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ESS 101: Midterm Exam Questions with
answers
Match the magma type with the appropriate tectonic setting where it likely forms: Iceland - CORRECT ANSWERS ✔✔basalt Match the magma type with the appropriate tectonic setting where it likely forms: Sierra Nevada Batholith - CORRECT ANSWERS ✔✔granite Match the magma type with the appropriate tectonic setting where it likely forms: Phillipine Islands - CORRECT ANSWERS ✔✔andesite The Columbia Plateau is composed of rock rich in - CORRECT ANSWERS ✔✔basalt The melting temperature of granitic magma (wet melt) - CORRECT ANSWERS ✔✔increases as pressure is reduced (as it rises) A partial melt of the asthenosphere will not rise toward the surface because - CORRECT ANSWERS ✔✔the above question is incorrect because an asthenospheric melt will rise towards the surface
How do we know that Earth was created from the debris of a previous star system? - CORRECT ANSWERS ✔✔Dense elements exist that could only have been formed through a Supernova event Steps of the Nebular Hypothesis - CORRECT ANSWERS ✔✔- Supernova and formation of primordial dust cloud
- condensation of primordial dust. Forms disk-shaped nebular cloud rotating counter-clockwise
- Proto sun and planets begin to form
- Accretion of planetesimals and differentiation of planets and moons
- Existing solar system takes shape Evidence to support the nebular hypothesis - CORRECT ANSWERS ✔✔- planets and moons revolve in a counter-clockwise direction (v. random)
- Planetary orbits are aligned along the sun's equatorial plane (v. random)
- Observations from Hubble and radio astronomy
What's the inner and outer core of the earth made of? - CORRECT ANSWERS ✔✔Iron-Nickel Core Inner core in which phase? - CORRECT ANSWERS ✔✔solid Outer core in which phase? - CORRECT ANSWERS ✔✔liquid What's the mantle made of? - CORRECT ANSWERS ✔✔Fe-Mg Silicate What's the crust made of? - CORRECT ANSWERS ✔✔Fe-Mg-Al Silicate Differentiated earth order (starting from center) - CORRECT ANSWERS ✔✔- Iron-Nickel Core
- Fe-Mg Silicate Mantle
- Fe-Mg-Al Silicate Crust (ocean and continental)
- Oceans
- Atmosphere How is the earth compositionally zoned? - CORRECT ANSWERS ✔✔Along a density gradient How did the earth become compositionally zoned? - CORRECT ANSWERS ✔✔- accretion of planetesimals
- initial heating due to kinetic energy of colliding planetesimals and compressional heating
- Additional heating from radioactive decay
- melting point reached, dense iron sinks to core while lighter minerals are displaced outwards
- earth becomes compositionally zoned based on density
- convective overturn in asthenosphere, mantle, and outer core continues today Why did the earth heat up and then rapidly cool during the differentiation process? - CORRECT ANSWERS ✔✔- Conduction: SLOW, rate of heat leaving too slow to cool the rapidly heating planet, therefore liquification
- Convection: FAST, liquid--> solid, rapid cooling Which heat transfer process is more efficient? - CORRECT ANSWERS ✔✔- CONVECTION. Conduction requires atom-to-atom heat transfer, a very slow process
crust and uppermost mantle, the earth's average density, and based on the understanding that the densest materials would form the center of the planet, we can infer that the density of the lower mantle and the earth's core should be around 10gm/cm> Describe the magnetic field evidence supporting differentiated earth - CORRECT ANSWERS ✔✔- background: when electrons flow around an iron-nickel spike, a weak magnetic force is generated
- in the cores: liquid metallic core is constantly undergoing convection, moving around a solid Fe-Ni core--> generating magnetic field
- evidence that: earth has a metallic core; a component of that core must be liquid and convecting around solid metallic core Seismic Wave Evidence supporting differentiated earth - CORRECT ANSWERS ✔✔- P waves cannot move through liquid--> when measuring waves from earthquake on opposite side of earth, no p waves show up-- meaning there's liquid somewhere in the core.
- Also, changes in density and rigidity cause refractions in s waves, so those can be measured and density conclusions can be made The lithosphere is in _______ with the asthenosphere - CORRECT ANSWERS ✔✔isostatic equilibrium
Why does basaltic magma, as it rise, become more and more liquid? - CORRECT ANSWERS ✔✔- basalt originally at 10-15$ melt when hits a low convecting hot post in the asthenosphere
- begins to rise
- melting temperature for magma begins to lower (less pressure--> lower melting temp)
- actual temperature also lowers (closer to the crust + less pressure)
- melting temperature of magma lowering at a faster rate than actual temperature--> magma liquefying the more it rises
- when actual temperature = melting temperature, magma is 100% fluid Where do divergent margins first form? - CORRECT ANSWERS ✔✔under continental crust because of the insulating properties. When the continental crust is first heated at its base what will its topographic expression look like at the surface? - CORRECT ANSWERS ✔✔- heated, less dense
Example of Ocean-ocean lithosphere convergence - CORRECT ANSWERS ✔✔Japan, Phillipines Ex of ocean-continent lithosphere convergence - CORRECT ANSWERS ✔✔Andes Mountains and Cascade Mountains Ex of continent-continent lithosphere collision - CORRECT ANSWERS ✔✔Himalaya Mountains and European Alps What are the mechanisms that drive subduction of ocean lithosphere?
- CORRECT ANSWERS ✔✔- ridge push-- diverging boundaries pushing plates together
- plate sliding-- more dense plate goes under
- slab pull-- weight of slab being subducted increases as flesic components rise by partial melting Elements of a subduction zone: - CORRECT ANSWERS ✔✔Volcanic arc: where lava erupts Deep sea trench: where subduction begins
Mountain range: accretion of ocean floor scraped off by top plate Forearc basin: b/w volcano and coastal mountains Example of volcanic arc - CORRECT ANSWERS ✔✔cascades Ex of accretionary mountain range - CORRECT ANSWERS ✔✔Olympic mts, Coastal mts Ex of forearc basin - CORRECT ANSWERS ✔✔Puget Lowland Ex of backarc basin - CORRECT ANSWERS ✔✔Columbia Plateau The type of rock that forms in a subduction zone - CORRECT ANSWERS ✔✔andesite What does ocean-ocean convergence form? - CORRECT ANSWERS ✔✔Island arcs like Japan What is the source of rising magma (what components are partially melting) in ocean-ocean convergence? - CORRECT ANSWERS ✔✔basalt marine sediments
Continental crust partially melting GRANITE--> produced from the partial melt of continental crust Uplift of ocean crust takes place --> marine sediments
- a bit of the upper mantle Three rock types formed from three major plate tectonic shifts - CORRECT ANSWERS ✔✔Ocean divergence--> partial melt of asthenosphere --> BASALT Ocean-Continental/ocean-ocean convergence--> partial melt of basalt + marine sediments--> volcanic rock ANDESITE Continental collisions--> partial melt of continental crust--> GRANITE What evidence did geologists use to determine the timing of plate motion of the Indian sub-continent relative to the collision with Eurasia? - CORRECT ANSWERS ✔✔Paleomagnetic properties preserved in ocean floor
Magnetite crystals have inclines that correspond with direction of magnetic field By measuring the inclination of the magnetite crystals will tell the paleolatitude of the ocean floor--> possible to date various continents How was the European Alps formed? - CORRECT ANSWERS ✔✔Collision of the African plate with the Eurasian plate How were the Appalachian Mountains - CORRECT ANSWERS ✔✔Collision of the African and European Plates with the North American Plate Where do transform boundaries form? - CORRECT ANSWERS ✔✔along mid-ocean rift zones--> varying spreading rates cause rigid ocean crust to fracture at various points Ex of land transform faults - CORRECT ANSWERS ✔✔San Andreas fault zone What can you say about the evolution of primates relevant to Africa and South America? - CORRECT ANSWERS ✔✔Both have monkeys--> plates separated later than all others
Characteristics of all minerals - CORRECT ANSWERS ✔✔- have a specific chemical composition
- have a specific atom arrangement (crystal form)
- are solid
- inorganic
- naturally occuring Which minerals have the highest m.t. in a porphyritic rock? Which ones have the lowest? - CORRECT ANSWERS ✔✔- first crystal to crystallize is the tiny crystals inside the large ones that cool underground
- large crystals grow around the crystals inside -- those tiny crystals have the highest m.t. -- lowest m.t. are the tiny ones that cool above ground
Good analogy for the Principle of Inclusion - CORRECT ANSWERS ✔✔If you have a chocolate chip cookie, what was there first the chip or the cookie? the CHIP -- you can't have large plagiocase crystals forming before the tiny ones inside of them Where can minerals form? - CORRECT ANSWERS ✔✔1. during crystallization of a magmatic melt (basalt, andesite)
- directly from an aqueous solution How can minerals form from aqueous solutions? - CORRECT ANSWERS ✔✔Salt water evaporates, leaving salt crystals behind Is quartz the first or last mineral to crystallize in granite? - CORRECT ANSWERS ✔✔Quartz has the lowest m.t. --> last to crystallize What determines a mineral's cleavage planes? - CORRECT ANSWERS ✔✔Chemical bond strength and the fixed arrangement of atoms Important chem facts - CORRECT ANSWERS ✔✔- the # of protons in the nucleus defines the chemical properties of the element
Best way to diagnose metallic minerals? - CORRECT ANSWERS ✔✔Streak test Hematite streak color? - CORRECT ANSWERS ✔✔Reddish-Brown Dominant elements comprising earth rocks? - CORRECT ANSWERS ✔✔Silicon and oxygen Olivine - CORRECT ANSWERS ✔✔- first silicate mineral to crystallize from a magmatic melt
- has no cleavage planes --> fractures
- major mineral of upper mantle
- forms phenocrysts in some basalts What is the ration of Si:O in the olivine mineral structure - CORRECT ANSWERS ✔✔1: Pyroxene - CORRECT ANSWERS ✔✔- two cleavage planes
- comprises basaltic ocean crust
- 1:
Amphibole - CORRECT ANSWERS ✔✔- two cleavage planes
- common mineral in subduction zone rocks (andesite)
- hydrous How did water get into amphibole? - CORRECT ANSWERS ✔✔Watter trapped in subduction zone, dissolves into magma. Muscovite/Biotite Micas - CORRECT ANSWERS ✔✔- sheet silicates
- one cleavage plane
- hydrous
- dark appearance (presence of Fe and Mg)
- 1:2. Quartz - CORRECT ANSWERS ✔✔- no cleavage planes
- covalent bonds exist b/w all tetrahedral oxygen atoms
- common mineral in granite + rhyolite -1: Feldspar - CORRECT ANSWERS ✔✔like quartz but with aluminum Oxides - CORRECT ANSWERS ✔✔- non-silicate metallic mineral
