Geologists believe that some 225 million years ago India was a large island off the Australian coast located well south of the equator. A vast body of water called the Tethys Sea separated India and Asia.

But over millions of years India moved north until it eventually collided with Asia about 40 to 50 million years ago. When the two landmasses smashed together the Earth’s crust crumpled and folded. Because both landmasses have roughly the same rock density, the only way to relieve the pressure was for the Earth to thrust upwards -- creating the jagged peaks of the Himalayan Mountains and the Tibetan plateau.

The speed of India’s northward progression was cut in half after the collision, but it does still continue to push north and slide under Asia. As a result, the Himalayas are still growing at a rate of 2.4 inches every year. But with the unbelievable amount of foot traffic this mountain sees during the climbing seasons, it's possible that climbers are eroding it just as quickly. Mount Everest itself is actually moving about 27 millimeters northeast a year. Because of this movement, tremendous stresses build in the Earth’s crust and are relieved through earthquakes throughout the region.

Under the massive heat and pressure caused by the collision, the rocks changed repeatedly. The Everest massif (which includes the peaks of Everest, Lhotse, Nuptse, and Changtse) is a showcase to the history of these changing rocks. The Himalayas are one of the best places to study the mountain building process.

The lower area of the Everest massif shows a history of rock that was heated and reheated under extreme pressure. The result is course and crystalline schist that splits easily into thin sheets.

Above the schist is a large outcropping of granite, an igneous rock formed under intense heat. This granite is very evident on the lower Nuptse-Lhotse wall. Granite is light in color and is known to erode in blocks.

Above the granite is a sedimentary rock that, in this case, was formed when material was deposited as sediment to the ocean floor and then was consolidated by the collision pressure. It’s shale, limestone, and sandstone. This is the area climbers know well as the famous Yellow Band.

And the Summit Pyramid itself is comprised of a gray, sandy, limestone. It’s amazing to think that this, the highest point on Earth, was actually a deep seabed some 325 million years ago.