Usu volcano

Updated: Aug 9, 2022 11:26 GMT - Refresh
stratovolcano 737 m / 2,418 ft
Hokkaido (Japan), 42.54°N / 140.84°E
Current status: normal or dormant (1 out of 5)

Mt Usu (有珠山) or Usu-zan volcano is Hokkaido is one of Japan's most well-known volcanoes, part of the active Toya caldera. The summit of Usu consists of several lava domes that formed in historic time.
The last eruption was in March 2000 - September 2001, when Usu erupted for the first time in 22 years and forced the evacuation of 13,000 residents.
In the official Global Volcanism Program's database, the volcano is referred to as Toya, the name of the large caldera, whose currently most active vent Usu represents.

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Typical eruption style: explosive
Usu volcano eruptions: 2000-01, 1977-82, 1944-45, 1910, 1853, 1822, 1769, 1663, 1638, 1626, 1611 (?)
Lastest nearby earthquakes: No recent earthquakes

Background

Usu is a small stratovolcano located astride the southern topographic rim of the 110,000-year-old Toya caldera. The center of the 10-km-wide, lake-filled caldera contains Naka-jima, a group of forested andesitic lava domes. The summit of the basaltic-to-andesitic edifice of Usu is cut by a somma formed about 7-8,000 years ago when collapse of the volcano produced a debris avalanche that reached the sea. Dacitic domes erupted along two NW-SE-trending lines fill and flank the summit caldera. Three of these domes, O-Usu, Ko-Usu and Showa-Shinzan, along with seven crypto-domes, were erupted during historical time. The 1663 eruption of Usu was one of the largest in Hokkaido during historical time. The war-time growth of Showa-Shinzan from 1943-45 was painstakingly documented by the local postmaster, who created the first detailed record of growth of a lava dome.

Usu Photos

An usually clear view of the interior of Benbow's crater in the evening. (Photo: Tom Pfeiffer)
An usually clear view of the interior of Benbow's crater in the evening. (Photo: Tom Pfeiffer)
Unusually powerful eruption at Stromboli volcano as seen on April 4, 2009 - bombs are reaching the Pizzo area (where visitors usually observe the volcano). The decision to temporarily close access to the summit was certainly right.  (Photo: Tom Pfeiffer)
Unusually powerful eruption at Stromboli volcano as seen on April 4, 2009 - bombs are reaching the Pizzo area (where visitors usually observe the volcano). The decision t...
Time to wake up and enjoy the last hour of darkness before sunrise! As usual, Gilles is already up before all others and standing at the crater rim behind, to watch the lava lake. (Photo: Tom Pfeiffer)
Time to wake up and enjoy the last hour of darkness before sunrise! As usual, Gilles is already up before all others and standing at the crater rim behind, to watch the l...
Individual explosions were usually directed to the west, strqight up high, or to the east. This one throws most bombs to the west. (Photo: Tom Pfeiffer)
Individual explosions were usually directed to the west, strqight up high, or to the east. This one throws most bombs to the west. (Photo: Tom Pfeiffer)
 


2000-01 eruption
The 2000 eruption of Usu volcano was the first in 22 years and followed several days of increased seismicity and ground deformation.
A first new vent opened in the West-Nishiyama area on 31 March 2000, followed by activity in the Kompira area on 1 April. Eruptive activity lasted for more than a year and gradually declined until September 2001. The eruptions were phreatic and phreato-magmatic, and caused small pyroclastic flows.
A large area of Usu volcano deformed during the eruption by uplift of up to 60 m vertical displacement and involving a volume of ca. 40 million m3.

1663 Plinian eruption
In 1663 Usu had a Plinian eruption (VEI5), one of the largest eruptions on Hokkaido during historical times. It caused wide-spread damage and fatalities.

See also: Sentinel hub | Landsat 8 | NASA FIRMS
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