CA Professional Geologist State Exam
Questions and Answers
Anorthosite - Answer-A plutonic igneous rock composed almost entirely of plagioclase
feldspar, found in the San Gabriel Mountains and dated at 1.022 billion years.
Connate Water - Answer-Water trapped in a formation at the time of deposition
Franciscan Formation or Group - Answer-A heterogeneous unit of sedimentary and
volcanic rocks consisting of greywacke and interbedded shale, minor amounts of chert,
limestone, greenstone, and metamorphic rocks of greenschist and blueschist facies.
The formation may be 50,000 feet thick. It is one of the basement types in the Coast
Ranges.
Great Valley Sequence - Answer-Shallow self to submarine fan deposits of sandstone,
shale, siltstone, and minor conglomerate and limestone of Late Jurassic to Late
Cretaceous age. These deposits, attaining a maximum thickness of approximately
80,000 ft, were thrust over the Coast Range ophiolite above the Franciscan formation.
Lake Corcoran - Answer-A freshwater lake that covered much of the western San
Joaquin Valley about 600,000 years ago (Late Pleistocene). Freshwater deposits lake
clays, volcanic ash, and diatomite of Corcoran Clay member of Tulare formation.
Los Angeles Basin - Answer-A large down-warped basin formed in Late Tertiary that
received thousands of feet of marine sediments. The basin produces petroleum in
prolific quantities. Located in the Peninsular Ranges in southwest tip of CA
Ophiolite - Answer-an igneous rock consisting largely of serpentine, believed to have
been formed from the submarine eruption of oceanic crustal and upper mantle material.
Monterey Formation - Answer-A widespread Miocene marine formation consisting of
siliceous shales and cherts. Silica was deposisted as diatomites and silicic ash beds.
Phosphates were also deposited in the formation. The Monterey Formation is the most
likely source of much of the petroleum and natural as in the Transverse Ranges
Province.
Overdraft - Answer-The condition of water withdrawal by pumping exceeding the
amount of water recharged, occurring over a time frame longer than a year.
Pelona Schist - Answer-Low-grade metamorphic rock of Cretaceous age in Transverse
Ranges.
Salinian Block - Answer-The structural block located west of the San Andreas fault zone
and east of the Nacimiento fault zone. The basement is composed of Late Cretaceous
,granitic rocks similar in composition to the Sierra Nevada granitic rocks. The granitics
are the other main basement type in the Coast Range Province (located along the
western coast)
San Andreas Fault - Answer-The most important fault in CA - a northwest-trending,
right-lateral strike slip fault, 750 miles long, extending from Shelter Cove in the north to
the east side of the Salton Trough. The fault forms the plate boundary between the
Pacific and North American Plates and separates Franciscan formation from the
Salinian Block in the Coast Ranges Province.
Sierra Nevada Batholith - Answer-A great uplifted block of granitic rocks intruded and
uplifted beginning in the Late Jurassic. The bulk of the rock was emplaced during the
Cretaceous. Granitic compositions range from granite to quartz monzonite, quartz
diorite, and granodiorite.
Santa Ynez Fault - Answer-Boundary fault between the Coast Ranges and Transverse
Ranges Province and separating Franciscan basement of Late Jurassic age from
Transverse Ranges basement.
Southern California Batholith - Answer-The dominant rock outcrop of the Peninsular
Ranges, consisting of gabbro, diorite, quartz diorite, quartz monzonite, and granite.
Quartz diorite predominates. Batholith was emplaced mainly during the Cretaceous.
Subjacent Series - Answer-One of two major subdivisions of rocks in the Sierra Nevada
and Klamath Mountains Province applied to the rocks younger than the Nevadan
orogeny that emplaced the Sierra Nevada batholith.
Sutter Buttes - Answer-A prominent circular feature in the Central Valley that is volcanic
in origin. The core is andesite and tuff and is surrounded by rhyolite porphyry. Explosive
activity was recorded in the Pleistocene. This feature has produced traps for natural
gas.
Klamath Mountains Province - Answer-Province found between the northernmost Coast
Ranges and Cascade Ranges and the Great Valley to the south. The western boundary
is defined by the South Fork Mountain thrust fault. Several irregularly oriented mountain
ranges are found in the Klamath Mountains, including: Trinity Alps, Salmon Mountains,
Scott Bar Mountains, Siskiyou Mountains, and Marble Mountains. Topography:
moderate peaks (6000-9000 ft EL). Abundant rainfall, Salmon, Shasta, Sacramento,
Scott, Klamath, and Trinity Rivers drain the area.
Key Formations:
1.alluvium/glacial deposits-gravel, sand, mud, Au bearing;
2.Pleistocene Red Bluff
3.Plio-Pleistocene Tehama-stream grvl, s, volcanics & lake sediments
4.Miocene Wimer-yngst marine unit, ss, sh, cgl, 150ft; cgl forms ridge tops; contains Ni
minerals
, 5. Oligocene Weaverville-folded & faulted ss, sh, tuff, & lignite deposited on swampy
floodplains; 2000 ft thick; similar to Ione, contains Au, phosphates
6a. Cretaceous Hornbrook (Great Valley seq, Upper)-Oldest superjacent series rocks,
2000ft thick, lie unconformably on granite & older fms. Shallow-water marine &
fossiliferous, well-bedded mudstone, sh, & cgl; basal cgl Au-bearing. Great Valley -
marine cgl at base, pebbles of mica schist; E K pelecypods & ammonites.
6b. South Fork Mountain schist-youngest subjacent series rocks; well-foliated quartz-
mica schist, with glaucophane-crossite; closely related to Franciscan fm; Klamath Mtns
were thrust over and attached to Coast Ranges along South Fork Mountain thrust.
.7..... AHHH TOOO MANY!!!
Active Fault - Answer-A fault that has exhibited surface displacement within Holocene
time (about 11,000 years) as determined by the California Geological Survey under the
Alquist-Priolo Earthquake Fault Zoning Act. Other state and federal agencies define
activity differently based on the faulting type and tectonic regime.
Afterslip - Answer-A seismic fault slip that occurs following a large earthquake.
Asthenosphere - Answer-Under the lithosphere, it is weak upper mantle where isostatic
adjustments are made, magma generated and seismic waves strongly attenuated.
Attenuation - Answer-A reduction in the amplification of seismic waves produced by
divergence, scattering, reflection, and absorption
Avalanche - Answer-A large mass of snow, ice, soil, rock or mixtures of these materials,
falling, sliding, or flowing very rapidly due to gravity.
Body Wave Magnitude - Answer-Magnitude of an earthquake as estimated from
amplitude of body waves.
Creep - Answer-Aseismic fault slip
Crown - Answer-The material that is still in place and adjacent to the highest parts of the
main scarp of a landslide.
Differential Settlement - Answer-The uneven lowering of different parts of an engineered
structure, often resulting in damage to the structure.
Dilatancy - Answer-The increase in volume of rocks due to elastic and nonelastic
changes during deformation
Earthquake Fault Zones - Answer-Areas along active faults, 1/4 mile or less in width, to
provide for public safety in hazardous fault zones.
Elastic Rebound Theory - Answer-A theory proposed by Reid to explain the cause of
earthquakes which states:
