Evening star., 1936-05-09

1Tentoil, Wilmington, bdlLliIlOIc, duo
Richmond are on the Fall Line.
Downtown Washington and the
eastern half of the city are built on
the sandy deposits of the Coastal
Plain. The higher western portion of
the Capital is founded on the hard
rocks of the plateau. The portion OF
the Piedmont Plateau included within
the boundary lines is strangely shaped
like the top of grand piano. Every
day Washington motorists apply their
brakes as they travel down steep
grades caused by the Fall Line. Six
teenth street at Meridian Park and
Thirteenth street at Central High
School are two Of these hills, pro-
saically marked by SLOW, steep
grade" signs.
ON CANAL ROAD, tour leader Nc
~ Henry next directs the party's
attention to the actual remains Of
towering ancient mountains. Huge
lichen-clad masses of igneous rock
tilt toward the sky. in mute teSti-
mony of the power of erosion and i'm
measurable time. He further ex-
plains that their Alpine heights can
not be definitely determined, although
scientists believe they ranged from
three to five miles high.
From these hoary sentinels the
motor caravan swings over to Rock
Creek Park, where the winding stream
has sliced valley through the north
east portion of the city. This ancient
and narrow stream was once very
broad and powerful as it swept over
the land, and now. having spent its
strength wearing away the resisting
terrain, it meanders slowly to the Po-
tomac and on toward the sea. The
rock seen everywhere along the creek
is so ancient that its age may never
be known.
Then the route leads to Harvard
street, at the foot Of Eighteenth where
the guide points out natures myS-
terry bank. an enigma that has puzzled
many scientists. Many paSsers-by
have paused and wondered why a
large bare patch Of unSeeded soil was
left exposed in the center Of this other
wise beautifully graSsed terrace. The
secret is out! Here is a gap OF mil
lions of years between the layers of
the earth's crust. Normally the Sc
quence of the strata reveals the story
of prehistoric life. But not here.
Gravels and sands Of recent age, geo.
logically speaking, rest upon a stra-
tum of ancient decayed rock. Only
an early and late chapter are read
here. Time and natural forces have
wiped out the rest of the story.
McHenry calls this phenomenon
an "unconformity."
lON ADAMS MILL ROAD, opposite
Clydesdale Place, is seen the Sec
ond protected natural wonder. A con-
crete and wire shelter shields a low
sand and rock bank. Dramatically
the reverse of the Harvard street
layers, the tour leader points to q
layer of rock. approximately 100000
900 years old, resting upon compare
lively recent sandy deposits. Old upon
| young. How is this possible? Geolo-
gists know the answer. 1t was caused
| by the earth's crust twisting and
| warping, as it does after a great span
of time. Here is visible evidence of
an underlying rock formation affected
by pressure powerful enough to thrust
it over a higher and newer deposit.
Exposures at the surface of the
ground that clearly exhibit such phe-
nomena are rare occurrences. That
is why biologists are anxious to pre-
serve them for future observation.
A short side trip to the Mormon
church is then made, and the natural
ist-guide points out the abundant fos-
sill seaweed in the limestone walls Of
this new structure.
Farther down Sixteenth street, in
the red sandstone walls Of picturesque
Henderson castle, McHenry tells that
dinosaur footprints are often found in
rocks of this age. No doubt, when
the hoary walls fall these impressions
will be revealed.
THEN the party will proceed to the
L site of Fort Totten, an old Civil
War fort. From the edge of the
earthworks the undulating nature Of
| the terrain is distinctly seen. Ana
costa lies to the south, distinct pur-
pie knob, rising above the surrounding
lower land. McHenry tells that
Washington is founded on five ter
races which were formed during the
Great Ice Age, known to scientists as
the Pleistocene epoch. Study has re-
vealed that this period was not sin
gle, simple episode, but series of gla-
! cial stages. each tens Of thousands Of