The volcano is a new terrain that is located at the center of the map. It has lava inside it and holds the giant healing stones. The big bubbles represent the lava popping. Giant Healing Stones spawn in the Lava. The Volcano appears similar to Mud on the minimap, however, there is no slowdown effect and it is much larger, taking up about 2 screens of Mouse FoV.
The volcano was meant o be used along with the Black Dragon, which drinks lava instead of water. The volcano came out in the same update as the Black Dragon, and same with Healing Stones.