Images of ...
The flight path
takes us from Oakdale, at the foot
of the Sierra Nevada, to the
Sonora-Columbia area in the
foothills. Our main objective was to
get a bird's-eye view of the
Stanislaus Table Mountain, regarded
by many as one of the finest
examples of an inverted stream in
the world. The mountain formed
around 9 million years ago, when a
latite lava flow streamed westward
from vents in the vicinity of the
Dardanelles, near Sonora Pass at the
crest of the Sierra Nevada. The lava
flowed down a river channel carved
out of the tuffs and mudflow
deposits of the Valley Springs
and Relief Peak formations, ending
somewhere just west of Knights
Ferry, having traveled 60 miles. The
lava resisted erosion better than
the softer surrounding rock, and the
flow eventually was exhumed, forming
a winding, sinuous ridge, especially
in the vicinity of Jamestown and
takeoff, we approach Knights Ferry.
Stanislaus River makes a
prominent loop, with orchards and
agricultural fields on the left-side
flood plain. The higher terraces are
drier, and are used primarily for
grazing. The exposed rocks in the
barren areas are mostly Mehrten
formation, which consists of
volcanic mudflow deposits around 4
to 9 million years old.
To the north of
Knights Ferry are exposures of the
Gopher Ridge volcanics, metamorphic
rocks dating from the Jurassic
period. These rocks formed as island
arcs on the oceanic crust of the
Pacific Ocean, but were scraped off
against the edge of the North
American continent as the rocks were
subducted. The rocks have been
metamorphosed, and turned almost
vertical by intense east-west
pressure. They are more resistant
than the surrounding slates, and so
stand out as a prominent ridge. The
town of Copperopolis is visible in
the upper right corner of the photo.
Farther along, we
pass the site of the Harvard Mine.
The open-pit mine was active from
1986 to 1994, producing about
660,000 ounces of gold from about 17
million short tons of rock. The lake
in the pit is about 300 feet deep.
Just prior to closing down, the
miners recovered a huge mass of
crystallized gold, weighing more
than 40 pounds. The gold is on
display at the Ironstone Winery in
Murphys. The body of water in the
background is New Melones Lake.
point was just east of the town of
Sonora. The town had its beginnings
in 1848 when gold was discovered by
Mexican nationals who had lost their
citizenship as California was signed
over to the United States. The
Mexicans were soon displaced
("invited to leave") by Americans.
The original town is visible in the
center-right part of the photo,
while the newer urban develop is
visible in the center and left-hand
part. Scars from the on-going
construction of a bypass can also be
Turning west, we start to see the
inverted stream of Table Mountain.
Highway 108 passes along the lower
left hand part of the photo. Very
little soil has developed on the top
of the old lava flow (note the lack
of trees, and widely scattered
grassy areas). The sinuous nature of
the flow is becoming evident.
A look out the
back of the plane offers the best
view of the flow.
Looking west, with
Knights Ferry in the far distance.
The flow is wider, especially where
some of the lava backed up into some
ancient tributary streams. Tulloch
Lake on the Stanislaus River is
visible to the right.
This flight was
made possible by Ken Iwahashi of KKI
Corporation in Modesto. Photos by