[meteorite-list] The World's Biggest Meteor Crater (Vredefort Dome)

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 6 Dec 2006 15:28:26 -0800 (PST)
Message-ID: <200612062328.PAA14046_at_zagami.jpl.nasa.gov>

http://www.southafrica.info/ess_info/sa_glance/geography/vredefort-080605.htm

The world's biggest meteor crater
Mary Alexander
South Africa Info
December 5, 2006

Two billion years ago a meteorite 10km in diameter hit the earth about
100km southwest of Johannesburg, creating an enormous impact crater.
This area, near Vredefort in the Free State, is now known as the
Vredefort Dome.

It was voted South Africa's seventh World Heritage site at Unesco's 29th
World Heritage Committee meeting in Durban in July 2005.

The meteorite, larger than Table Mountain, caused a thousand-megaton
blast of energy. The impact would have vaporised about 70 cubic
kilometres of rock - and may have increased the earth's oxygen levels to
a degree that made the development of multicellular life possible.

The world has about 130 crater structures of possible impact origin. The
Vredefort Dome is among the top three, and is the oldest and largest
clearly visible meteorite impact site in the world.

The original crater, now eroded away, was probably 250 to 300 kilometres
in diameter. It was larger than the Sudbury impact structure in Canada,
about 200km in diameter.

At 2-billion years old, Vredefort is far older than the Chixculub
structure in Mexico which, with an age of 65-million years, is the site
of the impact that led to the extinction of the dinosaurs.

Vredefort's original impact scar measures 380km across and consists of
three concentric circles of uplifted rock. They were created by the
rebound of rock below the impact site when the asteroid hit. Most of
these structures have eroded away and are no longer clearly visible.

The inner circle, measuring 180km, is still visible and can be seen in
the beautiful range of hills near Parys and Vredefort. It is this area
that was named a World Heritage site.

Internationally, there are 812 World Heritage sites, in 137 countries.
Africa has 65 sites and South Africa now a total of seven - three
cultural, three natural and one of mixed cultural and natural heritage.
The Vredefort Dome is a natural heritage site.

South Africa's other six World heritage sites are Robben Island, the
Greater St Lucia Wetlands Park, the Mapungubwe Cultural Landscape, the
Cradle of Humankind, the uKhahlamba Drakensberg Park and the Cape Floral
Region.

"The Vredefort site is rich in the symbolic representation of our
culture; it demonstrates the meeting between scientific and cultural
philosophy and practice," Arts and Culture Minister Pallo Jordan said
after the inscription of the site on the World Heritage list.

"At Vredefort, opportunities exist to engage in geological research and
explore and understand more sensitively the rich culture of the Basotho,
Batswana and Khoi-San and the early evidence of human cognitive and
artistic endeavour their cultures boast.

"This demonstrates that heritage can be a tool for nation-building."

The Vredefort Conservancy

Further evidence of the meteorite impact site can be seen in the columns
of granite that were injected into existing rock by the force and heat
of impact.

In 1937, earth scientists John Boon and Claude Albritton Boon were the
first to suggest that the Vredefort structure was the scar of an ancient
meteorite impact. Since then the site has been studied extensively by
earth scientists from around the world.

The Vredefort Dome Conservancy, as it is now known, is not just of
scientific value. It also has great scenic beauty, making it an ideal
tourist destination.

The Dome Conservancy contains a finely balanced ecosystem made up of
open plains, bushveld, mountains and ravines with abundant flora and
fauna. At least 99 plant species have already been identified, of which
the world's largest olive wood tree forest is probably the best known.

The area is considered an important birding area, with over 450 species
already identified. It also has as many identified butterflies as the
whole of Great Britain, and is home to rare animals such as the rooikat,
aardwolf, leopard and the endangered rock dassie.

The Department of Environmental Affairs and Tourism plans to spend
R18-million on tourism and infrastructural development at the site -
including the eradication of alien invasive vegetation, creation of
hiking trails and construction of a tourism centre.

The Vredefort Dome site fulfils all the criteria set by Unesco for a
World Heritage site. It is of outstanding universal value from a
scientific point of view, and is remarkable evidence of an important
moment in the earth's geologic history.
Received on Wed 06 Dec 2006 06:28:26 PM PST


Help support this free mailing list:



StumbleUpon
del.icio.us
reddit
Yahoo MyWeb