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Tuesday, June 30, 2009

Ancient river found beneath the Channel during Olympics survey

Very good color illustrations of this river at the citation/cite.

Ancient river found beneath the Channel during Olympics survey

By Daily Mail Reporter
Last updated at 11:54 PM on 26th June 2009

An ancient river bed that has lain unseen for 185,000 years has been
uncovered by scientists mapping the parts of the English Channel in
the run up to the 2012 Olympics.

The groundbreaking discovery was made during a two-year £300,000
project to map 500 square miles of seabed off the Jurassic coast in

Using new and incredibly accurate mapping techniques, experts traced
the river that may have once been used as a watering hole by woolly
mammoths that roamed the area.
Enlarge riverbed

Enlarge river course

An amazing river course on the bottom of the English channel has been
revealed (above). The prehistoric river bed is 8 miles from the
present day shoreline (below)

The mysterious river bed cuts through bedrock at the bottom of the
ocean and is eight miles long, ranges between 90 to 150 yards wide and
up to 30ft deep Scientists believe it would have flowed when Britain
was still attached to the continent.

As ice melted and refroze, it was washed over and uncovered a second
time, before finally being hidden at the bottom of the sea during the
last Ice Age 12,000 years ago.

As well as the river bed, shipwrecks, rugged cliffs and massive gravel
dunes have also been highlighted using the new techniques which can
pinpoint objects to within six inches.

Scientists are aiming to construct a complete and definitive map ahead
of the 2012 Olympics as thousands of boats are due to descend upon
Dorset for the sailing events.

Smaller yachts have recently come a cropper on submerged rocks that
maritime officials knew nothing about and they don't want this
happening in 2012.

The newly-found river bed poses no such danger as it lays 130ft

The project has been lead by the Dorset Wildlife Trust, which hopes
the new information will be invaluable in its conservation work.
Jurassic Coast

Dorset's Jurassic Coast is famous for its fossils

Dr Simon Cripps, director of the Dorset Wildlife Trust, said: 'On land
you can just look out of the window and see what's around, but we have
no real idea what goes on under the sea.

'This study will give us an understanding of what is actually
physically down there - it's very exciting.

'It's like putting a 3D jigsaw together in three layers and the
results will be quite spectacular.'

Now the Maritime and Coastguard Agency is planning to re-chart
nautical maps of the Channel. Some current charts are based on surveys
carried out 75 years ago.

The maps have been created using a high resolution multi-beam sonar,
which sends out 40 'pings' per second to the seabed.

The sonar has 500 beams which give 20,000 readings per second,
allowing scientists to gauge the depth of the ocean, with an accuracy
of six inches.

Not only can it tell how deep the sea goes, but the variation of
sounds created by the beams can identify the type of surface it is

The 'pings', which sound like the clicks made by dolphins to the human
ear, differ depending on whether they hit sand, hard rock, or any
matter in between.

The Dorset Integrated Seabed Study, or DORIS for short, is now one
year in and moving on to a second phase of video and photography.

Experts will use the maps to identify patterns in the seabed before
using cameras to take shots of underwater life.
Enlarge survey

The unique new underwater survey that has an accuracy of 15cm

They will visit a range of depths to study the animal and plant life,
taking still and moving images to create an elaborate picture of
previously hidden habitats.

Richard Edmonds, science manager for the Jurassic Coast World Heritage
Site, said: 'The pictures the study has produced are hugely exciting,
I was absolutely blown away when I first saw them.

'We now know that all the fascinating structures we see on the
Jurassic Coast, which are created by the hard and soft rocks eroding
at different paces, happen exactly the same on the seabed.

'When the river bed was uncovered, the land would have been used by
woolly mammoths, reindeer and wolves as well as early humans.'

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