September 3, 2009
A weekly feature provided by scientists at the Hawaiian Volcano Observatory.
Alaska's summer field season for volcanologists is quickly coming to a close
Summer is traditionally the best field season for volcanologists to conduct a variety of work on restless and active volcanoes, especially in remote locations. Snow has melted from most of the high slopes, mild weather enables strenuous traverses over rough ground, and long daylight hours make extra work possible in hard-to-reach areas.
Such is the case in Alaska this summer, especially after the eruption of Redoubt Volcano earlier this year. As long summer daylight hours yield to the approach of fall, scientists of the Alaska Volcano Observatory are working long hours to learn about the eruption. They are studying layers of new rock deposits, improving and hardening monitoring sites for the coming winter, and analyzing the enormous and still-growing amount of data collected in the past year.
The first sign of unrest at Redoubt occurred last summer, when sulfur dioxide gas emissions increased. Magma rose to shallow depths beneath the volcano through early 2009, as indicated by intense earthquake activity, increased heat at the surface that melted snow and ice in the summit crater, small displacements of the volcano's flanks, and continued release of volcanic gases.
The eruption began with a steam explosion on March 15. Between March 22 and April 4, at least 19 significant explosive eruptions lasting less than an hour each sent ash and gas as high as 20 km (65,000 ft) above sea level. Minor ash fall occurred on numerous communities in south-central Alaska, and air traffic was intermittently disrupted, canceling or delaying hundreds of flights. Several of the explosive eruptions triggered pyroclastic flows on the flanks of the volcano that melted snow and ice to form large mudflows in the Drift River valley all the way to Cook Inlet, about 35 km (22 miles) away.
The mudlfows forced the immediate closure of an oil-terminal facility at the mouth of the river. The facility shut down oil production from several Cook Inlet oil fields that produced about 7,500 barrels of oil per day. During the summer, it was modified so that oil can be piped directly from oil platforms into tanker vessels, thereby bypassing the large storage tanks. With Redoubt quieting down, oil production restarted in mid-August.
After April 4, the eruption continued, with extrusion of a lava dome in the summit crater. Unlike the 1989-90 eruption, during which the repeated collapse of many smaller lava domes down the steep north flank triggered numerous mudflows in Drift River valley and ash fall downwind, the 2009 lava dome has not yet collapsed.
On July 10, scientists stopped their 24/7 operations when they could no longer detect eruption of lava into the dome, but they still keep a close watch on the dome for any signs of renewed growth or potential collapse down the volcano's steep north flank. For more information about Redoubt and photographs of scientists working on the volcano, visit the Web site of the Alaska Volcano Observatory, http://www.avo.alaska.edu
Kīlauea Activity Update
Lava continues to erupt from the TEB vent, on Kīlauea's east rift zone and flow through tubes to the ocean at Waikupanaha. After weeks without active surface flows, a small lava breakout from the tube near the top of the Royal Gardens subdivision started on Wednesday. The breakout was still active on Thursday, the day of this writing, but had not progressed very far down the eastern margin of the TEB flow field.
Faint glow above the vent at Kīlauea's summit has been visible at night, and an incandescent hole has been seen on the floor of the vent after dark in the Halema`uma`u Overlook webcam. Volcanic gas emissions remain elevated, resulting in high concentrations of sulfur dioxide downwind.
One earthquake was reported felt this past week. A magnitude-3.2 earthquake occurred at 6:16 a.m., H.s.t., on Monday, August 31, 2009, and was located 47 km (29 miles) NNE of Kahakuloa, Maui, at a depth of 27.7 km (17.2 miles).
Visit our Web site (http://hvo.wr.usgs.gov) for detailed Kīlauea and Mauna Loa activity updates, recent volcano photos, recent earthquakes, and more; call (808) 967-8862 for a Kīlauea activity summary; email questions to askHVO@usgs.gov.
Updated: October 1, 2009 (pnf)