Most caves of the world are dissolved by water containing carbonic acid, which percolates into underground limestone rock. However, our Carlsbad Caverns formed differently: it formed by a sulfuric acid mechanism generated by reactions related to nearby oil and gas fields. We will study all types of caves: carbonic acid caves, sulfuric acid caves, lava tube caves, caves formed in gypsum or halite (evaporite) rock, seacoast caves and ice caves. We will also learn about the beautiful mineral formations (speleothems) in caves and the microbes that live there. We will end the class by watching the NOVA video: Mysterious Life of Caves. Professor Hill is the author of the books Cave Minerals of the World and Geology of Carlsbad Caverns.