Experts have a few assumptions of the origin and history of the magnificent hills' formation. Some of the theories included the seafloor's uplift, sub-oceanic volcanic activity, and the simple weathering of limestone. Many geologists have argued about the origin of the Chocolate Hills.
It says on plaques displayed all around Carmen, Bohol's viewing deck is that the hills result from a geologic uplift hundreds of years ago where coral reefs have erupted from the sea. With wind, rainwater, and erosion, the coral deposits formed the Chocolate Hills thousands of years after.