ES 4971-4973 Petrology Quiz 1
Name: __________________________
Mark or enter the correct answer, then copy your answer onto the answer sheet. Keep the quiz, turn in the answer sheet.
Take home. Open everything. Answer all questions.
You read the first set of review PowerPoints: 1a Review units, 1b Review slopes and areas 2 Review Plate Tectonics, 3 Review Silicate Basics, 4 Review Igneous Basics, 5 Review Extrusives Basics.
A. Review PowerPoints 1 Review Part 1 units
1. Suppose you have the units:
If you cancel as usual, what units are you left with?
a. kilogram meters/sec
2b. kilogram meters
7/sec
22. An object has potential energy when it is, for example a. above a place it could fall to
b. at the lowest position it can reach
3. In English units, gravitational acceleration is:
a. 9.81 ft/sec
2b. 32.2 ft/sec
2Matching. Match with formula or units in all questions.
4. Kinetic Energy _____ a. kg/m
35. Potential Energy _____ b.
6. Force (Newtons) _____ c. 1/2 mV
27. Pressure (Pascals) _____ d.
Q =Velocity . Area8. Density _____ e.
9. Flow Rate _____ f. mgh
10. Energy _____ g.
Use this figure for questions 11 and 12
11. The magma in a volcano has risen up the pipe and threatens to erupt. The surface (area 1) of the magma is exposed to the
atmosphere (so P
1= P
3= 0 gauge pressure). The magma surface is h
1= 400 m higher than a weak area in the pipe wall. Define the weak area to have height h
2= h
3= 0.
If the magma has a density of 2900 kg/m3, what is the pressure at (2), even with the weak area?
a. 93774200 Pa b. 11379600 Pa
12. The weak area ruptures suddenly, and the pressurized magma flows horizontally out of the rupture into atmospheric pressure P
3= 0.
What is the velocity of the lava/tephra as it erupts? Assume V
2= 0 and assume a constant density.
a. 1275.8 m/sec b. 88.6 m/sec
End of Questions for 1 Review Part 1 units
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Questions for Homework 1, covering
2 Review Plate Tectonics, 3 Review Silicate Basics, plus multi-layer Pressure calcs from Chapter 113.
Convection cells in the mantle are principally responsible for plate movements. Oceanic plates are pulled apart at thea.
mid-ocean ridges (aka MORs)b.
subduction zones.14.
Under the lithosphere is the aesthenosphere, a zone of heat softened rock located ina.
the upper mantle.b.
the liquid outer core15.
The lithosphere is the crust anda.
the cold brittle uppermost mantle.b.
the aesthenosphere Match the terms16.
Igneous definition _____ a. mostly Iron and Nickel17.
Andes form above ______ b. From molten rock18.
Core ____ c. a subduction zone19.
The Red Sea ____ d. Continents collided20.
Appalachian Mountains _____ e. Flooded Rift Valley21.
Aesthenosphere ______ f. hot mantle layer; flowsMatch the terms
22.
Quartz ____ a. Fine grain granitic23.
Gabbro ____ b. visible crystals24.
Andesite _____ c. Independent Tetrahedra25.
Rhyolite _____ d. Coarse grain basaltic26.
Aphanitic Texture _____ e. A Framework (3-D) Silicate27.
Olivine ________ f. Intermediate silica content28.
When ocean lithosphere is carried by subduction down into the earth’s interior, water is forced out. Some minerals in the mantle melt, forming basaltic magmas.a.
Trueb.
False29.
Granitic intrusions appear above subduction zones that dip beneathcontinents, and are formed when large rising magmas fractionate and assimilate (melt) silica-rich rocks in the crust.
a.
Trueb.
False30.
The silica tetrahedra in Olivine are bonded to one another.a.
Trueb.
False31.
The metals that balance the charge in Olivine are aluminum and copper.a.
Trueb.
False32.
In a pyroxene, the silicate ions, SiO4-4 are bonded together, asa.
single chainsb.
double chains33.
Multi-layer Pressure Calc.Calculate the pressure
P
500km at the base of a layer in the Mantle with the following information:The layer has a pressure at its top of P
400km=1.277 x 10
10Pa The top of the layer is at a depth of 400 km,
The layer has a constant density of = 3.6 x 10
3kg/m
3The base of the layer is at 500 km.
P
500km = P400km + gh
Your answer:
a. P
500km = about 1.63 x 1010 Pa b. P
500km = about 17.48 x 1016 Pa
Pa
Hint: for the units to cancel and give you Pascals, recall 1 km = 1000m Also pressure in Pascals has unit components kg m/sec
2x 1/m
2End of questions from Homework 1
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Questions from topics in Homework 2
Igneous Rock Summary.doc will help with many of these 34.
At divergent margins(rifts, MORs), the magmas that rise are typicallya. mafic b. felsic
c. intermediate in silica content
35.
When ocean lithosphere is subducted under continental lithosphere (Andes, Cascades) the lavas that erupt are typicallya. mafic b. felsic
c. intermediate in silica content
36.
Facts: A mafic lava, a basalt, is less viscous compared to a felsic lava, a rhyolite. Thin, runny basaltic lavas easily give up their volatiles (water, carbon dioxide) before they freeze, so they are less explosive.Question: Basaltic melts are less viscous than felsic because they are
a.
hotter and lower in silica compared to felsic meltsb.
cooler and higher in silica compared to felsic melts37.
You identify the following minerals along the bright white line in the thin section photo below, sampling every fifth mark on the reticle.Starting at the lower edge, you find Quartz, plagioclase, plagioclase, plagioclase, Orthoclase, Orthoclase, Orthoclase, Orthoclase, Quartz,
Orthoclase, Biotite, Magnetite, unknown, plagioclase, plagioclase, plagioclase, plagioclase, Orthoclase, Orthoclase.
You total the Quartz, Orthoclase (an Alkali Feldspar) and plagioclase) and get Q = 2 Quartz, A = 7 Orthoclase , and P = 7 plagioclase.
Calculate a multiplier 100/(Q + A + P) and convert these counts to percents.
You get:
a.
Q= 30%, A = 35%, P=35%b.
Q = 12.5%, A = 43.75%, P = 43.75%38.
Identify the rock using the chart. This is a(n)a.
Quartz Monzoniteb.
Quartz-rich GranitoidEnd of HW 2 questions.
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HW 3 questions on Igneous Textures Match the terms
39.
Surface Energy ___ a. forming a critical-sized embryonic crystal40.
Instability ___ b. addition of ions to an existing crystal41.
Nucleation ___ c. excess energy at the surface of a material42.
Undercooling __ d. the spread of something more widely43.
Crystal Growth __ e. tiny clusters separate due to high surface charge.44.
Diffusion __ f. cooling of a melt below the crystallization T of some mineralMatch the terms More questions on Igneous Textures
45.
Porphyritic __ a. dissolution of a mineral back into the melt46.
Phenocrysts __ b. the large xtals in a porphyry47.
Poikilitic ___ c. phenocrysts contain inclusions of minerals they surrounded48.
Ophitic Tx ___ d. raises melting point; forming minerals now more undercooled49.
Resorption ___ .e. having distinctly different crystal sizes50.
Dewatering ___ f. Pyroxenes (Augite, etc.) surround Plagioclase laths51.
Most substances expand as they melt. A decrease in pressure allows expansion and melting. This explains:a.
partial melting under the mid-ocean ridgesb.
partial melting at 150 km depth in a subduction zone.52.
A late fractionation melt has large amounts of water. Such a melt hasa.
lower viscosity, easier diffusion, better crystal growthb.
higher viscosity, poor diffusion, little crystal growth53.
In a cooling melt, different mineralsa.
all have the same freezing point, and nucleate and grow at the same rates.b.
have different freezing points, and nucleate and grow at different rates.54.
Sudden loss of the water-rich fluid phase will quickly raise the melting point, making the forming minerals significantly more undercooled at the current temperature. This can move mineral species toa.
a heavy nucleation temperature, forming many new nuclei, with low growth, producing many aphanitic crystals.b.
shift to a heavy growth temperature, forming some fast growing crystals, producing a few phaneritic crystals.55.
Which grows faster?a.
A plane with a low density of lattice points, larger interplanar distance, and high surface energy, and a smaller pocket of undepleted melt.b.
A plane with a high density of lattice points, smaller interplanar distance, and low surface energy, and a larger pocket of undepleted melt.56.
For a growing crystal, which area usually has a greater volume of undepleted melt from which it can obtain components?a. a corner
b. a planar side
57.
Plagioclase crystals forming from a cooling melt may show a CaAl - rich composition in the center, and a NaSi - rich composition on the outside. The reason is Plagioclase does not easily re- equilibrate with the melt when the cooling melt changes composition, which would require substitution of Al for Si in one position. This is difficult because Al-O and Si-O bonds are very strong, and Al+3 is a very slow diffuser.a. True b. False
58.
Oscillatory Zoning. Electron Microprobe scans of compositionally zoned Plagioclase crystals from center to rim show zones of decreasing Anorthite CaAl (AlSi2O8 ), followed by a sharp increase in Anorthite. One possible explanation for this is the arrival of fresh magma with an abundant supply of Anorthite components.a. True b. False
End of Homework 3 (Chapter 3) questions
Homework 4 Part 2 Free Energy Questions
59. Consider the reaction Kyanite Al2SiO5 => Sillimanite Al2SiO5 .(reaction 1) Preliminaries: For T = 298.15 K and P = 0.1013 MPa, the Gfo are:
Kyanite Gfo = -584000 cal/mol Sillimanite Gfo = - 583600 cal/mol
Then the G rxn = - 583600 cal/mol -(-584000 cal/mol) = +1000 cal/mol,
G rxn >0 , the reaction Kyanite => Sillimanite does not go, and Kyanite is stable at 298.15K and 0.1013 MPa.
TODO. Recalculate for T = 1000K. At P = 0.1013 MPa and 1000 K, the Gibbs Free Energies are
Kyanite GKy, 1000K, ).1013MPa = -499414 cal/mol Sillimanite GSill, 1000K, ),.1013MPa = -500944 cal/mol
G rxn = GSill, 1000K, ).1MPa
-
(GKy, 1000K, ).1MPa )Question: Which phase is stable at 1000K and P =0.1013 MPa?
a.
Kyaniteb.
SillimaniteEnd of HW 4 Part 2 Free Energy
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HW 5 Binary Phase Diagrams
60. In the cooling system Anorthite – Albite, if no fractionation occurs, the composition of the last crystals formed is
a. the same as the bulk composition
b. very different from the bulk composition
61.In the cooling system Anorthite – Albite, if fractionation occurs, the composition of the last crystals formed is
a. the same as the bulk composition
b. more silica rich than the bulk composition
62. Use the two component ( = binary) eutectic system Diopside-Anorthite
(NO solid solution) to explain why, in some rocks pyroxenes crystallize before plagioclases, contrary to Bowen’s Reaction Series.
a. If the bulk composition is left of the Eutectic, the Pyroxene Diopside forms first. If the bulk composition is right of the Eutectic, the
Plagioclase Anorthite forms first.
b. If the bulk composition is right of the Eutectic, the Pyroxene Diopside forms first. If the bulk composition is left of the Eutectic, the
Plagioclase Anorthite forms first.
63. In the binary eutectic system Diopside-Anorthite (no solid solution), the last liquid to crystallize is at the eutectic composition d.
a. True b. False
64. In the system Forsterite –Silica, crystals of early forming Olivines (Forsterite) are removed. This removes Mg++, and the melt shifts to more silica-rich compositions. This system is used as a model of Mantle partial melting; the addition of fractionation demonstrates the shift of the solids to more silica-rich minerals.
Question: At the Peritectic, how many phases are present?
a. Two, Enstatite + Liquid
b. Three, Enstatite + Liquid + Forsterite
65. At the Eutectic, how many phases are initially present?
a. Two, Enstatite + Liquid
b. Three, Enstatite + Liquid + Silica
ES 4971-4973 Quiz 1 ANSWER SHEET Name: __________________________
Pledge: I pledge my honor that I have neither given, taken, nor received unauthorized assistance during the course of this examination.
Signature: ______________________.
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