| This trip examines the many forms of rhyolite beautifully exposed along the north side of the Owyhee Mountains, south of Boise, from near Marsing to Walters Ferry, Idaho. This group of rhyolite units seems to have been erupted over a short time after the western Snake River Plain graben started to form and range between 11.7 and 10.6 Ma in age. Stops focus on examining features of rhyolite lava flows, rhyolite spatter, clastigenic units, ignimbrites, domes, and feeder dikes, as well as other features of the western Snake River Plain. |