Active volcanoes / Aktive vulkaner:
Asama, Japan  


Eruption from Asama in 1973 (Photo: E. Koyama)

The Asama-yama volcano in Japan is situated on the main island Honshu, mere exactly at
36°4' N and 138°53'E. It rises 2,550 m above sea level (asl).

Asama is a stratovolcano. Asama consists of a young stratovolcano with two craters, which
then again is lying upon a shield-volcano. The shieldvolcano lies further on the remains of an
older stratovolcano. (Rather complicated if you ask me...)

Monday, December 6th, 2004

It's been three months since Mount Asama erupted, spewing ash and cinders. But tourists still
quake with fear at the idea of visiting the region. The mountain still belches 2,000 to 4,000 tons
of volcanic gases a day. While a more than 500-degree temperature at the crater's bottom
keeps it red hot, local tourism has cooled drastically.

To make things worse, rumblings recorded from inside the mountain's belly may be the strongest since its last major eruption in 1973. Since hot-spring resorts in the area were immediately
flooded with cancellations.

There have been no damages or threats of danger in nearby Komoro. Still, the number of
visitors remains about half that of a normal year. In addition, the Japan Meteorological Agency,
indicated it is difficult to say just how unfounded tourists' fears may be.
From "Volcano joins earthquake in keeping tourists at bay"
The Asahi Shimbun

Monday, November 15th, 2004
Mt. Asama erupted Sunday evening, the Japan Meteorological Agency said, but there were no
immediate reports of injuries or damage. The 8:59 p.m.(local time) eruption was apparently
midsize in scale. The agency has issued a warning of falling ash in areas downwind of
the volcano. Minor eruptions have continued since large blasts occurred Sept 1.
(From Kyodo News)

Monday, November 8th, 2004
Still going strong. As of the 21st of October, the Japanese Meteorological Agency (JMA)
has reported that based on information from JMA, the Tokyo VAAC reported that Asama
erupted on 16 October at 1206, producing a SE-drifting ash cloud higher than 3.4 km a.s.l.,
and on 18 October at 1017, producing a N-drifting plume to a height of ~3.4 km a.s.l.

Thursday, October 7th, 2004

Still emitting....

Thursday, September 23rd, 2004
Latest (19:00 Central European Time)
An eruption, measuring three on a scale of zero to five, was observed at 7.44pm
(local time) from the 2568-metre high Mount Asama, according to JMA.
Tremors related to the mid-scale eruption continued,

A radar analysis conducted on 16 September confirmed that there was a lava dome in the
crater, the JMA and Geographical Survey Institute reported, the first since 1973.
Radar images showed a dome-shaped, layered form several dozen meters high with a radius
of about 100 m in the NE part of the crater; it is an estimated 500,000 cubic meters in volume.

By 18 September, JMA was reporting that ash plumes were still rising ~1,200 m, but only
about 23 small eruptions and nearly 140 tremors had been recorded that afternoon, a significant
change from the nearly consinuous activity of the previous few days.

Friday, September 17th, 2004
Asama sent smoke and ash high into the sky and spat out molten rock as it erupted for a
fourth straight day on Friday, and experts warned that eruptions may continue and possibly
grow in scale.

Asama was spewing smoke mixed with ash about 1,000 metres into the air, and molten rock
were being thrown at a distance of 200-300 metres from the summit.
Late on Thursday night, prevailing winds carried ash from the peak as far as central Tokyo.

By 23:00 GMT Thursday some 374 earthquakes related to the volcano had been detected,
all too small to be felt by humans. Nearly 1,400 similar quakes were detected on Thursday.

September 16th, 2004

MODIS/TERRA<> 09/16/2004 01:30 UTC
Tokyo is 140 km southeast of Asama

16:30 local time, 09:30 norsk tid
Still erupting, no further news.

September 15th, 2004

Wednesday morning, european time

Mount Asama belched columns of smoke over 300 metres high in two small eruptions
hours apart, according to JMA. Ash fell on Karuizawa, a resort town about 10 kilometres
away, during this second eruption in two weeks. No accompanying earthquakes were

The Meteorological Agency (JMA)warned residents to stay out of a four-kilometre radius
surrounding Mount Asama's crater, adding it expected ongoing small-to-medium sized
eruptions at the volcano.

September 4th, 2004
After reading reports in different media, as the news about this eruption has swept the
earth past three days, we have been uncertain what really happened. According to news-
releases it has been said that smoke came from the volcano - and that a violent eruption had forced hundreds of people to evacuate - that lava have flowed down the flanks etc etc.
All depending how far from Japan the news-media were, i.e. Argentine or New Zealand...

We now know a little more.
The eruption was preceded on Tuesday by 116 tremors, and 177 by 5pm on Wednesday.
Volcanic rock and ash has spread about a mile from the crater, (spewing ash and cinders
halfway down the mountain)
and volcanic tremor wascontinuing. A local meteorological
station in Karuizawa in Nagano Prefecture recorded ahuge explosion and shock waves at
the time of the eruption.

Television footage showed a red glow lighting up the night sky from the eruption, which
occurred shortly after 8 p.m. The eruption set fire to forest on the volcano slopes.
A ranch in the town of Naganohara in Gunma Prefecture, about 20 km north of the mountain,
was hit by a shower of molten rock at around 8:50 p.m. Volcanic ash falls were observed in
Tochigi and Fukushima prefectures.

There were no reports of casualties although some 50 people, mostly tourists, evacuated
voluntarily. The eruption was the biggest at the volcano in 21 years.
A characteristic of Wednesday's eruption was that it could not be predicted.
Smokes increased in late July, but no one expected the volcano to erupt.

JMA has reported that the eruption, which straddles Gunma and Nagano prefectures,
emitted volcanic ash over nearby areas, with potentially devastating consequences for
many farmers and businesses. Concern is mounting over the impact the ash could have on
agricultural products, particularly cabbages that are a speciality of the region.

In Naganoharamachi, Gunma Prefecture, rain that started falling Thursday morning mixed
with the ash to turn cabbages ready to be harvested a blackish colour. The rain washed
the ash right down to the stems of the cabbage leaves. Ash fell in 10 towns and village
s in the prefecture, including Naganoharamachi, Agatsumamachi and Katashinamura.
In a region abounding with fields of cabbage, lettuce, Chinese cabbage and other leafy
vegetables, minimizing the extent of the damage is a paramount priority.
Rain began falling in areas around Mt. Asama at about Wednesday midnight.
The summit of the volcano was covered in cloud and mist, making it difficult to tell
from the foot of the mountain if the eruption was continuing.

Efter å ha lest rapporter i forskjellige nyhetsmedia - for nyheten om utbruddet har gått som
en løpeild rundt jorden de siste tre dager, har vi vært usikker på hva som egentlig hendte.
Ifølge nyhetsmedia ble det sagt at røyk kom fra vulkanen - at det hadde vært et voldsomt utbrudd
som fikk flere hundrede til å evakuere - at lava hadde flommet nedover skråningen osv osv.
Alt avhengig av hvor langt fra Japan nyhetsmediene befant seg, d.v.s. i Argentina
eller New Zealand.l depending how far from Japan the news-media were, i.e. Argentine
eller New Zealand... Hvorfor nær sagt alle bragte nyheten om dette utbruddet,
og sjeldent om de fleste andre, vet vi ikke.

September 1st, 2004
The JMA lifted its activity rating for Mount Asama to "3" from "2," meaning that a small-
to medium-size eruption has occurred or was likely to occur.
It was not clear how high the smoke rose because of cloud cover, the agency said in an
emergency volcano bulletin. It asked residents to pay attention to further volcanic activity

Mount Asama has had several minor eruptions in recent years in which it spewed smoke into
the air. In 1947, 11 mountaineers were killed after being struck by molten rocks on the slope.

Television footage shown by public broadcaster NHK showed a red glow lighting up the
night sky from the eruption.Volcanic rock and ash has spread about a mile from the crater,
the Japanese news agency Kyoto reported. Tremors were continuing, the Japan's
Meteorological Agency said.

Pumice by the river Shiraito near the volcano

Asama is closed to the public owing to its rather regularly activity, but many people still climb
to Kurofu in the outer ring. It has about the same heighth as Asama, and one has a spectacular
view from that point. However, most death casualties the past 50 years have still been
climbers coming to close to an eruption.


 Field Excursion Guide to Asama Volcano
 Photo Album from Japan, by Masashi Koizumi


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