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Glaciers: Moving Ice

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Rita Gonzalez

on 18 December 2013

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Transcript of Glaciers: Moving Ice

Glaciers: Moving Ice
Rita Gonzalez
Kenna Collins

Formation of Glaciers
Firn- Grainy ice formed by cycle of melting and refreezing
The size of glaciers depend on the amount of snowfall received and amount of ice lost.
Types: Alpine Glaciers
An Alpine Glacier is a narrow, wedge-shaped mass of ice that forms in mountainous regions.
Formation of Glaciers
Glacier- A Large Mass of Ice
Snow can be left on the ground all year and form a motionless mass of ice and snow called Snowfield.
Snowline is the elevation above which ice and snow remain throughout the year.
Movement: Basal Slip
Basal Slip- The process that lubricates a glacier's base and causes the glacier to slide forward.
Also allows a glacier to work its way over small barriers in its path by melting and then refreezing.
Types: Continental Glaciers
Continental Glaciers are massive sheets if ice that may cover millions of square kilometers.
Also called Ice Sheets
Found in Greenland and Antarctica
Usually located in Alaska, The Himalayan Mountains, The Andes, The Alps, and New Zealand.
Movement: Internal Plastic Flow
In this process pressure deforms grains of ice under the glacier
When grains deform they slide over each other and cause the glacier to flow slowly
The rate of the flow varies for different parts of the glacier
The Interior of the glacier moves by internal plastic flow
Features of Glaciers
Large cracks in the glaciers due to uneven movement underneath the surface of the glacier are called Crevasses
Ice sheets that move out over the ocean form ice shelves
Most of an iceberg is below the surface of water making it very hazardous for ships
An iceberg studied in the Antarctic was twice the size of Connecticut
Glacial Erosion
Because of the size and density of glaciers the landforms formed are very different from the ones rivers form
Deep depressions form when moving glaciers loosen and dislodges a rock from bedrock at the base or side of glacier
Then the the rocks are dragged across the bedrock and cause abrasions
Landforms Created by Glacial Erosion
Cirque- a deep and steep bowl-like depression produced by glacial erosion
Arete- A Sharp, jagged ridge that forms between cirques
Horn- a sharp,pyramid-like peak that forms because of the erosion of cirques
Landforms Created by Glacial Erosion
As a glacier moves through a narrow, V-shaped rover valley. rock from the valley walls breaks off and the walls become steeper
As the glacier flows down it picks up large amount of rocks
U-shaped Valleys
A Stream forms a V shaped valley, but when a glacier comes through the valley becomes U shaped
Glacial Erosion is the only way U shaped valleys can be formed
Small Tributary glaciers have less ice and less cutting power so the U shaped valleys they create aren't as deep as the Alpine glacier
Erosion by Continental Glaciers

Landscapes formed by Continental Glaciers differs from the ones formed by Alpine Glacier
Continental glaciers leave landforms that are smooth and rounded, almost flattening the surface
Glacial Deposition
Deposition occurs when a glacier melts
Erratics- large rocks transported from a distant source by a glacier
Glacial Drift- rock material carried and deposited by glaciers
Till- unsorted rock material that is deposited directly by a melting glacier
Stratified drift is material that has been sorted and deposited in layers of streams flowing from the melted ice, or meltwater
Till Deposits
Moraines- a landform that is made from unsorted sediments deposited by a glacier
lateral moraine- a moraine that is deposited along the sides of an alpine glacier, usually as a long ridge
medial moraine- when two or more alpine glacier join, their adjacent lateral moraines combine
ground moraine- the unsorted material left beneath the glacier when the ice melts
Termial moraine- small ridges of till that are deposited at the lending edge of melting glacier
Drumline- long, low, tear-shaped mounds of till
Outwash Plains
Glacial meltwater may have have beautiful colors, such as milky whites, emerald green, or turquoise blue, because it carries very fine sediment
Outwash plain- deposit of stratified drift that lies in front of a terminal moraine and is crossed by many meltwater streams
Kettles
Kettles- a bowl-shaped depression in a glacial drift deposit
Forms when a chunk of glacial ice is buried in drift, as ice melts, a cavity forms in the drift
Then, the drift collapses into the cavity and produces a depression
Kettles commonly fill with water to form kettle lakes
Eskers
Esker- a long, winding ridge of gravel and coarse sand deposited by glacial meltwater
Eskers may extend for tens of kilometers
Consist of stratified drift deposited by streams of meltwater that flow through ice tunnels within the glaciers
Glacial Lakes
Lake basins commonly form where glaciers erode surfaces and leave depressions in the bedrock
These lakes exist in many areas of North America and Europe
Finger Lakes- long, narrow lakes
Minnesota to Ohio has belts or moraines and lakes
Formation of Salt Lakes
Water leaves lakes only by evaporation
When the water evaporates, salt that was dissolved in the water is left behind, which makes the water increasingly salty
Salt Lakes commonly form in dry climates, where evaporation is rapid and precipitation is low
History of Great Lakes
In their early ages, the lakes emptied to the south into the Wabash and Illinois Rivers
Later the lakes grew larger and also drained into the Atlantic Ocean through the Susquehanna, Mohawk, and Hudson River Valley
After the Glacial period, the crust rose as the weight of the ice was removed making the the lake beds lift and shrank
The uplift made lakes drain to the northeast through the St. Lawrence
Glacial and Interglacial Periods
Ice Age- A long period of climatic cooling during which the continents are glaciated repeatedly
The earliest known ice age is about 800 million years ago and most recent is 4 million years ago
Glacial Period- a period of cooler climate that is characterized by the retreat of glaciers
Glaciation in North America
Glaciers covered about one-third of Earth's surface during the last glacial period
Most glaciation happened took place in North America
Canada and the most mountainous regions of Alaska were buried under the ice
Glaciers flowed outward from the Rocky Mountains and the Cascade and Sierra Nevada Ranges
A Great ice sheet was centered on what now is the Hudson Bay region of Canada and spread as far south as the Missouri and Ohio Rivers
Glaciation in Eurasia and the Southern Hemisphere
In Europe, a continental ice sheet that was centered on what is now the Baltic Sea spread over Germany, Belgium, and the Netherlands and west over Great Britain and Ireland
Long Alpine glaciers formed in the Alps and Himalayas
A continental ice sheet formed in the Siberia
The Andes Mountains and much of New Zealand were covered by mountainous ice fields and alpine glaciers
Causes of Glaciation
One factor that caused glaciation might have been the movement of tectonics plates moving very slowly changing global circulation pattern of air and ocean water
The Milankovitch Theory
Milankovitch Theory- the theory that cyclical changes in Earth's orbit and in the tilt of Earth's axis occur over thousands of years and cause climatic changes
He thought the earth had three periodic changes
1. Eccentricity- The earth orbit
2. Tilt
3. Precession
Biological Evidence of Glaciation
Evidence has been found in the shells of dead marine animals found on the ocean floor
The temperature of the ocean affected the way these animals built their shell
Other Explanations for Glaciation
Some explanations say indicate that changes in the amount of solar energy that reached Earth's surface that weren't caused by earth's position relative to the sun
Another explanation is that volcanic dust blocked rays from the sun's rays
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