************************************************************************************************* Explosive eruption in Halema`uma`u Crater, Kīlauea Volcano, is first since 1924 From: James P Kauahikaua <jimk@xxxxxxxx> ************************************************************************************************* At 2:58 a.m. H.s.t on Wednesday, March 19, 2008, a small explosion occurred at Halema'uma'u Crater at the summit of Kīlauea Volcano in Hawai'i Volcanoes National Park. This event was erroneously reported as an earthquake earlier this morning. The explosion scattered debris over an area of about 75 acres (30 hectares), covering a portion of Crater Rim Drive and damaging the Halema'uma'u overlook. No lava was erupted as part of the explosion, suggesting that the activity was driven by hydrothermal or gas sources. In addition to damaging the overlook, explosive debris covers the trail to the overlook, the Halema'uma'u parking area, and the portion of Crater Rim Drive adjacent to the parking area. On Crater Rim Drive the debris was up to 2 centimeters in size, with the size and thickness of debris increasing toward the overlook. The largest observed block ejected during the explosion was about 1 cubic meter (35 cubic feet) and must have been propelled from the vent located more than 70 m (230 feet) below the crater rim. Small impact craters from 30 cm (1 foot) blocks are abundant in the Halema'uma'u overlook area. Rock debris also extends halfway across the floor of Halema'uma'u Crater. The debris is composed of rock fragments that were derived from the walls of Halema'uma'u Crater. No fresh lava was observed on the floor of Halema'uma'u or in the ejected debris. At 2:55 am, the Hawaiian Volcano Observatory recorded a series of seismic events that may have been shallow, high-frequency earthquakes or minor explosions. The main explosion at 2:58 was associated with long period seismicity. Low frequency sound waves were also detected by the University of Hawai`i infrasound laboratory, operated by Dr. Milton Garces. These signals have persisted through this morning indicating continuing energetic release of gas from the vent in Halema'uma'u Crater. The explosion produced a small crater along the east wall of Halema'uma'u that is about 20-30 meters (65-100 feet) in diameter. The crater occupies the area in which incandescence had been observed during the previous week. Sulfur dioxide emissions from the new explosion crater are still elevated, and sounds of rock breaking are frequent. This is the first explosion in Halema`uma`u crater since 1924 and the first eruption of any kind in Kīlauea caldera since September 1982. Future explosive activity is possible and the Hawaiian Volcano Observatory continues to monitor the activity. Photos, text updates, a new Halema`uma`u crater webcam, and details about the Kilauea 1924 explosive eruption can be found at the HVO website hvo.wr.usgs.gov. USGS provides science for a changing world. For more information, visit www.usgs.gov. Subscribe to USGS News Releases via our electronic mailing list ( www.usgs.gov/newsroom/list_server.asp) or RSS ( www.usgs.gov/rss/newsroom.rss) feed. ============================================================== To unsubscribe from the volcano list, send the message: signoff volcano to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxxx To contribute to the volcano list, send your message to: volcano@xxxxxxxx Please do not send attachments. ==============================================================
