[meteorite-list] Here we go again

From: Jerry <grf2_at_meteoritecentral.com>
Date: Wed, 13 Aug 2008 11:32:36 -0400
Message-ID: <530B498AD704464284CB839CB878EAD6_at_Notebook>

The widespread "return" to the surface of the planet of countless molten
rock debris which didn't attain escape velocity. That's one way. The heat
genetated by a huge explosive blast either on the surface or in the
atmosphere is at leastone more. There must be other options.
Jerry Flaherty
----- Original Message -----
From: "Darren Garrison" <cynapse at charter.net>
To: <meteorite-list at meteoritecentral.com>
Sent: Wednesday, August 13, 2008 11:08 AM
Subject: [meteorite-list] Here we go again


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.
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Received on Wed 13 Aug 2008 11:32:36 AM PDT