Japan and Volcanic Eruption Predictors


Last Saturday’s volcanic eruption in central Japan gives cause to explore predictors of the natural disaster. While it is impossible to prevent magmatic eruption, scientists have discovered warning signs of volcanic activity. Whether people nearest the recent eruptions were aware of or could detect these signs is unknown. The most recent eruption in Japan does shed light on prediction accuracy.

The bodies of 31 hikers were discovered near the peak of Mount Ontake, a 10,062 foot volcano that last erupted in 2007. Rescuers making a quick check determined that their hearts and lungs had stopped, but only four of the bodies were able to be recovered due to continued volcanic activity. The hikers were among many (estimated at 250 hikers) who climbed the mountain to observe the first signs of autumn.

Minor earthquakes over the course of weeks preceded the eruption, which was described as a “spectacular geyser of ash.” Smoke billowed from the mountaintop blanketing the upper slopes with ash, leaving an appearance that resembled that of a moonscape. However, seismologists did not consider the minor earthquakes prior to Saturday’s eruption to be warning of the major event. They report observing no change in the crustal movement below the mountain. The Japan Meteorology Agency failed to forecast the event. Their volcanic observation systems will be reviewed, particularly in light of the grown of tourism on the country’s mountains, some of which are active volcanoes.

Monitoring potential volcano eruption is expensive because active volcanoes do not often erupt, and there are many sites to observe. However, there are factors of prediction to consider. One indicator is sulfur dioxide and other gases being expelled from the mountain as magma moves below the surface. Sulfur dioxide can be detected through smell, as with the Mount Ontake explosion. Volcanologists can measure its temperature and composition of that and the other gases. The gases cause the mountain to swell or breathe which is another strong indicator of a possible eruption.

Active volcanoes are those showing some level of activity, likely to explode over time. There are about 1,900 active volcanoes on Earth. Others are dormant, showing no signs of exploding, but can become active at any point in the future. Some volcanoes are considered extinct.

A helicopter rescuing three of the stranded hikers on Sunday met ash-thickened air. Threats of subsequent eruptions and the release of toxic gases complicated further rescue efforts and death confirmations. Even on Sunday, the mountain continued to emit smoke.

Many hikers descended the mountain on their own while others awaited rescue in shelters. Thirty of those who descended on their own were being treated for minor to serious injuries. At least 45 are still reported missing, and here are concerns that ash would hinder their ability to breathe. It is uncertain whether any of the hikers were aware of any predictors of Japan’s volcanic eruption.

Cooling Magma

Volcanoes are formed from material spewed from the eruption of lava, rocks, and ash. Thus, the face of a volcanic mountain can change over a period of weeks or years. An eruption’s power is fueled by thick magma and accumulated gas. The size of the explosion correlates with the amount of gas build up.

For people living near a volcano, a large eruption can be extremely dangerous. Lava flow can reach 2,000 degrees Fahrenheit (1,250 degrees Celsius) burning everything in its path. The explosion could rain boulders on towns, cause landscape-altering mud flows that bury villages, and spew ash and toxic gases causing lung damage.

Scientists estimate that there have been over 260,000 volcano-related deaths in the past 300 years. With time and the improvement of monitoring devices, seismologists and volcanologists will more effectively be able to forecast eruptions and hope to reduce those numbers. The skills of volcano observers are improving, but all volcanoes are different, and similar signs of activity do not always equate to similar results.

By Charice Long


The New York Times
National Geographic
The Japan News
Annenberg Learner

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