CHAPTER THIRTY, in which the town realizes Becky and Tom are lost in the cave

CHAPTER THIRTY on Project Gutenberg

Most people remember them by their spelling: stalagmites come from the ground, and stalactites hang from the ceiling.  Stalagmites and stalactites form by deposits, the slow drip of calcite-rich water, developing over eons.  However, one cave formation occurs from erosion. 

Your mission for this chapter:

With the website below, answer the following question.  What are formations occuring from erosion called?

Use this website: http://www.goodearthgraphics.com/virtcave/virtmap.html