Message #61641

[Bianca]

Another surprising discovery was a great plain that took them over two and a half days to cross. The bottom of the deep ocean was thought by most geologists (at that time) to be covered with a great and uniform thickness of sediment--thousands of feet thick--which has accumulated upon it like a steady un-drifted snowfall since its formation and which remained forever undisturbed. However, from a point about 385 nautical miles northeast of Bermuda to a point about 945 miles west of the Azores the sediment was less than 100 feet thick. This would seem to indicate that accumulation of sediment had not been occurring in this area for very long. Why?

Dr Ewing also found what appeared to be "beach-like terraces two miles deep".5 His hypothesis was that the long, level terraces, with sediments ranging up to 3000 feet thick, were submerged shore lines. Ewing tried to label this as "extremely radical speculation to identify these level stretches more than two miles below the sea surface as former beaches6.” But obviously, that's what they looked like otherwise why bother to hypothesize about them? Just because, as Ewing noted, "such a theory would require the obvious but almost incredible conclusion that the land here has subsided two miles..."7 does not mean that such subsidence could not have occurred however.

Dr. Ewing's first expedition over the MAR was summarized by him by making note of the following discoveries:

On the western side of the Ridge stretches the great plain of the American Basin. It is very level and over 3 miles deep. No sedimentation is present. The American approach to the Ridge is rough and rises slightly and has a thick sediment layer 1,000 to 2,000 feet in about three-fourth's of the cases; none in the others. On the western flanks of the Ridge lie level stretches, 2 to 20 miles broad, like terraces or beaches. These stretches showed thick sediments, ranging up to 3,000 feet. Rough higher ground often separates successive terraces, and occasional isolated peaks punctuate this part of the Ridge. The Central Highland of the Ridge comes to within a mile of the surface in some areas and is always rugged with never a flat stretch and no sedimentation.8

Also discovered within a deep gorge was tremolite asbestos9 which is generally considered typical of continents and not of ocean basins. On the return voyage, about halfway between Bermuda and New York (300 miles from the coast) at a depth of over 2 miles they found beach sand which must have been a coastline at one time.10