Glaciers

Glaciers are flowing masses of ice, created by years of snowfall and cold local temperatures. Approximately one tenth of the Earth is covered by glaciers. Glaciers are most numerous near the poles, covering most of Antarctica and Greenland and parts of Iceland, Canada, Russia, and Alaska; they also exist in mountainous regions on every continent except Australia. From the air, a glacier looks deceptively smooth and pliant; in reality, it is an abrasive mass that can reshape the Earth. The glaciers themselves are being reshaped by human activity. Recent measurements show that glaciers have been melting worldwide since the beginning of the Industrial Revolution in the mid-nineteenth century (when human beings first began to add large amounts of greenhouse gasses to the atmosphere). Water from melting glaciers is a significant input to rising sea levels worldwide, which threaten coastal ecosystems and the approximately 100 million people who live 3.28 ft (or about 1 m) or less above sea level.