There are two basic types of glacie

There are two basic types of glaciers, those that flow outward in all directions with
little regard for any underlying terrain and those that are confined by terrain to a
particular path.
Line The first category of glaciers includes those massive blankets that cover whole
(5) continents, appropriately called ice sheets. There must be over 50,000 square kilometers
of land covered with ice for the glacier to qualify as an ice sheet. When portions of an
ice sheet spread out over the ocean, they form ice shelves.
About 20,000 years ago the Cordilleran Ice Sheet covered nearly all the mountains
in southern Alaska, western Canada, and the western United States. It was about
(10) 3 kilometers deep at its thickest point in northern Alberta. Now there are only two
sheets left on Earth, those covering Greenland and Antarctica.
Any domelike body of ice that also flows out in all directions but covers less than
50,000 square kilometers is called an ice cap. Although ice caps are rare nowadays,
there are a number in northeastern Canada, on Baffin Island, and on the Queen
(15) Elizabeth Islands.
The second category of glaciers includes those of a variety of shapes and sizes
generally called mountain or alpine glaciers. Mountain glaciers are typically identified
by the landform that controls their flow. One form of mountain glacier that resembles
an ice cap in that it flows outward in several directions is called an ice field. The
(20) difference between an ice field and an ice cap is subtle. Essentially, the flow of an ice
field is somewhat controlled by surrounding terrain and thus does not have the domelike
shape of a cap. There are several ice fields in the Wrangell, St. Elias, and Chugach
mountains of Alaska and northern British Columbia.
Less spectacular than large ice fields are the most common types of mountain
(25) glaciers : the cirque and valley glaciers. Cirque glaciers are found in depressions in the
surface of the land and have a characteristic circular shape. The ice of valley glaciers,
bound by terrain, flows down valleys, curves around their corners, and falls over cliffs