GEOG 101! 04 Chapter 12 Study Guide

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What is till?

Unsorted material deposited directly from glacial ice

What is a zone of fracture?

Uppermost 50 meters; ice is too brittle to flow; causes crevasses

Not all glaciers move at the same _____.

Velocity; some move several meters per day; some take hundreds of years

What are medial moraines?

Visible debris in active ice but not preserved when melted

What is the driftless area of the Upper Midwest?

Glaciers missed on last pass; Steep cliffs, deep river valleys, not flat, no till, not many lakes

What cycles are glaciers part of?

Hydrologic cycle and rock cycle

What are the three general extents/sizes of continental/sheet glaciers?

Ice field, ice cap, and ice sheet

What is permafrost?

If ground is frozen for at least two years; temperature only: not necessarily an abundance of actual ice; groundwater blocked in places

What are the 4 major glacial stages recognized on land?

Nebraskan, Kansan, Illinoian, and Wisconsinian

What does periglacial mean?

No glaciers, but ice action changes the landscape; all year or seasonal; tundra

How long ago was our most recent glacial maximum?

Occurred about 18,000 years ago and ended about 10,000 years ago

What percentage of Earth is covered in glaciers?

10%

What is ground moraine?

A blanket of till

What is the Laurentide Ice Sheet?

A massive sheet of ice that covered millions of square kilometers, including most of Canada and a large portion of the Northern United States (30% of Earth's land)

Melting glaciers result in what percentage of Earth's water?

About 2%

The Antarctic sheet has what percentage of the world's ice?

About 80%

What is glacial drift?

All sediments regardless of how, where, and in what shape deposited

From what do end moraines form?

Alpine glaciers and ice sheets

How do glaciers grow?

Anything left over from the summer before the last winter slowly turns into glacial ice and the glacier expands

What is the zone of accumulation?

Area where a glacier forms; precipitation and avalanches contribute to snowfield; outer limits are defined by the equilibrium line, approximated by the snowline

What is recrystallization?

Rain and summer snowmelt add water and air to the glacier

What is compaction?

Sedimentary-like layers make snow thicker and heavier, increasing pressure of underlying ice

What are drumlins?

Smooth, elongated hills of glacial deposits

What is washed or stratified drift?

Sorted sediments laid down by glacial meltwater

What is a terminal moraine?

The ridge of till at the farthest point reached by a glacier

What is plastic flow (creep)?

With enough pressure, the ice behaves plastically

What are kames?

mounds or steep -sided hills made of sand and gravel

What are kame terraces?

kame formation in a valley

What does glacial abbrasion leave behind?

Rock flour (pulverized rock), glacial striations (grooves in the bedrock), polished surfaces, and chatter marks

What are eskers?

Sand and gravel dropped from meltwater streams

What are outwash plains and valley trains?

Deposited by braided meltwater streams; broad flat plain composed of stratified sand and gravel; often pockmarked with basins or depressions called kettles

What are ice contact deposits?

Deposited by meltwater flowing over, under, within, or against the edge of unmoving ice; coarser and less well-sorted than proglacial deposits

What is an ice field?

Does not cover all topography

What is an ice cap

Domes; do cover all topography

What are clusters of drumlins called?

Drumlin fields

What is the Milankovitch hypoothesis (what drives climate cycles)?

Eccentricity, the shape of the Earth's orbit varies, Obliquity, the angle of the Earth's axis changes, Precession, Earth's axis wobbles

What are outlet glaciers?

Fed by ice caps and ice sheets, but become constrained by mountain valleys; flow over land and often out to the sea

What are tidewater glaciers?

Fed by valley glacier, to ocean

What are Piedmont glaciers?

Fed by valley glaciers; spreads into a lobed sheet on a plain; in broad lowlands at a mountain's base

What are some indirect effects of Ice Age glaciers?

Forced migration of animals and plants, pluvial lakes and rivers, rebounding upward of the crust in former centers of ice accumulation, change in sea level, and 18O concentration in ice/oceanic water

What are Alpine/Valley (non-continuous) glaciers?

High altitude, mountainous areas (Andes, Himalayas, European Alps); streams of ice which flow down a valley from a zone of accumulation at their heads

What are hanging glaciers?

High valley to low valley

What will happen to the sea level if the glaciers melted?

It would rise 60-70 meters

What are erratics?

Large boulders deposited randomly by glaciers

What are Continental/Sheet glaciers (continuous)?

Larger scale than valley glaciers; Greenland and Antarctica; ice flows out in all directions from one or more snow-accumulation centers

The elevation of the snowline varies greatly depending on...

Latitude and aspect

How many major stages are recognized in the ocean?

Less than 10

What is plucking?

Lifting and moving of blocks of rock

Where can you find drumlins?

Many in Michigan, Upper Midwest, and Northeast U.S.

What is an ice sheet?

Massive scale

If too much of the glacier is lost, the glacier ablates by...

Melting, calving, sublimation, wind erosion, and evaporation

Where are glaciers found?

On land or floating on an ice shelf adjacent to land

At the maximum extent of the Pleistocene glaciation period how much of Earth was covered in glaciers?

One-third of Earth's land

What are moraines?

Piles of rocks and debris left when glaciers melt

What causes glaciation?

Plate tectonics; continents were arranged differently in the past; need land in higher altitudes for ice masses to form; changes in oceanic circulation

During which epoch did most major glacial stages occur?

Pleistocene

In what age were glaciers formed?

Pleistocene Ice Age, two to three million years ago

In what two ways do glaciers erode?

Plucking and abrasion

What is abrasion?

Polishing and carving

What is a recessional moraine?

Ridge marking a place where glacial retreat was temporarily halted

What is the glacial budget?

The difference between total accumulation and total ablation for one year

What is a glacier?

Thick, year-round, gravity-mobile ice that originates on land from the repeated accumulation, compaction, and recrystallization of snow

What is a basal slip?

Where meltwater at the base of the glacier lubricates the glacier allowing it to slide - happens in warmer temperatures.

What are fjords?

glacial valleys flooded with seawater and freshwater


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