At first glance, the Tibet and Appalachian Plateaus appear to have nothing in common. The first is a high, stark, arid landscape while the latter is a heavily vegetated, humid swath of ridges and valleys. And while the Appalachian Plateau covers a large area, from Upstate New York to northern Alabama, the Tibet Plateau, the largest highland region in the history of our planet, is equal to half the area of the lower 48 States.
But from a natural history perspective, the two Plateaus were formed in a similar manner and may have looked much alike at different times in Earth's history. During the Permian Period, about 250 million years ago, the North American and African Plates collided as the megacontinent of Pangea formed. This collision forced up the Southern Appalachians and the adjacent Appalachian Plateau. Much later, about 55 million years ago, the Indian subcontinent began to collide with southern Asia, a process that continues today. This impact created the Himalayas and forced up the Tibet Plateau.
Over time, erosion has taken a toll on the Appalachians, where maximum elevations are now below 7000 feet. By contrast, the young Himalayas harbor the highest peaks on earth and the Tibet Plateau has an average elevation over 16,000 feet. Of interest, the Tibet region was originally formed by four separate exotic terranes that merged (in sequence) with the southern edge of Central Asia; mimicking the assembly of the Western U.S., this process occured during the Paleozoic and Mesozoic Eras, well before the Cenozoic uplift.