Erosion and Deposition by Glaciers Created By: Belinda Schmahl

Table of Contents 1. G laciers Defined 2. F ormation of Glaciers 3. V alley or Alpine Glaciers 4. C ontinental Glaciers or Ice Sheets 5. G lacier Movement 6. G lacial Deposition 7. L andforms caused by Glacial Deposition 8. L andscape Features

Roughly 18,000 yrs ago 30% of the earth’s surface was covered by glaciers. This period is known as the GREAT ICE AGE

1. Glaciers Defined A large mass of ice, formed on land by the compaction and recrystallization of snow, that is moving downhill or outward under the force of gravity. A large mass of ice, formed on land by the compaction and recrystallization of snow, that is moving downhill or outward under the force of gravity. Formed when snowfall > than rate of melting Formed when snowfall > than rate of melting

2. Formation of Glaciers Form when average incoming snowfall> than avg. amount lost by melting and evaporation  Snow increases each year Form when average incoming snowfall> than avg. amount lost by melting and evaporation  Snow increases each year –Picture A- Formation –Picture B- Growing –Picture C- Retreating

2. Formation of Glaciers cont.. As snow increases and evaporation occurs ice crystals become rounded forming granular snow. As snow increases and evaporation occurs ice crystals become rounded forming granular snow. As more snow falls (alternating melting and refreezing compacts snow into a layer called firn  grows into solid ice. As more snow falls (alternating melting and refreezing compacts snow into a layer called firn  grows into solid ice.

This diagram shows how the elevation of the snowline changes with latitude. The approximate elevation of the snowline is indicated on this diagram by the white line. North Pole 75N 60N 45N 30N 15N Equator 6,000m 5,000m 4,000m 3,000m 2,000m 1,000m Sea Level SNOWLINE

3. Valley or Alpine Glacier Gravity pulls downward and outward on bottom layers Gravity pulls downward and outward on bottom layers This type of glacier carves a U shaped valley. This type of glacier carves a U shaped valley. ***Remember streams carve a V shaped valley

U-Shaped Valley

4. Continental Glacier or Ice Sheets These are very old and thick and may cover entire land masses, snow is close to sea level These are very old and thick and may cover entire land masses, snow is close to sea level Moves very slowly because of weight Moves very slowly because of weight When it reaches ocean it can break off  Icebergs (called Calving) When it reaches ocean it can break off  Icebergs (called Calving) –Greenland- 1.7 million square Km (3 Km thick) –Antarctica million square Km (5 Km thick)

Depth of Greenland & Antarctic Ice Sheets

5. Glacier Movement Stationary Glacier- When rate of movement = rate of melting Stationary Glacier- When rate of movement = rate of melting Winter- Glacier moves more (WHY???) Winter- Glacier moves more (WHY???) Summer Glacier moves less and appears to move backwards (WHY???) Summer Glacier moves less and appears to move backwards (WHY???)

6. Glacial Deposition The sediment that is deposited by glaciers is unsorted (Called Glacial till) The sediment that is deposited by glaciers is unsorted (Called Glacial till) *Remember that sediment deposited by water is sorted. If sediment is transported by melt water of glacier than it is deposited the same as a river would deposit (Sorted)  Outwash If sediment is transported by melt water of glacier than it is deposited the same as a river would deposit (Sorted)  Outwash

Glacial till - unsorted

7. Landforms caused by Glacial Deposition Moraines- Unsorted Sediment along the edge of the glacier. Moraines- Unsorted Sediment along the edge of the glacier. Terminal Moraine-The furthest point of the glacier (Long Island) Terminal Moraine-The furthest point of the glacier (Long Island) Erratic- A large rock that looks misplaced Erratic- A large rock that looks misplaced Drumlins- Long smooth hills of glacial till, points in direction of glacier movement. Drumlins- Long smooth hills of glacial till, points in direction of glacier movement. Karnes- melt water from top of glacier Karnes- melt water from top of glacier Kettles- Circular lakes-Ice breaks off and melts underground Kettles- Circular lakes-Ice breaks off and melts underground Moraine Dammed lake- When a glacial moraine blocks a river valley, resulting in a long narrow lakes. (Finger lakes) Moraine Dammed lake- When a glacial moraine blocks a river valley, resulting in a long narrow lakes. (Finger lakes)

Moraine/Terminal Moraine

Erratic

Drumlins

Outwash Plains

Karnes

Kettle Lake

Moraine Dammed Lake

8. Landscape Features Cirques- Semi circular shaped bedrock formed as glacier moves back toward mountain. Cirques- Semi circular shaped bedrock formed as glacier moves back toward mountain. Arêtes- Steep sided bedrock formed as glacier retreated in opposite direction. Arêtes- Steep sided bedrock formed as glacier retreated in opposite direction. Horns- Where three arêtes meet up Horns- Where three arêtes meet up

Arête Cirque U-Shaped Valley

Kettle Lake Drumlins Esker Outwash plain Glacial Stream Till Moraine-dammed lake Terminal Moraine