1) Exploring underground spaces 
Caving — also traditionally known as spelunking in the United States and Canada and potholing in the United Kingdom and Ireland — is the recreational pastime of exploring wild (generally non-commercial) cave systems. In contrast, speleology is the scientific study of caves and the cave environment. The challenges involved in caving vary accord...
• (p. pr. & vb. n.) of Cave
The entering and exploration of caves.
collapsing of the walls of the wellbore. Also called sloughing. 
The sport of cave exploration using many of the same techniques and gear as climbing.