Evening star., 1951-12-31
Appuluchions Created
Four Times in History
Radioactive Rocks Are Found
From 100000, 900 Years Ago
By Thomos R. Henry

IIOhh oOUtUOU,UVV ieQfS ago
By Thomas R. Henry
PHILADELPHIA Dec. 31.-Four times
the Appalachians from Maine through
the Carolinas have been lifted out of
the sea into mountain ranges as high
as the present Himalayas
The present mountains, the loftiest
OF which is only little more than a
mile high, are the worn-down remains
OF such range which was born about
200,000,000 years ago.
The picture, resulting from determi-
nation OF the ages of Appalachian rocks
from the decay of such radioactive min
erals as uranium and thorium, was
presented to the American Association
for the Advancement of Science here
today by John Rodgers, assistant pro-
fessor Of geology at Yale
The first great Appalachian range,
Mr.. Rodgers said, appeared roughly
800,000,000 years ago. At that time
this was a lifeless planet, at least SO
far as any living things which have
left any traces are concerned. The
land surface, at least, must have been
as barren as Mars.
Crests Were Eaten Away.
But rain fell, frosts cracked rocks
and great winds swept over peaks prob
ably as high as the present. Mount
Everest. Over many, many millions
OF years the great crests were eaten
away and washed into the ancient
ocean which had very roughly the po-
sition Of the present Atlantic North
ern waters rushed into the trough thus
created.
The second Appalachians, the radio
active determinations show, were up-
lifted about 600 ZOO, 900 years ago. This
was just before the dawn of the Cam
brian geological era when life's earliest
traces are found in rocks. There still
are fragments Of these mountains, par
ticularly in the Adirondacks. where COL
lections Of Cambrian fossils have been
made.
The second Himalaya-like range
suffered the same fate as the first and
was succeeded. about 350,000,000 years
ago. by another of roughly the same
proportions. BY this time, the earth
had been covered with vegetation. It
was just at the start of the carboniferous
age when the great coal deposits were
laid down from the great forests of
tree ferns. In these forests were ex-
tremely primitive back-boned animals,
and the first fish were in the seas.
Earth Extremely Active.
Throughout most of this period, it
appears, the face Of the globe was ex-
tremely active and the mountains were
short-lived. In the course of about a
hundred million years they had been
washed away and another range raised
up along essentially the same line.
Then, about 100000 years later,
there were great earth commissions
which raised them a little higher. It is
the worn-down remains of these which
constitute the present Appalachians.
The process of erosion still is going on,
but not very violently, and the range
probably still has millions of years of
life.
Fragments of all these ranges, how
ever. still exist. They successfully
resisted the erosion processes and prob
ably remained for millions Of years as
underwater mountains before they were
uplifted again. The successive ranges
have been formed Of rocks created out
of sediments washed into the sea.
The present scenery Mr.. Rodgers
said, results from the wearing away
process which has lowered the areas
of relatively weak rocks to make valleys
and low hills and has left the areas of
stronger rocks, like granite, standing
up as the present-day mountains"
Many Cross Checks Made.
This picture rests, he explained. on
about so accurate determinations of the
age OF radioactive rocks. The process is
slow and tedious, but three samples have
been checked and double-checked and
can be used as standards for the others.
One Of these is mineral obtained near
Middletown, Conn, which was formed
during the mountain building episode of
260 million years ago. The other two
are minerals from Westchester County,
New York. which we're formed approxi-
mately $50 million years ago.
OF the other reliable determinations.
about Is, all from New England, agree
with the Middletown material. About
20, from New England and the Caro-
linas. agree with the Westchester min
erals In being about $50 million years
old. The other reliable determinations
are on older rocks, scattered from North
Carolina to Maine, and give ages of
either approximately 600 million or 800
million years.