<P> The origin for the conical karst of the Chocolate Hills is described in popular terms on the bronze plaque at the viewing deck in Carmen, Bohol . This plaque states that they are eroded formations of a type of marine limestone that sits on top of hardened clay . The plaque reads: </P> <P> The unique land form known as the Chocolate Hills of Bohol was formed ages ago by the uplift of coral deposits and the action of rain water and erosion . </P> <P> The plaque also makes reference to a fanciful explanation of the origin of the Chocolate Hills that is unsupported by any published scientific research, i.e. either Hillmer or Travaglia and others, when it states: </P> <P> the grassy hills were once coral reefs that erupted from the sea in a massive geologic shift . Wind and water put on the finishing touches over hundreds of thousands of years . </P>

What are the chocolate hills in the philippines