Two Volcanoes Erupt in Japan

Japan’s Asama volcano and Mount Sakurajima erupted early Monday, Asama spewing hot rocks and raining ash as far away as Tokyo.

Residents in population centers near Mount Asama about 150 kilometers (95 miles) northwest of Tokyo were advised to wear masks as Asama ejected fumes, hot rocks and ash about 1:51 am local time, spewing lava shortly afterward.

White smoke rises from Mount Asama in Tsumagoi, about 140 km (87 miles) northwest of Tokyo, Feb. 2, 2009. The volcano in central Japan erupted on Monday, spewing hot rocks and ash, but there was no major damage in the sparsely populated vicinity, the Japan Meteorological Agency said.  (Xinhua/Reuters Photo). Image may be subject to copyright.

The 2,568-meter (8,425-foot) volcano ejected a plume of fumes and ash about 2km into the air, covering the towns at the foot of Mt Asama with white volcanic ash.  The volcanic ash also reached Tokyo, traveling as far as Yokohama city southeast of Japan’s capital.

Mount Asama has been active for several thousand years, and frequently ejects small amounts of ash from its crater. It last erupted in August 2008, however, its last major eruption occurred on September 1, 2004, spewing hot rock and sprinkling ash as far as 180 km away, and causing damage to crops.  In 1783 it erupted violently causing extensive damage to property and killing as many as 2,000 people.

Japan’s meteorological agency also reported that Mount Sakurajima, a 1,117-metre (3,686-foot) volcano, had erupted eight times between Sunday evening and early Monday Morning.

Home to some 108 active volcanoes, Japan sits atop the Eurasian, Pacific, Philippine and North American tectonic plates whose movements cause numerous earthquakes and volcanic eruptions. The country experiences about 20 percent of the world’s major earthquakes of magnitude 6 or greater.

Asama, Honshu’s most active volcano, overlooks the resort town of Karuizawa, 140 km NW of Tokyo. The volcano is located at the junction of the Izu-Marianas and NE Japan volcanic arcs. The modern cone of Maekake-yama forms the summit of the volcano and is situated east of the horseshoe-shaped remnant of an older andesitic volcano, Kurofu-yama, which was destroyed by a late-Pleistocene landslide about 20,000 years before present (BP). Growth of a dacitic shield volcano was accompanied by pumiceous pyroclastic flows, the largest of which occurred about 14,000-11,000 years BP, and by growth of the Ko-Asama-yama lava dome on the east flank. Maekake-yama, capped by the Kama-yama pyroclastic cone that forms the present summit of the volcano, is probably only a few thousand years old and has an historical record dating back at least to the 11th century AD. Maekake-yama has had several major plinian eruptions, the last two of which occurred in 1108 (Asama’s largest Holocene eruption) and 1783 AD. Caption: Global Volcanism program. Photo by Richard Fiske, 1961 (Smithsonian Institution).

Sakura-jima, one of Japan’s most active volcanoes, is a post-caldera cone of the Aira caldera at the northern half of Kagoshima Bay. Eruption of the voluminous Ito pyroclastic flow accompanied formation of the 17 x 23 km wide Aira caldera about 22,000 years ago. The smaller Wakamiko caldera was formed during the early Holocene in the NE corner of the Aira caldera, along with several post-caldera cones. The construction of Sakura-jima began about 13,000 years ago on the southern rim of Aira caldera and built an island that was finally joined to the Osumi Peninsula during the major explosive and effusive eruption of 1914. Activity at the Kita-dake summit cone ended about 4850 years ago, after which eruptions took place at Minami-dake. Frequent historical eruptions, recorded since the 8th century, have deposited ash on Kagoshima, one of Kyushu’s largest cities, located across Kagoshima Bay only 8 km from the summit. The largest historical eruption took place during 1471-76. Caption: GVP

Copyrighted photo by Shun Nakano (Japanese Quaternary Volcanoes database, RIODB, http://riodb02.ibase.aist.go.jp/strata/VOL_JP/EN/index.htm and Geol Surv Japan, AIST, http://www.gsj.jp/).

Related Links:

• Volcanoes [Links page]
• Earthquake Forecast 2009 : Japan
• A New Era of Intense Volcanic Unrest May Have Begun