Evening star. [volume] (Washington, D.C.) 1854-1972, 1933-07-23
SEASONS Of AGES
ARE DESCRIBED TO
WORLD BIOLOGISTS
Temperature Fluctuations
Over Thousands of Years
Presented in Reports.
SILT LAYERS IN LAKES
IMPORTANT INDICATORS
DR.. Antevs Tells Congress Human
Race Has Been Living in
Cold Period.
BY THOMAS r. HENRY.

BY THOMAS r. HENRY.
There are seasons Of the ages.
Temperature fluctuations extending
over thousands Of years were pictured
by biologists who presented reports
before the International Geological
Congress here yesterday at the opening
OF its scientific sessions
They were advanced to explain such
periodic events as glaciations of the
Northern Hemisphere by Prof. Ernst
Antevs, foremost authority on the "clay
varve" method of dating events In the
distant past. During the Summers Of
glacial retreat lakes formed in the rear
OF the great ice sheets and into these
flowed the water from the melting ice.
carrying sediment with it. Thus each
year layer Of silt would be deposited
at the bottom of the lake. These layers
can still be found in North America and
Europe and constitute an important
geological clock for the period in the
earth's history just before.
Ice Has Chance to Melt,
Now, Dr. Antevs said, the periods of
melting ice and glacial retreat indicated
to recent astronomical calculations of
the recurring periods when the earth is
closest to the sun during the northern
Summer, while at the same time the
excentr1city Of the earth's orbit is large.
At such times the snow does not fall
on top OF the glaciers to form new ice,
and the underlying ice itself has q
chance to melt.
For the recent past, DR.. Antevs said,
both methods indicate there were
periods OF very warm Summers from
$4,000 to $4,000 and from $4,000 to
$500 years ago. There was a period
OF cold Summers from "a 900 to $4,000
years ago and the earth has been in
another such period for the past 45OO
years. The human race has been liv-
ing in a cold period, with the great
glaciers Still lingering on the edge of
the Arctic and on the high mountains,
almost since the beginning Of recorded
history.
Summers and Winters Reversed.
Presumably there were the same
fluctuations, roughly of from 10000 to
$4,000 years, before the pleistocene geo.
logical period which preceded the pres
ent. but no positive evidence of them
can be found. Mathematical calcula-
lions show the earth's position in Sum-
mer in respect to the sun is bound to
change In about that period. In the
southern hemisphere the recurring
Summers and Winters of the ages would
be approximately reversed. They are
shown In the variations of plant and
animal life as shown by fossils pre-
served in rocks.
This theme was carried further In
report prepared for the congress by
Charles Reyes Of the University Of
Arizona. who stressed that it might
soon be possible to pick up the record
Of the climatic variations in the tertiary
period which preceded the last series
Of glaciations.
"The cycle of hemisphere glaciation
Is known to be about 81 900 years." he
added, "and a glacial epoch, or group
OF glaciations, may include from to
10 climatic maxima, with a total dura-
ton Of from $4,000 to 100000 years"
Valuable Time Measure.
Other calculations have been report
ed, according to DR.. Keyes, which indi-
cate that there IS a cosmic year of l.
100000 years, in each repetition of
which identical temperature values are
bound to recur. II this cycle can be
substantiated. 1t was pointed out, it
would constitute valuable geological
time measure. Years, as such, mean
nothing in describing past time, the
biologists stressed. since they are such
brief periods in which nothing happens
which is preserved for the future.
More than 40 methods have been en-
ployed to estimate parts Of geological
time, reported Prof. A. C. lane nf Tufts
College, chairman of the committee on
the age of the earth. but all except one
assume that processes have gone on at
the same rate in the past as at present.
This, he declared, is an invalid assume
ton since It Is by no means certain
that even the speed Of light has been
the same since the beginning OF the
earth. When applied to thickness OF
deposits of erosion. he said. it Is I'M
likely that the rate has been the same
throughout time.
Rate Of Breakup Is Known
Prof. Lane stressed the value OF
measuring time by the rate Of atomic
disintegration. Uranium and few
other heavy elements which are widely
distributed In the earth's crust grad
ually break down into lead and the rate
at which this change takes place is
known. Thus the age Of the rock itself
can be estimated from the proportion
of the right kind Of lead found there.
The latest results from this method
reported to the congress, Prof. Lane
said, show the Oldest rocks are not
more than 1900. 100000 years old. The
actual age Of the earth, allowing for all
other considerations, is now placed at
q little more than twice this figure.
BY the uranium disintegration meth
Cd, he said, it IS possible to fix the ap-
Nf
geological upheavals. They show that
approximately every 10000 900 years
there is such . period Of great activity
which he interpreted as the result OF
the crust Of the earth yielding to &C
cumulated stresses. Others, he said.
have interpreted it as the result Of
great periodic heat pulsations from the
interior.
One method Of measuring time, he
said, Is by determining the amount OF
salt in the sea, although he believes
that this has been by no means con-
slant. It offers . convenient explana-
ton for the first, appearance OF life
about 500 ,000, 900 years ago, as shown
by fossils. At that time, Prot. Lane
said, it Is probable that the salt con-
centration In the water had just reached
the point where the sodium could be
drawn upon to form shells which would
make Impressions in the mud. These
impressions were preserved when the
mud was compressed into rock. Living
things previously could have had no
hard parts which would make prints
on the mud when they persisted.
Describing researches extending since
1878 In . report prepared for the Con-
gress, DR.. Gerard de Geer, noted Swed-
ish geologist and originator Of the varve
counting method, said the evidence was
now conclusive that the great glacia-
tons Of North America, Europe and
Asia took place at approximately the
.soont'nusd On Second FfssA