The wilderness is situated on high desert terrain and is associated with a volcanic rootless shield. This broad volcanic shield issued lava from a rootless vent. The lava flow dates to about 80,000 years old and comes from a main vent further up the slopes of Newberry Volcano. This main vent was located near Lava Top Butte and the lava that came out of this vent travelled through the Arnold Lava Tube System to arrive at the current location of the Badlands. An irregularly-shaped pit crater at the top of the shield marks the site where lava flowed in all directions to create the Badlands. Lava tubes acted as conduits for the lava in some instances and are evidenced on the surface by tumuli, also known as pressure ridges. Soils in the Badlands were largely formed from ash associated with the eruption of Mount Mazama some 7,700 years ago.