Evening star., 1948-01-02
Stars, Men and Atoms
New England Struto ! Iell
CIimute Of q, 900 Yeors
Pollen Deposits in Glacial Lake Bottom
Record History Since Ice Ass
Rv Thomns X. Henry

y
NEW HAVEN, Jan. 2.-The climatic history
az $4,000 years, since the retreat OF the last
great glaciers which covered this part Of the
country, is being revealed by . study Of the
pollen deposited In glacial lake bottoms o. the
northeastern United States.
An intensive study of these deposits Is under
way here under the direction Of Dr.. Edward s.
Deeyey. r.. Of the Yale faculty. It reveals. he
reports. four major climatic periods, each
characterised BY different type Of forest vese-
tation.
There has not been . steady temperature IN.
crease q mieht have been expected after an
Ice sge, and the country now apparsntly II
n the midst Of cool. wet period after reach.
ing maximum Of warmth.
Like That of Tundras.
Immediately following the retreat Of the
lee, DR.. Dewey reports, there was brief period
Of sub-Arctic conditions such as now would be
characterized by the tundra OF northern
Canada. This was quickly succeeded. however.
by . "sprlce-fir" period with vegetation sim
liar to that now found just south Of the
tundra.
The next phase, through the northeastern
and central States, was an "oak-hemlock" era
with . somewhat warmer and moister climate.
Then came the ak-hickory" period which
was warmer and dryer. This reached its eli"
max about 5000 years ago and was the warm.
est period since the end of the ice age. 1t
was followed by the present "oak-chestnut'
phase-colder and moister with tendency to
return to the earlier "spruce-nr" complex
further inland.
Dewey says, that the northeast now is in the
,~.yd 81 rf 1oy,u tiraa considered IN
terms OF centuries. There are ups and downs OF
temperature over shorter periods. but the gem
eral trend is towards increasing coolness. II
winters have become milder, as Weather Blu.
reau records indicate, the change can be con.
sidered quite temporary.
Recent pollen studies in Europe, DR.. Dewey
says, show about the same climatic trends
since the glaciers retreated, and they prob
ably have been general over most Of the north.
ern hemisphere.
The optimum Of warmth was reached about
the year 5000 B. C.,.at which time, recent ar
cheological evidence Blows. human beings were
already living In the northeastern United
States.
Change With Strata.
The lake bottoms show the characteristic
wind-blown pollens In well-dehned strata
which changed as the temperature changed and
persisted for thousands Of years Altogether.
Dewey points out, the evidence indicates that
the present is only partial interglacial per-
iod The earth has never been as warm since
the last Ice retreat as during other intervals
between glaciations and more ice remains In
both the Arctic and Antarctic-ready to ad-
vance again at . favorable opportunity.
The northeastern lake bottoms are especially
well adapted as thermometers Of the past, since
the lakes themselves have only existed since
the retreat Of the ice and the story b un-
complicated by any pollen deposits which may
have preceded the last glaciation. The same
alterations Of strata are found through the en-
tire region covered by the ice.