This news isn’t about new volcanic activity in Japan but rather the results of one of the most tragic volcanic events in the last few years. In September 2014, Ontake had a surprising phreatic (or phreatomagmatic) explosion. There was little in the way of clear signs that such a blast was going to occur beyond some volcanic earthquakes that started in the week before the eruption. Ontake is a very popular hiking destination, so many people were on the volcano when the eruption occurred and at least 54 people died as a result of the eruption.
Now, families of some of the victims are suing the local government over the eruption, claiming that they downplayed the threat posed by the volcano and that it was inadequately monitored (only three of five seismometers were working at the time). This is a little bit like the trial of the Italian geologists after the L’Aquila earthquake, where they were blamed for the deaths due to the earthquakes because they downplayed the risk.
The big problem is that geologists monitoring volcanoes or assessing earthquake hazards only have pieces of data from which to work, so making claims without a firm backing can be as bad. If geologists lose credibility because of too many “false positives” about an eruption, then getting people to leave when a real crisis arises can become nearly impossible. The volcanologists from the Japan Meteorological Agency (JMA) worked with the data in hand and determined no apparent threat in Ontake’s behavior. This ended up being incorrect, but not really due to misinterpreting the data that was being collected, however imperfect.
Is the local government (geologists) really to be blamed for the deaths or was it a unavoidable accident?
Why? – It is a very constant and large supply of magma feeding it.
They are formed at 3 locations:
1) Destructive plate boundaries (Convergent)
2) Constructive plate boundaries (Divergent)
3) Where Hot Plumes exist under Oceanic plate (Hawaii is formed this way)
Aogashima – one of the islands of the a volcanic island arc South of Japan (see the right of the Picture for a depression in the ocean –> Izu-Bonin Trench)
Aogashima, along with several other volcanic islands, form the Izu Islands – a volcanic island arc (possibly due to the convergence of Pacific plate and Philippine(?) plate)
For the residents of Aogashima, an island about 200 miles due south of Tokyo, 1785 was an unforgettable year. Although they weren’t alive to witness the deadliest event in island history, they know what unfolded all too well—and what they know hasn’t changed their mind about living atop a real-life volcano.
They’ve heard the stories about how, on May 18, the ground began to shake. Giant plumes of gas and smoke billowed out from the mouth of the island’s volcano, shooting rocks, mud and other debris into the sky. By June 4, the island’s 327 residents had no choice but to evacuate, but only about half succeeded and the rest perished. Those who live on the island that’s home to a volcano still registered as active by the Japanese Meteorological Agency, the governmental agency responsible for monitoring the nation’s 110 active volcanoes, know that there’s always the chance that history could repeat itself. But Aogashima’s inhabitants are willing to take that risk
Location and Topography of Sarychev Peak Volcano.
How do the contour intervals change as we approach the summit? What kind of volcano could this be?
Based on the volcano’s location, is it possible to predict the type of volcano, stratovolcano or shield?
Last year, a magnitude-6.0 earthquake rocked the Sabah region of Malaysia. The quake triggered massive rock avalanches on Mount Kinabalu and tragically took the lives of 18 people on the mountain.
Source: Looking back on the Sabah Quake one year later
Some notes on Volcanoes from Tulane University.
Some words used in here are taught at A Levels and beyond, e.g. andesitic, rhyolitic, however, otherwise many of the words should be familiar to you all at O levels.
The sections on Shield volcano and Stratovolcano will be most useful to us.