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The Great Islands Under The Sea

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Bianca
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« Reply #15 on: May 01, 2007, 08:12:52 am »




THE GREAT ISLANDS UNDER THE SEA                                                                continued



Continental shelves are the undersea edges of continents, relatively shallow
before they drop off into the oceanic abyss.  An evident proof of the sinking
of the continental shelves, or the risings of the oceanic waters over them,
can be found in the undersea mapping of sediment-filled river canyons that
flowed into the once more distant sea on both sides of the Atlantic.

As they left the land and entered the ocean, some of these rivers continued
their course along their ancient beds, now under the sea.  The upper reaches
of the underwater Hudson Canyon, 100 miles long and several hundred feet
deep, could have not been formed under water, but was cut at a time when
this present underwater extension of the Hudson was dry land.

Other oceanic canyons include the Baltimore Canyon, probably cut by the
Delaware River in ancient times and the Norfolk Canyon, cut by the Susque-
hanna. 

On the other side of the Atlantic, sonar soundings show that the same canyon-
making pattern at the edge of the ocean basin was followed by the Loire, Rhone
and the Seine in France and the Tagus from Portugal, while on the west coast
of Africa there are river canyons on the seabed, although there are no longer
feeding rivers flowing from the now-arid land.



« Last Edit: May 01, 2007, 08:39:32 pm by Bianca2001 » Report Spam   Logged

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