A line of cinder cones along a north-northwest- to south-southeast-trending fissure has produced a series of youthful-looking lava flows.


The most prominent of these is Devils Rock Garden, a thick, blocky andesitic lava flow complex that extends to the south from Tumble Buttes. Bear Wallow Butte (dated at 35 ka), the source of unvegetated lava flows on its eastern and western flanks, lies at the southern end of the chain. At the northern end is Eiler Butte, constructed on a topographic high, which has also produced blocky lava flows. The Devils Rock Garden lava flow erupted from Tumble Butte south is the youngest in the area. It blocked glacial outwash channels and overlies glacial gravels, thus is younger than about 15,000 years and is described as latest Pleistocene (Clynne and Muffler 2010).

Volcanoes Hazards Program Links