What is a cave?

An underground cavity that is normally formed by water dissolving the rock. Most caves are formed in limestone, but other host rocks include sandstone, granite, ice, volcanic tuff & basalt, marble & dolomite, and even mud.

What types of caves are there?

Classic Limestone Caves, Talus Caves, Sea Caves, Mud Caves, Ice Caves, Lava Tubes.

What types of caves are found in San Diego County?

Talus Caves, Sea Caves, and Mud Caves.

How are Talus caves formed?

San Diego Talus caves are made up of piles of large granite boulders that have active streams running underneath them. The water will wash away dirt and small rocks surrounding the boulders and leave empty cavities around the boulders. Usually the streams are running down a steep valley that helps hold the large boulders in place. Some Talus caves have boulders overlying a vertical joint that channels the water down the valley. Given enough time and water these vertical joints will be widened large enough so that the actual cave will be inside the joint. Talus caves above the bedrock joint are normally very mazey, as their passages meander around all of the boulders. Talus cave passages that lie in the joint of the bedrock are generally very straight with nearly perpendicular intersections of passages.

How are sea caves formed?

San Diego sea caves are cut into the coastal sandstone though tidal action. Most of these caves are also formed by widening of joints in the rock. Often these caves will also have sections that are wide and low. These sections are generally formed along the horizontal intersection of two different type of rock. Many San Diego sea caves are filled and emptied of sand with the changing ocean currents, as well as storms and human intervention.

Do San Diego caves have formations?

There are some simple formations in the local granite Talus caves as well as the sea caves. Cave formation such as stalactites and stalagmites are formed by water dissolving calcium (in limestone) and transporting it in liquid to the underground cave where it re-deposits the calcium as a formation. San Diego County does not have very much calcium in the soil, so there is not much to re-deposit. San Diego does have a fair amount of other minerals, so often the formations end up as interesting colors, though usually they are somewhat small.

What does the inside of a Talus cave look like?

The passageways generally follow a stream way, with small pools and waterfalls. The edges of the water are often coated with travertine (Calcium) that is deposited from the water. The granite boulders in the stream way are normally rounded and polished smooth, rocks on the edge of the passages are rougher and more rectangular. The cave passages in the joint layer are often vertical parallel walls that are smooth, polished granite.

How many caves are in San Diego County?

We know of about a dozen Talus caves and about forty sea caves. There are also about a dozen mud caves deep in the Anza Borrego desert. If you know of any others, we would love to hear about them.

How do I learn more?

Contact the NSS (National Spelelogical Society) or contact us (San Diego Grotto.)