HR: 1340h
AN: V53B-1565    [Abstracts]
TI: The Highway Flow in the Craters of the Moon Lava Field; A New Interpretation of Eruption History
AU: * Caress, M E
EM: marycaress@yahoo.com
AF: Craters of the Moon National Monument and Preserve, PO Box 29, Arco, ID 83213 United States
AU: Owen, D E
EM: Doug_Owen@nps.gov
AF: Craters of the Moon National Monument and Preserve, PO Box 29, Arco, ID 83213 United States
AB: The Highway flow is a trachyandesitic lava flow that lies west of Sunset Cone in the Craters of the Moon lava field, and is part of a complex series of eruptive events that took place in the vicinity of North Crater during the most recent eruptive episode of the field (2,500-2,000 years ago). The trachyandesitic Devil's Orchard and Serrate flows originated from the same vicinity during this period, and carried large masses of rafted cinder cone blocks and disaggregated cinder cone material up to 12 km to the east. The rafted blocks have long been thought to be the remnants of a disintegrating North Crater cinder cone. However, recent work has established that the flows carry a cumulative volume of rafted blocks too large to have come from the existing breach in North Crater. Previous studies had postulated the Highway flow vent to be on the north side of North Crater, and suggested the lava had flowed north, and later drained back to the south when the Highway fault downdropped the vent area. This study examined lava flow characteristics and flow direction indicators based on flow fold patterns interpreted from aerial photographs and field mapping to provide new insight into the complicated history of the Highway flow. We found two vents on the northern side of the flow, and evidence that the lava flowed to the south and ponded against a formerly present cinder cone, which we have named "South Highway Cone". The following sequence of events for eruption of the Highway flow is hypothesized: 1) eruption from two linear vent systems in the northern part of the present day flow 2) flow from the second vent southward, down the valley between Sunset and Grassy Cones 3) ponding of the lava flow at the base of the South Highway Cone and 4) downdrop to the south along the Highway fault due to collapse into a lava chamber beneath South Highway Cone. The rafted blocks in the Devil's Orchard and Serrate flows represent pieces of North Crater and the now hypothesized South Highway Cone, which were carried away, but the exact manner in which these flows fit into the sequence of events has yet to be determined.
DE: 8429 Lava rheology and morphology
DE: 8486 Field relationships (1090, 3690)
SC: Volcanology, Geochemistry, Petrology [V]
MN: Fall Meeting 2005