[meteorite-list] Ridge Said To Be Part Of Meteoric Crater In Japan

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:29:51 2004
Message-ID: <200309051958.MAA25578_at_zagami.jpl.nasa.gov>

http://www.yomiuri.co.jp/newse/20030906wo71.htm

Ridge said part of meteoric crater
Yomiuri Shimbun (Japan)
September 5, 2003

A semicircular ridge on Mt. Oike in Kamimura, Nagano
Prefecture, is highly likely the remains of a crater
created by a meteorite 20,000 to 30,000 years ago,
researchers announced Thursday at an international
symposium at the National Institute of Polar Research in
Itabashi Ward, Tokyo.

There are several geographical features across the nation
that some scientists say may have been formed by
meteorites, but the researchers are the first to announce
they have essentially confirmed that their finding is a
meteoric crater.

The researchers included Masao Sakamoto, head teacher at
Tatsuoka Primary School in Iida, Nagano Prefecture, and a
research team from the Okayama University of Science.

They said the crater in the southern part of the Southern
Japanese Alps was initially about 900 meters in diameter,
but most had crumbled away and only about 40 percent
remained.

By studying quartz found in the crater, the group
determined it was created by a meteorite about 45 meters
in diameter that crashed into the area 20,000 to 30,000
years ago.

Sakamoto found the semicircular outcrop 20 years ago and
could find no explanation for it among the geological
studies conducted in the area up to that time. He asked
the Okamoto University of Science to examine unusually
structured quartz he found in the bedrock of the site.

Using laser technology, the university discovered some of
the quartz crystals had traces of cracks 0.01 millimeters
and 0.02 millimeters wide as a result of a heavy impact.

This is accepted in the scientific community as strong
evidence that the quartz was taken from a meteoric
crater.

Masayuki Okuno, professor of mineralogy at Kanazawa
University, said, "Perhaps this discovery will push
forward crater research in the nation."
Received on Fri 05 Sep 2003 03:58:44 PM PDT