ANTARCTIC CRATER
IS MASSIVE
The Wilkes Land crater is a
proposed name for a 500km (300 mile) wide geological feature,
located in Wilkes Land, Antarctica, and centered at 70°′S 120°′E,
that has been explained as an impact crater. It was discovered in
2006 by a team of researchers led by Ralph von Frese and Laramie
Potts, using the gravity measurements by NASA's GRACE satellites to
identify a 200 mile (300 km) -wide mass concentration. This mass
anomaly is centered within a larger ring-like structure visible in
radar images of the land surface beneath the Antarctic ice cap. This
combination suggests that it is the result of a large impact event.
 Due
to the site's location beneath the Antarctic ice sheet there are no
direct samples to test for evidence of impact. There are alternative
explanations for this mass concentration, such as formation by a
mantle plume or other large-scale volcanic activity. If this feature
does indicate an impact event, then, based on the size of the ring
structure, it suggests an impactor roughly six times larger than the
one that created the Chicxulub Crater that is believed to have
caused the Cretaceous-Tertiary extinction event.
Based on the presence of the mass
concentration, the authors believe the structure must be less than
500 million years old. The structure also appears to have been
disturbed by the rift valley that formed 100 million years ago
during the separation of Australia from the Gondwana supercontinent.
It is possible that the impact and associated crater contributed to
this separation by weakening the crust at this location. These
bracketing dates make it possible that the site could be associated
with the Permian-Triassic extinction event that occurred 250 million
years ago, believed to be the largest extinction event since the
origin of complex multicellular life. However, it is currently under
debate whether or not an impact played any role in this extinction.
Other proposed causes include the possibilities of a different
impact site, the leading candidate for which is Bedout off Western
Australia, or of non-impact-related disasters.
From
Wikipedia -
see the link for fuller information.
A discovery in
2006 under the Antarctic ice cap may knock the Vredefort Dome off
its pedestal as the largest impact structure on Earth. Scientists,
however, cannot be sure that the "mass concentration" detected under
the ice sheet is, in fact, an impact crater - it could also be
explained as a mantle plume or other volcanic feature. More evidence
is needed. Like Vredefort itself, the find remains fairly controversial. |
I'm
a writer of popular science and technology books and
articles, a former Professor of Communication whose
hobby is now "backyard astronomy" with history thrown
in! I'm a keen mountain-biker and kayaker, so the
Dome and Vaal River are my playground.
I'm
a former teacher who has worked with Graeme on many
aspects of science & local history research, and I have
got to know the Dome by preparing the maps and data used
in our various presentations. My passions are mountain
running and education. I manage Otters' Haunt.