Graduate student Rowena Lohman finds her way into one of the many holes in the volcanic tuff at Hole-in-the-Wall in the Mojave Desert. The tuff (ash and rock fragments from a violent volcanic eruption) was deposited about 18 million years ago. This picture was taken during the Ge136 field trip, led by Professor Joann Stock, to the southeastern Mojave Desert and Lower Colorado River area.

Photo courtesy of Christopher DiCaprio