California Geology midterm Exam

What is the principle of Uniformitarianism?

"The present is the key to the past" - Earth processes have been the same over time - Geologic change is slow - Earth is old: Earth history = PRE-human history

What is the definition of a clastic sedimentary rock? Think of some examples you saw in section or lab

- layers of sediment compressed and pressured together. -examples: sandstone, mudstone, breccia, conglomerate, chert , coal, limestone

What is a chemical/biological sedimentary rock? Think of someexamples you saw in section or lab

- made of dead critters - chert, coal, limestone

What are the other main rock types on the UCSC campus. What are the basement rocks that you saw on the field trip? Know their names andwhat types of rocks they are. For the 3 types of metamorphic rocks, whatwere the sedimentary precursors to these rocks and how did they form?What are the rocks on top of the basement rocks - are they igneous,sedimentary or metamorphic? How old are they and how did they form?

- quartzite, schist, slate, marble , granite -quartzite: sandstone -schist: shale/mudstone -slate: shale/mudstone -marble: limestone

Be able to describe the difference between the rocks you learned insection/lab such as shale/mudstone, sandstone, conglomerate, breccia,limestone, evaporite and a chert.

- shale/mudstone: made of mud (deep ocean) -sandstone- made of sand (shallow ocean) -conglomerate: chunks of other rocks -brecia/ limestone- made of ca co3 shells of dead critters - chert- silica si02 critters

Where are the major occurrences of igneous rocks in California?

- transform plates: all rocks - divergent plates- mafic rocks -convergent plates- felsic and intermediates

What rock type of the UCSC campus has been important economically? What features of this local rock type cause it to be of importance from the perspective of building construction?

-limestone/ marble used to build in quarry and santa cruz mountains

What is the difference between a rock and a mineral.

-mineral is a chemical comp. -rock is an aggregate of minerals

What is the tectonic setting of each of these volcanoes? Which areassociated with subduction zones, which are associated with faulting due to basin and range extension?

-mt. shasta- techtonic setting is continental crust (subduction) - medicine lake: tech setting is continental rift zone. - long valey caldera- basin range extension

What silicate minerals did you see in section or lab (i.e. quartz, feldspar, mica, amphibole, serpentine)

-quartz, chert, feldspar, talc, garnet, mica, olivine, serpentine, amphibole, galena -non silicates: hematite(oxides) , pyrite (sulfide), magnetite, calcite (carbonate)

In terms of the shape of the volcano, temperature of eruption, associated rock type, and tectonic province, what are the differences between Mt. Shasta, Medicine Lake Volcano, and LongValley Caldera ?(there is a slide that covers this is the young volcanoes lecture)

-volcanoes shape and eruption depends on lava comp. the difference between mt. shasta, medicine lake and long balley 1. mt. shasta- andesite rocks, formed by melting above subduction plate via melting point depression. stratovolano 2. medicine lake-basalt, decompression melting of the mantle in a continental extension or rift zone 3. long valley-rhyolite

What are typical rates of plate motions?

1-10 cm per year

What kind of plate boundaries are in CA and where are they?

1. convergent plate boundaries- cascades 2. Divergent- salton sea 3. Transform- san andreas fault

Name the important characteristics used to identify minerals.

1. crystal form 2. fracture 3. specific gravity 4. cleavage 5. streak 6. hardness 7. luster

Low- temperature, high-pressure metamorphism is associated with whatkind of tectonic activity? How about low-pressure, high-temperaturemetamorphism? How about moderately high pressure and temperaturemetamorphism? (there is a figure in the metamorphic rock lecture on this)

1. low temp high pressure- regional metamorphism 2. low pressure high temp- contact metamorphism 3. high pressure high temp- burial metamorphism

What are the different kinds of faults and what is the relative ground motion?

1. normal fault due to tension. footwall slides up while hanging wall slides down. 2. reverse (thrust) fault due to compression: hanging wall slides up while foot wall slides down 3. strike slip fault due to shearing. slide past eachother

When did the San Andreas fault system begin in CA and what kind of plate motion did the San Andreas fault replace?

15-20 mya. The san andreas fault replaced divergent plate boundaries.

When did the Sierra plutons form? How long was the period of magmatic activity and when was the main pulse of magmatic activity that formed the Sierra?

200 mya. 150 my. Formed from late triassic to late cretaceous. he most voluminous eruptions were during the Cretaceous or from about 120-80 million years ago.

What are the different kinds of plate boundaries? what is the relative motion of each boundary?

3 types: 1. subduction (conversion) -plates crash into each other 2. Transform plate boundary- plates slide past each other 3. Divergent plate boundary- plates move away from each other (mid ocean ridges)

When was the huge eruption at Long Valley Caldera? Has there beenevidence of volcanic activity since in that area?

760,000 ya. yes earthquake swarm in 2014

Where are the major occurrences of sedimentary rocks in California?

Coast ranges, Great Central Valley, Eastern CA, and great basin

What is the difference between regional and contact metamorphism??How might rocks subjected to these two types of metamorphism bedifferent?

Contact Metamorphism- new minerals grow at the interface of an intrusive magma contacting old limestone. regional- metamorphism affecting rocks over an extensive area as a result of large scale action of heat and pressure. Contact metamorphism rocks will have larger crystals and will be darker and more dense as a result because the heat and pressure is more concentrated.

Where are the major occurrences of metamorphic rocks in the California?

Convict Lake, Eastern Sierras Death Valley, CA Coast Ranges (Franscican formation and Pacheco pass)

How are the boundaries between eras, epochs and periods determinedon the Geologic Time Scale?

End and begining of eras are determined by when a new species or type of animal first appeared. ie:humans appeared right before the beggining of the quarternary period

How does one use the principles of original horizontality,superposition, cross-cutting relationships and unconformities to figure outthe relative ages of rock units in a geologic section. Specifically, if I gaveyou a cartoon like the ones we studied during the Geologic Time lecture, beable to interpret the cartoon in terms of the geologic history of the section(i.e. which layer is youngest, oldest, if a fault runs through the section, howcould you bracket the age?)

Faults & dikes are younger than beds they cross

What is foliation and what does it tell you about the history of a metamorphic rock?

Foliation- verticle cutting across sedimentary layering. (will leave horizontal lines) the deeper a rock is metamorphosed in the earth the more foliated it willl be therefore older

What is an index fossil? Give some examples of index fossils. Arethere many index fossils in CA rocks? Why or why not? Can relative datingbe used extensively to work out the geologic history of CA - why or whynot?

Index fossils are used as guides to the age of rocks in which they are preserved. They contain organisms that lived for only a short period of time. THey are usually commonly preserved groups such as: trilobites, ammonites, forams, ostracods. While relative age dating can be used to sort out the order of geological history it can't really determine the length of time certain things existed. Which is why absolute dating is needed.

Describe the layered structure of the earth (crust-mantle-core). What is each layer composed of? About how thick is each layer?

Layered structure: Mantle and core. The core is composed of inner solid mostly iron core and outer liquid core. The Mantle is iron, magnesium, and silicates. The mantle contains lower mantle (thickest) , Asthenosphere (less thick), and Lithosphere (Thinnest).

What is the difference between the crust of the earth and thelithosphere?

Lithosphere is uppermost mantle, and brittle. Crust is part of lithosphere

What defines the "plate" in plate tectonics? How thick is an ocean plate?

Lithosphere= crust and rigid upper mantle BRITTLE. move relative to each other. An ocean plate is 5 miles in thickness, much thinner than continental plates.

How is the global pattern of earthquake and volcano locations related to plate tectonics?

Plates define earthquakes and volcanoes. Mainly subduction plate zones

What is the definition of a metamorphic rock?

Rock that has been altered by pressure and heat.

The earth is dominated by muddy sedimentary rocks like shales andmudstones. California has a higher proportion of coarse-grained sedimentaryrocks like sandstones and conglomerates. Why might that be? What does ittell you about the environment in which these rocks formed?

This is most likely because california has a very long coast. Coastal and marine areas are where rocks like conglomerate and sandstone are formed. Most parts of the geologic world do not have coastal regions. So they would have shale and mudstone.

Why do we believe that the rocks underlying the UCSC campus arerelated to the Sierra Nevada?

Volcanism in the Sierra intruding into The paleozoic seafloor.

What's a shield volcano and what kind of rock(s) is it make of? Give aCA example. What is a stratovolcano and what kind of rocks is it made upof - give CA example(s). What is a cinder cone and what kind of rocksresult? Give a CA example.

a shield volcano is a basalt cone shape located in medicine lake a stratovolcano is andesite- mt shasta a cinder cone volcano is basalt long valley

Which igneous rock type best represents the most abundant rock in thein: a) Sierra Nevada b) Mt. Shasta and Mt. Lassen (i.e.the Cascades Volcanicchain), c) Medicine Lake volcano, d) Long Valley, e) Mammoth Mountain, f) Mono craters, g) Coso volcanic field.

a) sierra nevada- granites b) Mt shasta/ Mt. Lassen cascades- andesite c)medicine lake volcano- basalts d) long valley- rhyloties and basalts e) mammoth mountain- f) mono craters- rhyolite g) coso volcanic-

What is a pluton? What is a batholith? Where is a batholith inCalifornia?

batholith- a very large igneous intrusion extending deep in the earth's crust. Ex Sierra nevada pluton - a body of intrusive igneous rock.

Recall the special kinds of schists that have basalt as a protolith: blueschist, greenschist. Why do we find these rocks in California?

because they form along subduction zones

What is the difference between obsidian and pumice?

both felsic rocks obsidian (volcanic) pumice (plutonic)

What are unconformities.

break in time in desposition

What drives volcanic explosions and which of the CA volcanoes aremost likely to have a catastrophic explosions? Which volcanoes are morelikely to have eruptions like those at the Hawaiian volcanoes?7) Describe the role of water in determining lava composition and thestyle of volcanic eruption?

buildup of magma causing pressure to explode. Felsic volcanoes are likely to erupt. Water causes the volcano to be explosive

How are rocks correlated from place to place?

by matching up rocks from different places that are similar in age. through physical criteria and fossils

Why do both compression and tension in the Earth's crust buildmountains?

causes uplift and spreading that builds mountains

What are the differences between continental and oceanic crust?

continental-formed from convergent plate boundaries, felsic + transitional rocks oceanic- formed from divergent plate bondaries, mafic rocks

What causes the plates to move?

convection currents in the mantle

Why do we believe that the rocks underlying the UCSC campus are related to the Sierra Nevada?

due to subduction of the plates

What are the various hazards associated with volcanic eruptions?What's a lahar and what is the likelihood of this being a problem for theCascade volcanoes like Mt. Shasta?

explosion, inhilation of phyroclastic flow. burning A lahar is Catastrophically melting snow and mud flows. Problem for cascades because there are glaciers at top of volcano

Why are fossils important in correlation and relative age dating?

fossils tell us when a certain species was alive.

Be familiar with the role certain minerals such as gold and mercuryhave played in the history of California.

gold- gold rush mercury- used for gold extraction

How do we know these rates?

gps- relative and absolute plate velocity

What is the most abundant rock type in the Sierra and what does thistell us about the tectonic setting in which the Sierra formed in?

granite. Subduction zones

What are the best kinds of rocks for absolute dating? What are some ofthe assumption that you need to make for absolute dating to give the mostaccurate dates?

igenous rocks can be used for absolute dating. assume the rock has these elements with half lives

Why does the oceanic lithosphere subduct?

its overall density is greater than the underlying mantle

What is the difference between a basalt and a gabbro? An andesite anda diorite? A granite and a rhyolite?

mafic rocks- basalt (volcanic) gabbro (plutonic) intermediate rocks- andesite (volcanic) diorite (plutonic) felsic rocks- rhyolite( volcanic) granite (plutonic)

What is the difference between a mafic and a felsic rock. Which of theabove rocks are mafic, felsic or intermediate between the two.

mafic- darker, high in mg, fe, low in si felsic- high in si, higher water cont. intermediate- have both qualities

What is the difference between a magma and a lava? What do the terms extrusive and intrusive refer to?

magma- inside mantle lava- outside on crust intrusive- plutonic rocks extrusive- volcanic rocks

What major compositional layer of the earth (crust, mantle, or core) do ultramafic rocks containing olivine or serpentine rocks represent?

mantle

What other rocks are associated with the Sierra Nevada other than granitic plutons? How old are they? How did they form?

metamorphosed sed rock. palezoic era formation. Formed from sediment collecting

What is a roof pendant and why are they important in inferring thehistory of the Sierra?

metamorphosed sedimentary rocks (dark outcrops)lying on granitic rocks (light rocks). They tell the age of the granitic rock

What is the CA state mineral? What is the CA state gem?

mineral- gold gem- benitoite rock- serpentinite

What is the definition of a mineral?

naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure

How old is the oldest ocean crust and how does that compare with theage of the continental crust?

ocean crust is consantly re forming, around 200 myo continental crust takes a long time to form rarely destroyed- 1 - 4 billion yo

Whats a pluton and whats a batholith and why do these terms refer tothe Sierra?

pluton: an intrusive igneous rock batholith:a giant plutonic intrustion. The sierras are granitic rocks that are plutons

What is a pyroclastic flow? Which CA volcanoes could have one?

pyroclastic flow-Exploding superheated gas and debris. Long valley caldera

How do you use absolute dating to assign actual ages to the boundaries on the geologic time scale? What kinds of rock relationships does one look for in using absolute dating and relative date together to form a more complete picture of geologic time?

radiometrically datable rocks, and clear relations between them and stratified rocks

How are sedimentary rocks used to understand the geologic record?

rising and falling of sea level

What factors around a volcano determine where the lava or lahar flowsare likely to go?

river channels, water, mud

n addition to the composition of the granitic plutonic rocks of theSierra, what other evidence argues for their origin beneath a continentalvolcanic arc, like the current Cascade volcanic chain?

roof pendants show there were sedimentary rock lying on the surface before plutonic rock formed and extruded from underneath

What rocks were present before the Sierra formed? How old are they?Where are these rocks in CA today?

roof pendants- sedimentary rocks. These rocks are from the paleozoic to mezozoic era and are on top of granitic rocks today

What Plate is Santa Cruz located on?

san andreas fault

The state rock is a metamorphic rock. What is it?

serpentinite- periododite

Be familiar with the metamorphic rocks you saw in section and lab suchas slate, schist, gneiss, quartzite, eclogite, marble.

slate- mudstone/shale schist- mudstone/shale gneiss-granite quartzite-sandstone ecoglite- basalt marble- limestone

What kind of faulting is responsible for uplift of the Sierra Nevada?

tension

How are external physical properties (crystal form, cleavage, hardness,density) controlled by atomic structure?

the atomic structure determines how it will look etc.

What is the nature of the change across the crust-mantle boundary and the lithosphere-asthenosphere boundary? (mineralogy/chemistry change versus mechanical change...)

the transition from lithosphere to crust is chemical the transition from asthenosphere to lithosphere is flowing magma to brittle

Why are sedimentary rocks important—what do they tell us, what theydo for us?

they tell us the history of the surface of the earth

What is the difference between volcanic and plutonic igneous rocks?What determines this difference and how might you tell a volcanic and plutonic rock apart? How do the terms volcanic and plutonic relate to the terms intrusive and extrusive?

volcanic rock- formed on earths surface, fine grained rocks plutonic rocks- formed inside earths upper mantle, coarse grained rocks