XXVI Congreso Internacional de Americanistas

A summary of the relation of North
American Prehistory to Post-Glacial
Climatic Fluctuations
BY
REGINALD G.
FISHER
Assistant Director School oí American Research Santa Fe,
New Mexico, U. S. A.
The following paper represents a brief sl1mmary of a preliminarv
monograph dealing with the clima tic fll1ctl1ations and their relation to
p rehistory. This monograph is entitled "The relation of N orth American
P rehistory to Post-Glacial Climatic FI uctl1atiol1s", and is pl1blishec1 by the
University of New Mexico Press. In SLlch a short paper it is impossible
to note the contributing bil;Jliographic references Or to give the proofs and
lines of reasoning sLlpporting the statements made. For these items
attention can only be directed to the main work already cited.
Climate is a variab:e phenomena. Like weather, its increment, whích
changes from day to day, climate the summation varíes from millenium
to millenium. The fluctuations of clima te in their local manifestations
are more a result of a shi ft in position of the c1imatic regions than of
a direct proportional world-wide change. The great readjustments of
the c1imatic regions come with the changes from glacial to non-glacial
conditíons 01' vice versa.
Since an ice-sheet has an ínherent cooling effect which varies in proportion
to its size, it follows that once the temperature of non-glacial
poles drops during the winter belaw the critical point of 27.7° F . an ice-cap
will develop and spread without any further decrease in general temperature
until it has attained a size of about 2,400 miles in radius. Once
such glacial conditions are established the cooling effect brings excessively
cold temperatures over the interior of the ice-cap. The law temperatures
at the poles today are examples. The average difference be­