2017 Volume 123 Issue 5 Pages 309-319
Japan Meteorological Agency reported that the mode of eruptions of Shindake Volcano in 2014 and 2015 was phreatomagmatic or magmatic, which generated high-velocity pyroclastic flows. This interpretation is based on the presence of fresh glass shards in the tephra deposits. However, the glass shards were non-vesiculated, and their groundmass were almost crystalline, hence they are regarded to have originated from consolidated intrusive bodies in the shallow vent.
Similar examples of ejecta were reported from the violent eruptions of Shindake Volcano in the 20th century. The representative sample consisted of high-temperature large volcanic jointed blocks erupted on 22 June 1966. The eruptions caused a forest fire, indicating high-temperature, probably more than 400 degrees Celsius. They have been interpreted as ejected blocks from a dike in shallow vent. Many explosive eruptions from Shindake Volcano in historical time have generated pyroclastic materials of the same origin. The 2015 eruption clouds, spouted out directly from the crater and flowed down the slope with high speed (>100 km/h), should be classified as a blast.
