March 23, 2013 Trip to Mennan Buttes
We left the Romney building at 1:00 and took the 1/2 hour trip to the Menan Buttes. The Menan Buttes are phreatic tuff cones (volcanic eruptions into water) that formed as Basalt erupted into the Snake River.
We hiked the North Butte and climbed around the rim of the crater. From the rime we could see the Snake River Plain, the Saint Anthony Sand dunes, the Beaverhead Mountains (basin and range), Big Southern Butte (rhyolite dome), the Tetons, and the Rexburg Bench (a fault).
We found the river cobbles trapped in the rock from the eruptions. It was perfect weather for March!