Phenomenon: Approximately 27.5% of Puerto Rico's surface is covered by a limestone region known as the karst belt, featuring some of the most spectacular landforms in the world, including mogotes (hummocks), extensive underground cave systems (like the Río Camuy Caves), and deep sinkholes (dolines).
The Science (HS-ESS2-5)
This topography is formed through chemical weathering. When rain falls through the atmosphere and decaying organic matter in the soil, it absorbs carbon dioxide (CO2), forming a weak carbonic acid (H2CO3).
This acidic water percolates through fractures in the limestone bedrock (CaCO3), slowly dissolving the rock over thousands of years and carrying the calcium and bicarbonate ions away in solution. This demonstrates water's unique property as a nearly universal solvent.
Simulation Instructions
- Rainfall: Increases the volume of water available to dissolve rock and fill the underground freshwater aquifer.
- Acidity (pH): Lower pH means stronger acid, which exponentially increases the rate at which limestone dissolves. (Note: Pure rain is slightly acidic at pH ~5.6, but acid rain can drop lower).
- Fractures: More cracks in the rock allow water to channel downwards faster, creating vertical sinkholes rather than just surface erosion.