Los Angeles daily herald., 1874-04-07
GEOLOGICAL STRUCTURE OF Los AnG
VALLEY.

In with loose, rich soil. I'm;
a lake being constantly sup
with water from three rivers,
loose, rich earth washed into the
from surrounding mountainsu unt
earth averages about ten feet abov
water, and you have the geolo
condition of Los Angeles Valley.
sinking of artesian wells over an
of thirty miles in length by n,
twenty in width, develops the fact
underneath this valley is clay
from ten to thirty feet in thicl
and from thirty to fifty feet beloN
surface of the valley. The rim
clay bed comes to the surface
ground around the outer edge
valley, especially around the foot
1t also appears near the surface
the coast and in Wilmington hs
The rim along the coast is low er
so that the water flowing into the
nevet can flood the surface, for
surplus escapes over the rim into
ocean. Three rivers, Los Angeles, !
Gabriel and Santa Anna, conveying
large quantities of water all Summer
from melting snow, and becoming i'm
mense torrents in winter when swol-
len by winter rains, empty over the
upper rim of this clay, filling the clay
basin even with the lower rim, and
the surplus finding its way into the
ocean. Many facts corroborate this
theory. Next the coast there are
immense numbers of fresh water
swamps and bayous. AT Wilmington
when the tide is out, a barrel sunk in
the road will at once fill with sweet
water, the clay being so near the sur
face. In times of extreme Winter
flood the large volume of water flow
ing into the basin does not escape fast
enough and the country bordering on
the coast is saturated to the surface
with water, the low portions for few
days being covered with it. In few
days however the surplus has escaped
into the ocean by drainage over the
rim of the basin. 1t must be borne in
mind that the loose soil along the
coast forms an elevation and through
this the water percolates in reaching
the ocean.
The Importance of this geological
feature can hardly be overestimated.
There is thus lying beneath the Los
Angeles Valley at an average depth of
say ten feet a body of water thirty
miles in length by fifteen miles wide,
with depth of say twenty or thirty
feet of water, held in clay basin con-
stantly fed by three rivers.
By proper scientific handling of this
water supply, we need never feel the
effect of drought on our permanent
farming interests. Windmills and
steam-pumps can irrigate the whole
valley and when the irrigable land
rises in value beyond certain figure,
then the lands now without irrigating
streams will be irrigated by lifting
the water from the subterranean lake
to the surface. The investment re-
quired to do this is fifty per cent less
than the cost of irrigable lands used
for semi-tropical fruits.
The surface of the valley is an undu-
lating plain terminating in the foot
hills and mountains around the valley
On large part of this plain the depth
to the surface of the lake is about
twelve to fifteen feet.
Another fact becomes quite certain.
II is this: by keeping the surface of
the ground well ploughed, pulverized
and free from weeds, trees and vines
will grow without irrigation. Water
rises up from the surface of the lake
through the soil to point where the
heat of the sun evoporates the water
as fast as it rises. Place the corner of
a clod in cup of water, and you will
see the water run through the whole
clod. This point is generally three or
four feet below the surface on unculti-
waited land or land on which is growth
of vegetation. Where the soil is well
pulverized and free from vegetation, it
is from one to three inches.
The reason is apparent on a mo-
ment's reflection. Where the land is
not ploughed deep there is hard, close
packed crust, caused by stock tramp
ing the ground for centuries. This
hard, close packed surface is good
conductor of the suns heat. Just as
solid brick will become hot with one
end in the fire, whereas if the brick is
crushed into Jumps and one end of the
pile placed in the fire, the other end of
the pile will not become nearly SO hot.
A sponge will hold more water than a
piece of wood, so the close packed sur
face will not hold as much moisture as
the loose, porous soil. The sun there
fore dries out the former much sooner.
Again, in the growth of weeds or
grass the roots absorb the moisture,
carry it up, making the green, juicy
stalk and leaves, thus transferring the
moisture from the ground to the vege-
tation. AS it ripens, the moisture es-
capes from the vegetation into the air,
leaving the ground exhausted of its
Winter supply of moisture, and dry.
The roots of trees and vines will run
down into the ground from five to fif-
teen feet. thus reaching. if the SURFACE