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Chokaisan

Photo of this volcano
  • Japan
  • Composite (Stratovolcano(es))
  • 1974 CE
  • Country
  • Landform (Volc 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 14 confirmed Holocene eruptive periods.

1974 Mar 1 - 1974 Apr 30 Confirmed Eruption Max VEI: 1

Episode 1 | Eruption Episode E side of Shinzan, W of Kojin-yama
1974 Mar 1 - 1974 Apr 30 Evidence from Observations: Reported

List of 6 Events for Episode 1 at E side of Shinzan, W of Kojin-yama

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Seismicity (volcanic)
   - - - -    - - - - Phreatic activity moderate
   - - - -    - - - - Ash
   - - - -    - - - - Earthquakes (undefined) Before.
   - - - -    - - - - Lahar or Mudflow moderate
1974 Mar 1    - - - - VEI (Explosivity Index)

1834 Jul 9 - 1834 Jul Confirmed Eruption Max VEI: 2 (?)

Episode 1 | Eruption Episode
1834 Jul 9 - 1834 Jul Evidence from Observations: Reported

List of 4 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity
   - - - -    - - - - Lahar or Mudflow Uncertain
   - - - -    - - - - Fauna Kill Aquatic.
1834 Jul 9    - - - - VEI (Explosivity Index)

1821 May 23 Confirmed Eruption Max VEI: 2 (?)

Episode 1 | Eruption Episode Near Shinzan and Shichiko-zan
1821 May 23 - Unknown Evidence from Observations: Reported

List of 2 Events for Episode 1 at Near Shinzan and Shichiko-zan

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity
1821 May 23    - - - - VEI (Explosivity Index)

1800 Dec - 1804 Jul (?) Confirmed Eruption Max VEI: 2

Episode 1 | Eruption Episode Shinzan (foot of Kojin-yama)
1800 Dec - 1804 Jul (?) Evidence from Observations: Reported

List of 13 Events for Episode 1 at Shinzan (foot of Kojin-yama)

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
   - - - -    - - - - Phreatic activity
   - - - -    - - - - Lava flow
   - - - -    - - - - Lava dome
   - - - -    - - - - Ash
   - - - -    - - - - Bombs
   - - - -    - - - - Blocks
   - - - -    - - - - Earthquakes (undefined) Time and Type Unknown.
   - - - -    - - - - Lahar or Mudflow
   - - - -    - - - - Fauna Kill Aquatic.
1800 Dec    - - - - VEI (Explosivity Index)
1801 Aug 10    - - - - VEI (Explosivity Index)
1801 Aug 14    - - - - Fatalities

[ 1764 ] Uncertain Eruption

Episode 1 | Eruption Episode
1764 - Unknown Evidence from Unknown

List of 4 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion Uncertain
   - - - -    - - - - Cinder Cone Uncertain
   - - - -    - - - - Scoria Uncertain
1764    - - - - VEI (Explosivity Index)

1740 Jun (?) - 1747 (?) Confirmed Eruption Max VEI: 2 (?)

Episode 1 | Eruption Episode Small crater at foot of Kojin-yama
1740 Jun (?) - 1747 (?) Evidence from Observations: Reported

List of 4 Events for Episode 1 at Small crater at foot of Kojin-yama

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity
   - - - -    - - - - Ash
   - - - -    - - - - Property Damage
1740 Jun
(?)
   - - - - VEI (Explosivity Index)

[ 1738 Dec 31 ± 365 days ] Uncertain Eruption

Episode 1 | Eruption Episode
1738 Dec 31 ± 365 days - Unknown Evidence from Unknown

List of 2 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion
1738 Dec 31 ± 365 days    - - - - VEI (Explosivity Index)

[ 1735 ] Uncertain Eruption

Episode 1 | Eruption Episode
1735 - Unknown Evidence from Unknown

List of 4 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion Uncertain
   - - - -    - - - - Cinder Cone Uncertain
   - - - -    - - - - Scoria Uncertain
1735    - - - - VEI (Explosivity Index)

1659 Apr - 1663 ± 1 years Confirmed Eruption  

Episode 1 | Eruption Episode
1659 Apr - 1663 ± 1 years Evidence from Observations: Reported

List of 1 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity

[ 1560 ] Uncertain Eruption

Episode 1 | Eruption Episode
1560 - Unknown Evidence from Unknown

List of 2 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion Uncertain
   - - - -    - - - - Volcanic "smoke"

[ 1477 ] Uncertain Eruption

Episode 1 | Eruption Episode
1477 - Unknown Evidence from Unknown

List of 1 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Ash Uncertain

[ 0999 ] Uncertain Eruption

Episode 1 | Eruption Episode
0999 - Unknown Evidence from Unknown

[ 0948 Dec 31 ± 365 days ] Uncertain Eruption

Episode 1 | Eruption Episode
0948 Dec 31 ± 365 days - Unknown Evidence from Unknown

0939 May 15 Confirmed Eruption  

Episode 1 | Eruption Episode
0939 May 15 - Unknown Evidence from Observations: Reported

List of 1 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity

[ 0915 Aug 23 - 0915 Sep 1 ] Discredited Eruption

[ 0884 Jul 26 - 0884 Aug ] Uncertain Eruption

Episode 1 | Eruption Episode
0884 Jul 26 - 0884 Aug Evidence from Unknown

List of 1 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion Uncertain

0871 May 5 Confirmed Eruption Max VEI: 2

Episode 1 | Eruption Episode
0871 May 5 - Unknown Evidence from Observations: Reported

List of 5 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion violent, strong, or large
   - - - -    - - - - Lava flow
   - - - -    - - - - Lahar or Mudflow
   - - - -    - - - - Fauna Kill Aquatic.
0871 May 5    - - - - VEI (Explosivity Index)

[ 0861 May ] Uncertain Eruption

Episode 1 | Eruption Episode
0861 May - Unknown Evidence from Unknown

List of 3 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion Uncertain
   - - - -    - - - - Cinder Cone Uncertain
0861 May    - - - - VEI (Explosivity Index)

[ 0857 May ] Uncertain Eruption

Episode 1 | Eruption Episode
0857 May - Unknown Evidence from Unknown

List of 1 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Earthquakes (undefined)

[ 0856 ] Uncertain Eruption

Episode 1 | Eruption Episode
0856 - Unknown Evidence from Unknown

[ 0839 Oct 14 ] Uncertain Eruption

Episode 1 | Eruption Episode
0839 Oct 14 - Unknown Evidence from Unknown

List of 1 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion Uncertain

0830 Jan Confirmed Eruption  

Episode 1 | Eruption Episode
0830 Jan - Unknown Evidence from Observations: Reported

List of 4 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity
   - - - -    - - - - Ash
   - - - -    - - - - Lahar or Mudflow
   - - - -    - - - - Fauna Kill Aquatic.

0817 ± 7 years Confirmed Eruption  

Episode 1 | Eruption Episode
0817 ± 7 years - Unknown Evidence from Observations: Reported

List of 1 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity

[ 0804 - 0806 ] Uncertain Eruption

Episode 1 | Eruption Episode
0804 - 0806 Evidence from Unknown

List of 1 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion Uncertain

[ 0717 Jul ] Uncertain Eruption

Episode 1 | Eruption Episode
0717 Jul - Unknown Evidence from Unknown

List of 1 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion

0711 ± 3 years Confirmed Eruption  

Episode 1 | Eruption Episode
0711 ± 3 years - Unknown Evidence from Observations: Reported

List of 3 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity
   - - - -    - - - - Cinder Cone
   - - - -    - - - - Evacuations

[ 0610 ± 18 years ] Uncertain Eruption

Episode 1 | Eruption Episode
0610 ± 18 years - Unknown Evidence from Unknown

List of 1 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion Uncertain

[ 0577 Dec 1 ± 30 days - 0578 Jul 15 ± 45 days ] Uncertain Eruption

Episode 1 | Eruption Episode
0577 Dec 1 ± 30 days - 0578 Jul 15 ± 45 days Evidence from Unknown

List of 3 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion Uncertain
   - - - -    - - - - Lava flow Uncertain
   - - - -    - - - - Cinder Cone Uncertain

[ 0573 Mar (?) ] Uncertain Eruption

Episode 1 | Eruption Episode
0573 Mar (?) - Unknown Evidence from Unknown

List of 5 Events for Episode 1

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Explosion Uncertain
   - - - -    - - - - Cinder Cone Uncertain
   - - - -    - - - - Scoria Uncertain
   - - - -    - - - - Audible Sounds Uncertain
   - - - -    - - - - Earthquakes (undefined) Uncertain

0450 BCE (?) Confirmed Eruption  

Episode 1 | Eruption Episode OD-12 tephra
0450 BCE (?) - Unknown Evidence from Correlation: Tephrochronology

List of 2 Events for Episode 1 at OD-12 tephra

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity
   - - - -    - - - - Tephra

0650 BCE (?) Confirmed Eruption  

Episode 1 | Eruption Episode Higashi-Chokai
0650 BCE (?) - Unknown Evidence from Isotopic: 14C (uncalibrated)

List of 5 Events for Episode 1 at Higashi-Chokai

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Phreatic activity Uncertain
   - - - -    - - - - Lava flow Uncertain
   - - - -    - - - - Lava dome Uncertain
   - - - -    - - - - Avalanche
   - - - -    - - - - Edifice Destroyed Collapse/avalanche

1050 BCE (?) Confirmed Eruption Max VEI: 0

Episode 1 | Eruption Episode West flank (Saruana crater)
1050 BCE (?) - Unknown Evidence from Correlation: Tephrochronology

List of 3 Events for Episode 1 at West flank (Saruana crater)

Start Date End Date Event Type Event Remarks
   - - - -    - - - - Lava flow
   - - - -    - - - - Lava flow Entered water.
1050 BCE
(?)
   - - - - VEI (Explosivity Index)
Deformation History

There is no Deformation History data available for Chokaisan.

Emission History

There is no Emissions History data available for Chokaisan.

Photo Gallery

Chokaisan is the largest of the NE Honshu volcanoes, seen here from the NE. The volcano is comprised of two main overlapping edifices, the younger eastern area contains the large collapse scarp that was the source of the Kisakata debris avalanche, seen here opening to the N. Smaller cones later filled much of the area near the rear scarp.

Photo courtesy Ichio Moriya (Kanazawa University).
The N flank of Chokaisan was the source of a large debris avalanche about 2,600 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 open scar with the eastern rim forming the left-center peak, and the western rim to the right. Following the collapse, a series of lava domes and lava flows filled the upper area and formed the center peak.

Photo by Ichio Moriya (Kanazawa University).
An ash plume rises from the Shinzan lava dome at the summit of Chokaisan on 1 March 1974 after a repose of 140 years. Phreatic eruptions occurred in March and April that produced small lahars. The eruptions took place from an E-W-trending series of vents extending from the eastern caldera wall across the 1801 Shinzan lava dome and the Kojinyama cone. This view from the NW shows the eastern caldera wall behind the dome.

Photo courtesy of Japan Meteorological Agency, 1974.
A plume rises from a vent on Chokaisan on 24 April 1974 near the end of an eruption that began on 1 March. Ash deposits cover the slopes of the summit and lahar deposits descend the flanks to the lower left in this view from the SW. Shinzan lava dome appears above the plume to the left, with the eastern caldera wall in the background. The 1974 eruption, the first from Chokaisan in 140 years, ended on 30 April.

Photo courtesy of Japan Meteorological Agency, 1974.
GVP Map Holdings

Maps are not currently available due to technical issues.

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.

Smithsonian Sample Collections Database

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

External Sites