Over five hundred million years ago, there was an ocean between the separate continents of Asia and India. Each year as the tectonic plates of the earth shifted, India moved 10cm toward Asia. When it finally collided with Asia fifty million years ago, that ocean receded as the Tibetan plateau raised higher and higher. As India gradually pushed another 2000km into Asia, parts of the sea floor were forced upward to form the Himalayan mountains -- in some places pushing fossils of ancient ocean creatures more than a mile above sea level. The land that makes up Bhutan was created in this continental collision. It lies on the southern rim of the Himalayan mountain chain that was thrust upward when the Indian peninsula rammed into Asia.

As time went on, rivers cut V-shaped valleys between the newly formed mountains. During the ice age, the movement of glaciers carved the valleys into a U shape. After the glaciers retreated, the rivers once again began to wear V shaped clefts into the valley floor.

The formation of mountains ended 37 million years ago. But the Indian subcontinent is still moving, and people in Bhutan often experience the consequences of this movement as earthquakes.