Lava tree mold

A lava tree mold, sometimes erroneously called a lava tree cast, is a hollow lava formation that formed around a tree trunk. They are created when lava flows through an area of trees, coating their exterior. The lava cools just enough to create a solid crust around the trunk, but the tree inside burns away leaving a cavity. Molds of trees may be vertical or horizontal. In many cases, mold formation requires slow moving lava, as well as enough time for the mold to chill.