The Eureka sentinel. [volume] (Eureka, Nev.) 1902-current, 1915-03-13
NEvADEs GEOLOGICAL HISTORY
History of State Written In Rocks
Now Exposed In the Mountains
and Valleys

OF q crust OF M earth contained with.
in the boundaries Of the State Of Ne
vada. 10 written In the rocks now ex-
posed in the mountains and valleys.
Unfortunasely there 10 no Rosetta Stone
for the hieroelyphics Of time, and the
deciphering Of records must Of necessity
come through the study and inference
Of the manner in which similar rocks
are being formed to-day.
We know that various faces on the
surface Of the earth. together with the
chemical activity Of the air and water.
are engaged in breaking mp the rocks
into the finer fragments that We know
as sand. We observe that the winds and
running water are carrying this dis
integrated rock from the higher to the
lower levels and that wei the greater
portion OF the earth the final resting
place Of the sediments is in the ocean.
We have discovered that these clays.
sands and g~ravels become oemented into
the shales and ssndstones, and the lime,
carried in solution BY the streams, lie
deposited as limy muds. largely through
the activity Of plants and animals even
tually forming the limestones.
We see the volcanoes pouring out
molten rock material or lava upon the
surface Of the earth and as the lava cools
tt for~s rocka .;r;l.r to sh> .hroI;so.
andesites and basalts 80 common In our
State and which the most u~nlearned in
geology instinctively recognizes as hard
ened lavas. Our experience has taught
rs that in many cases the rising lavas
do not reach the immediate surface OF
the earth. but cool at some considerable
depth below. and. as they must cool
very slowly owing to the very slow es-
cape Of the heat through the thick cover
Of rocks above them. they become fully
sranitio rocks.
We have become ware of the action
Of the internal forces of the earth through
the elevatedsbeaches along our coast and
high mountains with the depressed val.
eys between them. We have seen bent
aud folded rocks exposed by the forces
u erosion and an occasional earthquake
calls attention to the relative movement
between the different blocks Of the
-arth's crust along the lines of fracture
that we call faults.
We now realize that our old earth is
not so stable as We once believed, but
its surface Is ever changing, the noun
tains being torn down and leveled
through the forces acting ct ths surface
md occasionally being renewed by in
fernal forces. the everlasting hills Of the
Psaimiss only seeming so because the
lifetime OF man is so brief.
AS in human history. we are MOS
fsmiliar with the more recent events.
and the farther back we go the less def.
mite is our information. In Nevada the
lldest rocks Of which we have any
knowledge are found in the canyon OF
the Colorado river, where certain gran
ties aud sediments are found underlying
III the other rocks. These are so changed
md altered that it 10 often quite impos.
-ible to tell definitely just how they
originated. Little evidence has been
found of the life that must of had it.
being at this time and it is only when
we get into the higher rocks that we
find many fossils. Presumably these
oldest rocks underlie the whole State
and are concealed by the younger rocks
lying owe them.
East of a line running north of Austin
and including Silver Peak to the south,
a series Of limestones, shales. sandstones
and quartzites form a large part Of the
mountain ranges These rest upon the
oldest rocks and are separated from them
by an old erosion surface that tells of a
very long period when Nevada was dry
land. From the fossils found in this
series we know that it was deposited in
the ocean, for the animals are similar to
those living in the ocean at present.
The most striking difference in this an
cient life was the complete absence of
the large animals we have at present,
and only a few primitive and slow NOV
ing fishes represented the vast and var
led throng Of animals with back bones
that we have to-day. This ancient
fauna was composed almost exclusively
Of corals. CLANS. snails, End similar ami
mails. together with strange animals
now extinct, that looked like jointed
tugs and are known as trilobites.' The
thickness of the rocks formed at this
time is estimated to be 80. 900 feet in
the vicinity of Eureka. This mean that
the ocean covered the eastern part of
Nevada at least until nearly five and
three.quarters miles of sediments were
deposited on its bottom. This mus
have taken a very long time and it is
largely on such evidence that the geolo.