California Geology!
“Rocks are records of events that took place at the
time they formed. They are books. They have a
different vocabulary, a different alphabet,
but you learn how to read them.”
-John McPhee
The Coast Range
Coast Range Summary:
• Mostly marine sedimentary, some granitic and
volcanic
• Series of individual Mnt Rnges 2,000 – 4,000 ft
• Major structural feature is San Andreas Fault,
San Francisco Bay
The Sierra Nevada
The mountains are typically higher in the south and lower in the north
Highest point- Mt. Whitney (14,495 ft)
Uplift along the Eastern Sierra Fault System has
been accompanied by westward tilting producing
a gradual western slope.
Drainage Patterns
• West of crest into
Pacific Ocean
• East of Crest into the
Basin & Range
Glaciated
Landscape
Cirques
Hanging valleys
U-shaped valleys
Pyramidal peaks and horns
~11,000 yrs BP
Exfoliation or Sheeting,
a type of weathering
Big Rocks!
Happy Isles Rockfall
This is the shoulder of
Glacier Point
before July 10, 1996.
And then,
at 6:52 pm….
31,500 Tons of rock fell, causing a
20 sec earthquake; resulting air blast
snapped or toppled >1,000 trees
some >0.5km away. Caused many injuries
and 1 fatality. Air velocities exceeded
110 m/s or 396 Km/hr.
Hi 7
Table Mountain, an inverted stream
Sierra Nevada Summary:
• Mostly granitic, volcanic and marine
sedimentary
• Tilted to west along fault system on east
• Glaciated in last 1.6 my
• Creates major orographic effect, resulting with
a rain shadow to the east
• “old rocks, young landform”………
The Great Valley
Fill Diagram
Sutter Buttes
Great Valley Summary:
• Marine sedimentary below, non marine
sedimentary on the surface
• Sediments are extremely thick, up to 30,000
feet
• Sediments are thicker to the west, thinner to
the east
• Agriculture is the major industry, along with
fossil fuels
• Extremely flat with few outcrops, except
Sutter Buttes which are volcanic
Cascade Range / Modoc Plateau
Mt. Shasta
Shasta
ValleyValley
Debris Flow
Shasta
~675Km2 ~50m thick, ~45Km3
Travelled ~49 Km
Black Butte
The Modoc Plateau is a southern extension
of the Columbia Plateau flood basalts
Modoc Plateau
Modoc Plateau Topography
The Warner Range
Warner Range
The Warner Mountains are an 85-mile-long mountain
range running north-south from the Basin & Range,
through the Modoc plateau, into Oregon.
Cascade Range / Modoc Plateau
Summary:
• Mostly volcanic rock
• A very young province
• Warner Range is in the eastern portion of
Modoc Plateau (the Surprise Valley Fault)
• Mnt Shasta and Mnt Lassen are part of the
Cascade Range and the Modoc Plateau is part
of the Columbia River Plateau
Klamath Mountains
• Ranges in the California portion of the
province from South to North are:
•
•
•
•
•
•
•
•
South Fork Mountains
Trinity Mountains
Trintiy Alps
Salmon Mountains
Scott Mountains
Scott Bar Mountains
Marble Mountains
Siskiyou Mountains
Exposed Josephine
Ophiolite at Smith River
Trinity Ophiolite
Castle Crags
Klamath Mountain Summary:
• Granitic, marine sedimentary and metamorphic
• Comprised of many different micro plates or
accreted oceanic tectonostratigraphic terranes.
• Siskyou, Salmon, Trinity and Marble Mnts
• Coast Range is north west border, South Fork
Mountain Thrust Fault