Vashon Island news-record. [volume] (Vashon, Wash.) 1919-1954, 1922-02-24

them in books of geology, Local
Ily Vashon and Maury island,
offer many interesting features.
The first and proper place tc
begin would be with the origin
of the two islands. The origin
goes back to many thousand
years ago. Scientists have by
fairly accurate ways traced the
age of the earth back as far AS
over one hundred million years
SO it is feasible that many
changes could have taken place
on the earth s surface.
The whole Puget Sound basin
was one large uphcavel Of land,
which was IA part Of the Cas-
cadc Mountains. There was a
disturbance that caused a fold
ing which formed general de-
Iprcssion along the western base
of the mountains. This is the
first step in the history of the
trough.
Then deposits of clay, sand
and gravel were brought down
by streams from glaciers in
British Columbia. These depos-
It's, accommodating in the trough,
! became so thick and widespread
that they completely filed up
the old valleys, buried most OF
the hills and constructed a new
plain. The material deposited
IN that period is now exposed
in the high bluffs along the
Tacoma docks and at Point De
fiance. Following this deposi-
ton the lowland was slowly up
lifted until it reached an eleva-
ton of one thousand and i've
hundred feet. In the course Of
many years streams wore the
surface of this upheaval down
to about five hundred feet.
Gradually as time passed the
climate which was tropical chang
ed to that of a cold one. Then
great ice sheets OVERRIDE the
basin. These ice sheets gouged
out great troughs. This accounts
for the deep harbors of Tacoma
and Seattle.
There We're two ice sheets,
The first one was known as
the Admiralty Sheet and the
second as the Vashon Sheet. The
Admiralty Sheet left thick de.
post of clay containing some
stone. This deposit can be dis,
tinguished from the Vashon de.
post by It's dark color and by
the angular shape of the rocks
In many places the Admiralty
deposit is so thick that its
depth has not been ascertain,
ed. The second deposit consists
of light colored clay with round
ed rocks scattered throughout
along with gravel and sand de,
|posits. AS these two ice sheets
extended down from British
Columbia it is safe to say that
Vashon and Maury Islands We're
at one time transported from
British Columbia to there pres
ent location.
After the retreat of the Wash
on glacier the sea water enter
ed the trough. Indications, which
are not very distinct, show that
the water was for short per-
iod of time at two hundred and
fifty feet above the present level
of the sea. Thus the islands
were practically submerged. At
the hundred and sixty foot level,
many shore features were found
on the main land. The only
indications found on the islands
are occasional fossils of clam
lshellS.
Within the last thousand years
lit is estimated that the islands
have risen ten feet above the
present level of the sea. The
shore line at this mark can be
traced from the Burton wharf
to the Assembly Grounds at
Gospel Point. There is a level
shelf from eight feet to one
hundred and fifty feet wide run
lining from the shore back 10 the
steep banks that We're at one
time sea cliffs. This shelf is
known as wave built terrace
formed by the action of the
waves undermining and cutting
down the banks.
Despite the upheavel of the
land the water continues its at
tack OH it. Within the last
fifteen years the writer has
noticed that the waves have
washed away six to ten feet of
the shore line along the beach