Number 3 looks the best with number 1 following in second. 2 and 4 seem way to grainy. But since this is supposed to be a volcanoe, none really matches. Strata are great for cliffs and canyons, but you need something dark and rough (which 2 is, somewhat) for the inside of a volcanoe: Here's a picture of the crater at Mt. St. Helens, maybe it will give you some ideas. Good luck with it. http://www.perrochon.com/photo/MountHelens/Helens7.jpg