TheBaltoro Glacier in the Karakoram Mountains. 62kilometres (39 mi) in length, one of the longest alpine-type glaciers
Aglacier is a large body ofice andsnow. It forms because the snow in an area does not all melt insummer. Eachwinter, more snow is added. Theweight of all the snow createspressure. This pressure turns the lower parts of the snow into ice. After this happens for many years, the glacier will start growing large. It becomes so heavy thatgravity causes the ice to move. It flows downwards like water but very slowly. A glacier only moves about 50 metres (160 ft) per year. New snowfalls replace the parts that flow away.[1][2]
Icebergs breaking off glaciers at Cape York,Greenland
Glaciers will only form in places that are cold enough and get enoughsnow over time. This can take a long time. It often takes tens or hundreds of years for a glacier to form. There are two kinds of glaciers:continental glaciers andalpine glaciers. Alpine glaciers are also calledmountain glaciers.
Continental glaciers are glaciers that spread out over a large area of land. They were created mostly during theIce Ages a long time ago. There are still some continental glaciers inGreenland andAntarctica. They often flow downwards into thesea and break up. The broken parts that float in the sea are calledicebergs.
Alpine glaciers form inmountain areas. They are smaller than continental glaciers. Alpine glaciers usually flow until they reach a point where thetemperature is warm enough that the ice melts completely during thesummer.
Glaciers are very important. They have a large effect on theenvironment. They do this because they are very large and heavy. When they move, theyerode mountains and land. Also, since they froze long ago, snowcrystals and air bubbles inside are kept in good condition. These can provide a large amount of information forscientists. Recently glaciers have been melting more than they did in the past. Many scientists think this is happening becauseglobal warming is changing theclimate[source?].[3]
Glaciers are blue in color. This is because water is very good at absorbinglight. Only the strongest light, with the most energy, is able to escape. Blue is the color of light that has the most energy. Because of this, blue is the only color of light that can escape without being absorbed. The thicker the glacier is, the more blue it appears.
NOVA scienceNOW - A 7-minute video of the NOVA broadcast ofJuly 26, 2005. Hosted by Robert Krulwich, the video is about the world's fastest glacier and why it is moving too fast.
