Large Scale Mapping and New Interpretation of the Geology in Proximity to the Visitor Center: Evidence for a Missing Cinder Cone and Refined Mapping of Volcanic Feature, Craters of the Moon National Monument and Preserve, Idaho

Recent detailed field mapping near the visitor center at Craters of the Moon National Monument and Preserve (CRMO) revealed proof for a missing cinder cone, named the South Highway cinder cone (SHC), partially swallowed during magma chamber collapse and rafted away by younger flows. To support hypothesis by previous workers at CRMO, we present evidence for five potential remnants of SHC. In addition to mapping the missing cinder cone, we present here a sequence of events explaining the creation and destruction of SHC.

A volume analysis of SHC was conducted to compare with previous volume calculations of rafted material near the mapping area that show the volume of rafted material is too great to be contained within existing cone edifices. The volume of SHC remnants would reduce the volume of excess rafted material by 10% and yet the total volume of SHC remains too large to be accounted for simply through rafted blocks. Thus, a collapsing magma chamber appears to be a reasonable mechanism for the removal of a moderately sized cinder cone.

Finally, we generated a 1:12,000 digital geologic map of our reinterpretations and a Points of Interest section. We identified previously unmapped eruptive and non-eruptive fissures that provide relative ages for cinder cones and vent complexes in the mapping area. The map and accompanying section promotes mapping and understanding of volcanic terrains by offering the reader a series of features with explanations for their formation. The publication is available to the public via the CRMO website (www.nps.gov/crmo) and encouraged for use by geology field camps.