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.
Seismic monitoring equipment on Mount Hood detected small debris flows on the White River over the past several weeks. No significant damage has been reported, but it may have made the Timberline Trail crossing over the White River temporarily more difficult.
The seismic signals of the debris flow rumbling down channel were best recorded by monitoring station PALM, located next to the Palmer chairlift in the Timberline Ski Area. Although the station has a lot of cultural noise, especially during chair lift operations, the debris flow signals are clearly visible. The signals in the spectrograms have gradual onsets, relatively high frequency content (5-10 Hz), and extended durations.
USGS-Cascades Volcano Observatory geologists working in the area on August 21 observed higher sediment-laden stream flows and broad areas adjacent to channels that had recently been inundated by mud and gravel.
Small debris-flow events are not uncommon in the upper reaches of the White River, particularly during periods of extended warm weather or intense rainfall. In this case, meltwater apparently released from the terminus of the White River Glacier, mixed with loose sediment as it traveled down steep narrow channels to create debris flows.
As a reminder to visitors in the area, if you are in a narrow river channel and you feel ground shaking, hear prolonged rumbling, or see a rapidly rising river level, move to the safety of higher ground.
As of August 9, 2015, Dr. Seth Moran takes over the leadership of USGS-Cascades Volcano Observatory from John Ewert, who served as the scientist-in-charge for the past five years.
Seth Moran began his USGS career as a research seismologist for the Alaska Volcano Observatory in 1997. In 2003, Moran joined the staff of CVO as the principal USGS seismologist responsible for studying and monitoring Cascade volcanoes. Seth's timing was fortuitous - in the fall of 2004 Mount St. Helens reawakened after 18 years of quiet. As is typical in all eruption responses, Seth assumed many different roles during the response: conducting his own seismic analyses, coordinating research by others outside CVO, being interviewed by the news media, assembling statements for the news media and working with partner agencies in emergency response.
In addition to Mount St. Helens, a significant percentage of Seth's time has been spent maintaining and improving seismic monitoring capabilities at other Cascade volcanoes, such as installing new seismic stations at Mount Rainier National Park, and developing a new network of eight seismic stations at Newberry Volcano in 2011. Seth has also been active in the larger scientific community being a critical player in the Imaging Magma Under St. Helens experiment, known as iMUSH, jointly funded by the National Science Foundation and USGS to produce a better "picture" of the magma "plumbing system" under the volcano.
John Ewert will rotate back to a staff position at CVO with Volcano Disaster Assistance Program focusing on novel approaches to eruption forecasting and updating National Volcano Warning System documents.
On August 13, a series of small debris flows rumbled down Tahoma Creek, in Mount Rainier National Park. No one was injured and damage was limited to the stream channel inside the Park.
Observations and photos taken by National Park Service geologists during an overflight in the afternoon indicate that the debris flows appear to have started at the terminus of South Tahoma Glacier. Some sediment from the debris flow was visible 8 miles downstream at the Highway 706 crossing.
Looking at seismic data from the Pacific Northwest Seismic Network, the vibrations from the debris flow are recorded on seismograms from Rainier station RER, located at Emerald Ridge overlooking Tahoma Creek. The debris flow signal starts at ~9:50 AM PDT. Signals are emergent, pulsatory, and relatively high-frequency, all characteristics of debris flows. There was a period of time from ~9:50 AM through to ~12:45 PM where signals were occurring relatively continuously, with several tens-of-minutes-long higher-amplitude bursts at 10:15-11:10, 11:25-11:50, and 12:30-12:40 that probably correspond to major debris-flow pulses. No debris-flow-like signals showed up overnight.
This event is similar to numerous debris flows that have occurred at Mount Rainier in past decades. Water stored in the glacier was released and quickly gathered up loose mud, sand, soil, and rock to form a debris flow. Small flows are common at Mount Rainier during late summer and early fall; a second group of debris flows commonly develops from torrential rainfall during early winter storms. Between 1985 and now, more than 30 debris flows have rushed down the Tahoma Creek valley.
The visiting public is reminded to stay clear of valley floors during debris flows and to the safety of higher ground when a debris flow is passing.
The May 18, 1980, eruption of Mount St. Helens included a debris avalanche, lateral blast, pyroclastic flows, lahars, and tephra falls, all of which dramatically altered the drainage basins on the volcano. Since the eruption, scientists have been conducting repeat stream channel cross-section surveys to monitor the response of these channels, as part of a long-term hydrologic monitoring project managed by the U.S. Geological Survey. These data are now available in a new online database that contains 243 survey lines, representing ~100 km of topography, collected over more than 30 years. Cross sections are located within two primary drainage basins—the Toutle River on the north and west flanks of the volcano and the Lewis River on the south and east flanks. The dynamic nature of the database will accommodate the addition of future surveys and data revisions as appropriate. Download the Digital database of channel cross-section surveys, Mount St. Helens, Washington, to see more.