A. Question the students on how many of them have been in a cave, what they think a cave is, how caves form, if they know any of the names of the formations in caves, what live in them, etc... Those aspects about caves vary quite a bit, so accept just about any answer. Aside from getting them psyched to learn more, you'll learn what they think about caves, which will give you a base to build on.

B. You might explain at this point that there are several types of caves, and that you're going to be studying mostly one type, solutional caves. They form as acidic groundwater dissolves away the rock along a crack. The other types of caves that your students may have visited are lava tubes (which form as flowing lava cools), wind or sea caves (formed through the erosional action of wind or waves), or talus caves (these are the cracks between large piles of rocks and boulders). Almost all tour caves are of the solutional variety.