Caves and Caverns

We just returned from a family vacation that included a walking tour through the California Caverns in Mountain Ranch. For the rest of the week we pondered the question “What is the difference between a cave and a cavern?” As is typical in my family, everyone made up their own answer (“cavern is larger,” “cave is above ground,” “cavern is formed by calcite,” and so on.) I promised all that I would find the REAL answer and report it in my column, so here goes: the words are interchangeable!