1. Unit 5 Chapter 17
Glaciers

2. Section 1 Glaciers: Moving Ice
Glacier - It is a large mass of snow & ice that moves under the force of gravity.

3. Formation of a Glacier Snow line:
A snow line is the lowest level that permanent snow reaches in the summer. This means that in higher latitudes, the snow line can be at sea level, but at the equator, the snow line will be on a mountaintop. A mountain that gets covered in snow during the winter, but melts all the way down in the summer, does not have a snow line.
Example:
1. The mountains we ski on in the winter (Vermont, New York, Penn), they offer summer sports like hiking and other things.
2. The mountains of Colorado have a high snow line they have snow
even in summer.

4. How glaciers form In order for a glacier to form you need
1. Cold temperatures year round
2. More snow precipitating than snow that melts
3. Buried snow becomes more & more compact
4. It starts to re-crystallized into rough granular ice know as firn.
5. The weight of the material on top compresses more & more turning the firn into solid ice.
6. The weight of the snow & firn causes the ice to move with gravity, downward & outward.

5. Types of Glaciers Valley (Alpine) Glacier –
An Alpine glacier is a glacier that covers a mountain valley (very big)
They occur in all parts of the world where mountains reach above the snow line; except in Australia. The smallest glacier can be approximately 2 kilometers long. The largest ones are in Alaska one of them is Muldrow Glacier in Denali National Park. It is approx. 56 kilometers long. The Himalayas have very large valley glaciers also.

6. Continental Glacier
A continental glacier is a glacier that covers most of a land mass
They are roughly circular or oval in shape. They occur in areas where all of the precipitation that falls in snow. Summer is not warm enough to melt it either. This forms landmasses almost entirely covered with ice and snow except for the highest mountain peaks, known as Nuntaks.
Greenland – approx. 1.7 million Km2, approx 3 Km2 thick
Antarctic – approx 13.7 million Km2, approx 5 Km2 thick, (the ice may descend more than 2 Km below sea level at the coast.)

7. Movement of Glaciers 1. They always move forward, never backward
2. Heavy winters with little melting will cause them to move fast
3. Warm summers cause then to recede (rate of melting is more rapid).
4. They move like a bulldozer by grabbing and pushing everything in its way.
5. They can move a few centimeters or thousands of centimeters in a day.
6. The speed is rapid at the surface, but faster in the center due to the friction

8. Movement:
Basal Slip –
Is the movement at the base caused by the mixing of the melting ice, grains of sand & gravel. This creates a slushy layer allowing the glacier to move at the base. It also moves in smaller areas by melting and then refreezing.
Internal Plastic Flow
This occurs when the pressure of the ice & snow, the grains change shape and become flat. This flatter shape makes the glacier “flow” forward.

9. Features of Glaciers
Crevasses – cracks formed because the ice near the surface is rigid and cracks due to the movement.
Ice Front – the thinnest part of the glacier. The place where it moves as fast as it melts. If the glaciers rate of melting is more than its rate of movement, the ice front recedes.
Calving – when part of the glacier reaches the coast, it breaks off and becomes an iceberg.
Ice Shelves – when the ice front overhangs into the water. The largest one is the Ross Ice Shelf, off the coast of Antarctica. It is 100’s of kilometers wide. In 2000 an iceberg broke off the size of Connecticut (approx 295 kilometers long and 37 kilometers wide).

10. Section 2 Glacial Erosion and Deposition
Material movement – glaciers bulldoze almost everything in its path
Striation is the parallel scratches left on rocks after a glacier passes. It shows the general direction of the movement of the ice.
Glaciers leave different kinds of features due to the way they move, melt and deposit. Rivers and lakes can be formed by them.

11. Landforms Created by Glacial Erosion
Cirque – a semi-circular basin at the head of a glacial valley where the valley glacier began.

12. Horn
Horn – when three or more cirques cut the same peak it forms a pyramid-shaped peak (the Matter horn in Switzerland & Italy).

13. Arête
Arête - sharp pointed mountain peak formed by multiple cirques

14. Roche Moutonnees
Roche Moutonnees – the glacier smoothes the side of an outcrop and leaves the other side rough.

15. U-Shaped Valleys
Areas in the US like the Rocky Mountains & the Sierra Nevada of California have valley glaciers. These glaciers produce sharp mountain peaks.
Glacial trough – U shaped valleys, the glacier removes the valley and the walls.

16. continued:
Cirque Lake – when a cirque fills in with water (Lake Louise in the Canadian Rockies)

17. continued:
Hanging Valleys – a valley carved out by tributary glaciers. A river that flows from these valleys are called hanging waterfalls. Yosemite Falls in California.

18. Erosion by Continental Glaciers
Unlike valley glaciers, continental glaciers grind down mountain peaks. The are very familiar in the Northeast US, Canada, Iceland and the Antarctic.
Nunatak

19. Glacial Deposits
Rock Flour – a mixture of sand and silt crushed by a glacier.
Glacial drift – a name for any glacial deposit
Stratified drift – is material that has been sorted and deposited inlayers by steams flowing from the melting ice.

20. Till – unsorted rock material that is left by the glaciers movement

21. Erratic – large glacial boulders transported from somewhere else

22. Ventifact – wind and sand smooth rocks

23. Drumlins – canoe shaped hills formed when a glacier moves over earlier glacial moraines; shows direction of the movement (Eastern Wisconsin and West & Central New York)

24. Kames – small cone shaped hills of layered sand and gravel

25. Till Deposits
Moraine – is the accumulation of glacial till; glacial garbage
Terminal Moraine – a pile of material left at the ice front. Long Island has two terminal moraines. The terminal moraines mark the furthest advance of a glacier.

26. Recessional – when other end moraines form behind the end moraine.
Other moraines
Lateral- forms along the sides of the glacier, runs the same direction as the flow
Medial – when two or more glaciers combine, the combined lateral moraines form this
Recessional – when other end moraines form behind the end moraine.

27. Outwash Plains
Outwash – sand deposits made from glacial streams (melted ice)

28. Outwash plains are glacial alluvial fans that overlap each other.
Most of Long Island is an outwash plain. We have the Hempstead Outwash plain and the Terryville Outwash plain.

29. Kettles
Kettle Holes – circular holes in the ground at terminal moraines
Step 1 – Large blocks of ice break off of the front of a glacier. As it
moves it gets buried.
Step 2 – the ice melts and leaves a hole. Water may re-fill the hole
making it a kettle lake (Lake Ronkonkoma, Wildwood Lake,
Scuttle hole road)

30. Esker
Esker – long winding glacial deposit formed from internal glacial streams

31. Glacial Lakes
Finger Lakes – Long narrow deposits formed by glacial erosion and deposition
Lake George – Moraine damned lake
Kettle Lakes – found in Minnesota (land of 1000 lakes), Michigan, Wisconsin, NY and New England.

32. Formation of Salt Lakes
The Great Salt Lakes in Utah formed because of the streams were cut off by the deposition of glacial material. These streams became lakes which than evaporated some of the water leaving large salt mineral deposits behind. They now are considered some of the saltiest lakes around.
The history of the Great Lakes

33. Section 3 Ice Ages Glacial and Interglacial Periods
Ice Age – a long period of climate cooling during which the continents are glaciated repeatedly.
Earliest – 800 million years ago
Latest – 4 million years ago
Glacial and Interglacial Periods
Glacial period is when glaciers advance
Interglacial periods are when glaciers have retreated. We are in this period of retreat.

34. Glaciation in North America
How the Glacier Formed Long Island.
About 1,000,000 years ago
The temperature was very cold
Ice Sheets formed over Central and Eastern Canada and Northern Scandinavia. In North America they formed over the area where the Mississippi River and Ohio River meets and eastward to Long Island.
3. There is evidence that the glacier advanced and receded about 4 times. We have evidence that on Long Island it occurred 2 times:
1. The first one extends from Brooklyn to Montauk (225kms)
2. The second is from Nassau County to the North Shore

35. Map of Long Island

36. Glaciation in Eurasia and the southern hemisphere
Ice sheets centered in the Baltic Sea which spread over Germany, Belgium and the Netherlands, west over to Great Britain and Ireland; Eastward to Poland and Russia; to the Alps and the Himalayas.

37. Glacial Causes: Causes of Glaciation
The last time glaciers retreated was about 11, 000 years ago.
Causes:
1. Change in the position of the land on the earth’s crust (former position of the continents)
2. Change in weather patterns (climate)
3. Change in the amount Carbon Dioxide in the atmosphere
4. Change in the amount of solar energy being absorbed by the land and reflected by the atmosphere.
5. Mountain building may have caused more land area above the snowline.