Inflation and increased seismicity were detected at Ontakesan in February, causing JMA to raise the Alert Level. Inflation ceased in late February and deformation rates had stabilized. Seismicity continued to fluctuate, but decreased in mid-March and volcanic tremor ceased on 19 March.
Inflation and increased seismicity were detected at Ontakesan in February, causing JMA to raise the Alert Level. Inflation ceased in late February and deformation rates had stabilized. Seismicity continued to fluctuate, but decreased in mid-March and volcanic tremor ceased on 19 March.
Ontake-san volcano today (image: Kaidakogen webcam)
The Japan Meteorological Agency (JMA) detected an elevated seismic activity over the past month.
JMA reported that the number of volcanic earthquakes at Ontakesan began increasing at 1415 on 23 February. Four minutes later a volcanic tremor signal was detected along with uplift on the S flank. At 1635 JMA raised the Alert Level to 2 (on a scale of 1-5).
JMA reported that activity at Ontakesan continued to decline during 26 June-3 July, although the volcano continued to be seismically active and emit white plumes to less than 1 km high. The Alert Level was lowered to 2 (on a scale of 1-5).
JMA reported that cloud cover mostly prevented visual observations of Ontakesan during 13-20 February; white plumes rose 50-200 m above the crater rim. Seismicity remained low. The Alert Level remained at 3 (on a scale of 1-5).
White steam plumes were observed during the past week. JMA reports seismic activity remained low, but maintains alert level 3, as sudden phreatic explosions could occur again.
JMA reported that cloud cover mostly prevented visual observations of Ontakesan during 10-16 December; white plumes rose 50 m above the crater rim and drifted SW on 10 December. Seismicity remained low. The Alert Level remained at 3 (on a scale of 1-5).
Wed, 3 Dec 2014, 06:00
JMA reported that cloud cover mostly prevented visual observations of Ontakesan during 3-9 December; white plumes rose 100 m above the crater rim on 7 December. The Alert Level remained at 3 (on a scale of 1-5).
Read allFri, 14 Nov 2014, 07:48
JMA reported that cloud cover often prevented visual observations of Ontakesan during 5-11 November; white plumes rose 200-300 m above the crater rim and drifted NE, E, and SE.
Read allWed, 12 Nov 2014, 06:00
JMA reported that cloud cover often prevented visual observations of Ontakesan during 12-18 November; white plumes rose 200 m above the crater rim and drifted E during 16-17 November. The Alert Level remained at 3 (on a scale of 1-5).
Read allFri, 7 Nov 2014, 13:16
White plumes rose 100-300 m above the crater rim and drifted NE and SE during 29-30 October and 4 November. The Alert Level remained at 3 (on a scale of 1-5).
Read allWed, 5 Nov 2014, 06:00
JMA reported that cloud cover often prevented visual observations of Ontakesan during 5-11 November; white plumes rose 200-300 m above the crater rim and drifted NE, E, and SE. The Alert Level remained at 3 (on a scale of 1-5).
Read allWed, 29 Oct 2014, 06:00
JMA reported that cloud cover often prevented visual observations of Ontakesan during 29 October-4 November; white plumes rose 100-300 m above the crater rim and drifted NE and SE during 29-30 October and 4 November. The Alert Level remained at 3 (on a scale of 1-5).
Read allFri, 24 Oct 2014, 14:59
The volcano continues to produce white steam plumes rising a few 100 m above the crater. According to press articles, 7 people are still missing from the 27 Sep eruption, but search and rescue operations are being suspended until springtime because of the winterly conditions. The Alert Level remained at 3 (on a scale of 1-5).
Wed, 22 Oct 2014, 06:00
JMA reported that cloud cover often prevented visual observations of Ontakesan during 22-28 October; white plumes were periodically observed rising 100-300 m above the crater rim and drifting E and SE. Seismicity remained low. The Alert Level remained at 3 (on a scale of 1-5).
Read allWed, 15 Oct 2014, 06:00
JMA reported that cloud cover often prevented visual observations of Ontakesan during 15-21 October; white plumes rose 100-200 m above the crater rim and drifted NE and SE during 16-18 October. White plumes rose 600 m on 19 October. A news article from 17 October noted that the search for the seven people still missing from the 27 September eruption was stopped due to wintery conditions; the search was expected to resume in the springtime.
Read allWed, 8 Oct 2014, 06:00
JMA reported that during 8-9 October ash emissions from Ontakesan continued. The plume turned white on 10 October, but during 10-14 October the emissions may have contained small amounts of ash. Tremor was below detection limits during 8-14 October.
Read allSat, 4 Oct 2014, 21:52
The volcano continues to emit plumes of steam and possibly some ash Tokyo VAAC reports.
Read allWed, 1 Oct 2014, 15:21
The death toll from Saturday's powerful, and deadly explosion of the volcano has now climbed to 48, press reports. The eruption was a sudden, unexpected (and unpredictable) phreatic explosion, i.e. caused by sudden evaporation of overheated water in the hydrothermal system of the volcano.
Read allWed, 1 Oct 2014, 06:00
JMA reported that ash emissions from Ontakesan likely continued during 1-7 October. The plume height could not be determined due to poor visibility although on 7 October observers noted that the plume rose 300 m above the crater rim and drifted E. Seismic levels fluctuated; tremor continued to be detected.
Read allSun, 28 Sep 2014, 06:52
In a screen grab from a YouTube video, hikers flee from Ontake on Saturday, Sept. 27, 2014, in Japan.
Yesterday's eruption might have caused more than 30 fatalities, Japanese press reports. Most of them were apparently killed by heart and respiratory failure after inhaling ash when caught in the outer areas of a pyroclastic flow or ash cloud descending the mountain.
Read allSat, 27 Sep 2014, 20:59
Pyroclastic flow during Ontake volcano's eruption today (Asahi.com)
A large explosive eruption occurred at Japan's second highest volcano today at 11:56 local time. An explosion produced an ash plume that rose approx. 4 km and a large pyroclastic flow that swept down the southwestern flank.
Read allWed, 24 Sep 2014, 06:00
According to the Japan Meteorological Agency, an unexpected phreatic eruption at Ontakesan occurred at 1152 on 27 September after an 11-minute period of tremor and uplift detected just minutes beforehand. The eruption produced a pyroclastic flow that traveled more than 3 km down the S flank and an ash plume that rose 7-10 km and drifted E. Ashfall was extensive in the area and up to 50 cm thick near the craters.
Read all