Upload
leo-king
View
213
Download
0
Tags:
Embed Size (px)
Citation preview
Slide 1
Glacial ErosionCh 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 Earths 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:Alpine (aka Valley)Continental (ice sheets)Mountainous areaslong, narrow-wedged mass of iceBest developed valley glaciers found in Alaska, the Himalayas, the AlpsCovers large land areasFound only in Greenland and Antarctica today
Valley Glacier
The Antarctic Ice Sheet is 1.5 times the size of the US and in some places more than 4,000 m thickContinental ice sheet
How Glaciers form:
Step 1: Snow accumulates.More snow falls during the winter than melts in the summer.
http://tlhwy.com/south/winter/index.htmlTrans-Labrador HighwayWOAH!Step 2: Snow changes to firn.
As snow accumulates, its weight compresses the individual snowflakes to form firn.
Step 3: Firn is compressed to form solid glacial ice
Step 4: The ice begins to move.
ValleyContinentalSome FactsGlaciers hold 75% of the Earths fresh water.10% of land is covered by them.If they all melted the sea level would go up about 70mArtic ice is over 4,200 m thick in some spots.2 types glacial movement:Basal SlipInternal plastic flow
The weight of the ice exerts enough pressure to melt the ice where it contacts the groundThis melt water acts as a lubricant and allows the glacier to slip forward, including over small barriersThe weight of the ice and gravity causes the ice crystals to slip over each otherSpeed of this flow is faster nearer the surface and at its centerwhy?... friction!
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.
http://www.geographyjim.org/Newzealandglacier.jpg
http://daac.gsfc.nasa.gov/DAAC_DOCS/geomorphology/GEO_9/geo_images_9/Fig9.20.gifValley glacier featuresCirqueA bowl-shaped depression located where a glacier begins to form
http://crevassezone.org/Photos/Graphics/4163L-(Cirque).jpgHornA tall, pointed rock peak left at the top of a mountain
http://www2.nature.nps.gov/geology//parks/glac/car0348.jpgKinnerly Peak - Glacier National Park The most famous horn in the Alps The MatterhornLocated on the boundary between Switzerland and Italy, the Matterhorns summit is 4478 m above sea level.
Arete spines or ridges of rock that separate glacial valleys
U-shaped Valley - Yosemite National Park
V-shaped valleys become U-shaped valleys as glaciers move through them
A typical river valleyOver time, running water cuts a deeper V-shape.Step 1Step 2Step 3Step 4Glacier fills valley, widening and straightening the channelGlaciers melt leaving a U-shaped valleyU-Shaped Valley Formation
Hanging Valleya small valley that has not eroded as deep as the main valley that it is connected to
Waterfalls often form at hanging valleys.
Striations- parallel scratches made from rocks in ice scraping against bedrockContinental features
Kettle LakesA shallow body of water made from ice blocks
Glacial Deposition:Drumlins--hills of sediment deposited by the glacier- till
Drumlin Formation
Glacial DEPOSITIONEskersWinding ridges of stratified driftDeposited by meltwater streamsMined for gravel (aggregate)
Esker Formation
Glacial DEPOSITIONKamesCone shaped stratified depositsDeposited at end of meltwater streams
Kames
MORAINESMADE OF TILL- unsorted sediment
http://www.helsinki.fi/~jhyvonen/PB/M/Cerro%20Tronador%20moraine-pp.JPGmoraineoutwashMorainesTerminal 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)
moraineoutwashGround Moraine- flat till deposits between recessional moraines
outwashTerminal moraineRecessional moraineRecessional moraineGround moraineOther MorainesLateral Moraines- These are on the sides of valley/mountain glaciersMedial Moraines When two glaciers run along one another/collide these moraines form.Both are composed of till
Glacial DEPOSITION
MORAINES
Types of Glacial sediment:
Boulders carried great distance by the glacier
Dont match surrounding rock
ERRATICS-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