The Tuff Stuff
For 10,000 years wind and dirt have blown in a circular fashion scouring away the tuff (rock composed of compacted volcanic ash). Wind erosion fashioned windows, arches, pillars, caves, channels and this large circular basin. For numerous years prevailing winds have blown from the southwest. During eruptions, the winds carried the molten material to the northeast of the vent giving the volcanic cones their elongated shape.
Wind-swept rocks at the top of Menan Butte, otherwise known as the amphitheater.
Wind is also responsible for the sharp crescent shape of each dune at St. Anthony Sand Dunes. The tips of the crescent-shaped dunes face northeast which indicate the winds from the southwest.
The South Butte volcano is visible from “The Amphitheater” on North Menan Butte. WIND, not water, erodes the volcanic tuff into spaces and shapes that stir the imagination. A stream trickles into this basin and off the side of this volcano.
BELOW: Aerial view of North Menan Butte reveals an elongated bowl shape driven by southwest winds during and after eruptions.