During the Pleistocene epoch or Mesolithic period about 10,000 years ago, there was a 5 degrees Celsius drop in the global temperature. At mountaintops, snow accumulated as ice caps and glaciers (including Mount Kinabalu), thus disrupting the global hydrological cycle. Due to lack of water discharge into the sea, the sea level was 120 meters lower than it is today. The South China Sea dried up, exposing the Sunda Shelf and previous deep trenches became huge ancient rivers called the North Sunda River.