Molten rock forced upward for 30 to 50 miles through fissures in the earth cooled into the hard lava found here. Continued pressure from below made great cracks in the contorted surface. This lava solidified only a few thousand years ago, and not very much soil covers it yet. But vegetation is getting a start, and unless new flows intervene, windblown soils will cover these rock layers. Then the surface here will look the same as the surrounding plains, which also are layers of lava and windblown soils.