An agent of erosion, weathering, and deposition Ice--Glaciers by Moira Whitehouse
Glaciers form when, over many years moresnow falls each year than melts. As aresult, a deep layer of compacted snowaccumulates. This layer of snow becomescompressed into a thick sheet of ice.What makes glaciers unique is that theymove. Due to their mass and the force ofgravity, glaciers flow down hill a fewinches or feet per year.
These great sheets of ice– glaciers--create landforms through both erosionand deposition.
There are two types of glaciers:1. Continental glaciers--glaciers that form over large areas of continents close to the North and South Poles.2. Mountain glaciers--relateively small glaciers that form near the tops of mountains.
Continental glacier in Antarcticahttp://www.coolantarctica.com/gallery2/glaciers/Glacier-10.html
Mountain glacier in the Rocky Mountains http://pics4learning.com
During the past IceAges, very thickcontinental icesheets overlaid muchof the continent ofNorth America asshown in this diagram.These very thickglaciers covered allbut the highestmountains andresulted in significant Grey shaded area—continental glacierserosion.
Many lakes in North America including the GreatLakes, were created by glacial moving over therock and gouging out deep “holes” which filledwith water when the glaciers melted. Wikipedia Commons
In the last glaciation period, which endedapproximately 10,000 years ago, 32 percent ofEarths land area was covered with glaciers.Glaciers now cover only about 10 percent ofthe land area.
That glacial ice is found mainly over Antarctica.Most of the other glaciers cover Greenland; theremaining small percentage are mountain glaciersfound in places such as Alaska, the CanadianArctic, New Zealand, the HimalayanMountains, the Rocky Mountains and the Alps.
Glaciers are not landforms. The action ofglaciers, however, creates landforms.Glaciers move, and as they do, they scourthe landscape, "carving" out landformsand eroding material.This happens because friction breaks thebedrock into pieces of smaller rock andsoil. This debris becomes embedded inthe bottom of the moving glacier and iscarried downhill.
Like a big bull dozer, glaciers drag and push rocky debris downhill to the end of their travel for that winter (or for that ice age).As theymove, the rocksand soil stuck inthe bottom ofthe glacierscrape andscratch the landunderneaththem.In the photo above, you can see these “scratches”.
Imagine that scrapping continuing for millionsof years and you can see how glaciers turnV shaped valleys into U shaped valleys.
http://www.flickr.com/theslowlaneAs the glacier moves through a V-shaped valley,it sculpts a “U”.
A horn is apyramid-shapedmountain peakcreated byseveral glacierseroding away atdifferent sides ofthe samemountain. http://www.geology.wisc.edu
Glaciers leave a predictable mark on thelandscape through their deposition.As the weather warms, glaciers pullback, leaving deposits of the rockymaterial along the sides and at theend of their travels.This deposition creates landformfeatures called moraines.
Rocks and . sediment deposited on the sides orWikipedia Commons the end of glaciers create moraines, like these. Wikipedia Commons
It seems that many of the world’s glaciers areshrinking or disappearing as the earth heatsup. They are awesome sights. Hope you getto see one.