Idaho, United States Generated by the same northwestern volcanism that produced the Columbia Plateau, Craters of the Moon Monument exhibits many different kinds of volcanic formations. Based on radiocarbon analysis, the lava flows at the monument occurred 2,000 years ago. Samples for this analysis were collected in a novel fashion. Students dug tunnels under the lava flow in hopes of finding burnt plant material that had been both produced and then preserved undisturbed by the advancing lava. Some material was indeed preserved under the lava, which had advanced as a smoothly flowing mass and covered the plants in its path without displacing their charred remains. Craters of the Moon Monument includes an area of “tree molds” formed when lava surrounded the trunks of trees. The trees burned away, but the impressions of their trunks remained. Here again, charcoal derived from roots of the original tree was preserved under the lava, and radiocarbon dating yielded a date of approximately 2,200 years ago for the lava flow that overwhelmed the trees and produced the charcoal.