The Beauty of Bohol Chocolate Hills

About two million years ago, most of the island of Bohol was below a shallow sea. Coral reefs, similar to those now found offshore of northern bohol, thrived and extensively covered the sea floor.


During stormy days, fragments of corals and shells derived by waves from the reefs were deposited mostly at the landward side of the reefs. The coral and shell fragments formed relatively thin layers (brown) surrounding the live coral reefs (pink). Slowly, the land rose causing the coral reef formations to emerge out of the sea. This is the reason why the southern sections of bohol island had been uplifted more than the northern section.

The unique land-form known as the "Chocolate Hills" of bohol was formed after ages of coral deposits and the action of rainwater and erosion. Gullies were developed in the low lying areas and lakes occupied pre-existing depressions.

Coral and Shell fragments are largely composed of calcium carbonate, a chemical compound which can be dissolved by acidic solution. Rainwater becomes slightly acidic by dissolving some carbon dioxide from the atmosphere. Thus, rainwater can dissolve coral and shell fragments but this happens very slowly. With rainwater acting on the layer of coral and shell fragments for tens to hundreds of thousand of years. Gullies were deepened and widened to become streams. Lakes were emptied by underground rivers and interconnected conical hills were formed from the original flat surface.

When the base of the soluble formation was reached, downcutting ceased and lateral erosion became dominant. Valleys were widened, the remnant of the layers in the highly dissected areas were dissolved away, and the connections between neighboring hills were also dissolved away. Thus, the chocolate hills that you now behold are products of the patient laboring of rainwater on a thin soluble limestone formation.

These hills scattered throughout the towns of Carmen, Batuan and Sagbayan, and consist of  1,268 mounds of the same general shape.

The area is located in the town of Carmen in Bohol and was once called as Carmen Hills but due to the seasonal change of weather, these hills change its color from green on rainy seasons and brown on the summer which gave the idea of a chocolate hill.

To have a 360 degree view, tourists must climb up on a stairway with 220 steps above the hill.