The Earth's Shifting Crust by Charles Hapgood - wire of information

CONTINENTS AND OCEAN BASINS 141
It must have been a large continent, for the sand and gravel and
mud which the rivers washed out to sea and the waves ground up on
the shore have built up most of half a dozen big states, while in some
places the deposits are a mile thick (45:134-35).
Umbgrove says that while it is impossible
to estimate the
size of the land mass (called "Appalachia" by the geologists),
it was clearly large, to judge from the fact that it has been
possible to trace out in the sedimentary beds of the Appalachian
Mountains the outline of an enormous delta formed
by a giant river flowing
out of the land mass to the east
(430:35-38).
Now the continental shelf of North America ends abruptly
a very short distance from the coast. It is an extremely narrow
strip between the coast and the so-called "continental slope,"
where the rock formations dip down suddenly and steeply
into the deep sea. Its average width is only 42 miles, and its
maximum width does not exceed 100 miles (46). If the sediments
had been derived from a land mass on this continental
shelf, this very narrow land mass would have had to carry
huge and repeatedly uplifted mountain ranges. Furthermore,
since drainage would naturally have carried sediments
down both slopes of these mountain ranges, a large proportion
of the material would have been carried eastward and
deposited in what is now the deep ocean; but there is no evidence
of this.
The suggestion that the enormous volume of sediments
forming the northeastern states of the United States came
from the continental shelf must be considered improbable. On
the other hand, it is plain
that the former continent in the
North Atlantic could not have been eroded away by rivers
any farther down than approximately sea level. Erosion did
not dispose of the continent, nor create the deep-sea basin.
After erosion had finished its work, the continent itself sank
to a great depth. Umbgrove has cited recent oceanographic
research by Professor Ewing of Columbia, showing that this
ancient land mass of Appalachia now lies subsided about two
miles below the continental shelf (430:35-38).