1. Chapter 7: Erosion and Deposition
7.1: Forces wear down and build up Earth’s surface
7.2: Moving water shapes land
7.3: Waves and wind shape land
7.4: Glaciers carve land and move sediments

2. 7.4 Glaciers carve land and move sediments
Before, you learned:
Running water shapes landscapes
Wind changes landforms
Now, you will learn:
How moving ice erodes land
How moving ice deposits sediment and changes landforms

3. Glaciers are moving bodies of ice
Glacier: a large mass of ice that moves over land
Forms in a cold region where more snow falls than melts per year
The weight of each following year’s snow compresses the snow below  ice
On a mountains: becomes a heavy mass and can flow
On flatter land: can spread out as ice sheets

4. Extent of Glaciers
Must be cold enough for water to remain ice year round
Mountains (high elevation/altitude) and land regions near the poles (high latitude)
= COLD!
Currently cover ~10% of the Earth’s land surface
Ice Ages
~30,000 years ago (ya) glaciers covered 30%
“Last Glacial Maximum” ~17,000 ya
Lasting until ~13 to 10,000 ya

5. Two Types of Glaciers: (1) Alpine
Aka “valley glaciers”
Form in mountains and flow down
through valleys
Cause erosion (and deposition)
Can change a “V-shaped” mountain valley into a “U-shaped” valley overtime
Melting can occur at the base
Carries sediment
Can break off into the ocean: icebergs

6. Two Types of Glaciers: (2) Continental
Aka “ice sheets”
Larger than alpine glaciers
Can cover entire continents
One covered North America until about
10,000 years ago
Still cover most of Greenland and Antarctica
As much as 4500 meters (15,000 ft) thick!

7. Glacial Movement Gravity causes glacial ice to move downhill:
Flowing: ice near the surface is brittle and cracks often form in it, but pressure deep inside does not
Inside ice flows like toothpaste tube being squeezed
Sliding: weight of a glacial and heat from Earth cause melting
Layer of water forms under the glaicer - sliding

8. Interesting
During the last glaciation (~26 to 13,000 ya), woolly mammoths and saber-toothed cats roamed just south of the glaciers
At the end of the last ice age ~10,000 ya, these large mammals became extinct
Why?
Hunting?
Climate?
Diseases from humans?

9. Glaciers deposit large amounts of sediment
As glaciers melt and treat: shape landscape
As glaciers move and expand: transport sediment (boulders, rocks, sand, clay)
Scratches and scrapes rock: abrasion

10. Glaciers deposit large amounts of sediment
Moraines
Glaciers push sediment to their sides and front
These sediment deposits remain after glacial retreat
Till: the sediment left directly on the ground surface by a retreating glacier
Moraine: a deposit of till left behind by a retreating glacier
Lateral moraine: till at sides of glacier
End moraine: till at farthest advance of glacier
Ground moraine: blanket of till along the ground
Till is different than the rocks from the area

11. Glaciers deposit large amounts of sediment
Lakes
Melting glaciers leave behind depressions than can become lakes
Kettle lakes: bowl-shaped depression that was formed by a block of ice from a glacier

12. Great Lakes Formation
Glaciers in valleys melted and left behind moraines
A million years ago, the Great Lake region had many river valleys
Ice sheets gouged out large depressions and left piles of rock and debris
Prevented water from draining out
Weight of glacier caused the land to sink as much as one kilometer