year around. Humidity and warm temperature provide the optimal environment for a rich eco-system in this tropical rain forest. Natural History 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. Human History The first migrants to Thailand migrated during the Ice Age from Borneo around 37,000 BCE. The first accounts of people living in Khao Sok were found in the 1800s, during the reign of Rama II. In the Burmese-Siamese of (1809-1812), the Burmese army invaded the western portion of the area, forcing the inhabitants to flee inland. They found the area to be extremely alluring, in beauty, wildlife abundance, and good soil. As news spread of this discovery, more people immigrated to settle the region. In 1944, the inhabitants of this region were stricken by a deadly epidemic. A large number of the villagers died while the few survivors escaped from the area to settle in nearby Takua Pa. In 1961, Route 401 was built from Phun Pin in Surat Thani Province to Takua Pa in Phang Nga Province. At the turn of the millennium, they began the process of expanding Route 401 to a 4 lane freeway. In the 1970s, Thai student activists and communist insurgents set up strongholds in the caves of Khao Sok. Settled in the shelter of the rainforest they protected the region from the Thai army, loggers, miners, and hunters for seven years. Khao Sok became a national park in 1980. The government and the Electricity Generating Authority of Thailand (EGAT) were interested in this region because Khao Sok holds the largest watershed in southern Thailand. Only 2 years later, EGAT completed the high Ratchaprapha Dam, blocking off the Klong Saeng