TeXes Science Practice Test

What substance is primarily responsible for the erosion process that forms caves?

1. Granite

2. Limestone

3. Basalt

4. Sandstone

The correct answer is: Limestone

Limestone is primarily responsible for the erosion process that forms caves due to its solubility in acidic water. When rainwater mixes with carbon dioxide in the atmosphere and soil, it forms a weak carbonic acid. This acidic water can easily dissolve limestone, which is primarily composed of calcium carbonate. Over time, the continuous dissolution of limestone creates underground cavities and passages, leading to the formation of caves. In contrast, granite, basalt, and sandstone are less susceptible to chemical weathering because they are harder and less reactive with acidic solutions. Granite, a hard igneous rock, does not dissolve like limestone does, nor does it have the same capacity to form solution caves. Basalt, also an igneous rock, generally forms different types of landforms and is not typically involved in the formation of caves. Sandstone, while it can erode, does not undergo the same chemical weathering process that is responsible for cave formation in limestone. Thus, the unique properties of limestone make it the primary rock type associated with the cave formation process.