End Of A Glacier Ice Moves example essay topic

Continental Glaciers The Action of Ice on Land As glaciers become extremely large, they eventually reach the lowlands, which is essentially more gentle terrain. As these huge glaciers reach the lowlands, they travel much more slowly, because they no longer have the steep mount ian sides to push the ice down faster. Once on the lowlands, the glacier spreads out for they are no longer restricted by valleys, and become known as Ice Sheets. As long more snow falls than ice melts, Ice Sheets will continue to expand. Ice Sheets NEVER move backwards- although they appear to do this when the melting process exceeds the accumulation process. Ice Sheets move by being pushed from up above by masses of ice accumulating in the higher valleys.

These ice sheets are capable of a lot of erosion, seen in the picture below. Erosional Features As seen in the above the picture, the land is fairly smooth, due to the continentalgalciers. The thick, heavy ice has cut some edges into the ground, but there are no high mountains, just a bit of rough topography. Ice Sheets often carry debris within their layers, due to erosion. In fact, the Canadian Prairies were largely formed by the deposition of sediment from these continental glaciers as they moved outwards from the centres of theice accumulations. The more debris that an ice sheet carries, however, the slower it moves.

The reason for this is that in order to carry millions of tons of solid material, such as dirt and rock, a lot of energy must be consumed, and these massive sheets don't have alot of energy to begin with. If the glacier runs out of energy, the erosion stops, and the debris is dropped off in dropping zones called drumlins. An example of a drumlin is shown in the photograph above. The diagram above shows the features of glacial deposition in Denmark, and north Germany.

The terminal moraine marks the place where the ice sheet melted as fast as it arrived. Here the debris piled up into a hil because the ice was no longer able to carry it along. Instead, some of the lighter material floats down with the water, and the fine material is sorted from the coarse at the outwash plain. Notice how the original land was flat and featureless, but after the continental glacier, some rough topography was formed. These ice sheets, however, due to their erosion capabilities, can also work to smooth some areas. Factors Affecting Ice-ages The Ice-age's biggest enemy is the climate's warming.

Glaciers have proven to be resilient, however, for they have returned and retreated three times in the past half a million years. Most of the Continental Glaciers that have melted are now higher up, an dare known as Alpine Glaciers. As the weather warms, there is less snow, and much of theice sheet melts into lakes rivers, and even oceans. One example of ice sheets melting isBritain's sheets that melted from the lowlands in just a couple thousand years. This may seem like a long time, but considering the magnitude of the glaciers (some get toapporximately 200 m deep), this is extremely rapid.

The Continental Glaciers in North America disappeared within about 8000 years, but once they melted back to the base of mountains, their retreat slowed down because of the steep ascent of the mountains. Many glaciers stopped moving when they came to mountains, and instead deposited recessional moraines (to find out more about this, search under "Alpine Glaciers"). These moraines block valleys, such as the marines in Penticton, southern British Columbia. Most moraine, however, are washed away by rivers. According to Milutin Milankovitvh, the variation in the Earth's orbit through time has caused changes in the amount and the distribution of sunlight and other solar radiation reaching the Earth's surface. The Illinois State Museum says that the Earth's orbit changes approximately every 100,000 years.

In the orbit's more elliptical shape, there is great seasonal contrast in the not hern and southern hemispheres. For example, one hemisphere will have hot summers and cold winters, whereas the other hemisphere will be the reverse. When the orbit is in its more circular shape, however, both hemispheres will have similar seasonal contrasts in temperature. This change in radiation, although small (0.2%), is extreme enough to expand and melt ice sheets.

The tilt of the Earth aslo affects radiation, and so therefore galciers in the same way as the orbit. End Of A Glacier Ice moves very slowly, but over millions of years a glacier can move a great distance and grow to a great size. Glaciers, being composed genrally of water, have the ability to move across land and pick land up for a slow motion ride. Ice moves from it " source by the pressure of pushing form the back of a glacier causing the front to move forward and take over more land. When the pressure from the back is no more then theice stops moving and genrally starts to cool down.

Streams of water begin nearly ten km back from the front of the glacier and slowly run and move there way down into the glacier until the are flowing across the ground, here they lay sediment and carve there way into the earth. The carves in the earth form gravel beds and are called eskers. When the front of a glacier is really warm and melting very fast the water pours out from all sorts of holes and caves onto whatever plain is out front. This deposits lots of gravel intothe plan and a forest soon grows over and the land is hard to recognize. Kinds Of Movement There are three main ways that glaciers move; they are internal deformation, basal sliding, and deforming substrate. With internal deformation the ice deforms under it " sown weight because of gravity.

Temp., thickness of the ice, and pressure all effect the rate at which the glacier will move. Movement here is slow and around ten to twenty meters per year. Basal sliding is when the base of an ice sheet is near the pressure melting point and water is being made present. The larger the ice sheet the less likely this will happen because at the bases of huge ice sheets the temp. for melting is -1.6 deegreescelcius.

Water reduces friction and allows the ice to move faster in response to gravity. Basal sliding can move an ice sheet up to a few hundred meters a year and it erodes landscapes very badly. Water is not the only thing that induces sliding or movement. The sediment under the glacier (if it's weak) can give way to the big weight. If the sediment has a little water in it than the glacier might tend to use it as a water slide. Depositional Features Millions and millions of tonnes of ice pushed, crushed, and carved their way through all the geographical features of yesterday and made them what they look like today.

Along the way the ice picks up rock and dirt of all sorts, in small and big quantities moving it around and setting it down in a different place. When a glacier becomes saturated with rocks and can no longer move it begins to melt leaving drumlins and eskers, and from the eskers: stream plains. The glaciers, due to the enormous amount of pressure within, could shove anything in it's way easily to the side. Deep trenches where rivers now rule are foot prints of glaciers as well as drumlins lining themselves across Canada.