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Alaska from space.

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Presentation on theme: "Alaska from space."— Presentation transcript:

1 Alaska from space

2 Leveling Forces: Glaciers

3 Glaciers: Huge masses of ice that form when more snow accumulates in the winter than melts in the summer.

4 Valley or alpine glaciers form up in the mountains, when snow accumulates in river valleys.

5 Ice sheets, or continental glaciers are landmasses at high latitudes that are covered in ice. Today, there are ice sheets covering Greenland and Antarctica.

6 Evidence of Ice Ages Ice Ages have occurred repeatedly throughout earth’s history, during periods of global cooling. We are presently in a period of global warming (and have been for a long time). The last four ice ages occurred over the last 2 million years. The last bit of ice left our area 10,000 years ago. gak and flow activity ( rs.html )

7 ice in last glaciation

8 Axis and ice ages

9 Ocean currents

10 Temperature changes in time

11 Carbon dioxide levels

12 As the snow accumulates and becomes packed, it becomes ‘locked’ around objects, hills, boulders, etc. The lower parts of the glacier begin to move when the weight of snow is great enough. Any objects and sediments in the glacier’s path are ripped out and moved.

13 Glacial movement

14 The valley becomes ‘u-shaped’ due to this erosion.
Continental glaciers cause hills to become rounded and scoured. They can completely reshape the landscapes.

15 Yosemite shape

16 Tom McGuire’s glacial images:
Describe other evidence of glacial erosion including: striations, cirques, horns, kettles, hanging valleys and waterfalls.

17 Edge of glacier

18 Valley glacier and flow

19 Ribbons of ice

20 Latitude and glaciers

21 Valley glacier diagrams

22 Glacial deposition (handout)
Glaciers deposit sediments either as: unsorted glacial till, abruptly at the edges and sides of the glacier; or as sorted glacial outwash as the glacial meltwaters move out from the glacier.

23 Drumlins from space

24 Glacial Striations

25 erratic

26 Glacial plain

27 U-shaped

28 Describe these depositional features from your text:
Outwash plains, kames, eskers, drumlins, erratics and moraines. ions/continental%20glacier.swf

29 Regents glacial picture

30 ( Glacial sediments and erratics.)
Sediments carved or carried by glaciers tend to be: polished by the ‘rock-tumbler effect’, rounded, scratched and unlike the underlying bedrock ( Glacial sediments and erratics.)

31 til and moraine

32 Glacial sediments

33 Glacial striations and polish

34 Old sea terraces

35 From Glacial till: sediments are unsorted and dumped by glaciers at the sides or end. Sediments are unsorted, and dumped in huge piles, ridges or hills

36 Glacial outwash: Meltwater from the glacier carries sediments onto plains, valleys, etc. Sediments are sorted by the running water, but show signs of having been scratched and polished in a glacier.

37 Transported soils are found where a glacier has moved through an area
Transported soils are found where a glacier has moved through an area. New York’s soils are transported soils.

38 Glacial streams

39 NYS glacial remains: Long Island, Quarternary Geology of NYC area: ‘fields’ of drumlins that look like flocks of sheep from the air, the Finger Lakes, the gravel/sand/rock deposits that are important as resource, hanging troughs and waterfalls, bashakill map huge glacial erratics, striated bedrock, unsorted transported soils.

40 17-35 and 51 http://media. pearsoncmg

41 https://www. google. com/maps/embed. pb=. 1 m13. 1m11. 1m3. 1d235
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