This face of Pele, the goddess of fire, in a lava rock in Hawaii Volcanoes National Park was created by an artist.
The rock is an example of an accretionary lava ball which forms on the surface of an `a`a flow. The rock grows when a small fragment of solidified lava rolls along the surface of an active flow and lava sticks to its surface, like a growing snowball rolling down a hill.
More information about the “Volcano + iPad” tour: http://hawaiioutdoorguides.com/tours/tour-kilauea-volcano/