[meteorite-list] A Blast From Heaven?

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:17:39 2004
Message-ID: <200312041643.IAA02808_at_zagami.jpl.nasa.gov>

http://www.usnews.com/usnews/issue/031208/misc/8meteor.htm

A blast from heaven?
By Charles W. Petit
US News
December 8, 2003

In 1989, Edward Bryant climbed a point on the southeast coast of his
native Australia with a colleague and found an odd jumble of boulders
well above the surf. A big wave, he thought, maybe a tsunami from an
earthquake, must have tossed them up there. Over the next few years,
however, the University of Wollongong geologist explored hundreds of
miles of coast and found more signs of wave action, hundreds of feet
above the water--too high for any quake-spawned surge.

An astonishing hypothesis of devastation from outer space formed in his
mind. It gathered some praise, along with many ferocious brickbats from
doubting colleagues. But what may be a geologic smoking gun has now
turned up in 1,000 feet of water just south of New Zealand. Columbia
University geologist Dallas Abbott has found what appears to be an
impact crater 13 miles across, implying that something enormous, maybe
half a mile wide, smashed into the crust there.

If further research confirms that the circular depression is a recent
crater, it would lend dramatic ammunition to Bryant's controversial
scenario: Five hundred years ago or so, as Europe was beginning its
colonial explorations, a comet or perhaps an asteroid plunged to Earth
seaward of Australia's New South Wales coast. It would have sent
mega-tsunamis ripping into nearby islands and Australia, where Bryant
has found not just rocks but trees and beach sand hurled far up bluffs
and cliffs, along with whirlpool-carved cavities as much as 150 feet
across--testimony, he says, to the sea's onslaught. At one place, Jervis
Bay, waves apparently surmounted a headland 420 feet high. "Only a
bolide could do this," says Bryant, using a technical term for a
sky-bursting cosmic missile. Geologists know such things can happen--a
much bigger impact is believed to have ended the reign of the
dinosaurs--but no such catastrophe is known in recorded history.

People would notice something like that. Sure enough, Bryant found
recorded tales from Australian aborigines and New Zealand's Maori people
recounting how, not long before the arrival of Europeans, the sky heaved
and split, stars fell, and immense floods swept the land. Aborigine
tales told of a huge, disintegrating ball of blue fire shooting
overhead. Around 1500, Maori people on New Zealand's South Island
abandoned the seashore and moved inland. Huge impact-generated waves,
Bryant thinks, may have destroyed not only their villages but also beds
of shellfish that provided food. "It all added up," he says. "Something
big hit the Earth, near here."

In 2001, he published a textbook, Tsunami--The Underrated Hazard,
including his circumstantial tale of a missile from space. Some
colleagues liked his daring conjecture. "It's a big idea, and it
deserves attention," says Victor Baker, a planetary sciences professor
at the University of Arizona who has visited Bryant's tsunami sites and
believes the signs of gargantuan waves are legitimate. Something has to
account for them, he says, "whether or not it is an object into the
sea." Others are deeply skeptical of Bryant's evidence and impact scenario.

New Zealand geologist James Goff, a former government researcher,
calls Bryant a usually excellent scientist who has "gotten religion" on
mega-tsunamis. In a paper just out in the Journal of the Royal Society
of New Zealand, he rips Bryant's thesis apart. Goff for years has honed
the idea that tsunamis did indeed sweep much of his island nation around
1500, driving the Maori inland. But he says the waves were of the more
ordinary sort that earthquakes generate, a few tens of feet high at
most, not what he calls Bryant's "mega-tsunami from hell." He says
Bryant has joined events that may have happened centuries apart and
mistranslated Maori place names to stress a link with fire and celestial
destruction--taking the Maori syllable Ka to mean fire, for example,
when Goff says fever is a better meaning.

But Goff wrote his critique before last month's Geological Society of
America meeting in Seattle, where Abbott reported her discovery. Early
this year, intrigued by Bryant's book, she had pored over topographic
maps of the seafloor in the region and found an apparent impact scar on
the edge of the continental shelf just south of New Zealand.

When Abbott checked samples that oceanographic expeditions had scooped
from the area, she found shattered minerals typical of meteor impacts. A
field of tektites--globules of rock that melted and cooled in
midair--spreads to the southeast of the crater just as it should from a
impacter striking at a low angle from the northwest, the direction
Bryant infers from the Australian tales. The crater, which Abbott calls
Mahuika after a Maori fire deity, lies in a spot that would send waves
against Australia at just the angle Bryant had already calculated. "It's
young, almost surely less than a thousand years," she says, judging from
the near absence of the sediment that normally builds up on the ocean floor.

"This is pretty exciting if the story holds up," says Steven Ward, a
geophysicist at the University of California-Santa Cruz, who has a keen
interest in comet and asteroid impacts. Goff agrees, but with neither a
firm date for the crater nor sure evidence that cataclysmic waves hit
New Zealand at the same time as it was formed, "the jury is still out,"
he says. Abbott hopes to settle the issue by gathering and dating
samples of debris. An impact would have scattered material for hundreds
of miles, creating a distinctive layer in the New Zealand soil, says Ward.

But even if a giant rock did plunge into the sea 500 years ago, it may
not be enough to explain Bryant's catalog of devastation. Ward
calculated that an object that leaves a 13-mile-wide crater off New
Zealand might send waves washing 100 feet up the Australian coast 1,000
miles away, but not a cliff-scaling 400 feet. Bryant, however, has no
doubts. "I don't like to believe it, but we had something mighty big hit
out there."
Received on Thu 04 Dec 2003 11:43:37 AM PST