Geog Ch. 14

Glaciers can form only in places where ______ exceeds ______, usually at higher elevations or latitudes.

snowfall; snowmelt

The principle behind the saying "the present is the key to the past" can be applied to glaciers by ______.

studying the deposits of modern glaciers in order to understand the processes that formed ancient glacial deposits

More greenhouse gases tend to warm the planet.

Release of CO2 and CH4 into atmosphere

Identify effects of permafrost.

Geometric patterns can develop at the surface. It prevents or limits the growth of trees.

What is the general term for any sediment carried by ice, icebergs, or meltwater?

Glacial drift

The _________________were created by the combined action of the Laurentide Ice Sheet carving the land surface, depositing moraines, leaving meltwater, directing drainage, and finally the land surface rebounding as the ice receded.

Great Lakes

Glacial Lake Bonneville was extensive during the Ice Age. It has since shrunk in size; what remains are the Bonneville salt flats and the_____________ ________________ Lake in Utah

Great Salt

What landforms would you expect to see in the diagram after the glaciers melted completely away?

High, sharp peaks Narrow, sharp ridges U-shaped valleys

In what ways do glaciers lose mass?

Ice breaking off the glacier Via glacial meltwater Via sublimation

Large, regionally continuous masses of ice more than 50,000 km2 in area

Ice sheets

Which of the following are true regarding the location of ice sheets and glaciers?

Most glaciers are in high latitudes or high elevations. The largest ice mass is on Antarctica. The second-largest ice mass is on Greenland.

East and West Antarctica each have their own ice sheet and are separated by the Transantarctic

Mountains

Continents move over geologic time and affect climate by both their latitudinal position and how they influence the flow of ________

Ocean Currents

What is till?

Sediment carried far out to sea by icebergs

Which are true of the ice in West Antarctica?

The ice sheet carries massive amounts of ice toward the sea and ice shelves. The ice shelves are losing large volumes of ice every year. The base of the ice sheet is below sea level. The central part is as thick as 3,500 m.

Why does continental glaciation tend to smooth the surface of the land, causing the ground topography to have relatively low relief (minor height differences between lower and higher topographic locations) once the ice sheet melts?

The ice sheets round and erode any of the higher areas over which the ice flows. The ice sheets tend to deposit sediment in topographic lows.

Which of the following statements is true regarding the internal flow within an ice sheet that is retreating?

The ice within the ice sheet flows forward but the rate of forward flow is slower than the rate of melting at the front.

Based on the image and your knowledge of the relationship between melting ice and sea level, what is true?

The melting of block A will raise the level of water in the tub.

A glacier flowing over a steep drop-off or around a curve will develop cracks in its surface called

crevasses

Cracks in the surface of a glacier are known as ______ and form in areas of dramatic slope change and where the ice flows around a curve.

crevasses

Plucking, abrasion, and the work of glacial meltwaters are the three primary ways in which glaciers__________ the underlying landscape.

erode

A large rock that has been plucked by a glacier, carried far away from its source, and eventually deposited is a glacial

erratic

The deposition of sediment by glacial streams is ______ deposition.

glaciofluvial

The creation of large amounts of glacial ice during ice ages preferentially leaves behind ______ oxygen isotopes in seawater and enriches the ice with the ______ isotopes.

heavier; lighter

a period of time in which large regions of land are covered year-round with ice and snow, especially in the last 2 million years

ice age

Glaciers can be the source of this windblown silt

loess

Sediment transported on top of a glacier is being transported ______, whereas sediment being transported within the glacier is being transported ______.

supraglacially; englacially

The lower end of a glacier, where the glacier ends either on land or in the sea, is the

terminus

Glaciers erode the underlying surface _____.

through abrasion by glacial meltwaters through plucking

Rivers and streams flowing away from glaciers deposit ______.

outwash plains

A condition in which water in the uppermost part of the ground remains frozen all or most of the time is

permafrost

Northern Canada and Alaska are the only locations in North America where ______ exists in large continuous areas.

permafrost

The melting of continental glaciers in Antarctica would cause global sea levels to ____________ , and would effect coastal areas of the eastern US.

rise

What is the major input source for glaciers?

Snow

Order the steps of glacier ice formation from snowflakes, beginning with the snowfall. (Place the first step at the top.)

1. Snow falls as individual flakes 2.Snowflakes are pressed together; air is forced out 3.Snowflakes are compressed into irregular, dense spheres. 4.Snow changes into interlocking crystals and has a bluish color.

Which axial tilt angle would most encourage the growth of glaciers?

22.5°

Correctly identify the different types of moraines shown in the picture.

A - Lateral moraine B - Medial moraine

Match the locations on the image with descriptions of glaciers present there.

A -Antarctica: it is the largest ice mass on Earth and has mostly ice sheets with some valley glaciers. B-Andes (especially Patagonia): glaciers occupy high peaks, mostly in the southern part of the mountain range. C-North America: glaciers present mainly in the higher peaks in the west. D-Greenland: large ice sheets and smaller glaciers occupy 80% of this landmass. E-Tibetan Plateau and the Himalaya: glaciers cover many of the highest parts of this area.

Which of these situations would cause a very full glass of lemonade to spill over?

A cube of ice is melted and added to the drink

Imagine you are in a recently glaciated region and you come upon a large pile of sediment. The rocks are many different sizes, many of them are angular, and you don't see any layering. Which of the following is the correct interpretation?

A glacier deposited the sediment.

What is a glacial erratic?

A large rock carried far from its source by a glacier

What is permafrost?

A layer of soil that remains frozen year after year

What is a nunatak?

A small area of bedrock high enough to protrude through an ice sheet

______ is the process of scraping bedrock by an overriding glacier, and the removal of pieces of the bedrock by an overriding glacier is ______.

Abrasion; plucking

In North America, permafrost is located in ______.

Alaska northern Canada

Glaciers that begin in mountainous terrain and flow down valleys

Alpine glaciers

What is the formational history of the Great Lakes?

Ancestral lakes formed 14,000 years ago between moraines and ice fronts, then drained at spillways. The modern lakes formed about 4,000 years ago.

Ice sheets exist in ______.

Antarctica Greenland

What is glacial drift?

Any sediment transported by glaciers, icebergs, or meltwater

Which of the following describe the role of ocean currents and continental positions on glaciations and global climate?

Cold ocean currents may inhibit the growth of glaciers by putting less moisture into the atmosphere. Upwelling ocean currents may bring cold water to the surface, helping to cool the land.

These are fractures in a glacier, formed when internal stresses cause its upper surface to break.

Crevasses

On the image, identify the terminus of the glacier.

D

Climate cools slightly.

Decreased sunspot activity

Match the feature with its description and how it may indicate the past presence of glaciers.

Erratic - A huge out-of-place block deposited on a landscape; glaciers transport huge rocks to places where such rock types are not present in the bedrock. Dropstone - A larger stone that is deposited in otherwise fine-grained marine and lake sediment; floating icebergs dropped the stone. Tillite - Consolidated till; poorly sorted, glacially deposited sediment that has now become a sedimentary rock. Polished and scratched bedrock - Bedrock that has been smoothed and grooved; glacially carried sediment erodes away at the bedrock below.

Match the glacial features with their descriptions.

Eskers - Long, sinuous ridges deposited by meltwater stream beneath a glacier as it retreats Kettle lake - Formed as a block of ice left behind by a glacier melts, leaving a depression that fills with water Glacial outwash - River-carried sediment that may either be deposited near or distant to a retreating glacier Recessional moraine - Forms as the front of a glacier melts back and stagnates for some period of time in one location, depositing a pile of sediment Till - The general name given to deposited glacial sediment Drumlins - Streamlined hills formed as a moving glacier sculpts material into this shape

The area on a glacier where the accumulation of ice and snow exactly balances the loss is the

Firn line

Which of the following statements accurately compares the average relative length of glacial and interglacial periods over the past 2.5 to 3 million years?

Glacial periods last longer than interglacial periods.

How are till and tillite related?

Glacial sediment called till hardens into the rock called tillite.

What are the two names of the scratches and gouges created by sediments and rocks that glaciers carry at their bases?

Glacial striations Glacial grooves

Ice sheets exist in all of the following locations except ______.

Glacier National Park, Montana

What are some characteristics of glaciers and glacial areas?

Glaciers flow. Glaciers may fracture, forming crevasses. Glaciers form where snow and ice accumulate faster than they melt.

What area of the Northern Hemisphere covered by ice 28,000 years ago is also ice covered today?

Greenland

These are created as sediment trapped in the glacier base is being carried by the flow.

Grooves and streaks

Increased albedo makes a cooler climate.

Increased snow and ice cover on Earth

Which of the following correctly describes Antarctica?

It has two sides, East and West, each with its own ice sheet. The sides are separated by the Transantarctic Mountains.

Match the names of lakes that existed in glacial times with the features that remain today.

Lake Bonneville - Great Salt Lake; salt flats Lake Missoula - Channeled Scablands

Ash and dust block sunlight, resulting in cooling.

Large volcanic eruptions

Earth's orbit is slightly more circular; cycles last about 100,000 years.

Less eccentricity

Increases the effects of the seasons; warmer summer temperatures melt more polar ice; cycles about every 40,000 years.

Maximum tilt angle of the Earth

Decreases the effect of the seasons; cooler summers lead to an increase in glaciation; cycles about every 40,000 years.

Minimum tilt angle of the Earth

Earth's orbit is slightly more elliptical; cycles last about 100,000 years.

More eccentricity

If global sea levels rise, what could happen to West Antarctica?

More of the ice sheet could float and detach; collapsed parts would melt and raise sea level more.

Which of the following best describes the amount of energy given off by the Sun and the composition of the atmosphere, both of which affect Earth's global climate?

Neither one is constant over time.

What land areas were largely covered by a large continuous ice sheet 28,000 years ago but are not largely covered by an ice sheet today?

Northern Europe Northern Asia Canada Northern United States

Which of the following help scientists identify past glacial and interglacial periods?

Oxygen and carbon isotopes in marine fossils Oxygen isotopic compositions in cores taken from glacial ice

Broad glaciers that form when a more restricted glacier spreads out as it moves into less confined topography

Piedmont glaciers

Each cycle lasts about 23,000 years; this "wobble" may affect global climate.

Precession

Which of the following control the Milankovitch cycles that influence global climate?

Precession (the wobble of Earth's rotational axis) Eccentricity (the varying shape of Earth's orbit) Obliquity (varying tilt angles of the Earth)

This is created as glacial movement grinds up pieces of surrounding rock.

Rock powder

Huge ice dams broke numerous times during the Ice Age to create enormous floods that carved the Channeled _________ in Washington.

Scablands

Snow and ice slide downhill and are not allowed to pile up.

Steep, exposed slopes

Glacial lakes, or _________commonly form in a series we call paternoster lakes.

Tarn

Which of the following statements are true regarding the North America ice sheets 28,000 years ago?

The Laurentide Ice Sheet was centered over Hudson Bay in northern Canada. The Cordilleran Ice Sheet covered western Canada but not much of Alaska.

What is the equilibrium line on a glacier?

The area where the accumulation of ice and snow exactly balances the loss

Which of the following are true of how glaciers move?

The coldest glaciers become locked to the bedrock at their base. Rates at which glaciers move are extremely variable (a few centimeters to tens of meters per day). The upper part of a glacier flows faster than the lower part.

What is rock flour?

The finely ground sediment formed by glacial erosion

True or false: There were many glacial and interglacial periods over the past two million years.

True

This valley shaped like the letter ___________ is a clear indication of glacial erosion in an alpine landscape.

U

tHE _____________ Antarctic Ice Sheet is the smaller of the two on the continent. Much of it's base is below sea level.

West

Which of the following are true of how proportions of oxygen isotopes are changed over interglacial and glacial periods in seawater and glacial ice?

When glaciers melt, oxygen-16-rich water is released back into seawater. Oxygen-16 is preferentially evaporated out of seawater. When glaciers accumulate on land, more oxygen-16 is locked away in glacial ice and does not make it back into seawater.

Match the features on the image with their names.

a - Esker b - Kettle lake c - Drumlins d - Recessional moraine e - Terminal moraine

If we described a land as having kame and kettle topography, what would it look like? The land would have ______.

a bunch of scattered and rounded topographic highs and a bunch of scattered and rounded depressions

A positive feedback in a climatic sense would cause ______.

a cooling climate to become even cooler a warming climate to become even warmer

The uppermost layer of permafrost that thaws in the summer is called the __________layer

active

How does the movement of ice sheets differ during glacial and interglacial periods? During glacial periods, ice sheets ______.

advance, but during interglacial periods, they retreat

The Ice Ages ______.

are times when there was more ice and snow over the past 2 million years

Glacial ice forms ______.

as snowflakes are buried and compressed, eventually becoming crystalline ice

The top of a glacier moves in a ______ fashion; the middle of the glacier behaves ______.

brittle; plastically

At the leading edge of a glacier entering into a body of water, blocks of ice may break off in a process called ______. When these blocks are floating in the water, they are called ______.

calving; icebergs

When sunspot activity is at a low, it causes Earth's climate to ______.

cool by a tiny amount

Scientists are concerned that rising sea levels could ______ the West Antarctica ice sheet from the underlying bedrock, which would lead to more of the collapsed parts melting.

detach

Ancient glaciation events are indicated by the presence of ______.

dropstones erratics tillite ridges of moraine, eskers, and drumlins

Lower axial tilt angles ______ the growth of glaciers.

encourage

The finely ground sediment that is formed by glacial erosion and is often carried away by meltwater is known as rock

flour

Ice sheets are ______.

found in Antarctica and Greenland large continental-scale accumulations of ice

During an ice age, when most glaciers and ice sheets are advancing, the time is a(n) ______ period, but when they are retreating, the time is a(n) ______ period.

glacial; interglacial

A moving mass of ice, which may range in size from a huge ice sheet that covers large regions to a smaller mass that is restricted to a single mountain or valley, is called a(n) __________

glacier

A moving mass of ice, which may range in size from a huge ice sheet that covers large regions to a smaller sheet that is restricted to a single mountain or valley, is called a(n)

glacier

The rocks that glaciers transport at their base scratch the underlying surface and create striations and deeper gouge marks that we call glacial

grooves

A glacier ______.

is a moving mass of ice can cover a continent may be restricted to a single valley

Glaciers form only in areas where snowfall _______ snowmelt.

is greater than

Calculations of the effect of melting the West Antarctic Ice Sheet on global sea level estimate a 6 m rise. Much of the East Coast of the United States is at high risk because of low elevations; the most vulnerable areas are barrier

islands

Geologists study the chemistry and ______________ preserved in ocean fossils and sediments to better understand the timing of glaciations.

isotopes

A glacier will move faster if ______.

it's bottom surface has a thin film of water it moves over a smooth surface

Bumpy glacial terrain that is composed of numerous small, conical hills and small, round depressions (that are commonly filled with water) is called ________ and _______

kame and kettle

Sediments that are directly deposited by a glacier will ______.

lack bedding be generally angular

Compared to glacial periods, interglacials are marked by ______.

lower ratios of oxygen-18 to oxygen-16 in seawater lower ratios of oxygen-18 to oxygen-16 in the compositions of marine shells (less heavy isotopes)

Geologists use all of the following except ______ to investigate the where and when of glaciations.

magnetic reversals

Sunspot activity has a ______ effect on Earth's climate.

measurable but small

Glaciofluvial deposits are associated with glacial

meltwaters

A_____________________feedback is one in which a change in the system causes the system to continue to move in that same direction. Ice, for example, increases the surface albedo, and this tends to cool the climate even more, resulting in more ice cover and further cooling.

positive

The wobble in Earth's axis, its _____________causes the timing of the seasons between hemispheres to be reversed on a 23,000 year cycle.

precession

By studying the processes occurring in modern glaciers and the sediment that results from those processes, we can more fully understand ancient glaciations. We are applying the concept behind the saying "the ______ is the key to the ______."

present; past

What is the difference between glacial abrasion and plucking?Plucking is the ______.

removal of rocks from the bedrock, whereas abrasion is the scraping (smoothing) of the bedrock

The precession of Earth's axis ______.

reverses the timing of the seasons by hemisphere

The largest accumulations of ice are in glaciers we call ice _________. Glaciers that flow down valleys in mountainous regions are _________ , cirque, or valley glaciers. When either of these two glacial types spread out in less confined topography, they are ___________ glaciers.

sheets Alpine piedmont

The rock shown in this image is called tillite. It formed from glacial sediment called

till

This is the (single) word we use to describe the unsorted and unstratified sediment deposited directly by ice.

till

When a glacier encounters a sea or lake ______.

- a large ice shelf may be formed, if a large quantity of ice is floating on the water - ice along the leading edge of the glacier may calve and form icebergs - it may float on the water

Correctly identify the features indicated on the ima

A- Cirque B- Tarn C- Hanging valley D- Aréte

Match the erosional glacial landform with its description.

Aréte - This is a jagged ridge formed between two glaciers, as they eroded from both sides. Tarn - This is a small lake in a glacially scoured depression. Hanging valley - The side valley is higher than the main valley; created because larger glaciers scour deeper into bedrock than smaller, side valley glaciers. U-shaped valley - Smoothing action of a glacier creates this large-scale feature. Cirque - A bowl-shaped depression is created as ice plucks pieces from the bedrock at the uppermost end of a mountain glacier.

This forms as snow gets buried and compressed.

Blue ice

Match the phrases to describe how different parts of a glacier move.

Brittle behavior - occurs on the top of the glacier. Ductile behavior- occurs due to the overlying weight of the ice. Plastic behavior - is caused by internal shearing.

Match the term on the left to its definition regarding the relative location of transport of sediment by a glacier.

Englacially - Sediment is transported within the glacier. Supraglacially - Sediment is transported on top of the glacier. Subglacially - Sediment is transported at the base of the glacier.

What processes associated with glaciers affect the landscape they exist in?

Erosion and deposition

The movement of a glacier in retreat means that all ice is moving backwards, e.g., in the opposite direction of glacial advance.

False

What is the active layer of permafrost?

It is the uppermost layer that thaws during the warmer periods.

Match the name of the moraine with its description.

Lateral moraine - Forms along the sides of a glacier Medial moraine - Forms down the center of a glacier when two tributary glaciers meet Terminal moraineForms at the farthest extent of a glacier advance

How are tarns and pasternoster lakes related?

Tarns that are connected by streams are referred to as pasternoster lakes.

Between 28,000 and 11,000 years ago, which of the following occurred in North America?

The Great Lakes formed. Glacial ice retreated. The upper Mississippi River began to develop.

Through both erosion and deposition, glaciers have ______ affect on the landscape.

a dramatic

A period of time in which large regions of land are covered year-round with ice and snow, especially in the last 2 million years, is ______.

an Ice Age

Ice sheets are ______ ice masses, such as those found in Antarctica and Greenland.

continental-scale

As a continental glacier passes over the land, it tends to erode the topographic highs and deposits sediment in topographic lows. This results in land with a ______ relief than existed prior to the glaciation.

lower

This bit of bedrock sticking up out of the ice sheet in Antarctica is a(n)

nunatak

In high-latitude locations where trees are short and leaning in random directions, ______ is most likely preventing the trees from developing a deep root structure.

permafrost

The Channeled Scablands in eastern Washington were formed during the last ice age ______.

when floodwater caused rapid and large-scale erosion when ice dam failures created enormous floods