[meteorite-list] Here we go again

From: Darren Garrison <cynapse_at_meteoritecentral.com>
Date: Wed, 13 Aug 2008 11:08:53 -0400
Message-ID: <but5a4d011pmtovfhmbmgamfimvqj7ne13_at_4ax.com>

Okay-- here's my question-- could an impact that leaves no crater cause global
(or large-fraction-of-the-global) forest fires? My idea of what causes firest
fires in large impacts-- like Chixalub (sp? too lazy to look it up this morning)
is molten "splash" launched from the-- wait for it-- crater. Impactites and
tektites, if you will.


http://www.thisiswesternmorningnews.co.uk/news/Comet-strike-end-world-scenario/article-265193-detail/article.html

Comet strike would be cataclysmic

A DEVASTATING collision between the Earth and a wayward comet which wiped out
nearly every living thing across an entire continent will happen again and cost
millions of lives, a Westcountry scientist claims.

The three-mile wide comet, named Clovis after the fledgling North American
civilisation it drove to extinction, exploded in the atmosphere 13,000 years ago
with a force of 20 million megatons ? larger than a simultaneous blast by all
the nuclear weapons in history, says Professor Chris Turney, of the University
of Exeter.

It left no impact crater but sparked the biggest wildfires in history, which
stretched across the continent and suffocated humans and animals with
overwhelming amounts of soot and smoke, leaving the few survivors with no
vegetation or prey to live on.

Fiery debris from the comet also melted huge portions of the ice sheet, which
drastically altered the planet's climate. Massive volumes of fresh water found
their way into the oceans and changed their currents, plunging the Earth into an
Ice Age for 1,000 years.

Although NASA is tracking up to 5,000 comets and asteroids throughout the Solar
System, of which 700 are over a mile wide, scientists say the vastness of space
means many inevitably have not been detected, and only one has to be on a
collision course with Earth to cause unprecedented carnage.

The theory is the subject of a new TV documentary on the History Channel at 8pm
tonight.

Speaking on the programme, Prof Turney, professor of physical geography at the
University of Exeter, said another large comet would cause unimaginable damage.

He said: "We're just starting to work out for a fact that comets are far more
frequent than we were led to believe.

"If it just exploded as an air burst, it would fry a city and basically just
destroy it. There would not really be much left at all, apart from a bit of
rubble.

"It would be the end of the world scenario for those people."

Experts believe the aftermath of such an impact would accelerate global warming
and cause the destruction of large areas of coastline around the world as sea
levels rose.

Prof Turney said the Clovis explosion caused the largest forest fires ever seen.

"It would have been a very strange place with charcoal and dust everywhere on
the surface where these fires had gone through," he said.

Prof Turney said it was only pure chance the famous Tunguska Event, a meteorite
which exploded above Siberia exactly 100 years ago, destroyed a remote area of
forest instead of heavily populated cities like London, Paris or New York.

"Had it entered the atmosphere a few hours earlier, it would have hit Western
Europe, potentially costing millions of lives," he said.

"If the comet of Tunguska had actually exploded over London, it would have
caused widespread devastation.

"We were just incredibly fortunate that this thing exploded over Siberia. It was
a total fluke."

The Tunguska meteorite was just 165ft in diameter, compared with the three-mile
wide Clovis comet.

Clovis archaeological sites across North America show a two-inch "carbon mat" in
the rock dating back 13,000 years, indicating huge amounts of soot in the
atmosphere, as well as elements like iridium, which is brought to Earth from
space.

At the time, much of the continent was covered by forests and vast grasslands,
enabling wildfires to spread uncontrollably.

Huge shockwaves from the explosion started hurricane-force winds which fanned
the flames at incredible speeds across the land.

As the soot fell onto the ice sheet, the darker material absorbed more sunlight
which melted the ice and forced fresh water into the oceans, sending global
temperatures plunging by 5C to 10C.

Prehistoric Megastorms: Comet Storm is on the History Channel at 8pm tonight.
Received on Wed 13 Aug 2008 11:08:53 AM PDT