by Ker Than
March 07, 2007
from FoxNews Website
A team of scientists will embark on a
voyage next week to study an "open wound" on the Atlantic seafloor
where the Earth's deep interior lies exposed without any crust
The lesion is located mid-way between the Cape Verde Islands and the
Caribbean in the Atlantic Ocean.
A map of the Earth
showing relative crust thickness.
The red dot indicates
the location of the rupture.
It lies nearly 2 miles beneath the ocean
surface and extends over thousands of square kilometers.
"It's quite a substantial area,"
said Chris MacLeod, a marine geologist at Cardiff
University in Wales, who will be part of the expedition.
An outer crust of varying thicknesses covers most of the surface of
the Earth like a shell. The crust is about 20 miles deep beneath
continents and about 4 miles deep under the ocean floor.
The Earth's middle layer is called the
mantle; it is heated by the Earth's
core and is much hotter and softer than the crust.
Earth's crust is constantly being
destroyed and created, and this cycle of destruction and renewal
occurs faster with ocean crust than with continental crust.
New ocean floor crust forms at seams on
the Earth's surface, called mid-oceanic ridges, where the
planet's tectonic plates meet and where molten magma rises up from
the planet's upper mantle.
The upwelling drives seafloor spreading, which is the movement of
two oceanic plates away from each other. Oceanic crust is destroyed
subduction zones where two plates
collide and typically the denser one slips beneath another plate.
This is how scientists think it works, but areas of exposed
mantle on the Earth's surface aren't easily explained by this
They are regions,
"where this process seems to have
gone wrong somehow," MacLeod said. "There's no crust formed, and
instead we've got mantle - which is normally in the deep Earth -
on the seafloor."
Really nail it
Scientists have known about such anomalies for years, but it is only
within the past decade that they have actively begun investigating
them, MacLeod said.
In 2001, MacLeod was part of a team that visited the Atlantic
"We ended up answering one or two
questions but posing many more," he said. "What we're going to
do with this expedition is try to really nail down what's
There are two popular hypotheses about
how these holes in the Earth's crust form.
"One is that the original volcanic
crust did form, but that it's been ripped away by a huge
rupture," MacLeod told LiveScience.
MacLeod likens this process to
stretching a person's skin until it ruptures, exposing the flesh
"You take the crust and you stretch
it and you pull it and pull it until it breaks," he said.
The other idea purports that somehow the
area of exposed mantle was never covered by a magma crust in the
Regardless of how they formed, the exposed mantle provides
scientists with a rare opportunity to study the Earth's rocky
Many attempts to drill deep into the
planet barely get past the crust.
"One of our objectives now that
we've got direct access to these mantle rocks is to try and look
at their internal properties and try to find out about the deep
Earth process that we can't get at directly," MacLeod said in a
Getting equipment down onto the seafloor
where the exposed mantle is will be difficult, however.
"It's a very hazardous, very
unforgiving environment," he said. "There are very steep slopes
and huge pressures. So getting samples back from these areas is
The team of researchers, led by Roger
Searle of Durham University in England, will begin traveling to
the site on March 5 aboard the new British research ship RSS James
Over the course of about six weeks, the team will use sonar to image
the seafloor and a robotic seabed drill to collect rock cores.
Scientists Probe 'Hole in Earth'
1 March 2007
A drill will be used to extract samples of the exposed mantle
Scientists are to sail to the
mid-Atlantic to examine a massive "open wound" on the Earth's
Dr Chris MacLeod, from Cardiff University, said the Earth's
crust appeared to be missing across an area of several thousand
square kilometers. The hole in the crust is midway between the Cape
Verde Islands and the Caribbean, on the Mid-Atlantic Ridge.
The team will survey the area, up to 5km (3 miles) under the
surface, from ocean research vessel RRS James Cook. The ship is on
its inaugural voyage after being named in February. Dr MacLeod said
the hole in the Earth's crust was not unique, but was recognized as
one of the most significant.
He said it was an "open wound on the surface of the Earth",
where the oceanic crust, usually 6-7km thick (3.7-4.3 miles), was
simply not there.
"Usually the plates are pulled apart
and to fill the gap the mantle underneath has to rise up. As it
comes up it starts to melt. That forms the magma," he said.
"That's the normal process. Here it has gone awry for some
"The crust does not seem to be repairing itself."
Dr MacLeod said the research could lead
to a "new way of understanding" the process of plate tectonics.
The scientist will test theories he developed after visiting the
area in 2001 - including the possibility the missing crust was
caused by a "detachment fracture".
"Effectively it's a huge rupture -
one side is being pulled away from the other. It's created a
rupture so big it's actually pulled the entire crust away.
A rock called serpentinite is exposed at the surface
"We also think the mantle did not
melt as much as usual and that the normal amount of mantle was
As a result, the mantle is exposed to
seawater, creating a rock called
The survey voyage, costing $1m (£510,000), will be led by marine
geophysicist Professor Roger Searle, from Durham University.
Dr Bramley Murton, from the National Oceanography Centre,
Southampton, is the third expert taking part.
They will set sail from Tenerife on Monday and return in April.
The team intends to use sonar to build up an image of the seafloor
and then take rock cores using a robotic seabed drill developed by
the British Geological Survey in conjunction with Dr MacLeod.
The progress of the voyage
can be followed online.