10/23/2014 — Large volcanic eruption could destroy Japan : Bury cities under lava in 2 hours

Some troubling news out of Japan comes from a recently released study done by Yoshiyuki Tatsumi, and Keiko Suzuki of Kobe University Graduate School of Science, Department of Earth and Planetary Science Department.

Talk of lava flows which could bury entire populations in 2 hours, and ash fallout which would bury the nation, killing or displacing 127 million people within hours, or days.

Here are a few recent examples of unexpected Japanese eruptions:


Above: .gif of Nishinoshima erupting on Oct 17 2014


Here is the full release (in Japanese):


Here is the full release translated:


Translated version below:

Announces risk mechanisms and huge caldera eruption

October 22, 2014

Illustrations and text data of this press release is available for download at the following link.

Summary of the research results

Statistical analysis of the frequency and scale of the volcanic eruption that occurred 120,000 years in the Japanese archipelago, Keiko Suzuki, Associate Professor and Professor Yoshiyuki Tatsumi of Kobe University Graduate School of Science, Department of Earth and Planetary Science Department, the following findings got. October 22, I am pleased to announce, such as Education, Culture, Sports, Science and press conference for this finding.

  1. The huge eruption, such as with the formation of the caldera and mountain body eruption of normal, that the integrated-eruption of magma occurs at a different mechanism I understand. I thought cracked by buoyancy due to the size of their own, magma chamber, which causes huge caldera eruptions, leading to the eruption.
  2. The volcano cause huge caldera eruption, be located in the region of crust deformation rate is small I understand. You will be considered in a place like this, effectively, high viscous magma rises the crust one after another, and to form a huge magma chamber.
  3. Probability that the huge caldera eruption occurs in the next 100 years in the Japanese archipelago is about 1%. This probability is the same level as the probability of occurrence ’30 Kobe earthquake in (the Great Hanshin-Awaji Earthquake) occurred the day before. In other words, it should be recognized that it is not a wonder when huge eruption even if such occurred. In the worst case, non-life person of 100 million 20 million people are expected by the huge caldera eruption.

(Proceedings of Japan Academy, Series B, Physical and Biological Sciences) in Japan Academy Bulletin, this research results, will be posted on November 11, 2014.

Background of research

Japan is a volcanic powers that about 7% of the (volcano erupted in the last 10,000 years) active volcanoes on Earth are concentrated. The volcanic activity of these, so far has caused a lot of damage. In recent years, the possibility of Mount Fuji eruption has been focused Mitake volcano is also, to erupted the other day. To represent the scale of the volcanic eruption, eruption magnitude scale that (M) is used. This is obtained by subtracting 7 from the logarithm of the (kg) total weight of the ejecta. For example, large-scale eruption Mount Fuji and Hoei eruption, such as Sakurajima Taisho eruption was in Rikutsuzuki and Osumihanto Sakurajima is represented M5.3, and M5.6, respectively. Sakurajima Taisho eruption is one of the eruption in history largest in Japan. On the other hand, in the Japanese archipelago, (0.01% or less of the total) what frequency low, but the huge eruption of M7 more than spewing more than 60% of the volcanic products of all has also happened.Eruption like this is typical enormous damage is expected to be happens once the “low-frequency large-scale disaster”. For example, Kikai Akahoya eruption in (M8.1), Jomon culture of southern Kyushu destroyed at least, that it took in 1000 near to the recovery occurred in Satsuma Iwo Jima volcano in Kagoshima Prefecture, southern about 7300 years ago from now has been said.

Therefore, it is desirable to understand the mechanism of generating huge eruption like this, to recognize correctly the risk is very important for us Japanese living in volcanic powers.

The contents of the study


Relationship of the size and frequency of [Figure 1] eruption

Looking at the relationship between the frequency scale of volcanic eruptions around the world and (magnitude), stunning linear relationship is observed up to M8, but the frequency has dropped obviously eruption of M9 scale (Figure 1A).

This is due that there is a limit to the size of the volcanic system that causes the eruption, that there is an upper limit to the thickness of the crust, for example, magma chamber is formed. On the other hand the relationship of the size and frequency of volcanic activity of the Japanese archipelago is somewhat complex, a linear relationship has been broken between the M6 ​​and M5 (Figure 1A).

In the Japanese archipelago, there is a possibility that the mechanism of magma eruption and the occurrence of specific working. To investigate this point, I tried to examine the relationship of the size and frequency of eruption a little more detail we (Figure 1B).

To handle statistically such a phenomenon there is an upper limit to the scale as volcanic eruptions, that analysis “extreme value theory” using the Weibull function is particularly effective has been known.

120 000 years, and to analyze the eruption of M4 more than a total of 447 times in the Japanese archipelago, it can not be represented well in (4 ≤ M ≤ 9 in Figure 1B) Weibull function of a single eruption all of these. On the other hand, the cumulative frequency of the M7 and more than M5.7 or less, can be reproduced well by the Weibull function separately.

In addition, the eruption of scale in the middle of these, you can be understood as a superposition of a small eruption and eruption massive than that.

The important point here, eruption of each Weibull two functions can be applied, is that the style of eruption is different. In other words, all of the eruption from the mountainside or summit whereas the (volcano eruption), the eruption of the M7 or more is associated with the formation of a collapse caldera eruption all of M5.7 or less (Figure 1B).

The worst-case scenario of the huge caldera volcanic eruptions and distribution of huge volcanic caldera of [Figure 2] Japanese archipelago

From the above, the huge caldera eruption involving the caldera forming eruption mountains and body of normal, that it takes place in a different mechanism is expected.

Volcano eruption can be thought of foaming due to temperature rise and pressure increase due to the fact that a new magma is supplied to the magma chamber to be the cause. On the other hand I think the case of the huge caldera eruption, cracks occur at the top of the magma chamber in the buoyancy of the magma itself of a huge magma chamber within. Furthermore, it is in the area slow (deformation) crustal strain rate was understand volcano that has caused a huge caldera eruption (Figure 2).

Basaltic magma hot bottom of the crust up to rise occurred in the mantle, has combed the crust of the archipelago. It is thought the strain rate is small at that time, rhyolitic magma Deki melted crust is separated and rise one after another effectively, and to form a huge magma chamber.

As we have analyzed statistically the frequency of giant caldera eruptions in the past, it becomes possible to determine the eruption probability of future by using the results (Table 1).As a result, the probability of huge caldera eruption takes place 100 years in the Japanese archipelago is about 1% was seen. This probability is the same level as the probability of occurrence ’30 Kobe earthquake in (the Great Hanshin-Awaji Earthquake) occurred the day before. In other words, it is a translation it is not surprising when huge eruption even if such occurred.

Occurrence of a huge caldera eruption in [Table 1] Japanese archipelago
Occurred in southern Kyushu in about 28 000 years ago (now huge caldera eruption of past information geological most are aligned Aira Aira With reference to the caldera eruption), we examined the effects of the huge caldera eruption (Figure 2).


Above: October 17 2014 eruption of Nishinoshima Volcano in Japan


At the moment, it is not possible to identify huge caldera eruption would happen anywhere in the Japanese archipelago, but it is repeated eruptions of this class up to seven times in 120 000 years, crustal strain rate also think about the small central-southern Kyushu I considered, and it also appropriate from the viewpoint of assuming the worst.

Because volcanic ash carried by the westerlies in the Japanese archipelago. Pyroclastic flow of several hundred ℃ as high will fill than 700 million people of the population range within two hours from its occurrence.

Flow and volcanic ash and to the east, it becomes impossible life in Japan throughout with the exception of the eastern part of Hokkaido by ash fall. The important thing here is that I can not help thinking the relief efforts to Honshu residents of 100 million 20 million people fell, transportation and lifeline hopeless almost complete paralysis.

The future development of

(Dashed lines and numbers) risk of [Figure 3] disaster

Massive earthquake gives extensive damage to Japan. For example, it is said the number of deaths of Nankai earthquake is said to be 70% probability of occurrence of the next 30 years even with more than 30 million people.

It is not an exaggeration to say huge caldera eruptions, and extinguish the country of Japan, on the other hand. Compared to the disaster multiplied by the probability of occurrence in the number of deaths to “risk”, huge caldera eruption that you’ll understand what is a serious threat to how (Figure 3).

One of the things is we have to do, and to ensure its technology to accurately capture the state of the magma chamber spread thinly in a few km or less in thickness, which is formed in the middle of the crust, which is also about 30km thick future , That’s what we will do the monitoring of underground of Kyushu Island is the danger zone of the huge caldera eruption.

You also must not forget to refine the data on the history of the eruption and generation ages, the scale of the huge caldera eruptions in the past.

Watch the report here:


“One major volcanic eruption could make Japan “extinct,” a study by experts at Kobe University warns, although the chances of that happening are relatively slim.

The study, by Prof. Yoshiyuki Tatsumi and Associate Prof. Keiko Suzuki, concludes that the chance of a big eruption that would disrupt the lives of everyone in Japan are about 1% over the next 100 years.

The researchers based their findings on the cycles and impacts of major eruptions in Japan on the study of the Aira Caldera near what is now the city of Kagoshima on southern Kyushu island. The caldera was created 28,000 years ago and has a diameter of 20 kilometers.

If a similar eruption were to take place in the area today, within about two hours the flow of molten rock, lava and ash would cover an area in which seven million now live. A large amount of ash would be carried across the country, shutting down transportation and other key systems, disrupting the lives of nearly 120 million people, or almost everyone in Japan.

“We should be aware,” the researchers warn in their report to be published in November. “It wouldn’t be a surprise if such gigantic eruption were to take place at any moment.”

The study pointed out that following the eruption of the Kikai Caldera over 7,000 years ago off what is now the southern tip of Kyushu, it took 1,000 years for human settlement in the area to recover.

The study also said approximately 7% of all volcanoes that have erupted over the past 10,000 years are located in Japan.

The professors warned that volcanic activity, especially in Kyushu, should be closely studied and monitored.

The eruption of Mount Ontake in central Japan in September killed 56 people and left seven still missing. It was the first fatal eruption in 14 years in Japan.”


“Tokyo (AFP) – Japan could be nearly destroyed by a massive volcanic eruption over the next century, putting almost all of the country’s 127 million-strong population at risk, according to a new study.


“It is not an overstatement to say that a colossal volcanic eruption would leave Japan extinct as a country,” Kobe University earth sciences professor Yoshiyuki Tatsumi and associate professor Keiko Suzuki said in a study publicly released on Wednesday.

The experts said they analysed the scale and frequency of volcanic eruptions in the archipelago nation over the past 120,000 years and calculated that the odds of a devastating eruption at about one percent over the next 100 years.

The chance of a major earthquake striking the city of Kobe within 30 years was estimated at about one percent just a day before a 7.2-magnitude quake destroyed the Japanese port city in 1995, killing 6,400 people and injuring nearly 4,400 others, the study noted.

“Therefore, it would be no surprise if such a colossal eruption occurs at any moment,” it added.

The new research comes weeks after Japan’s Mount Ontake erupted without warning — killing 57 people and leaving at least six others missing in the country’s deadliest volcanic eruption in almost 90 years.

The Kobe University researchers said their study was critical because Japan is home to about seven percent of the volcanoes that have erupted over the past 10,000 years.

A disaster on the southernmost main island of Kyushu, which has been struck by seven massive eruptions over the past 120,000 years, would see an area with seven million people buried by flows of lava and molten rock in just two hours, they said.

Volcanic ash would also be carried by westerly winds toward the main island of Honshu, making almost all of the country “unliveable” as it strangled infrastructure, including key transport systems, they said.

It would be “hopeless” trying to save about 120 million living in major cities and towns across Honshu, the study said.

This prediction was based on geological findings from the eruption of a gigantic crater, 23 kilometres (14 miles) across, in southern Kyushu about 28,000 years ago.

The study called for new technology to accurately grasp the state of “magma reservoirs” which are spread across the earth’s crust in layers a few kilometres deep.”

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