Lake Roosevelt boasts some of the most interesting geology in the state of Washington. Starting 17 million years ago, sheets of volcanic lava flowed from giant cracks in the earth near the Washington/Oregon/Idaho border and covered eastern Washington. In places the basalt rock that was formed as the lava cooled is more than two miles thick. Ice Age glaciers covered much of the norther part of Washington and have sculpted the landscape. Glaciers also blocked rivers like the Columbia, forming giant lakes. One such giant lake, Glacial Lake Missoula in Montana, ruptured its ice dam and unleashed one of the largest floods that mankind has ever known onto the plains of eastern Washington. Even more amazingly, such a giant flood did not happen just once; geologists have evidence that Glacial Lake Missoula caused more than 40 giant floods during the last Ice Age. To help students understand the rocks in their own backyards, Lake Roosevelt National Recreation Area has developed a Geology Traveling Trunk that illustrates and elucidates many of the geologic forces that have shaped eastern Washington in the past and continue to shape the landscape today. Designed for third, fourth, fifth and sixth grades, the trunk comes with videos, visual aids, rock samples, and equipment as well as a curriculum guide that addresses the geologic processes central to the history of eastern Washington.