The Himalayan Mountains
Comparison With the Late Paleozoic Alleghanian Orogeny
Mission to Earth: Landsat Views The World: NASA, 1976
Landsat imagery of the kingdom of Nepal, located between India and Tibet, including the Himalayan mountains. Asia is to the north (top) and India to the south (bottom). The mountains were compressed and thrust faulted when the Indian continent slammed into Asia, and then plunged under it along a great thrust fault.
The Siwalik Hills (bottom-most deep red colored hills) are low, approximately 3300-4300 feet, which is still higher than most mountains in the Mid-Atlantic region today. The more rugged Lesser Himalayans to the north of the Siwalik Hills are around 10,000 feet. This is close to the height of the Colorado Rockies, whose highest peaks are something over 14,000 feet.
Further north, in the white snow-covered peaks, are the highest mountains in the world, ranging from 20,000 to 29,000 feet. Mt Everest, the highest peak in the world is toward the upper right of the picture. It is twice as high as Pikes Peak in Colorado, and about ten times higher than the Blue Ridge
The Late Paleozoic Alleghanian orogeny along the east coast of North America was the result of a similar mountain building event. If reconstructing the orogeny in North America, Africa would be at top of the landsat image, forming the bulk of the mountains, but sitting on top of the edge of North America. The North American Craton
would be at the bottom of the image. The Allegheny Front
might run right along the edge of the Siwalik Hills.
One of the main differences in this comparison is that Relative Sea Level
was higher during the Alleghanian orogeny and, so, much of North America was under water. Sediments eroding from the Allegheny mountains then poured into those seas building deltas and forming Coal
Contributed by Lynn Fichter