Koalin Loess(Glacier&Periglacial landscapes) Essay

Koalin Loess(Glacier&Periglacial landscapes) - Essay Example a terrain: A terrane is a crustal block or fragment that preserves a distinctive geologic history that is different from the surrounding areas and that is usually bounded by faults. Accreted terranes are those that become attached to a continent as a result of tectonic processes. In more elaborate words, it is a large geographical feature, often a mountain range, that geomorphologists believe was once a group of islands that sat on one tectonic plate that was being subducted under a continental plate. When the part of the plate on which the islands rode began to be subducted, the islands jammed up the subduction zone and the plate behind it broke. As a result, the islands became attached to the side of the continent. As this happened again and again, the island arc became an inland mountain range. The Himalayas ,according to the modern theory of plate tectonics, was formed as a result of a continental collision or orogeny along the convergent boundary between the Indo-Australian Plate and the Eurasian Plate. This is referred to as a fold mountain. The collision began in the Upper Cretaceous period about 70 million years ago, when the north-moving Indo-Australian Plate, moving at about 15 cm per year, collided with the Eurasian Plate. About 50 million years ago, this fast moving Indo-Australian plate had completely closed the Tethys Ocean, the existence of which has been determined by sedimentary rocks settled on the ocean floor and the volcanoes that fringed its edges. Since these sediments were light, they crumpled into mountain ranges rather than sinking to the floor. The Indo-Australian plate continues to be driven horizontally below the Tibetan plateau, which forces the plateau to move upwards. The Indo-Australian plate is still moving at 67 mm per year, and over the next 10 million years it will travel about 1,500 km into Asia. About 20 mm per year of the India-Asia convergence is absorbed by thrusting along the Himalaya southern front. This leads to the