when did the himalayan mountains start to form
Himalayas During the Upper Cretaceous, about 70 million years ago, the north-moving Indo-Australian Plate (which has subsequently broken into the Indian Plate and the Australian Plate[10]) was moving at about 15Â cm per year. 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 both plates were composed of low density continental crust, they were thrust faulted and folded into mountain ranges rather than subducting into the mantle along an oceanic trench.[9] An often-cited fact used to illustrate this process is that the summit of Mount Everest is made of marine limestone from this ancient ocean.[11]
Appalachian Mountains The Appalachian Mountains[a] (French: les Appalaches), often called the Appalachians, are a system of mountains in eastern North America. The Appalachians first formed roughly 480 million years ago during the Ordovician Period. They once reached elevations similar to those of the Alps and the Rocky Mountains before experiencing natural erosion.[4][5] The Appalachian chain is a barrier to east-west travel, as it forms a series of alternating ridgelines and valleys oriented in opposition to most highways and railroads running east-west.