MADE OF CORAL
Palawan's limestone was created by coral reefs over 50 million years ago. Corals growing at that time produced huge quantities calcium carbonate - the main component of limestone.
The islands that make up the northern half of modern-day Palawan lie on on Sunda Plate and, until around 33 million years ago, were part of mainland Asia. While it drifted south-eastwards to its current position, the limestone was eroded and what we see now are the remnants of a much larger rock formation that has been weathered and broken up over millions of years.