Caves and Karst in Tropical Thailand – Krabi
by Matt London
Krabi (Kra-bee) holds some of the worlds most magnificent scenery and abounds with towering limestone mountains and caves. Perhaps the most Rising high above the subterranean valleys or plains below, these “tower” like mountains are distinguishable by their sheer cliff walls are indeed referred to as “Tower Karst”.
It’s hard not to wonder in awe at how the massive karst monuments towering above deep flat interior valleys and the beautiful Andaman sea far below had been formed and just how much the landscape must have been changed over the last 25-30,000 years or so… Indeed the giant foreboding Karst Towers that cast their long shadows and the deep flat interior valleys far below are both directly related to the rapid “dissolution” of limestone (Moore 1952).
In tropical climates a thick warm organic blanket of fertile soil, laying near the surface, forms a lid or cover that holds in carbon dioxide. This carbon dioxide later combines with rain water to form a weak carbonic acid that interacts with the limestone layer below. The limestone that lays underneath this organic layer is slowly removed or dissolved over time forming into the lowland flat areas or plains termed ‘interior valleys’
The development of the “Tower” Karst features require that the dissolution process that effects the limestone is faster then the “normal” erosion process that affects all other kinds of rocks in the proximity.
Where moisture or humidity is insufficient and/or lower surface temperatures prevail, the distinctive Tower Karst landscape can not develop. Because in cold and arid terrain, where dissolution is slow, the limestone tends to form mountains, where as in warm humid areas, like those found so predominately throughout South East Asia, the dissolution process is accelerated and the limestone can develop into the magnificent Tower Karst type landscape found in Krabi and the south of Thailand.
The Speed of Erosion
Dissolution type erosion on Limestone in the tropical setting is much more rapid if compared to limestone in colder climates. Limestone in hot humid climates tends to erode more rapidly to base level (short lived) than Limestone in colder climates. As a consequence the great Karst and cave areas of the world can be found in two distinct settings: warm tropical regions of rapid mountain uplift, and colder arid regions where limestone beds are being exposed by the faster mechanical erosion of surrounding “non-carbonic” rock cover.
NOTE: Please stay out of caves unless cave trained!
REFERENCES:
- Speleology, The Study of Caves by George W. Moore, G Nicholas Sulivan
- Annals of the Former World by John McPhee