2GlaciersGlaciersA huge mass of ice slowly flowing over a land mass, formed from compacted snow in an area where snow accumulation exceeds melting and sublimation.Sublimation is the process in which a solid changes directly into a gas, or a gas changes directly into a solid.
4Formation Formation of Glaciers Generally, rain water quickly runs of and flows to rivers and oceans or seeps into the earth as ground water. However, at higher elevations, and in polar regions, water reaches the earth as snow and will remain as snow all year long.
5Snow Line These elevations are above the “snow line”. The snow line is defined as the elevation above which ice and snow remain throughout the year.The snow line varies around the earth.At the equator the snow line is about 5,500ft above sea level and at the poles the snow line is at sea level.
7SnowfieldA snowfield is an almost a motionless mass of permanent snow and ice.Snowfields are formed by an accumulation of ice and snow above the snowline.They cover most of the land near the poles and the tops of some mountains at lower latitudes.
11Glacial FormationDue to layers of accumulated snow, the pressure on the lower layers of the firn is great enough to flatten and squeeze out the air between the molecules. This forms glacial ice, which is a bright blue color that is a common characteristic of glaciers.When the snow and ice accumulate to a great enough thickness, that the ice starts to move downslope due to gravity, a glacier is formed.
13Types of Glaciers Types of Glaciers There are two main types of glaciers: Valley Glaciers and Continental Ice Sheets.
14Valley GlaciersA valley glacier is formed in mountainous areas, but is named after the ice has moved down into the valley.Valley glaciers are defined as long, narrow, wedge-shaped masses of ice, and are common in high mountain regions such as Alaska, the Himalayas, the Andes, the Alps, and New Zealand.
16Continental Ice Sheets Continental ice sheets cover millions of square kilometers and are found only in Greenland and Antarctica.The Antarctica continental ice sheet is one and a half times as large as the mainland US, and is as thick as 4,000m.
18Continental Ice Sheets The Greenland continental ice sheet covers 90% of Greenland and is over 3,000 m at its maximum thickness.If these two ice sheets were to melt, the water would raise worldwide sea levels by more than 60 meters.
20Glacial Movement Movement of Glaciers On average, a glacier moves about 100m per year. However, some only travel a few centimeter and some a kilometer or more.Glacier movement is categorized into two different processes: Basal Slip and Internal Plastic Flow.
21Basal SlipBasal Slip occurs when the pressure of the ice is great enough to melt the ice at the bottom of the glacier that is in contact with the land. This, now water, acts as a lubricant and allows the glacier to “slip” forward.Basal slipping also allows water to melt, move around a barrier, and refreeze to move the glacier forward.
22Internal Plastic FlowInternal plastic flow is the process in which solid ice crystals slip over each other, causing a slow forward motion.The speed of internal plastic flow varies throughout the layers of the glacier. Areas of less friction, such as top and center, flow quicker than areas that are in contact with the earth.
23Glacial Features Glacial Features Crevasses are large cracks formed in the brittle surface of the glacier by buckling of the ice from tension and compression.