A new geologic map and pamphlet provides information on a young volcanic field of intraplate basalts located just east of the Cascade Arc―the Simcoe Mountains volcanic field, in south-central Washington State.
The map shows, in various colors, the areas covered by 223 different eruptive units, mostly lava flows and cinder cones ranging in age from ~4 million to 600,000 years old. Most of these units were produced by short-lived (a few years) basaltic eruptions that featured localized lava fountains and/or lava flows that extended at most several miles, creating small volcanic cones that are now extinct. The only large long-lived volcano in this field capable of erupting again in the future is Mount Adams, located on the western boundary.
Read more in Scientific Investigations Map 3315, Geologic Map of the Simcoe Mountains Volcanic Field, Main Central Segment, Yakama Nation, Washington. This product was produced by USGS on behalf of the Water Resources Program of the Yakama Nation.
Beginning the afternoon of October 22, 2015, a swarm of mostly small earthquakes occurred about 10 km (6 miles) NW of the towns of Crescent and Gilchrist, Oregon. Through the morning of October 23, the Pacific Northwest Seismic Network (PNSN) located 29 events (maximum magnitude M 2.6) and a number of additional events are too small to locate. The PNSN locations are spread out over a 5 by 10 km (3 by 6 miles) area in the vicinity of Ringo and Cryder Buttes, with depths ranging from 1 to 15 km (0.6 to 9 miles). Since the nearest network station is about 40 km (25 miles) to the northeast, location and depth determinations have a high degree of uncertainty and it is quite possible that events are occurring over a much smaller area.
This area has experienced periods of elevated seismicity in the past. In June-August 2001, the PNSN located 6 events (maximum magnitude M 2.6), and in July-August 2012 the PNSN located 20 events (maximum magnitude M 1.1). Prior to the expansion of the Newberry seismic network in 2012 earthquakes were much harder to detect and locate in central Oregon in general and in this area in particular, so it is conceivable that other Crescent-area swarms could have occurred prior to 2012 that were not detected by CVO or the PNSN.
On October 10, intense rain at Mount St. Helens eroded volcanic deposits on the southwest flank of the volcano above Butte Camp dome. Field observations revealed unmistakable tracks of recent debris flows that started in two separate channels some distance above the Loowit 216 trail, and continued as a debris flow at least as far as the Toutle 238 trail crossing. By the time runout reached and merged with the clear-running Kalama Springs discharge, it was all fine material that was easily suspended in the flow and transported far downstream into the Kalama River. Similar debris flow run-outs may have entered the Kalama through another tributary channel. Because the source material for this debris flow consisted of creamy white volcanic deposits, it imparted an unusually light color to the river. With time, the river color will change as the sediment settles out of the water. Additional analysis is underway to better define source material.
Read more about Hydrologic Monitoring at Mount St. Helens on our webpage.
Scientists, civil authorities, and emergency managers from Chile and the U.S. met in California to discuss the challenges of effective volcanic hazard education, response planning, hazard mitigation, and risk reduction, as part of the second Bi-national Exchange program for Volcanic Risk Reduction in the Americas.
The program focused on the Long Valley volcanic region (California, USA) and Chaitén Volcano (Región de los Lagos, Chile). Both of these restless volcanic systems have erupted rhyolite lava. Eruptions of rhyolite lava exhibit extremely diverse behavior, from sluggish lava flows to catastrophic explosions. The similarities in the nature of the hazards posed at Long Valley and Chaitén and the challenges of communicating with at-risk communities provide opportunities for scientists and civil authorities to learn from one another and strengthen risk reduction in their home countries. In the U.S. and Chile, participants inspected volcano monitoring networks, learned about the geologic history of volcanoes, volcanic hazards, eruption forecasting, disaster preparedness, and communications with affected communities.
The principle coordinators of the Chile-USA exchange are Dr. Margaret Mangan, Scientist-in-Charge of the USGS-California Volcano Observatory in Menlo Park, California, and Dr. Luis Lara, the Head of the Volcano Hazards Program at Servicio Nacional de Geología y Minería in Santiago, Chile. The program is funded by the U.S. Agency for International Development/Office of Foreign Disaster Assistance with cooperation from the USGS' Volcano Disaster Assistance Program.