MORE VIGOROUS ERUPTIONS ON MIYAKEJIMA AND AT
on the Japanese island of Miyakejima
have deteriorated in mid August with further episodes of caldera collapse
and two major eruptive episodes at the summit of the island's central
volcano Oyama. Both episodes were accompanied by intense seismic activity,
including earthquakes that could be felt as far as Tokyo, about 200 km
to the NNE. By early August the newly
formed caldera was about 450 m deep and had an area of more than 1.2
square kilometers (see also here
for a collection of photos documenting the evolution of the caldera -
note that almost all of these links are leading to pages in Japanese).
On the morning of 10 August, a dark eruption column rose at least 3 km
above the summit of the volcano, causing heavy ash falls on the NE side
of the island. The eruption was described as the most vigorous of several
eruptive episodes associated with caldera collapse that had occurred since
mid July. Aerial
photos taken after that event showed that the caldera floor had flattened,
and a small cone had formed there, emitting hot mud and water. Minor phreatic
explosions continued during the following days, including a larger
emission of ash on 14 August. By that time a monitoring
camera had been installed in the town of Tsubota on the SE side of
the island (images are posted every 20 minutes on the web).
The largest eruptive episode so far occurred on the afternoon of 18
August. It lasted more than 3 hours and produced an impressive black
eruption column up to 8 km high. For the first time it seems that fresh
magma was involved in this activity, since hot rock fragments were reported
falling during the activity. Tephra was deposited to a thickness of up
to 15 cm in the NW part of the island.
As of 20 August, the caldera is continuing to enlarge and now occupies
an area of 1.89 square kilometers. Stills captured from a video taken
during an overflight over the caldera on 20 August are available here.
In Chile, eruptive activity is continuing at Copahue
volcano. The activity intensified in mid August, and ejections of incandescent
rock fragments were observed for the first time. The southern Chilean
newspaper "El Sur" frequently
reports on the activity of the volcano.
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