GSI HOME > The latest survey results of Nishinoshima Island (as of July 2016): no major changes were identified. Last Updated : August 17, 2016

The latest survey results of Nishinoshima Island (as of July 2016): no major changes were identified.

Outline

Geospatial Information Authority of Japan (GSI) took aerial photographs of Nishinoshima Island on July 25th, 2016 using its Unmanned Aerial Vehicle (UAV). The latest analysis results are now publicly available.
The area was approximately 2.75 square kilometers. The elevation of highest point was approximately 142 meters. The volume was 87.22 million cubic meters. (These values are unofficial and provided for reference purposes.)

Photographing

This photographing was performed by GSI’s Unmanned Aerial Vehicle (UAV) launched from Chichijima Island, Ogasawara Village, Tokyo, with the cooperation of the Ministry of Defense. GSI initiated photographing from December 2013 and obtained topographic changes on a regular basis. This operation was the tenth photographing.

Comparison of measurement results

Comparison of measurement results with aerial photographs and orthophotographs taken around Nishinoshima Island in this March is shown in the table below.
Date of photography New land area
(unofficial values)
Highest elevation
(unofficial values)
Volume of lava emitted and accumulated over the sea level
(unofficial values)
March 3rd, 2016 2.73km2 142 m 87.21 mil. m3
July 25th, 2016 2.75km2 142 m 87.22 mil. m3
 

Comments on the measurement results from Professor Setsuya Nakada

Here are comments on these latest measurement results from Professor Setsuya Nakada, Earthquake Research Institute, The University of Tokyo, (Leader of The Nishinoshima General Observation Team, Coordinating Committee for Prediction of Volcanic Eruption):
  • These latest measurement results have identified that the elevation of the central pyroclastic cone, the highest point of the island, has not changed. Also, considering measurement error, it is indicated that land volume above sea level was almost the same as that obtained from the last survey.
  • At the coastline, slight erosion of lava can be observed, while sand-gravel deposition area was increased. In the surface structure of the lava field, no significant changes can be recognized. Around the south rim of the crater of the central pyroclastic cone, area where sulfur is seen has obviously become larger than last time. Small rift structure consisting of obviously uneven cracks has been formed. 
  • This fact shows that contraction under the south side of the central pyroclastic cone proceeded, resulting that the cracks were formed on land surface due to subsidence, and that sulfurous gas emissions continually occurred along the cracks.
  • From these results, it can be concluded that major volcanic activities of Nishinoshima have almost ceased from late last year to early this year, and that contraction which might be caused by lava drainback occurred underground by July.

Aerial photographs and related information

Aerial photographs and related information are being published on the Internet under "GSI Maps".
URL: http://maps.gsi.go.jp/#15/27.244557/140.879660/&base=std&ls=std%7C20160725dol&disp=11&lcd=20160303dol&vs=c1j0l0u0f0&d=vl   (in Japanese)
Website for information relating to eruption activity in and around Nishinoshima Island
URL: http://www.gsi.go.jp/gyoumu/gyoumu41000.html  (in Japanese)

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