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Chokaisan

Photo of this volcano
  • Japan
  • Japan, Taiwan, Marianas
  • Stratovolcano(es)
  • 1974 CE
  • Country
  • Volcanic Region
  • Primary Volcano Type
  • Last Known Eruption
  • 39.099°N
  • 140.049°E

  • 2236 m
    7336 ft

  • 283220
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number

Most Recent Bulletin Report: April 1974 (CSLP 50-74)

Explosions cause ashfall in March and April

Card 1835 (01 April 1974) Large ash eruptions on 1 March from the E side of the central cone

After a long period of inactivity (since 1821), Tyokai volcano blew up on 1 March. Explosions at 1010 and 1130 (0110 and 0230 GMT) were the biggest, and repeated about ten times. Black smoke rose, and the volcanic ash fall lasted for ten minutes. According to aerial observations that same day, the eruption site was confirmed to be located on the eastern side of Sinzan, a central cone of this volcano. At first black smoke was spewing from the crater, and black ash was deposited on the eastern slope of the snow-covered volcano. According to an aerial observation on 3 March, this black smoke had turned into white vapor. Temporary seismic observations were carried out by the Tohoku University and the JMA around the skirt of this volcano, and scores of volcanic earthquakes were detected. A black belt (about 1.5 km long and 20-30 m wide) composed of ash-deposits and snow flowed down to the north side on 6 March. This belt is considered to be the result of a snow slide and there was no change or re-activity in the volcanic state. Gray volcanic smoke was observed on 5 March from the slope of the volcano, but there was no smoke after that.

Card 1850 (30 April 1974) Intermittent variable actiivty; ashfall on 24 April

The activity of Tyokai volcano started with the black smoke eruption and the volcanic ash fall on 1 March, but showed decreasing activity thereafter. Recently, however, the activity increased, and the following phenomena took place:

1) According to a visual observation on 8 April, and an aerial observation on 15 April, white smoke several tens of meters in height erupted from the new crater on the eastern flank of Sinzan, a central cone of this volcano, and white vapor about 20 m in height erupted from the 500 m long fissure on the western flank of Sinzan. On the fissure about ten fumaroles have formed.

2) On 24 April, black smoke, about several hundred meters in height, rose from the fissure on the W flank of Sinzan, and ash fell on the E foot of Tyokai volcano. On that day this black smoke gradually turned into white vapor. Simultaneously, a mud flow started from the summit crater and flowed down the W side, and this belt reached 3 km in length.

Information Contacts: Card 1835 (01 April 1974)T. Tiba, Dept. of Geology, National Science Museum, Tokyu, Japan.
Card 1850 (30 April 1974)Seismological Division, JMA.

The Global Volcanism Program has no Weekly Reports available for Chokaisan.

Bulletin Reports - Index

Reports are organized chronologically and indexed below by Month/Year (Publication Volume:Number), and include a one-line summary. Click on the index link or scroll down to read the reports.

04/1974 (CSLP 50-74) Explosions cause ashfall in March and April




Information is preliminary and subject to change. All times are local (unless otherwise noted)


April 1974 (CSLP 50-74)

Explosions cause ashfall in March and April

Card 1835 (01 April 1974) Large ash eruptions on 1 March from the E side of the central cone

After a long period of inactivity (since 1821), Tyokai volcano blew up on 1 March. Explosions at 1010 and 1130 (0110 and 0230 GMT) were the biggest, and repeated about ten times. Black smoke rose, and the volcanic ash fall lasted for ten minutes. According to aerial observations that same day, the eruption site was confirmed to be located on the eastern side of Sinzan, a central cone of this volcano. At first black smoke was spewing from the crater, and black ash was deposited on the eastern slope of the snow-covered volcano. According to an aerial observation on 3 March, this black smoke had turned into white vapor. Temporary seismic observations were carried out by the Tohoku University and the JMA around the skirt of this volcano, and scores of volcanic earthquakes were detected. A black belt (about 1.5 km long and 20-30 m wide) composed of ash-deposits and snow flowed down to the north side on 6 March. This belt is considered to be the result of a snow slide and there was no change or re-activity in the volcanic state. Gray volcanic smoke was observed on 5 March from the slope of the volcano, but there was no smoke after that.

Card 1850 (30 April 1974) Intermittent variable actiivty; ashfall on 24 April

The activity of Tyokai volcano started with the black smoke eruption and the volcanic ash fall on 1 March, but showed decreasing activity thereafter. Recently, however, the activity increased, and the following phenomena took place:

1) According to a visual observation on 8 April, and an aerial observation on 15 April, white smoke several tens of meters in height erupted from the new crater on the eastern flank of Sinzan, a central cone of this volcano, and white vapor about 20 m in height erupted from the 500 m long fissure on the western flank of Sinzan. On the fissure about ten fumaroles have formed.

2) On 24 April, black smoke, about several hundred meters in height, rose from the fissure on the W flank of Sinzan, and ash fell on the E foot of Tyokai volcano. On that day this black smoke gradually turned into white vapor. Simultaneously, a mud flow started from the summit crater and flowed down the W side, and this belt reached 3 km in length.

Information Contacts: Card 1835 (01 April 1974)T. Tiba, Dept. of Geology, National Science Museum, Tokyu, Japan.
Card 1850 (30 April 1974)Seismological Division, JMA.

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Eruptive History

There is data available for 32 Holocene eruptive periods.

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1974 Mar 1 1974 Apr 30 Confirmed 1 Historical Observations E side of Shinzan, W of Kojin-yama
1834 Jul 9 1834 Jul Confirmed 2 Historical Observations
1821 May 23 Unknown Confirmed 2 Historical Observations Near Shinzan and Shichiko-zan
1800 Dec 1804 Jul (?) Confirmed 2 Historical Observations Shinzan (foot of Kojin-yama)
[ 1764 ] [ Unknown ] Uncertain 2  
1740 Jun (?) 1747 (?) Confirmed 2 Historical Observations Small crater at foot of Kojin-yama
[ 1738 Dec 31 ± 365 days ] [ Unknown ] Uncertain 2  
[ 1735 ] [ Unknown ] Uncertain 2  
1659 Apr 1663 ± 1 years Confirmed   Historical Observations
[ 1560 ] [ Unknown ] Uncertain    
[ 1477 ] [ Unknown ] Uncertain    
[ 0999 ] [ Unknown ] Uncertain    
[ 0948 Dec 31 ± 365 days ] [ Unknown ] Uncertain    
0939 May 15 Unknown Confirmed   Historical Observations
[ 0915 Aug 23 ] [ 0915 Sep 1 ] Discredited    
[ 0884 Jul 26 ] [ 0884 Aug ] Uncertain    
0871 May 5 Unknown Confirmed 2 Historical Observations
[ 0861 May ] [ Unknown ] Uncertain 3  
[ 0857 May ] [ Unknown ] Uncertain    
[ 0856 ] [ Unknown ] Uncertain    
[ 0839 Oct 14 ] [ Unknown ] Uncertain    
0830 Jan Unknown Confirmed   Historical Observations
0817 ± 7 years Unknown Confirmed   Historical Observations
[ 0804 ] [ 0806 ] Uncertain    
[ 0717 Jul ] [ Unknown ] Uncertain    
0711 ± 3 years Unknown Confirmed   Historical Observations
[ 0610 ± 18 years ] [ Unknown ] Uncertain    
[ 0577 Dec 1 ± 30 days ] [ 0578 Jul 15 ± 45 days ] Uncertain    
[ 0573 Mar (?) ] [ Unknown ] Uncertain    
0450 BCE (?) Unknown Confirmed   Tephrochronology OD-12 tephra
0650 BCE (?) Unknown Confirmed   Radiocarbon (uncorrected) Higashi-Chokai
1050 BCE (?) Unknown Confirmed 0 Tephrochronology West flank (Saruana crater)
Deformation History

There is no Deformation History data available for Chokaisan.

Emission History

There is no Emissions History data available for Chokaisan.

Photo Gallery

Massive Chokai volcano, the largest of NE Honshu, is seen here from the NE. Chokai is composed of two large overlapping stratovolcanoes. The younger eastern volcano is cut by the large horseshoe-shaped caldera, seen here breached to the north, that was the source of the Kisakata debris avalanche. Pyroclastic cones later filled much of the area near the back wall of the caldera. Chokai has erupted frequently since one of the earliest historically documented eruptions in Japan in 573 CE.

Photo courtesy Ichio Moriya (Kanazawa University).
See title for photo information.
The north flank of Chokai volcano was the source of a massive debris avalanche about 2600 years ago that traveled 25 km into the Japan Sea and underlies much of the foreground area. Collapse of the summit left a 3 x 4 km horseshoe-shaped caldera whose eastern rim forms the peak at left center and western rim descends from the cloud bank at the right. Following the collapse a series of lava domes and lava flows filled the upper part of the caldera and formed the center peak.

Photo by Ichio Moriya (Kanazawa University).
See title for photo information.
An ash plume rises from the flanks of Shinzan lava dome at the summit of Chokai volcano on March 1, 1974, after a long repose of 140 years. Phreatic eruptions occurred at Chokai in March and April, and were accompanied by small mudflows. The eruptions took place from an E-W-trending series of vents extending from the eastern caldera wall across the flanks of the 1801 Shinzan lava dome and the Kojin-yama cone. This view from the NW shows the eastern caldera wall behind Shinzan.

Photo courtesy of Japan Meteorological Agency, 1974.
See title for photo information.
Steam pours from an eruptive fissure on Chokai volcano on April 24, 1974, near the end of an eruption that began on March 1. Ash darkens the slopes of the summit cone and mudflow deposits descend the flanks at the lower left. Shinzan lava dome appears above the steam plume at the left, with the eastern caldera wall in the background, in this view from the SW. The 1974 eruption, the first from Chokai in 140 years, ended on April 30.

Photo courtesy of Japan Meteorological Agency, 1974.
See title for photo information.
GVP Map Holdings

The maps shown below have been scanned from the GVP map archives and include the volcano on this page. Clicking on the small images will load the full 300 dpi map. Very small-scale maps (such as world maps) are not included. The maps database originated over 30 years ago, but was only recently updated and connected to our main database. We welcome users to tell us if they see incorrect information or other problems with the maps; please use the Contact GVP link at the bottom of the page to send us email.


Title: Computer Generated Geologic Map of Japan
Publisher: Geological Survey of Japan
Country: Japan
Year: 1990
Series: No 22
Map Type: Geology
Scale: 1:2,000,000
Map of Computer Generated Geologic Map of Japan

Title: Japan, South Korea
Publisher: DMA Aerospace Center
Country: Japan, S Korea
Year: 1988
Series: ONC
Map Type: Topographic
Scale: 1:1,000,000
Map of Japan, South Korea

Title: (A) Q Maps of Japan Landforms, Geol, Tect: NEast
Publisher: Univ of Tokyo Press & Japan Association for Quaternary Research
Country: Japan
Year: 1987
Map Type: Geology
Scale: 1:1,000,000
Map of (A) Q Maps of Japan Landforms, Geol, Tect: NEast

Title: Japan
Publisher: DMA Aerospace Center
Country: Japan
Year: 1985
Series: TPC
Map Type: Topographic
Scale: 1:500,000
Map of Japan

Title: Historical Japan
Publisher: National Geographic Society
Country: Japan
Year: 1984
Series: National Geographic
Map Type: Geographic
Scale: 1:2,982,000
Map of Historical Japan

Title: Geol Map of Japan/ Geol Atlas
Publisher: Geol Survey of Japan
Country: Japan
Year: 1982
Map Type: Geology
Scale: 1:1,000,000
Map of Geol Map of Japan/ Geol Atlas

Title: Central Japan
Publisher: Geographical Survey Institute of Japan
Country: Japan
Year: 1980
Series: CIM 1:1 mil
Map Type: Topographic
Scale: 1:1,000,000
Map of Central Japan

Title: North Japan
Publisher: Geographical Survey Institute of Japan
Country: Japan
Year: 1980
Series: CIM 1:1 mil
Map Type: Topographic
Scale: 1:1,000,000
Map of North Japan

Title: North Japan
Publisher: Geographical Survey Institute of Japan
Country: Japan
Year: 1980
Map Type: Topographic
Scale: 1:1,000,000
Map of North Japan

Title: North Japan
Publisher: Geographical Survey Institute of Japan
Country: Japan
Year: 1980
Map Type: Topographic
Scale: 1:1,000,000
Map of North Japan

Title: Geological Map of Japan
Publisher: Geological Survey of Japan
Country: Japan
Year: 1978
Map Type: Geology
Scale: 1:1,000,000
Map of Geological Map of Japan

Title: Geological Map of Japan
Publisher: Geological Survey of Japan
Country: Japan
Year: 1978
Map Type: Geology
Scale: 1:1,000,000
Map of Geological Map of Japan

Title: Chokai-san
Publisher: Geographical Survey Institute of Japan
Country: Japan
Year: 1977
Map Type: Topographic
Scale: 1:50,000
Map of Chokai-san

Title: Fukura
Publisher: Geographical Survey Institute of Japan
Country: Japan
Year: 1977
Map Type: Topographic
Scale: 1:50,000
Map of Fukura

Title: Distribution Map of Hot Springs in Japan
Publisher: Geological Survey of Japan
Country: Japan
Year: 1975
Series: 1:2,000,000
Map Type: Unknown
Scale: 1:2,000,000
Map of Distribution Map of Hot Springs in Japan

Title: (Japanese) Geol map of Japan
Publisher: Geographical Survey Institute of Japan
Country: Japan
Year: 1974
Series: from Natl Atlas Japan
Map Type: Geology
Scale: 1:2,500,000
Map of (Japanese) Geol map of Japan

Title: Landform Classification
Publisher: Geographical Survey Institute of Japan
Country: Japan
Year: 1972
Series: from Natl Atlas Japan
Map Type: Unknown (Land)
Scale: 1:2,500,000
Map of Landform Classification

Title: Land Use
Publisher: Geographical Survey Institute of Japan
Country: Japan
Year: 1972
Series: from Natl Atlas Japan
Map Type: Unknown (Land)
Scale: 1:2,500,000
Map of Land Use

Title: Population Distribution
Publisher: Geographical Survey Institute of Japan
Country: Japan
Year: 1972
Series: from Natl Atlas Japan
Map Type: Unknown
Scale: 1:2,500,000
Map of Population Distribution

Title: River Systems
Publisher: Geographical Survey Institute of Japan
Country: Japan
Year: 1972
Series: from Natl Atlas Japan
Map Type: Unknown
Scale: 1:2,500,000
Map of River Systems

Title: North Japan
Publisher: Geographical Survey Institute of Japan
Country: Japan
Year: 1966
Map Type: Topographic
Scale: 1:1,000,000
Map of North Japan

Title: Sendai
Publisher: US Army Map Service
Country: Japan
Year: 1954
Series: AMS
Map Type: Topographic
Scale: 1:250,000
Map of Sendai

Title: Akita
Publisher: US Army Map Service
Country: Japan
Year: 1954
Series: AMS
Map Type: Topographic
Scale: 1:250,000
Map of Akita

Title: Fukura
Publisher: US Army Map Service
Country: Japan
Year: 1944
Series: AMS
Map Type: Topographic
Scale: 1:50,000
Map of Fukura

Title: Chokai-San
Publisher: US Army Map Service
Country: Japan
Year: 1944
Series: AMS
Map Type: Topographic
Scale: 1:50,000
Map of Chokai-San

Title: Sendai
Publisher: US Army Map Service
Country: Japan
Year: 1943
Series: AMS
Map Type: Topographic
Scale: 1:1,000,000
Map of Sendai
Smithsonian Sample Collections Database

There are no samples for Chokaisan in the Smithsonian's NMNH Department of Mineral Sciences Rock and Ore collection.

Affiliated Sites