Moving At A Glacial Pace How Glaciers Have Shaped Our World

From Snow to Ice When snow falls in the winter and does not melt in the summer or spring, this causes a positive feedback of snow accumulation. when snow accumulates, the pressure compresses the snow and changes the crystalline structure, causing the air to be expelled and more compact crystals to form

Glacier Movement A glacier moves the fastest in the center, similar to the hydrology of a river. Movement along the underside of the glacier is slower than movement at the surface due to friction along the grounds surface A glacier can flow far below the snow line, sometimes even reaching sea level, becoming “tide water” glaciers.

Glacial Movement Cont’d Once a glacial mass of compressed ice reaches a certain thickness (~20meters thick) it becomes heavy and starts to change shape and move. Combined with the pressure from the mass of the ice and gravity, they can flow very slowly downhill A glacier is also able to break free from the bedrock and glide across it, this is called BASAL SLIP

Continental Ice Sheets These are known as vast expanses of land that completely covers the underlying terrain and spreads outward in all directions. They play a major role in forming and maintaining the Earth’s climate because of their increased Albedo effect and impact on ocean currents The base of the ice sheet is generally wamer due to geothermal heat, in some places this can cause the underlying ice to melt and lubricate the ice sheet so that it flows more rapidly, causing ice streams

Ice Ages Some theories of how ice ages begin include the movement of land masses towards polar ice caps as well as wobbles and non-circular rotation of the Earth which causes global cooling. They have also been attributed to changes in the atmospheric composition of gases. –There is a theory that about BC prehistoric man, by killing the mammoths, removed a major grazing factor and ameliorated the growth of trees in the NA and EU tundra, which decreased the albedo effect and ended the last ice age There have been at least 5 major ice ages in the Earth’s past. Rivers run faster during ice ages because their base level is lower due to the high sea level, this causes downward erosion of streams

Glittering Glacial Caves Glaciospeleology: study of ice caves Formed in two ways: melting water runs through or under a glacier, or volcanic vents/hot springs underneath a glacier Located near meltwater streams pouring into or out of glaciers They are extremely ephemeral, sometimes the crevasses/caves are filled with meltwater and the next minute they are empty and dry This may be due to ice dams that form over the outlets or flow being higher at daylight hours