic rocks contain very low amount of silica and are common 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.

underground mine

Mining that occurs within tunnels and shafts inside the Earth.

universal solvent

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.

vadose zone

Place where pores are filled with some water and some air, above the water table.

valley glacier

An alpine glacier that fills a mountain valley.


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


Opening of a volcano where 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, frozen in place as gases escaped from the cooling lava.


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


Components of magma which are dissolved until it reaches the surface, where they expand. Examples include water and carbon dioxide. Volatiles also cause flux melting in the mantle, causing volcanism.

volcanic arc

Place with a chain of mountain volcanism on a continent, from oceanic-continental subduction.


Place where lava is erupted at the surface.

volcanogenic massive sulfide

Metallic mineral deposit which forms near mid-ocean ridges.

Wadati-Benioff zone

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

water right

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

water table

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

wave base

The depth in which the movement of waves can be felt, specifically by sediments. This is approximately equal to 1/2 the wavelength. Wave base can change depending on fair weather verses stormy weather.

wave crest

Top of a wave.

wave cut platform

Flat erosional surface cut by wave action.

wave height

Twice the amplitude, or, the distance between the crest and trough of a wave.

wave notch

Erosional notch in bedrock cut by waves.

wave period

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

wave train

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

wave trough

Bottommost part of a wave.

wave velocity

Speed at which a wave travels past a fixed point.


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


Current conditions within the atmosphere.


Breaking down 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.

Wilson Cycle

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

winter berm

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. This can be 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.

yazoo stream

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

yield point

An amount of strain where the substance has a maximum amount of elastic deformation and switches to ductile deformation.


ZrSiO4. Relatively chemically inert 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.

zone of accumulation

Part of a glacier in which there is a net gain over the course of a year.

zone of melting

Part of a glacier which has a net loss of material over the course of a year.


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Introduction to Earth Science Copyright © 2023 by Laura Neser is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License, except where otherwise noted.

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