This area is estimated to be over 160 million years old, built through tectonic movements, climate changes, erosions and sediment accumulations. Approximately 300 million years ago, shallow water and warm temperatures in this region led to the creation of a huge coral reef. Estimated to be 5 times as big as the Great Barrier Reef in Australia, it originally stretched from China all the way to Borneo. Due to the collision of the Indian and Eurasian plate 0-66 million years ago, the Himalayas were formed, and what is now Thailand shifted dramatically near the continental divide and the limestone rocks were forced upward creating the dramatic limestone karsts for which the region is known today. Finally, melting ice established the river-rich landscape as well as dozens of waterfalls around the national park.