A glacier is a persistent body of dense ice that forms on land from the accumulation of snow over many years, centuries or millennia. Glaciers flow slowly as a result of their own weight and gradually deform and create crevasses and other distinguishing features. They also abrade the underlying rock structures to create characteristic landforms such as cirques, moraines, and fjords. Glaciers are distinct from the much thinner layers of ice that form on the surfaces of bodies of water. Most of the world’s glacial ice is found in Antarctica and Greenland, but glaciers also exist on every other continent except Australia. The largest glacier is the Lambert glacier in Antarctica, which is more than 60 miles wide at its widest point, about 270 miles long, and about 8,200 feet deep at its center.
Glaciers, as well as ice sheets, worldwide are shrinking at an accelerating pace as a result of global warming. This shrinking is the major cause of the continual rise in sea levels, which will eventually have disastrous effects, particularly for heavily-populated costal areas and coastal ecosystems. The loss of glaciers will also result in less water being available for human consumption, for irrigation, and for hydroelectric power generation. In addition, it could disrupt, or even halt, the major ocean currents, thereby not only severely affecting marine life and fisheries, but also bringing about severe changes in climate to some heavily populated regions such as Western Europe.
The shrinking and loss of glaciers will also lead to the extinction of numerous species of animals and plants, both terrestrial and aquatic, whose natural habitats are on or near glaciers or the rivers and other water bodies they sustain and which play an important role in the food web. This is because glaciers act as reservoirs that contribute water to the ecosystems throughout the dry months, creating perennial stream habitats for many species. This cold runoff also affects downstream water temperatures, and thus protects many aquatic species which are particularly sensitive to higher temperatures.