During my 2007 Idaho long weekend road trip, I spent an afternoon checking out the sites of Craters of the Moon National Monument in central Idaho. The lava field at Craters of the Moon is 618 square miles, the largest on the U.S. mainland, bigger than all of the island of Oahu in Hawaii. The most recent eruptions along the rift zone occurred only 2000 years ago - the volcanos here are considered dormant rather than extinct. Sites include lava fields, cinter cones, splatter cones, and lava tubes.

Mark Wasson, http://www.markwasson.com > Trips has detailed summaries of my trips

http://www.markwasson.com/u2007i07aidaho.htm