A fast-moving ice or ice stream is a region of an ice sheet that moves significantly faster than the surrounding ice. Ice streams are a type of glacier. They are significant features of the Antarctic where they account for 10% of the volume of the ice. They are up to 50 km wide, 2 km thick, can stretch for hundreds of kilometres, and account for most of the ice leaving the ice sheet.
The speed of an ice stream can be over 1,000 metres per year, an order of magnitude faster than the surrounding ice. The shear forces at the edge of the ice stream cause deformation and recrystallization of the ice, making it softer, and concentrating the deformation in narrow bands or shear margins. Crevasses form, particularly around the shear margins.
Most ice streams have some water at their base, which lubricates the flow. The type of bedrock also is significant. Soft, deformable sediments result in faster flow than hard rock.
Read more about Ice Stream: Antarctica, Greenland
Famous quotes containing the words ice and/or stream:
“Every incident connected with the breaking up of the rivers and ponds and the settling of the weather is particularly interesting to us who live in a climate of so great extremes. When the warmer days come, they who dwell near the river hear the ice crack at night with a startling whoop as loud as artillery, as if its icy fetters were rent from end to end, and within a few days see it rapidly going out. So the alligator comes out of the mud with quakings of the earth.”
—Henry David Thoreau (1817–1862)
“They who know of no purer sources of truth, who have traced up its stream no higher, stand, and wisely stand, by the Bible and the Constitution, and drink at it there with reverence and humility; but they who behold where it comes trickling into this lake or that pool, gird up their loins once more, and continue their pilgrimage toward its fountain-head.”
—Henry David Thoreau (1817–1862)