[meteorite-list] Rock 'Bomb' Evidence Of Ancient Comet Strike

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:07:04 2004
Message-ID: <200210270512.WAA09499_at_zagami.jpl.nasa.gov>

http://www.insidedenver.com/drmn/local/article/0,1299,DRMN_15_1504387,00.html

Rock 'bomb' evidence of ancient comet strike
By Jim Erickson
Rocky Mountain News
October 26, 2002

Denver geologist Charles A. Sandberg says he's found "the clincher,"
rock-solid evidence that a 3-mile-wide comet slammed into present-day Nevada
370 million years ago.

Sandberg has been researching the so-called Alamo Impact for more than a
decade, building the case that a comet hit in the ocean, triggering
1,000-foot-high tsunamis and raining rock over a circular area 175 miles
across.

Nevada and much of western North America was under water at the time. The
comet hit in the deep ocean, said Sandberg, a geologist emeritus at the U.S.
Geological Survey in Lakewood.

Debris from the impact has been found, but the crater itself has not.
Sandberg believes ground zero was about 100 miles north-northwest of Las
Vegas. The crater was buried long ago by younger rock layers, he said.

The latest piece of the puzzle is a fist-sized "bomb," a rare chunk of the
ancient sea floor that was blasted into space, then fell back to Earth. The
projectile was found last year in the southern end of the Hot Creek Range in
southern Nevada.

"I think this is the clincher," Sandberg said Friday.

But University of Arizona impact expert David A. Kring said Sandberg's rock
bomb doesn't appear to strengthen or weaken the case for the Alamo Impact.

"I'm at a little bit of a loss to understand how this piece of evidence
makes the case stronger that there was an impact event, because I think the
consensus has already been established that there was an impact event off
the coast of North America," Kring said Friday.

Sandberg and colleague Jared Morrow will present their latest findings next
week at a Denver meeting of the Geological Society of America.
Received on Sun 27 Oct 2002 01:12:13 AM PDT