[meteorite-list] Scientists Search for Evidence of Asteroid Impact in Colorado

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Mon Aug 8 13:53:32 2005
Message-ID: <200508081752.j78HqZB06455_at_zagami.jpl.nasa.gov>

http://www.gazette.com/display.php?id=1309596

Did a giant meteor kill dinosaurs?
By BILL VOGRIN
THE GAZETTE (Colorado)
August 8, 2005

A team of scientists and volunteers will descend on Colorado Springs
this month to search for evidence of a monster asteroid they believe
smashed into Mexico's Yucatan Peninsula about 65.5 million years ago.

Many scientists believe the asteroid caused an eruption of ash that
blanketed the planet and created an environmental holocaust that wiped
out most life on the planet, including dinosaurs.

The ash, with its unique space dust, crystals and soot from global
fires, is said to have eventually compressed into a layer of clay that
circled the Earth and now lies buried beneath 65 million years of
sedimentary rock.

A team from the Denver Museum of Nature and Science says it has found
evidence of the clay and its asteroid ash in Colorado Springs and the
surrounding region. They hope a three-day dig this month will produce
more proof.

"We are studying all the rock underlying the city," said Kirk Johnson,
chief curator of paleontology at the Denver museum.

Scientists believe the asteroid was about six miles in diameter -
imagine a space rock the size of the Air Force Academy grounds - moving
at 20,000 mph.

When the asteroid hit, scientists believe, the impact was catastrophic,
superheating the Earth's atmosphere and incinerating all large forms of
animal life including dinosaurs, large mammals and 50 percent of all
insect and plant life.

"It really kind of wrecked the planet,' Johnson said.

The asteroid's impact left a crater upward of 100 miles wide - about the
distance from Denver to Pueblo. Scientists believe they have discovered
the crater 200 miles west of Cancun beneath millions of years of
sediment on the tip of the Yucatan Peninsula and in the waters of the
Gulf of Mexico.

The impact also caused an eruption of ash and debris that, according to
theory, swept across the Earth, eventually choking out sunlight,
lowering the global temperature, contributing to acid rain and other
dramatic climatic changes.

It's only a theory; many scientists dismiss it in favor of a theory that
volcanic eruptions are to blame for the cataclysmic loss of animal and
plant life and disruption of the global climate.

But Johnson believes it was an asteroid, and he's among a large number
of scientists who search the globe for the layer of clay with its unique
space dust, quartz crystals fractured by massive force and soot from
fires that resulted from the impact.

That's what Johnson and a team of a dozen or so scientists, students and
volunteers will be searching for in Colorado Springs.

The key is finding the layer laced with iridium, an extremely rare
metallic chemical element similar to platinum.

Two sources of iridium exist. It is found in the Earth's core, brought
to the surface in eruptions of certain types of volcanoes. And it is
found in space rock, like meteors and asteroids, and the cosmic dust
that constantly showers Earth's atmosphere.

The theory is difficult to prove because, generally, the layer of clay
is buried deep below the Earth's surface.

Except in Colorado Springs and other places where the Earth's crust has
been disturbed by uplift and erosion.

Here, the clay can be found at the surface or just below. It's often
unearthed by construction of roads, buildings and homes.

That's because the uplift that created the Rocky Mountains pushed layers
of prehistoric rock to the surface, especially in places such as Garden
of the Gods and the Pulpit Rock area of the Austin Bluffs Open Space.

The Springs' topography gives scientists access to rock as deep as the
Pierre Shale formation, which dates to 70 million years ago, and Fox
Hills, a layer of ancient beach deposits from a time when Colorado was
covered by an ocean.

Then comes the distinctive iridium-laced clay, which is 65.5 million
years old and separates the Cretaceous period - the last age of
dinosaurs - from the Tertiary/Paleocene, when mammals became the
dominant species on Earth.

Above those layers are the Laramie and Dawson formations, which are only
about 55 million years old.

In recent years, Johnson's team discovered the clay in an outcropping
east of Kiowa in Elbert County.

"We actually found the layer where the dinosaurs went extinct," said
Beth Ellis, project manager of Johnson's team. "You could put your
finger on it. It was really cool."

There have been specific discoveries in the Springs, Ellis said.

For example, a student working on private property got "within a few
feet" of pinpointing the clay layer at a site near the proposed Jimmy
Camp Creek reservoir northeast of the Colorado Springs Airport. The
student found rock from the thicker layers above and below the thin clay
layer. But more work is needed to unearth the clay, Ellis said.

Previous expeditions to Colorado Springs have led scientists back to the
Pulpit Rock area, as well.

"It takes a couple years to get a good understanding of an area," Ellis
said. "Then we go back and look hard. That's when it gets fun."

The fun will start Aug. 28 when the team returns, Ellis said. It will
visit Pulpit Rock, a road construction site near Garden of the Gods Road
and, perhaps, the Jimmy Camp Creek site.

Along the way, scientists expect to unearth other fossils, like they did
a few years ago when a prehistoric crocodile skull was found.

"We've been doing work in Colorado Springs since 1991," Johnson said.
"We amped that work up in the late 1990s. It's a really interesting
project. We've found some pretty interesting, cool fossils there. We're
excited about it."
Received on Mon 08 Aug 2005 01:52:34 PM PDT