Although caves are most widely known for their recreational opportunities, caves are important laboratories for scientists, archaeologists, and anthropologists as they reveal much about our previous geologic history and human habitation. Speleothems and layers of sedimentary rock allow us to study patterns of climate change and geologic events, while cave drawings and artifacts found in caves indicate that these systems were important to many early humans for shelter, religious practices, and cultural traditions. There are many different types of caves, found in nearly every climate, and they are widely distributed across earth’s surface.
Solution caves are the most frequently occurring. Solution caves form when water mixes with carbon dioxide creating a weak acid called carbonic acid. This acid is strong enough to dissolve soluble bedrock, like limestone, marble, dolomite, gypsum, salt, etc.
Lava tubes are caves that are carved out of volcanic rock by hot, flowing lava. These tubes are cylindrical and contain speleothems and mineral deposits unique to these types of bedrock.
Anchialine, or anchiahaline caves, are caves that are filled with saltwater. Most anchialine caves occur in coastal areas and are often associated with endemic species. In many cases, there is a layer of less dense freshwater, or a freshwater lens, that lies on top of the saltwater layer.
Caves can also form from the production of sulfuric acid from microbial activity. Bacterial colonies reduce sulfide, and when mixed with groundwater, generate sulfuric acid that dissolves porous bedrock.