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ハレマウマウが噴火 1924年以来

ハワイ・キラウエア火山の山頂にあるハレマウマウが 3月19日02時58分(ハワイ時間)に噴火した。ハレマウマウの噴火は1924年以来のこと。爆発で飛び散った岩石がクレーターリムドライブの路上に散乱した。ハレマウマウ展望台が損壊した。爆発源に新しい溶岩は現れていない。

US36[1]s

ハレマウマウはキラウエア火山の中心を占めるカルデラの中にある直径1キロの火口である。そばに広い駐車場がつくられている。キラウエア火山を見物に来た観光客はそこに車を停め、遊歩道をハレマウマウの縁まで歩いて、平らな火口底をのぞき込む。爆発が夜間でよかったが、二酸化硫黄濃度上昇を理由に、この駐車場と道路は2月20日から昼間も閉鎖されていた。


20080319-3974-TRO_L[1]

Kilauea Information Release issued Mar 19, 2008 14:29 HST Volcanic-Alert Level WATCH - Aviation Color Code ORANGE
Explosive eruption in Halema`uma`u Crater, Kilauea Volcano, is first since 1924

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 Kilauea 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.

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