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Glacial Erosion. Ch 15: p 277-281. Glaciers:. Enormous masses of moving ice created by the accumulation and compaction of snow. Powerful agents of erosion ~ have carved some of the most spectacular features on Earth’s surface

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glacial erosion

Glacial Erosion

Ch 15: p 277-281

glaciers
Glaciers:

Enormous masses of moving ice created by the accumulation and compaction of snow.

Powerful agents of erosion ~ have carved some of the most spectacular features on Earth’s surface

The growth of a glacier depends on whether the snowfall from winter is greater than the snow melt in summer!

2 types of glaciers
2 types of Glaciers:

Alpine (aka Valley)

Continental (ice sheets)

  • Mountainous areas
  • long, narrow-wedged mass of ice
  • Best developed valley glaciers found in Alaska, the Himalayas, the Alps…
  • Covers large land areas
  • Found only in Greenland and Antarctica today
slide5

Continental ice sheet

The Antarctic Ice Sheet is 1.5 times the size of the US and in some places more than 4,000 m thick

step 1 snow accumulates
Step 1: Snow accumulates.

More snow falls during the winter than melts in the summer.

slide9

Trans-Labrador Highway

WOAH!

http://tlhwy.com/south/winter/index.html

step 2 snow changes to firn
Step 2: Snow changes to firn.

As snow accumulates, its weight compresses the individual snowflakes to form firn.

some facts
Some Facts
  • Glaciers hold 75% of the Earth’s fresh water.
  • 10% of land is covered by them.
  • If they all melted the sea level would go up about 70m
  • Artic ice is over 4,200 m thick in some spots.
2 types glacial movement
2 types glacial movement:

Basal Slip

Internal plastic flow

  • The weight of the ice exerts enough pressure to melt the ice where it contacts the ground
  • This melt water acts as a lubricant and allows the glacier to slip forward, including over small barriers
  • The weight of the ice and gravity causes the ice crystals to slip over each other
  • Speed of this flow is faster nearer the surface and at its center…why?...
    • friction!
how do glaciers erode the surface
How do glaciers erode the surface?
  • Plucking –freeze/thaw process lifts particles into ice
  • Abrasion- like sandpaper-rocks caught up on the bottom scrape the ground under it, making striations
glaciers pick up lots of sediment as they advance over the land
Glaciers pick up lots of sediment as they advance over the land.

http://www.geographyjim.org/Newzealandglacier.jpg

slide18

Valley glacier features

http://daac.gsfc.nasa.gov/DAAC_DOCS/geomorphology/GEO_9/geo_images_9/Fig9.20.gif

cirque
Cirque
  • A bowl-shaped depression located where a glacier begins to form
slide21
Horn

Kinnerly Peak - Glacier National Park

  • A tall, pointed rock peak left at the top of a mountain

http://www2.nature.nps.gov/geology//parks/glac/car0348.jpg

the most famous horn in the alps the matterhorn
The most famous horn in the Alps… The Matterhorn
  • Located on the boundary between Switzerland and Italy, the Matterhorn’s summit is 4478 m above sea level.
v shaped valleys become u shaped valleys as glaciers move through them
V-shaped valleys become U-shaped valleys as glaciers move through them…

Step 2

Step 1

A typical river valley

Over time, running water cuts a deeper V-shape.

Step 3

Glacier fills valley, widening and straightening the channel

Step 4

Glaciers melt leaving a U-shaped valley

hanging valley
Hanging Valley
  • a small valley that has not eroded as deep as the main valley that it is connected to
  • Waterfalls often form at hanging valleys.
slide30

Continental features

Striations- parallel scratches made from rocks in ice scraping against bedrock

slide32

Kettle Lakes

A shallow body of water made from ice blocks

glacial deposition
Glacial Deposition:
  • Drumlins--hills of sediment deposited by the glacier- till
glacial deposition1
Glacial DEPOSITION
  • Eskers
    • Winding ridges of stratified drift
    • Deposited by meltwater streams
    • Mined for gravel (aggregate)
glacial deposition2
Glacial DEPOSITION
  • Kames
    • Cone shaped stratified deposits
    • Deposited at end of

meltwater streams

moraines
MORAINES

moraine

  • MADE OF TILL- unsorted sediment

outwash

http://www.helsinki.fi/~jhyvonen/PB/M/Cerro%20Tronador%20moraine-pp.JPG

moraines1
Moraines
  • Terminal Moraine – Till deposit that marks the furthest advance of the glacier.
  • Recessional Moraine – Till deposit that marks pauses in the ice fronts retreat

Till (moraine)

slide41

moraine

outwash

ground moraine flat till deposits between recessional moraines
Ground Moraine- flat till deposits between recessional moraines

Recessional moraine

Recessional moraine

Ground moraine

Terminal moraine

outwash

other moraines
Other Moraines
  • Lateral Moraines- These are on the sides of valley/mountain glaciers
  • Medial Moraines – When two glaciers run along one another/collide these moraines form.
  • Both are composed of till
types of glacial sediment
Types of Glacial sediment:

ERRATICS-

  • Boulders carried great distance by the glacier
  • Don’t match surrounding rock
types of glacial sediments drift
Types of Glacial Sediments (drift)
  • TILL- unsorted; deposited by ice
  • STRATIFIED DRIFT- layered (sorted into layers by size); deposited by meltwater streams
  • OUTWASH- sorted sand; deposited by meltwater
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