August 13, 2009
A weekly feature provided by scientists at the Hawaiian Volcano Observatory.
Kīlauea's summer break pau for now?
While baseball fans nationwide at this time of year think about "trades" in terms of swapping average for exceptional ball players, we here in Hawai`i rely on "trades" (northeasterly trade winds) for dispersing volcanic emissions from the active vents on Kīlauea Volcano.
Beginning in early July, sulfur dioxide (SO2) gas emissions from Kīlauea's summit vent decreased by about 60 percent from the average measured since the vent opened in March 2008. The withdrawal of magma from within the vent, and multiple collapses of the vent rim at the end of June 2009, resulted in a wispy, lazy plume and an eerily quiet vent with no glow. But as the "trade" season for baseball players came to a close on July 31, emissions from Halema`uma`u began to pick up again and, as of this writing (August 13) appear to have returned to the average value measured since the vent opened. The return of incandescence, gas rushing noises, and elevated vent temperatures over the past week also suggest that lava is once again higher in the vent conduit.
The recent reprieve in volcanic activity from the summit vent tantalizes us with memories of pre-eruptive conditions, and both anecdotal reports and measured concentrations confirm improvements in air quality in Ka`u and Kona districts. However, even with the reduced SO2 summit emissions during July, interruptions in the trade winds resulted in several episodes of elevated volcanic pollution in Hawai`i Volcanoes National Park and adjacent communities.
The return of Kīlauea's SO2-rich summit plume and proximity of tropical depression Felicia set the stage for extreme SO2 concentrations in the National Park this week. On Tuesday, August 11, light southwesterly winds blew the plume toward the Kīlauea Visitor Center where concentrations exceeded 5 ppm, resulting in a "hazardous" condition advisory, the highest defined level. Other communities in East Hawai`i also experienced elevated levels of volcanic pollution as a result of the interrupted trade winds, with some residents of Volcano Village reporting extreme vegetation burn.
The current cycling in summit activity is reminiscent of last December, when SO2 emissions dropped a commensurate amount for a similar period of time, and the vent was also dark, quiet, and produced little ash and tephra.
While Kīlauea's summer break may be over for now, historically, long-lived summit eruptions have typically waxed and waned. Thus, we can look forward to the possibility of future time-off from our volcano's copious gas and modest ash emissions.
Kīlauea Activity Update
Lava continues to erupt from the TEB vent, on Kīlauea's east rift zone, and flows through tubes to the ocean at Waikupanaha. Breakouts from the tube on the pali have been supplying surface flows in the Royal Gardens area. Over the past week, the Waikupanaha ocean entry has had small littoral explosions.
After a month of darkness, faint glow returned to the vent at Kīlauea's summit on August 9, following the opening of a small gas vent deep within the cavity in Halema`uma`u crater. Volcanic gas emissions remain elevated, resulting in high concentrations of sulfur dioxide downwind.
Four earthquakes beneath Hawai`i Island were reported felt this past week. A magnitude-3.1 earthquake occurred at 8:39 p.m., H.s.t., on Thursday, August 6, 2009, and was located 10 km (6 miles) WNW of Ka`ena Point at a depth of 9.9 km (6.2 miles). Two magnitude-2.8 earthquakes occurred N and NW of Hualalai summit on August 8 at 10:12 p.m. and August 12 at 5:19 p.m.; both were deeper than 25 km (15.5 miles). A magnitude-1.9 earthquake at 7:35 p.m., H.s.t., on Monday, August 10, was located 13 km (8 miles) NNW of Mauna Kea summit at a depth of 24 km (15 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 2, 2009 (pnf)