1. How Do Glaciers Shape the Land?
What causes Glaciers?
How Do Glaciers Shape the Land?

2. Glaciers –masses of ice on land
Continental
Valley
Ice sheets on land
Rivers of ice moving through mountains
They move like rivers (faster in the center) only much slower

3. How glaciers form?
Glaciers occur where the temperature is such that there is an accumulation of snow.
Current Glaciers form at high latitudes (poles) and high elevations (Mountain peaks)
Glacial sheets of the past formed during ice ages. These sheets covered the northern section of the United States.

4. Pleistocene Epoch: the Great Ice Ages
2.0 Ma to 10,000 years ago
Four (or more) distinct episodes expansion and melting of ice sheets (continental glaciers)
Each ice advance lasted for 40,000 to 200,000 years
Warm spells lasted 10,000 to 30,000 years
Are we living in a warm period now between ice ages?

5. Why did the climate change so drastically and repeadedly?
Past hypotheses:
Climate change and variations in Earth’s orbit
Earth was further from the sun at certain points
“Wobble” – Earth tilt was larger
If we were tilted more we would have colder winters and warmer summers
Milankovitch cycles are in the right time range to possibly explain cyclic changes in climate

6. Effects of Pollution
Variations affect amount and distribution of solar energy received by Earth
Pollution could block sunlight from reaching the earth, creating colder temps
Meteor and volcanic dust could have blocked sunlight in the past creating the ice age that killed off the dinosaurs.

7. What Makes a Glacier Move?
The weight of overlying layers compact the snow
The friction with the underlying rocks creates heat and melts the bottom and sides that are scratching against rock layers.
It slips and slides downhill under the pressure of its own weight and gravity pulls it down slope

8. Advance and Retreat of Glaciers
Advance: Glaciers grow and appear to move forward as snow accumulates due to colder weather.
Retreat: Glaciers “appear” to move backwards as they melt. **The glaciers are not moving backwards the front edge is just melting as the temperature increases.*** melting glacier national park

9. Valley Glaciers move like rivers
Glaciers are moving fastest in the center of the valley b/c there is less friction there

10. Erosional Marks Left by Glaciers
1. U shape Valley

11. 2. Striations
Deep scratches in rocks. As Glaciers move they are carrying a mix of large and small sediments. The larger sediments scratch the underlying rocks.
These scratches could help determine the direction the glacier came from.

12. 3. Polish
Smooth surfaces on large rocks created as small sediments in glaciers sand down the rough surfaces.

13. 3. Kettle Lakes
Block of ice is deposited and creates a lake as the water wears out a hole in the land.

14. Glacial Deposits - Drift
Till
Outwash
Deposits left directly by the ICE
Unsorted and not layered
Deposits left by the melting water of a glacier
Sorted and layered

15. Depositional Marks Left by Glaciers
1. Erratics- large Boulders left behind by glaciers

16. 2. Moraines Pile of unsorted sediments at the edges of glaciers
Lateral moraines – side edges of glaciers
Terminal moraines – front edge of glaciers.
*** mark where a glacier stopped advancing

17. Terminal Moraine

18. Long Island – was created by terminal glacial moraines

19. Eskers – winding ridge of sediments deposited in a tunnel under glacier

20. Drumlins- long narrow hills of glacial till- trails off to south
Gentle sloping side is the direction the ice was moving

21. Kames- fan shape deposits left at the edge of valley glaciers
Kames- fan shape deposits left at the edge of valley glaciers *** like a delta only created by glacier instead of river