Cave/Karst Systems

The main entrance to Oregon Caves, a rare marble solution cave.

A cave is a natural void beneath the land surface that is large enough for a human to fit into. A cave system refers to a group of interconnected or related caves like Mammoth Cave System in Kentucky. The study of caves, cave systems, and karst landscapes is called speleology (from the Greek spelaion, meaning cave). Speleology encompasses many different aspects of science including geology, chemistry, hydrology, meteorology, and even microbiology.

 

Cave Types

There are many different types of caves that differ greatly in origin and appearance. Caves are most commonly classified by origin, how they formed. This includes:

• Solution (Dissolution) Caves: Solution caves are the largest and most common caves in the world. They form by the dissolving action of underground water and naturally occurring acid (like carbonic acid) as it passes through pores and fissures in soluble carbonate bedrock like limestone and evaporites like gypsum. That dissolving process is called dissolution. Oregon Caves is an example of one of the rare solution caves that occur in marble. Other examples of solution caves include Mammoth Cave in Kentucky, Carlsbad Caverns in New Mexico, and the largest cave currently known, Hang Sơn Đoòng Cave in Vietnam.
• Volcanic Caves: Volcanic caves, also known as lava caves, are typically formed when lava erupts to Earth’s surface and cools to form a crust on the outer surface. The remaining liquid underneath flows out to leave a hollow space or tube. Volcanic caves are most commonly found near volcanic peaks that are either still active, periodically active, or have been active in the last few thousand years. Examples of volcanic caves are common found on the islands of Hawaii or in previous volcanically active areas like in central Oregon, California (Lava Beds National Monument),or Idaho (Craters of the Moon National Monument & Preserve).
• Glacier Caves: Glacier caves form within the ice of a glacier. Although they are often called ice caves, this term is better used to describe bedrock caves that contain year-round ice. Glacier caves are often carved out by water running through or under the glacier's ice.
• Erosion Caves: Erosion caves are rare and small in size. They form entirely by flowing water and streams that carry rocks and other sediments. These can form in any type of rock, including hard rocks such as granite. Generally there must be some zone of weakness to guide the water, such as a fault or joint. A subtype of the erosional cave is the wind or aeolian cave, carved by wind-born sediments. Sea caves are a common example of erosional caves.
• Talus Caves: Also known as boulder caves, talus caves occur in the voids between boulders in talus piles at the bases of cliffs or steep slopes. Talus caves can form in all rock types but tend to favor regions with little soluble or volcanic rock. Large talus caves are rare.

This classification scheme can be difficult, as caves can have multiple origins or the origin may be unknown. Artificial mines and tunnels are not considered caves but can have natural deposits like a true cave.

 

To learn more about caves and the formations that occur in them please visit our Speleothems page.