April 16, 2016 - JAPAN - After a series of deadly earthquakes in Japan, a “small-scale” eruption
of Mount Aso has been recorded by the Japan Meteorological Agency.
However, it decided to keep the alert level at 2, as it was not
immediately clear whether the natural disasters were related.
Plumes of smoke rose some 100 meters into the sky, according to
local media and videos captured by witnesses.
The eruption of Mt. Aso,
located in southern Japan, was recorded at around 11:30pm GMT Friday.Since
small eruptions had been recorded at Mt. Aso even before the series of
deadly quakes hit the area on Thursday and Friday, the Japanese
Meteorological Agency has reportedly decided to keep the alert level at 2
on a scale of 1-5.The volcano eruption follows two deadly earthquakes and dozens of powerful aftershocks that devastated Japan earlier this week.
On Friday (1:25am Saturday local time) a violent 7.1 magnitude earthquake struck the city of Kumamoto on the island of Kyushu. At least 11 people have so been confirmed dead in the disaster so far, while several dozens are feared to still be trapped under the rubble. Some 760 were treated in hospitals while rescue teams continue to search ruined houses.
Just a day beforehand, the same region was rattled by a 6.5 quake, in which at least ine people were killed and more than 850 injured. Authorities went on to evacuate over 40,000 people as scientists began to monitor nearby volcanoes for any signs of activity.
WATCH: Mount Aso volcano erupts.
Japanese authorities were also worried about a potential repeat of the 2011 Fukushima disaster scenario, when a 15-meter post-quake tsunami caused a nuclear meltdown. However, so far the Nuclear Regulation Authority said no irregularities had been recorded at three nuclear plants on the island of Kyushu and nearby Shikoku.
Over a hundred aftershocks have hit the region following the initial Thursday tremor. Officials have warned that the risk of further strong aftershocks will linger for about a week. - RT.
Kirishima of southern Kyushu have one after another volcanic tremors
that indicates the movement, such as magma underground,
Meteorological
Observatory, it has urged to be aware of the catastrophic blowout
phenomenon.
February 10, 2016 - JAPAN - In the vicinity of the Iozan of Ebino Kirishima mountain range that
spans Miyazaki Prefecture and Kagoshima Prefecture, on the 10th early in
the morning, volcanic tremor that becomes the third time earlier this
month has been observed.
With performing the Japan Meteorological Agency
is again field survey, we urged to be aware of the catastrophic
blowout, such as fumaroles and volcanic gas as volcanic activity has
been slightly increased.
And depends on the Japan Meteorological Agency, in the vicinity of the Iozan of the Kirishima mountain range, from before 5:00
on the 10th morning, a small volcanic tremor amplitude is considered to
indicate the movement of the hot water and volcanic gas underground has
been observed over a period of approximately 2 minutes .
WATCH: Volcanic tremors at Kirishima volcano.
Also, in
addition to changes in the small ground with the tremor was observed,
volcanic earthquakes have been observed four times up to 6 am and the
front and rear of the fine.
The volcanic tremor was observed in the vicinity of the Iozan, is the third time this time following the month 7th and 8th.
For
this reason, the Japan Meteorological Agency 10 morning, have carried
out a dispatch to investigate the two officials again to local, state
and of the fumaroles that up from, such as in the crater, the
temperature of the ground in the vicinity of the jet is not spread high
range we have examined and whether.
In Iozan now, other than the
interval of approximately 30 meters mountain trail through the directly
in front of the jet has not been carried out, such as intrusiveness
regulation, Miyazaki Prefecture, such as the 10th afternoon, to consider
the expansion of regulation to open the conference to have.
Location of the volcano. Google Maps
Kirishima (新燃岳 in Japanese), one of Japan's most active volcanoes. It is
actually a group of 18 young, small stratovolcanoes north of Kagoshima
Bay: Takachihonomine, Nakadake, Ohatayama, Karakunidake, Tairoike,
Ohachi, and Shinmoedake are the principal vents.
Historic eruptions have been recorded since 742 and there are more
than 60 recorded eruptions, mainly from Ohachi and Shinmoedake, with the
exception of a small lava flow from Iwoyama in 1768. Relatively large
eruptions occurred in 788, 1235, 1716-17 and 1768, and in 2011.
A violent eruption started at Kirishima on January 26, 2011, the largest one for more than 50 years.
Background:
The large Kirishima volcanic group covers an NW-SE
elongated area of about 20 x 30 km. The late-Pleistocene to Holocene
volcanoes are dominantly andesitic in composition and consist of
stratovolcanoes, conder cones, maars overlying shield volcanoes. The
larger edifices are the centrally located, 1700-m-high stratovolcanoes
Karakuni-dake, and the large maars Onami-ike and Mi-ike, located SW of
Karakuni-dake. Eruptions in the past 10,000 years have been concentrated
along an E-W line of vents from Mi-ike to Ohachi, and at Shinmoe-dake
to the NE. Frequent small-to-moderate explosive eruptions have been
recorded since the 8th century. Fumaroles are located on North slope of
the Karakunidake.
Eruptive history of Kirishima volcano
By most authors, the "Kirishima volcano" is referred to those
volcanic edifices overlying (younger than) the Kakuto ignimbrite,
related to the Pleistocene Kakuto caldera that formed around 300,000
years ago.
A series of stratovolcanoes, now poorly preserved, grew in the early
stage of activity following the Kakuto caldera formation. An interval
of volcanic quiet followed until about 60-70,000 years ago, when the
present-day stratovolcanoes which make up the Kirishima complex started
to grow.
About 35,000 years ago, a major eruption triggered the collapse of
Hinamoridake volcano at the northeastern end of the complex. It produced
a major debris avalanche that covers the area of present-day Kobayashi
City.
22,000 - 18,000 years ago, Iimoiyama and Maruokayama stratovolcanoes and a number of smaller edifices formed.
18,000 years ago, the Old-Karakunidake, Koshikidake and Shinmoedake volcanoes grew.
15,000 years ago, a large eruption built present-day Karakunidake
volcano, by rapid accumulation and welding of pyroclastic fall and flow
deposits draped over the older cone. Shortly later, lava flows erupted
from a vent on the southeast flank of Shinmoedake, building Nakadake.
9000 years ago, Shinmoedake had a larger explosive eruption.
7000 years ago, Old-Takachiho volcano formed from a vent on the
southeastern area of Kirishima. Other monogenetic volcanoes that
probably formed about that time include Ohataike and Biwaike maar.
6300 years ago, a major eruption from Old-Takachiho volcano occurred and built up the main cone present today.
The next 1000 years, only minor activity if any took place.
About 5000 years ago, Takachiho-no-mine stratovolcano formed on the
western slope of Old-Takachiho.
Small lava flows erupted from Fudoike
and Ohatayama.
4000 years ago, Shinmoedake had another larger explosive eruption.
The Miike maar formed 3000 years ago, following a powerful explosion
that ejected a large pumice deposit and produced base surges.
Only about 1000 years ago, Ohachi volcano formed on the western slope of Takachiho-no-mine and has remained the most active vent of Kirishima volcano since then.
Explosive eruptions from Kirishima volcano
During the past 22,000 years, volcanic activity was concentrated in a
zone running NW-SE and in the past 10,000 years mainly from Takachiho
volcano in the southeastern part of the Kirishima complex. Kirishima's
activity during the past 22,000 years comprises a number of large
explosive (vulcanian to subplinian) eruptions that have left important
tephra layers, including:
- Karakunidake scoria (ca. 18,000 years ago)
- Kamamuta scoria (ca. 7000 years ago)
- Ushinosune ash (ca. 6500 years ago)
- Miikee pumice (ca. 3000 years ago)
- Araso tephra ca. 700 AD
- Katazoe tephra 788 AD. This eruption was studied by Miyamoto
(2005) as an example of a case where 3 types of magma were erupted:
basalt, basaltic-andesite and andesite.
- Miyasugi tephra (ca. 1000 AD): several scoria layers from powerful
vulcanian-type eruptions, similar to the recent 2011 eruption. They
occurred in historic time, but the exact date is unknown.
- Takaharu tephra (ThT) in 1235 AD, the largest tephra layer from an
eruption in historic time (subplinian eruption, ca. 0.3 cubic km of ash
and pumice)
- Shinmoedake-Kyoho pumice 1716-1717 AD
- Shinmoedake-SHowa ash 1959 AD
Ohachi volcano
Ohachi Volcano is the youngest and most active of the Kirishima
group of stratovolcanoes, located at the southeastern part of the group.
It has a considerably large crater compared to the size of the cone,
with thick layers of welded scoria visible in the crater walls.
The oldest tephra recognized from Ohachi Volcano is the Araso tephra
(AsT), which erupted around 700 AD, thus suggesting that Ohachi is
little over 1300 years old.
Ohachi's rate of activity was not constant throughout its history.
In its early stage from AD 700 to 1235, 80% of its present-day volume
was erupted.
The magma chamber of Ohachi volcano has been estimated to be shallow, at around 4-6 km (ca. 1-2 kbar lithostatic pressure).
Magma discharge rates from Kirishima volcano
Based on magma discharge, the past 22,000 year interval of volcanic activity at Kirishima can be divided in 3 phases:
22,000 - 15,000 years ago: 0.8 million m3 / year
15,000 - 7,000 years ago: a relatively quiet period with only 0.04 m3 average magma output /year
7,000 years ago - present: 0.5 million m3 / year
In total, Kirishima volcano has erupted about 10-15 cubic kilometers
of magma during the past 22,000 years. In the earlier period from
22-15,000 years ago, 5 stratovolcanoes, and 2 smaller cones were formed.
The eruptions were dominantly effusive (lava flows).
Following an 8000 year long interval with much less activity, the
rate of eruptions increased again. Activity in the recent epoch has been
more explosive and concentrated in the southeastern part of the
complex.
Geothermal activity
The Kirishima volcanic area contains various thermal waters.
Hydrogen sulfide springs, acidic sulfate springs and chloride springs
are found in geographically narrow zone. Bicarbonate springs are
distributed in the Shinkawa ravine in the southwestern periphery of the
Kirishima volcanic area and the Hinatayama-Himegi region, both of which
are on the southwestern periphery of the Kirishima volcanic area.
Sources:
- Tsutsui et al (2006) "Eruptive History of Ohachi Volcano,
Kirishima Volcano Group, Southern Kyushu, Japan", Bull Volc Soc Japan
(Kazan), 52: 1-21
- Ryusuke IMURA (1989) "Eruptive History of the Kirishima Volcano
during the past 22,000 years" Master Thesis Kagoshima University, March
1989
- Tsuyoshi Miyamoto (2005) "Magma chamber structure of Katazoe
scoria eruption, Ohachi volcano at Kirishima volcanoes", PhD thesis,
CNEAS, Tohoku Univ.
- Fujita Shun'ichi (2000) "Geochemical aspect on the genesis of the
hydrothermal system of the Kirishima volcano and its southwestern area"
Journal of the Balneological Society of Japan, v50 (1), pp 1-11
November 29, 2014 - JAPAN
- Dozens of flights were disrupted in Japan on Thursday as Mount Aso,
the largest active volcano in the country, spewed ash and stones. This
comes just two months after more than 60 were killed in the Mount Ontake
eruption.
Japanese airlines were forced to cancel 49 flights as
Mount Aso, which dominates the south-west Japanese island of Kyushu,
spewed stones and ash, the local Jiji news agency reported on Thursday. "Today we canceled eight flights departing from Kumamoto and four flights arriving there," a Japan Airlines spokesman told AFP. "There was also one flight which changed destination to a nearby airport," he added.
The
massive volcano, one of the largest active ones in the world, started
rumbling on Tuesday, while the next day it sent a stream of ash 1,000
meters into the air, local media reported citing Japan’s meteorologists.
Japanese
media also said volcanic ash fell on Bungo-Ono, in Oita Prefecture, and
the town of Gokase, in Miyazaki Prefecture, about 40 km from the
volcano.
Rocks flew 200 meters high from belching Mount
Aso on Thursday, while meteorologists warned that flying rocks and ash
could hit within a 1 km radius from the volcano. Local Asahi Shimbun
reported that it was the first time the volcano had spewed rocks since
1995.
On Wednesday, Japan’s meteorological agency issued a warning
– a level 2 alert out of 5 - to residents around the volcano in
Kumamoto Prefecture. The second alert level restricts approach the
volcano to no nearer than 1 km.
The meteorological agency’s
Fukuoka Regional Headquarters reported slight distortions in the shape
of Mount Aso, which indicate that magma was possibly involved in the
latest eruption, according to Asahi Shimbun. Magmatic eruptions are
characterized by gas release and explosions.
Mount Aso’s activity
comes just weeks after 60 people were killed in Mount Ontake unexpected
eruption in September. This forced a revaluation of volcanic activity
risks and the possibility of its prediction. Questions have also arisen
over whether Mount Fuji - the highest and most famous mountain in Japan,
which was last active in 1707–08 – could erupt.
WATCH: Mount Aso erupts.
The
stratovolcano’s activity would not only threaten those in the adjacent
Shizuoka and Yamanashi prefectures, but also the highly populated
Japanese capital, meteorologists said.
Recent research conducted
by Japanese scientists and released by Kobe University in October said
that about 95 percent of Japan’s population is at risk of being
devastated by a major volcanic eruption, which could happen “at any moment” within the next century. "It is not an overstatement to say that a colossal volcanic eruption would leave Japan extinct as a country," the authors of the study said, according to AFP. - RT.
