14 Glaciers
Learning Objectives
By the end of this chapter, students should be able to:
- Differentiate the different types of and contrast them with sea icebergs.
- Describe how form, move, and create landforms.
- Describe ; describe the zones of accumulation, equilibrium, and melting.
- Identify erosional and depositional landforms and interpret their origin; describe lakes.
- Describe the history and causes of past and their relationship to , sea-level changes, and .
The Earth’s , or ice, has a unique set of erosional and depositional features compared to its , or liquid water. This ice exists primarily in two forms, and icebergs. are large accumulations of ice that exist year-round on the land surface. In contrast, masses ice floating on the ocean are icebergs, although they may have had their origin in .
Glaciers cover about 10% of the Earth’s surface and are powerful erosional agents that sculpt the planet’s surface. These enormous masses of ice usually form in mountainous areas that experience cold temperatures and high precipitation. Glaciers also occur in low lying areas such as Greenland and Antarctica that remain extremely cold year-round.
14.1 Glacier Formation

form when repeated annual snowfall accumulates deep layers of snow that are not completely melted in the summer. Thus there is an accumulation of snow that builds up into deep layers. Perennial snow is a snow accumulation that lasts all year. A thin accumulation of perennial snow is a snow field. Over repeated seasons of perennial snow, the snow settles, compacts, and with underlying layers. The amount of void space between the snow grains diminishes. As the old snow gets buried by more new snow, the older snow layers compact into , or , a granular mass of ice crystals. As the continues to be buried, compressed, and recrystallizes, the void spaces become smaller and the ice becomes less porous, eventually turning into ice. Solid glacial ice still retains a fair amount of void space and that traps air. These small air pockets provide records of the past .
There are three general types of : alpine or , , and ice caps. Most are located in the world’s major mountain ranges such as the Andes, Rockies, Alps, and Himalayas, usually occupying long, narrow valleys. Alpine may also form at lower elevations in areas that receive high annual such as the Olympic Peninsula in Washington state.


Ice sheets, also called , form across millions of square kilometers of land and are thousands of meters thick. Earth’s largest are located on Greenland and Antarctica. The Greenland Ice Sheet is the largest ice mass in the Northern Hemisphere with an extensive surface area of over 2 million sq km (1,242,700 sq mi) and an average thickness of up to 1500 meters (5,000 ft, almost a mile).
The Antarctic Ice Sheet is even larger and covers almost the entire . The thickest parts of the Antarctic are over 4,000 meters thick (>13,000 ft or 2.5 mi). Its weight depresses the Antarctic to below sea level in many places. The cross-sectional diagram comparing the Greenland and Antarctica illustrates the size difference between the two.

Ice cap are smaller versions of that cover less than 50,000 km2 and usually occupy higher elevations and may cover tops of mountains. There are several ice caps on Iceland. A small ice cap called Snow Dome is near Mt. Olympus on the Olympic Peninsula in the state of Washington.


The figure shows the size of the ancient Laurentide Ice Sheet in the Northern Hemisphere. This was present during the last glacial maximum event, also known as the last Ice Age.
sheet[/pb_glossary] was present during the last glacial maximum event, also known as the last Ice Age.
Take this quiz to check your comprehension of this section.
If you are using an offline version of this text, access the quiz for section 14.1 via the QR code.
14.2 Glacier Movement

As the ice accumulates, it begins to flow downward under its own weight. In 1948, glaciologists installed hollow vertical rods in into the Jungfraufirn Glacier in the Swiss Alps to measure changes in its movement over two years. This study showed that the ice at the surface was fairly rigid and ice within the was actually flowing downhill. The cross-sectional diagram of an alpine (valley) shows that the rate of ice movement is slow near the bottom, and fastest in the middle with the top ice being carried along on the ice below.

One of the unique properties of ice is that it melts under pressure. About half of the overall movement was from sliding on a film of meltwater along the surface and half from internal flow. Ice near the surface of the is rigid and to a depth of about 50 m (165 ft). In this zone, large ice cracks called form on the ’s moving surface. These can be covered and hidden by a snow bridge and are a hazard for travelers.
Below the brittle zone, the pressure typically exceeds 100 kilopascals (kPa), which is approximately 100,000 times atmospheric pressure. Under this applied force, the ice no longer breaks, but rather it bends or flows in a zone called the plastic zone. This plastic zone represents the great majority of ice. The plastic zone contains a fair amount of of various grades from boulders to silt and clay. As the bottom of the slides and grinds across the surface, these act as grinding agents and create a zone of significant .
Take this quiz to check your comprehension of this section.
If you are using an offline version of this text, access the quiz for section 14.2 via the QR code.
14.3 Glacial Budget

A glacial budget is like a bank account, with the ice being the existing balance. If there is more income (snow accumulating in winter) than expense (snow and ice melting in summer), then the budget shows growth. A positive or negative balance of ice in the overall determines whether a advances or retreats, respectively. The area where the ice balance is growing is called the . The area where ice balance is shrinking is called the zone of ablation.
The diagram shows these two zones and the equilibrium line. In the , the snow accumulation rate exceeds the snow melting rate and the ice surface is always covered with snow. The equilibrium line, also called the or firnline, marks the boundary between the zones of accumulation and ablation. Below the equilibrium line in the zone of ablation, the melting rate exceeds snow accumulation leaving the bare ice surface exposed. The position of the firnline changes during the season and from year to year as a of a positive or negative ice balance in the . Of the two variables affecting a ‘s budget, winter accumulation and summer melt, summer melt matters most to a ’s budget. Cool summers promote advance and warm summers promote retreat.

If a handful of warmer summers promote retreat, then global warming over decades and centuries will accelerate glacial melting and retreat even faster. Global warming due to human burning of is causing the to lose in years, an amount of mass that would normally take centuries. Current glacial melting is contributing to rising sea-levels faster than expected based on previous history.
As the Antarctica and Greenland melt during global warming, they become thinner or deflate. The edges of the break off and fall into the ocean, a process called , becoming floating icebergs. A is a steep-walled valley flooded with sea water. The narrow shape of a has been carved out by a during a cooler . During a warming trend, meltwater may raise the sea level in and flood formerly dry valleys. retreat and deflation are well illustrated in the 2009 TED Talk “Time-lapse proof of extreme ice loss” by James Balog.
Video 14.1: Time-lapse proof of extreme ice loss, by James Balog.
If you are using an offline version of this text, access this TED Talk via the QR code.
Take this quiz to check your comprehension of this section.
If you are using an offline version of this text, access the quiz for section 14.3 via the QR code.
14.4 Glacial Landforms
Both alpine and create two categories of landforms: erosional and depositional. Erosional landforms are formed by the removal of material. Depositional landforms are formed by the addition of material. Because were first studied by 18th and 19th century geologists in Europe, the terminology applied to and features contains many terms derived from European languages.
14.4.1 Erosional Glacial Landforms
Erosional landforms are created when moving masses of ice slide and grind over . ice contains large amounts of poorly sorted sand, gravel, and bouldersthat have been plucked and pried from the . As the slide across the , they grind these into a fine powder called rock flour. Rock flour acts as fine grit that polishes the surface of the to a smooth finish called . Larger rock fragments scrape over the surface creating elongated grooves called .


Alpine produce a variety of unique erosional landforms, such as U-shaped valleys, , , tarns, , , , and . In contrast, -carved canyons have a V-shaped profile when viewed in cross-section. Glacial erosion transforms a former V-shaped stream valley into a U-shaped one. are typically wider than of similar length, and since tend to erode both at their bases and their sides, they erode V-shaped valleys into relatively flat-bottomed broad valleys with steep sides and a distinctive “U” shape. As seen in the images, Little Cottonwood Canyon near Salt Lake City, Utah was occupied by an that extended down to the of the canyon and into Lake Bonneville. Today, that U-shaped valley hosts many erosional landforms, including polished and striated rock surfaces. In contrast, Big Cottonwood Canyon to the north of Little Cottonwood Canyon has retained the V-shape in its lower portion, indicating that its did not extend clear to its , but was confined to its upper portion.

When carve two U-shaped valleys adjacent to each other, the ridge between them tends to be sharpened into a sawtooth feature called an . At the head of a glacially carved valley is a bowl-shaped feature called a . The represents where the head of the eroded the mountain by plucking rock away from it and the weight of the thick ice eroded out a bowl. After the is gone, the bowl at the bottom of the often fills with and is occupied by a lake, called a tarn. When three or more mountain erode headward at their , they produce , steep-sided, spire-shaped mountains. Low points along or between are mountain passes termed . Where a smaller flows into a larger trunk glacier, the smaller cuts down less. Once the ice has gone, the valley is left as a , sometimes with a waterfall plunging into the main valley. As the trunk straightens and widens a V-shaped valley and erodes the ends of side ridges, a steep triangle-shaped cliff is formed called a .

14.4.2 Depositional Glacial Landforms

Depositional landforms and materials are produced from deposits left behind by a retreating . All deposits are called drift. These include , , , , , , , , silt, , , , lakes, crevasses, , kames, and .
ice carries a lot of , which when deposited by a melting is called . is poorly sorted with grain sizes ranging from clay and silt to pebbles and boulders. These clasts may be striated. Many depositional landforms are composed of . The term tillite refers to lithified rock having origins. Diamictite refers to a lithified rock that contains a wide range of clast sizes; this includes but is a more and descriptive term for any rock with a wide range of clast sizes.
Moraines are mounded deposits consisting of carried in the ice and rock fragments dislodged by from the U-shaped valley walls. The acts like a conveyor belt, carrying and depositing at the end of and along the sides of theice flow. Because the ice in the is always flowing downslope, all have build up at their terminus, even those not advancing.
Moraines are classified by their location with respect to the . A is a ridge of located at the end or terminus of the . Recessional are left as retreat and there are pauses in the retreat. Lateral moraines accumulate along the sides of the from material mass wasted from the valley walls. When two merge, the two combine to form a running down the center of the combined glacier. Ground is a veneer of left on the land as the melts.

In addition to , leave behind other depositional landforms. Silt, sand, and gravel produced by the intense grinding process are carried by streams of water and depositedin front of the glacier in an area called the . Retreating may leave behind large boulders that don’t match the local . These are called . When retreat, they can leave behind large blocks of ice within the . These ice blocks melt and create a depression in the called a . If the depression later fills with water, it is called a .
If meltwater flowing over the ice surface descends into crevasses in the ice, it may find a channel and continue to flow in sinuous channels within or at the base of the . Within or under , these carry . When the ice recedes, the accumulated sediment is deposited as a long sinuous ridge known as an . Meltwater descending down through the ice or over the margins of the ice may deposit mounds of in hills called kames.

are common in areas of Germany, New York, and Wisconsin, where they typically are found in fields with great numbers. A is an elongated asymmetrical teardrop-shaped hill reflecting ice movement with its steepest side pointing upstream to the flow of ice and its streamlined or low-angled side pointing downstream in the direction of ice movement.
scientists debate the origins of drumlins. A leading idea is that are created from accumulated being compressed and sculpted under a that retreated then advanced again over its own ground moraine. Another idea is that meltwater catastrophically flooded under the glacier and carved the into these streamlined mounds. Still another proposes that the weight of the overlying ice statically deformed the underlying .
Complete this interactive activity to check your understanding.
If you are using an offline version of this text, access this interactive activity via the QR code.
14.4.3 Glacial Lakes

lakes are commonly found in alpine environments. A lake confined within a is called a tarn. A tarn forms when the depression in the fills with precipitation after the ice is gone. Examples of tarns include Silver Lake near Brighton Ski resort in Big Cottonwood Canyon, Utah and Avalanche Lake in Glacier National Park, Montana.

When recessional create a series of isolated basins in a glaciated valley, the resulting chain of lakes is called .
Lakes filled by glacial meltwater often looks milky due to finely ground material called rock flour suspended in the water.

Long, glacially carved depressions filled with water are known as . form along the edges of all the largest , such as Antarctica and Greenland. The is depressed isostatically by the overlying ice sheet and these basins fill with meltwater. Many such lakes, some of them huge, existed at various times along the southern edge of the Laurentide Ice Sheet. Lake Agassiz, Manitoba, Canada, is a classic example of a . Lake Winnipeg serves as the remnant of a much larger proglacial lake.

Other were formed when dammed and flooded the valley. A classic example is Lake Missoula, which formed when a lobe of the Laurentide ice sheet blocked the Clark Fork River about 18,000 years ago. Over about 2000 years the ice dam holding back Lake Missoula failed several times. During each breach, the lake emptied across parts of eastern Washington, Oregon, and Idaho into the Columbia River Valley and eventually the Pacific Ocean. After each breach, the dam reformed and the lake refilled. Each breach produced a catastrophic flood over a few days. Scientists estimate that this cycle of ice dam, , and torrential flooding happened at least 25 times over a span of 20 centuries. The rate of each outflow is believed to have equaled the combined of all of Earth’s current combined.

The landscape produced by these massive floods is preserved in the Channeled Scablands of Idaho, Washington, and Oregon.


form in humid environments that experience low temperatures and high . During the last , most of the western United States’ was cooler and more humid than today. Under these low-evaporation conditions, many large lakes, called , formed in the basins of the Province. Two of the largest were Lake Bonneville and Lake Lahontan. Lake Lahontan was in northwestern Nevada. The figure illustrates the tremendous size of Lake Bonneville, which occupied much of western Utah and into eastern Nevada. The lake level fluctuated greatly over the centuries leaving several pronounced old shorelines marked by wave-cut . These old shorelines can be seen on mountain slopes throughout the western portion of Utah, including the Salt Lake Valley, indicating that the now heavily urbanized valley was once filled with hundreds of feet of water. Lake Bonneville’s level peaked around 18,000 years ago when a breach occurred at Red Rock Pass in Idaho and water spilled into the Snake River. The flooding rapidly lowered the lake level and scoured the Idaho landscape across the Pocatello Valley, the Snake River Plain, and Twin Falls. The floodwaters ultimately flowed into the Columbia River across part of the scablands area at an incredible rate of about 4,750 cu km/sec (1,140 cumi/sec). For comparison, this rate would drain the volume of Lake Michigan completely dry within a few days.
The five Great Lakes in North America’s upper Midwest are proglacial lakes that originated during the last . The lake basins were originally carved by the encroaching . The basins were later exposed as the ice retreated about 14,000 years ago and filled by precipitation.
Take this quiz to check your comprehension of this section.
If you are using an offline version of this text, access the quiz for section 14.4 via the QR code.
14.5 Ice Age Glaciations
A (or ) occurs when the Earth’s becomes cold enough that expand, covering large areas of land. Four major, well-documented have occurred in Earth’s history: one during the -early , ~2.5 billion years ago; another in late , ~700 million years ago; another in the Pennsylvanian, 323 to 300 million years ago, and most recently during the Pliocene-Pleistocene starting 2.5 million years ago (chapter 8). Some scientists also recognize a minor around 440 million years ago in Africa.
The best-studied is, of course, the most recent. This infographic illustrates the and changes over the last 20,000 years, ending with those caused by human actions since the Industrial Revolution. The Pliocene-Pleistocene was a series of several cycles, possibly 18 in total. Antarctic ice- records exhibit especially strong evidence for eight advances occurring within the last 420,000 years. The last of these is known in popular media as “The ,” but geologists refer to it as the Last Glacial Maximum. The advance reached its maximum between 26,500 and 19,000 years ago.
14.5.1 Causes of Glaciations
Glaciations occur due to both long-term and short-term factors. In the geologic sense, long-term means a scale of tens to hundreds of millions of years and short-term means a scale of hundreds to thousands of years.
Long-term causes include breaking up the (see Wilson Cycle, chapter 2), moving land masses to high latitudes near the north or south poles, and changing ocean circulation. For example, the closing of the Panama Strait and isolation of the Pacific and Atlantic oceans may have triggered a change in precipitation cycles, which combined with a cooling to help expand the .

Short-term causes of fluctuations are attributed to the cycles in the Earth’s rotational- and to variations in the earth’s orbit around the Sun which affect the distance between Earth and the Sun. Called , these cycles affect the amount of incoming solar radiation, causing short-term cycles of warming and cooling.
During the Era, carbon dioxide levels steadily decreased from a maximum in the Paleocene, causing the to gradually cool. By the Pliocene, began to form. The effects of the created short-term cycles of warming and cooling within the larger event.
are three orbital changes named after the Serbian astronomer Milutan Milankovitch. The three orbital changes are called , , and . Precession is the wobbling of Earth’s with a of about 21,000 years; is changes in the angle of Earth’s with a of about 41,000 years; and is variations in the Earth’s orbit around the sun leading to changes in distance from the sun with a of 93,000 years. These orbital changes created a 41,000-year-long – Milankovitch Cycle from 2.5 to 1.0 million years ago, followed by another longer cycle of about 100,000 years from 1.0 million years ago to today (see Milankovitch Cycles).
Complete this interactive activity to check your understanding.
If you are using an offline version of this text, access this interactive activity via the QR code.
Watch the video to see summaries of the , including their characteristics and causes.
Video 14.2: Ice ages and climate cycles.
If you are using an offline version of this text, access this YouTube video via the QR code.
14.5.2 Sea-Level Change and Isostatic Rebound
When melt and retreat, two things happen: water runs off into the ocean causing sea levels to rise worldwide, and the land, released from its heavy covering of ice, rises due to . Since the Last Glacial Maximum about 19,000 years ago, sea-level has risen about 125 m (400 ft). A global change in sea level is called sea-level change. During a warming trend, sea-level rises due to more water being added to the ocean and also thermal expansion of sea water. About half of the Earth’s sea-level rise during the last century has been the result of melting and about half due to thermal expansion. Thermal expansion describes how a solid, liquid, or gas expands in volume with an increase in . This 30 second video demonstrates thermal expansion with the classic brass ball and ring .
Video 14.3: Thermal expansion.
If you are using an offline version of this text, access this YouTube video via the QR code.
Relative sea-level change includes vertical movement of both sea-level and continents on . In other words, sea-level change is measured relative to land elevation. For example, if the land rises a lot and sea-level rises only a little, then the relative sea-level would appear to drop.
Continents sitting on the can move vertically upward as a result of two main processes, uplift and . uplift occurs when collide (see chapter 2). Isostatic rebound describes the upward movement of lithospheric sitting on top of the asthenospheric layer below it. crust bearing the weight of ice sinks into the displacing it. After the melts away, the flows back in and continental crust floats back upward. can also create by removing large masses like mountains and transporting the away (think of the removal of the Alleghanian Mountains and the uplift of the Appalachian plateau; chapter 8), albeit this process occurs more slowly than relatively rapid melting.

The isostatic-rebound map below shows rates of vertical crustal movement worldwide. The highest rebound rate is indicated by the blue-to-purple zones (top end of the scale). The orange-to-red zones (bottom end of the scale) surrounding the high-rebound zones indicate isostatic lowering as adjustments in displaced subcrustal material have taken place.
Most is occurring where continental ice sheets rapidly melted about 19,000 years ago, such as in Canada and Scandinavia. Its effects can be seen wherever ice or water bodies are or were present on surfaces and in terraces on floodplains that cross these areas. occurred in Utah when the water from Lake Bonneville drained away. North America’s Great Lakes also exhibit emergent features caused by since the ice sheet retreated.
Take this quiz to check your comprehension of this section.
If you are using an offline version of this text, access the quiz for section 14.5 via the QR code.
Summary
form when average annual snowfall exceeds melting and snow compresses into ice. There are three types of , alpine or that occupy valleys, that cover areas, and ice caps that cover smaller areas usually at higher elevations. As the ice accumulates, it begins to flow downslope and outward under its own weight. ice is divided into two zones, the upper rigid or zone where the ice cracks into and the lower plastic zone where under the pressure of overlying ice, the ice bends and flows exhibiting behavior. Rock material that onto the ice by or is plucked and carried by the ice is called and acts as grinding agents against the creating significant .
have a budget of income and expense. The zone of income for the is called the , where snow is converted into then ice by and , and the zone of expense called the , where ice melts or sublimes away. The line separating these two zones latest in the year is the Equilibrium or Line and can be seen on the separating bare ice from snow covered ice. If the is balanced, even though the ice continues to flow downslope, the end or terminus of the remains in a stable position. If income is greater than expense, the position of the terminus moves downslope. If expense is greater than income, a circumstance now affecting and worldwide due to global warming, the terminus recedes. If this situation continues, the will disappear. An average of cooler summers affects the stability or growth of more than higher snowfall. As the Greenland and Antarctic flow seaward, the edges calve off forming icebergs.
create two kinds of landforms, erosional and depositional. carve U-shaped valleys and carried in the ice polishes and grooves or striates the . Other landscape features produced by include , ridges, , , , and . may contain eroded basins that are occupied by post lakes called tarns. Depositional features result from deposits left by retreating ice called drift. These include , and deposits (terminal, recessional, lateral, medial, and ground), , kames, and , , and . A series of in glaciated valleys may create basins that are later filled with water to become lakes. meltwater carries fine grained onto the . Lakes containing meltwater are milky in color from suspended finely ground rock flour. was more humid and that did not become ice filled regional depressions to become . Examples of include Lake Missoula dammed behind an lobe and Lake Bonneville in Utah whose remnants can be seen on mountainsides. Repeated breaching of the ice lobe allowed Lake Missoula to rapidly drain causing floods that scoured the Channeled Scablands of Idaho, Washington, and Oregon.
Take this quiz to check your comprehension of this chapter.
If you are using an offline version of this text, access the quiz for chapter 14 via the QR code.
URLs Listed Within This Chapter
Infographic: Infographic. “A Timeline of Earth’s Average Temperature since the Last Ice Age Glaciation” xkcd https://xkcd.com/1732
Milankovitch cycles: https://en.wikipedia.org/wiki/Milankovitch_cycles
Text References
- Allen, P.A., and Etienne, J.L., 2008, Sedimentary challenge to Snowball Earth: Nat. Geosci., v. 1, no. 12, p. 817–825.
- Berner, R.A., 1998, The carbon cycle and carbon dioxide over Phanerozoic time: the role of land plants: Philos. Trans. R. Soc. Lond. B Biol. Sci., v. 353, no. 1365, p. 75–82.
- Cunningham, W.L., Leventer, A., Andrews, J.T., Jennings, A.E., and Licht, K.J., 1999, Late Pleistocene–Holocene marine conditions in the Ross Sea, Antarctica: evidence from the diatom record: The Holocene, v. 9, no. 2, p. 129–139.
- Deynoux, M., Miller, J.M.G., and Domack, E.W., 2004, Earth’s Glacial Record: World and Regional Geology, Cambridge University Press, World and Regional Geology.
- Earle, S., 2015, Physical geology OER textbook: BC Campus OpenEd.
- Eyles, N., and Januszczak, N., 2004, “Zipper-rift”: a tectonic model for Neoproterozoic glaciations during the breakup of Rodinia after 750 Ma: Earth-Sci. Rev.
- Francey, R.J., Allison, C.E., Etheridge, D.M., Trudinger, C.M., and others, 1999, A 1000‐year high precision record of δ13C in atmospheric CO2: Tellus B Chem. Phys. Meteorol.
- Gutro, R., 2005, NASA – What’s the Difference Between Weather and Climate? Online, http://www.nasa.gov/mission_pages/noaa-n/climate/climate_weather.html, accessed September 2016.
- Hoffman, P.F., Kaufman, A.J., Halverson, G.P., and Schrag, D.P., 1998, A neoproterozoic snowball earth: Science, v. 281, no. 5381, p. 1342–1346.
- Kopp, R.E., Kirschvink, J.L., Hilburn, I.A., and Nash, C.Z., 2005, The Paleoproterozoic snowball Earth: a climate disaster triggered by the evolution of oxygenic photosynthesis: Proc. Natl. Acad. Sci. U. S. A., v. 102, no. 32, p. 11131–11136.
- Lean, J., Beer, J., and Bradley, R., 1995, Reconstruction of solar irradiance since 1610: Implications for climate change: Geophys. Res. Lett., v. 22, no. 23, p. 3195–3198.
- Levitus, S., Antonov, J.I., Wang, J., Delworth, T.L., Dixon, K.W., and Broccoli, A.J., 2001, Anthropogenic warming of Earth’s climate system: Science, v. 292, no. 5515, p. 267–270.
- Lindsey, R., 2009, Climate and Earth’s Energy Budget : Feature Articles: Online, http://earthobservatory.nasa.gov, accessed September 2016.
- North Carolina State University, 2013a, Composition of the Atmosphere.
- North Carolina State University, 2013b, Composition of the Atmosphere: Online, http://climate.ncsu.edu/edu/k12/.AtmComposition, accessed September 2016.
- Oreskes, N., 2004, The scientific consensus on climate change: Science, v. 306, no. 5702, p. 1686–1686.
- Pachauri, R.K., Allen, M.R., Barros, V.R., Broome, J., Cramer, W., Christ, R., Church, J.A., Clarke, L., Dahe, Q., Dasgupta, P., Dubash, N.K., Edenhofer, O., Elgizouli, I., Field, C.B., and others, 2014, Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (R. K. Pachauri & L. Meyer, Eds.): Geneva, Switzerland, IPCC, 151 p.
- Santer, B.D., Mears, C., Wentz, F.J., Taylor, K.E., Gleckler, P.J., Wigley, T.M.L., Barnett, T.P., Boyle, J.S., Brüggemann, W., Gillett, N.P., Klein, S.A., Meehl, G.A., Nozawa, T., Pierce, D.W., and others, 2007, Identification of human-induced changes in atmospheric moisture content: Proc. Natl. Acad. Sci. U. S. A., v. 104, no. 39, p. 15248–15253.
- Schopf, J.W., and Klein, C., 1992, Late Proterozoic Low-Latitude Global Glaciation: the Snowball Earth, in Schopf, J.W., and Klein, C., editors, The Proterozoic biosphere : a multidisciplinary study: New York, Cambridge University Press, p. 51–52.
- Webb, T., and Thompson, W., 1986, Is vegetation in equilibrium with climate? How to interpret late-Quaternary pollen data: Vegetatio, v. 67, no. 2, p. 75–91.
- Weissert, H., 2000, Deciphering methane’s fingerprint: Nature, v. 406, no. 6794, p. 356–357.
- Whitlock, C., and Bartlein, P.J., 1997, Vegetation and climate change in northwest America during the past 125 kyr: Nature, v. 388, no. 6637, p. 57–61.
- Wolpert, S., 2009, New NASA temperature maps provide a ‘whole new way of seeing the moon’: Online, http://newsroom.ucla.edu/releases/new-nasa-temperature-maps-provide-102070, accessed February 2017.
- Zachos, J., Pagani, M., Sloan, L., Thomas, E., and Billups, K., 2001, Trends, rhythms, and aberrations in global climate 65 Ma to present: Science, v. 292, no. 5517, p. 686–693.
Figure References
Figure 14.1: Glacier in the Bernese Alps. Dirk Beyer. 2005. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:Grosser_Aletschgletscher_3178.JPG
Figure 14.2: Greenland ice sheet. Hannes Grobe. 1995. CC BY-SA 2.5. https://commons.wikimedia.org/wiki/File:Greenland-ice_sheet_hg.jpg
Figure 14.3: Thickness of Greenland ice sheet in meters. Eric Gaba. 2011. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:Greenland_ice_sheet_AMSL_thickness_map-en.svg
Figure 14.4: Cross-sectional view of both Greenland and Antarctic ice sheets drawn to scale for size comparison. Kindred Grey. 2022. CC BY 4.0. Adapted from Steve Earle (CC BY 4.0). https://opengeology.org/textbook/14-glaciers/14-2_steve-earle_antarctic-greenland-2-300×128/
Figure 14.5: Snow Dome ice cap near Mt. Olympus, Washington (left) and Vatnajökull ice cap in Iceland (right). Mount Olympus Washington by United States National Park Service, 2004 (Public domain, https://commons.wikimedia.org/wiki/File:Mount_Olympus_Washington.jpg). Vatnajökull by NASA, 2004 (Public domain, https://commons.wikimedia.org/wiki/File:Vatnaj%C3%B6kull.jpeg).
Figure 14.6: Maximum extent of Laurentide ice sheet. USGS. 2005. Public domain. https://commons.wikimedia.org/wiki/File:Pleistocene_north_ice_map.jpg
Figure 14.7: Glacial crevasses (left) and Cravasse on the Easton Glacier in the North Cascades (right). chevron crevasse by Bethan Davies, 2015 (CC BY-NC-SA 3.0, https://www.antarcticglaciers.org/glacier-processes/structural-glaciology/chevron-crevasse/). Glaciereaston by Mauri S. Pelto, 2005 (Public domain, https://en.wikipedia.org/wiki/File:Glaciereaston.jpg).
Figure 14.8: Cross-section of a valley glacier showing stress (red numbers) increase with depth under the ice. Kindred Grey. 2022. CC BY 4.0. Adapted from Steve Earle (CC BY 4.0). https://opengeology.org/textbook/14-glaciers/14-2_steve-earle_ice-flow-and-stress/
Figure 14.9: Cross-sectional view of an alpine glacier showing internal flow lines, zone of accumulation, snow line, and zone of melting. Kindred Grey. 2022. CC BY 4.0. Adapted from Steven Earle (CC BY 4.0). https://opentextbc.ca/geology/chapter/16-2-how-glaciers-work/
Figure 14.10: Fjord. Frédéric de Goldschmidt. 2007. CC BY-SA 3.0. https://sco.wikipedia.org/wiki/File:Geirangerfjord_(6-2007).jpg
Figure 14.11: Glacial striations on granite in Whistler, Canada (left) and Glacial striations in Mt. Rainier National Park (right). Glacial striations by Amezcackle, 2003 (Public domain, https://en.m.wikipedia.org/wiki/File:Glacial_striations.JPG). Glacial striation 21149 by Walter Siegmund, 2007 (CC BY-SA 3.0, https://commons.wikimedia.org/wiki/File:Glacial_striation_21149.JPG).
Figure 14.12: The U-shape of the Little Cottonwood Canyon, Utah, as it enters into the Salt Lake Valley. Wilson44691. 2008. Public domain. https://commons.wikimedia.org/wiki/File:UshapedValleyUT.JPG
Figure 14.13: Formation of a glacial valley. Cecilia Bernal. 2015. CC BY-SA 4.0. https://commons.wikimedia.org/wiki/File:Glacier_Valley_formation-_Formaci%C3%B3n_Valle_glaciar.gif
Figure 14.14: Cirque with Upper Thornton Lake in the North Cascades National Park, Washington (left). Thornton Lakes 25929 by Walter Siegmund, 2007 (CC BY-SA 3.0, https://commons.wikimedia.org/wiki/File:Thornton_Lakes_25929.JPG). Kinnerly Peak by USGS, 1982 (Public domain, https://uk.wikipedia.org/wiki/%D0%A4%D0%B0%D0%B9%D0%BB:Kinnerly_Peak.jpg). Closeup of Bridalveil Fall seen from Tunnel View in Yosemite NP by Daniel Mayer, 2003 (CC BY-SA 1.0, https://commons.wikimedia.org/wiki/File:Closeup_of_Bridalveil_Fall_seen_from_Tunnel_View_in_Yosemite_NP.JPG).
Figure 14.15: Boulder of diamictite of the Mineral Fork Formation, Antelope Island, Utah, United States. Jstuby. 2002. Public domain. https://commons.wikimedia.org/wiki/File:Diamictite_Mineral_Fork.JPG
Figure 14.16: Lateral moraines of Kaskawulsh Glacier within Kluane National Park in the Canadian territory of Yukon (left) and Medial moraines where tributary glaciers meet. Kluane Icefield 1 by Steffen Schreyer, 2005 (CC BY-SA 2.0 DE, https://commons.wikimedia.org/wiki/File:Kluane_Icefield_1.jpg). Nuussuaq-peninsula-moraines by Algkalv, 2010 (CC BY-SA 3.0, https://commons.wikimedia.org/wiki/File:Nuussuaq-peninsula-moraines.jpg).
Figure 14.17: A small group of Ice Age drumlins in Germany. Martin Groll. 2009. CC BY 3.0 DE. https://commons.wikimedia.org/wiki/File:Drumlin_1789.jpg
Figure 14.18: Tarn in a cirque. Jrmichae. 2012. CC BY-SA 4.0. https://commons.wikimedia.org/wiki/File:Verdi_Leak_in_The_Ruby_Mountains.JPG
Figure 14.19: Paternoster lakes. wetwebwork. 2007. CC BY-SA 2.0. https://en.wikipedia.org/wiki/File:View_from_Forester_Pass.jpg
Figure 14.20: Satellite view of Finger Lakes region of New York. NASA. 2004. Public domain. https://commons.wikimedia.org/wiki/File:New_York%27s_Finger_Lakes.jpg
Figure 14.21: Extent of Lake Agassiz. USGS. 1895. Public domain. https://commons.wikimedia.org/wiki/File:Agassiz.jpg
Figure 14.22: View of Channeled Scablands in central Washington showing huge potholes and massive erosion. DKRKaynor. 2019. CC BY-SA 4.0. https://commons.wikimedia.org/wiki/File:Channeled_Scablands.jpg
Figure 14.23: Pluvial lakes in the western United States. Fallschirmjäger. 2013. CC BY-SA 3.0. https://en.wikipedia.org/wiki/File:Lake_bonneville_map.svg
Figure 14.24: The Great Lakes. SeaWiFS Project, NASA/Goddard Space Flight Center, and ORBIMAGE. 2000. Public domain. https://commons.wikimedia.org/wiki/File:Great_Lakes_from_space.jpg
Figure 14.25: Atomospheric CO2 has declined during the Cenozoic from a maximum in the Paleocene–Eocene up to the Industrial Revolution. Robert A. Rohde. 2005. CC BY-SA 3.0. https://commons.wikimedia.org/wiki/File:65_Myr_Climate_Change.png
Figure 14.26: Rate of isostatic rebound. NASA. 2010. Public domain. https://commons.wikimedia.org/wiki/File:PGR_Paulson2007_Rate_of_Lithospheric_Uplift_due_to_post-glacial_rebound.png
A body of ice that moves downhill under its own mass.
The net gain or loss of ice within a glacier.
Deposition and erosion tied to glacier movement.
A period of cooler temperatures on Earth in which ice sheets can grow on continents.
Long term averages and variations within the conditions of the atmosphere.
An upwards movement of the lithosphere when weight is removed, such as water or ice.
The part of the hydrosphere (water) that is frozen, found mainly at the poles.
The water part of the Earth, as a solid, liquid, or gas.
Two or more atoms or ions that are connected chemically.
Snow which has been compressed, and is starting to turn into ice.
The gases that are part of the Earth, which are mainly nitrogen and oxygen.
The mineral makeup of a rock, i.e. which minerals are found within a rock.
An alpine glacier that fills a mountain valley.
Thick glaciers that cover continents during ice ages.
A glacier that forms on a mountain.
The act of a solid coming out of solution, typically resulting from a drop in temperature or a decrease of the dissolving material.
A body of ice covering large stretches of land over a continent (mainly found in Antarctica).
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.
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.
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.
Cracks that form with glacial movement in the upper, brittle part of the glacier.
Pieces of rock that have been weathered and possibly eroded.
The transport and movement of weathered sediments.
Part of a glacier in which there is a net gain over the course of a year.
The line between the zone of accumulation and the zone of ablation.
Waves that bounce off of a boundary between mediums of different properties.
Energy resources (typically hydrocarbons) derived from ancient chemical energy preserved in the geologic record. Includes coal, oil, and natural gas.
A process where ice from the ends of glaciers falls off into the ocean.
Glacial valley filled by ocean water.
A unit of the geologic time scale; smaller than an era, larger than an epoch. We are currently in the Quaternary period.
Smooth surface carved in harder rocks by glacial action.
Grooves scratched in rock by glacial action.
A ridge that is carved between two glacial valleys.
Glacially-carved, bowl-shaped valley.
Steep spire carved by several glaciers.
Low point within an arête.
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.
An eroded arête that forms a triangular shape.
A channelled body of water.
The end of a river.
A natural stream that flows into a larger river or other body of water.
General term for very poorly sorted sediment that is of glacial origin.
Term for a rock made definitively of glacial till.
A sedimentary rock containing two distinct grain sizes, typically cobbles (or larger) mixed with mud.
Moraine that forms at the end of a glacier.
A terminal moraine that forms as a glacier melts.
Moraines that form at the sides of glaciers.
A place where two or more glaciers combine, and the lateral moraines combine to form a moraine within the glacier.
Moraine that forms beneath a glacier.
Accumulation of fine-grained sediment formed downhill of the terminal moraine.
Large sediment (e.g. boulder) carried and then dropped by a glacier.
Depression formed by ice resting in sediment, then preserved after the ice melts and the sediment lithifies.
Ridge of sediment that forms under a glacier by meltwater which forms a river.
Ridge of sediment that forms under a glacier, with a steep uphill (with respect to the glacier) side and gentle downhill side.
An observation that is completely free of bias, i.e. anyone and everyone would make the same observation.
Any downhill movement of material, caused by gravity.
Accumulation of sediment at the margins of glaciers, including the base, sides, and end.
Lake that forms in a kettle.
Series of lakes between moraines within an alpine glacier basin, typically a cirque.
Lake that fills a glacial valley.
Lake that forms next to a glacier because of crustal loading.
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.
A feature with no internal structure, habit, or layering.
Amount of water that leaves a system, such as a river or aquifer.
Lakes that form via increased precipitation with glacial climate shifts.
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).
An elevated erosional surface caused by glacial or fluvial action.
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.
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 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.
A unit of geological time recognized by geologists; smaller than a period. We are currently in the Holocene epoch.
The innermost chemical layer of the Earth, made chiefly of iron and nickel. It has both liquid and solid components.
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.
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.
Dividing two-dimensional line between the two sides of a fold.
A series of changes in the Earth's orbit/position in relation to the Sun which can fluctuate climate over varying periodicities.
The last (and current) era of the Phanerozoic eon, starting 66 million years ago and spanning through the present.
Wobbles in the Earth's axis.
The angle of the Earth's axis with respect to the plane of rotation.
The measure of the amount of circular or elliptical nature of the Earth's orbit.
Period of warming within a glacial or ice age cycle.
An overall global sea level change, either due to climate or seafloor spreading rate.
The measure of the vibrational (kinetic) energy of a substance.
A test of an idea in which new information can be gathered to either accept or reject a hypothesis.
Erosional rock face caused by sand abrasion.
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.
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.
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.
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.
The entire area which is related to land-sea interactions.
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.
The concept that any rock type (igneous, sedimentary, and metamorphic) can change into another rock type under the right conditions over geologic time.
Stresses that push objects together into a smaller surface area or volume; contracting forces.
The process of changing a mineral without melting.
Part of a glacier which has a net loss of material over the course of a year.
The part of the coastline which is directly related to water-land interaction, specifically the tidal zone and the range of wave base.