http://www.archive.org/stream/earthupheaval010880mbp/earthupheaval010880mbp_djvu.txt
EARTH IN UPHEAVAL
Excerpt:
“While the question of the age of the falls thus becomes
complicated, the discovery shows that the post-glacial
period was of much shorter duration than generally as-
sumed, even if the rate of retreat of the falls is reduced
to the minimum figure of under four feet per year, as
observed in more recent years. R. F. Flint of Yale writes:
“We are obliged to fall back on the Upper Great
Gorge, the uppermost segment of the whole gorge, which
appears to be genuinely postglacial. Redeterminations by
W. H. Boyd showed the present rate of recession of the
Horseshoe Falls to be, not five feet, but rather 3.8 feet,
per year. Hence the age of the Upper Great Gorge is cal-
culated as somewhat more than four thousand years
and to obtain even this [low] figure we have to assume
that the rate of recession has been constant, although we
know that discharge has in fact varied greatly during post-
glacial times.” 4 Jt due allowance is made for this last
factor, the age of the Upper Great Gorge of Niagara
Falls would be somewhere between 2500 and 3500 years.
It follows that the ice retreated in historical times, some-
where between the years 1500 and 500 before the present
era.
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