The eruption on Mt Ontake in japan where more than 30 hikers are presumed dead is a tragic reminder that volcanoes can be unpredictable.
But scientists are constantly looking at events like this one to help us better understand them.
Similar eruptions are quite common in New Zealand as well - the most recent example was Mt Tongariro in 2012.
Massey University biosciences lecturer Heather Hendrickson said on Firstline this morning the Japan eruption was a "tragic reminder" of how dangerous volcanoes can be.
"This was a volcano that was under incredible amounts of surveillance and the reason that we can't predict this particular type of eruption is that it doesn't involve magma rising to the surface.
"So there aren’t going to be any other kinds of seismic signs in advance."
Groundwater had probably hit magma deep down in the volcano and "flashed" to become steam, she said.
"That immediately just sets off an eruption and so there aren’t warning signs of the kind that we might expect."
Watch the video for the full interview.
source: newshub archive