Geology 101 - Review for Midterm and Final - Swanson_

Geology 101 - Review for Midterm and Final - Swanson_ -...

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Unformatted text preview: Geology 101 Review Material (Midterm and Final) 1. How does the earth become compositionally zone? You should have knowledge of the 6 evolutionary stages that show how the earth could evolve from a “homogeneous mixture of primordial dust (planetesimals) to the compositionally zoned planet containing an Fe-Ni core, Fe—Mg silicate mantle and Fe~Mg-Al Crust. Compositional zonation based on density, When will the earth become compositionally zoned?. .. when the melting temperatures of silicate minerals and eventually iron and nickel are exceeded. Earth becomes molten and the lighter material are displaced outward and denser iron-nickel sinks to the core, 2. Physical properties of asthnosphere and lithosphere. You should have knowledge of the composition and physical properties of the lithosphere and asthenospher’e. Asthenosphere-lithosphere relationship is important to understanding plate tectionics, 3. Evidence of compositional characteristics of the internal structure of the earth. —overall densisty of earth is 5.5 gin/cm3 density of crust 26—30 gin/cm3 provides some information regarding the density of the interior zones -meteorites are inferred to be composed of same material that earth was derived -earth has a magnetic field supports the argument fOr' the core being metallic and the outer core being liquid (i.e., convecting electrons surrounding metallic solid inner core will generate magnetic field), -seismic properties (velocities, absorption of' S—waves by outer core). —Why do P-wave and S—wave shadow zones form? Why is the S-wave shadow zone larger“? 4. What is isostasy? (from your text book rading) -think about the lighter continents versus denser ocean crust floating on the asthenosphere -why is the oceans present over ocean lithosphere (think density) 5. Melting temperature versus geothermal gradient. -why is the outer core liquid and inner core solid when the outer core’s actual temperature is lower than the inner core’s? Melting temp dependent upon composition and pressure Actual temperature (geothermal gradient) is simply dependent upon pressure (depth), The two curves do not have the same slopes“ The outer core is liquid because the actual temperature is greater than the melting temperature of iron-nickel for this depth (pressure). The opposite is true for the inner" core You can use a similar argument for the parital melt of the ashenosphere” 6. Plate Tectonics. -know the relationship of all three plate boundaries. -what type of igneous rocks form at each respective plate boundary (Let, basaltic/gabbroic magma at divergent margins from partial melt of asthenosphere; andesitic/dioritic magma at subduction zones from partial melt of ocean crust and associated marine sediment); granitic magma from partial melt of continental crust at colhson boundaries. —why do transform faults form? Is all the stress translations (think about bends in transform faults —How can we use paleomagnetism to prove that new ocean crust is being created at seafloor spreading (divergent margins) zones? polarity reversals form symetric stripes on either side of spreading ridge as new crust forms and diverges. .2- —You should be able to draw the structure of a typical subduction zone showing the trench, accrtionary wedge (forearc ridge); fore arc basin; volcanic arc; back arc basin. What physical features in Washington correspond to these respective subduction zone structures? -How does the subduction angle and distance of volcanoes from the trench relate? -Can you subduct a spreading ridge? (Think about the future of the Juan de Fuca spreading ridge and how the San Andreas fault formed). Where is the spreading ridge that was subducted under California today (maybe under Nevada and Utah?) Think about the past and future palte configurations based on your knowledge of present palte motions (i.e., if the Atlantic Ocean getting bigger or smaller?) 7. Minerals —be able to draw a silicate tetrahedron. Understand its charge balance (SiO4)'4 How does it achieve charge and chemical balance (shares oxygen atoms between tetrahedra; forms ionic and metallic bonds with other available cations). -understand the differences between the silicate minerals. Why does quartz fracture and amphibole cleave? —IfI show you a diagram of pyroxene (single chain silicate) can you explain why its Si—O ratio is 1:3? —Remember to read the section on nonsilicate minerals in your text. 8. Igneous Rocks and Processes —know about the three composistional types of magma/lava (properties: silica vs Fe-Mg mineralogy, viscosity, explosive of eruption, landform type. -Understand dry vs wet melts. Why does granitic composition magma rarely make it to the surface? (Gr‘anitic magma is a wet melt and the melting temp increases with decreasing pressure so that is solidifies as is rises to the surface, aas pressure decreases Opposite is true for dry basaltic magma (it further melts as it rises to the surface). —What type of tectonic setting do you find the different magma types. —Bowen’s Reaction Series (magmatic fractionation by partial melting and fractional crystallization) _—Be familiar with the igneous rock classification diagram in Chapter 3 of the text. Can you identify and igneous rock ifI give you mineral composition and texture information (the diagram will be provided). -Volcanic Landforms (shield, strato and pyr‘oclastic volcanos, calderas, basaltic plateaus). How do they form and what are their compositional characteristics and tectonic setting. -What does the linearity of hotspot volcanos tell you (absolute plate motions). ~Ophiolite Sequences Plutons (how are they classified). Volcanic Hazards —tec’mnic setting and lava characteristics vuuu Compare the volcanic hazards on the Hawaii or Iceland versus Mt. Rainier or Mt. Vesuvius 9. Weathering and Soils: -Understand the difference between mechanical and chemical weathering. Understand the respective processes (How do joints form? Frost weathering, bioturbation). -Understand the chemical reactions involved in weathering. Do not memorize the reactions. Could generally explain what is happening if you given the reaction, (i.e., Where do H+ ions come from that are involved in a hydolosis reaction? How does carbonic acid f0r*m?, etc.) - 3. «How do different weathering features f0rm (Why spheroidal weathering patterns?) -Soils: What is a soil. Know how soil fOIming factors (CLORPT) influence soil development” 10. Sedimentary Rocks -Sediment to sedimentary rock (accumulation, compaction, cementation) —How do we classify sedimentary rocks (elastic, chemical and biogenic). —Know how different sedimentary structures form (ie, symmetric ripples vs asymmetric ripples, graded bedding form because of turbidity currents), How can sediementary rocks and structure help you understand the depositional environment (eg, where does chert generally form?) 11. Stratigraphy and Geologic Time ~What is the Principle of Uniformitarianism? How did it evolve from catastrophism? —How did early estimates attempt to date the age of the Earth? —Underestand the principles of stratigraphy“ —Understand the three types of unconfbrmities“ How do they fbrm and how do you recognize them in the field? Read about the geologic time scale in the text book. Know how its major subdivisions are defined (do not simply memorize the subdivisions). 12. Radiometric Dating -What is radioactivity? How do radioactive elements decay over time (exponential decay)? Understand the age equation (do not memorize) The number of existin daughter atoms in a closed system will be proportional to the number of existing parent atom as a function of the exponential decay (which is a constant) and time. —Types of decay (simple, branch, chain). —How is half-life and dating range related (Large half-live date older materials) Once an isotopic system has gone through 10 half—lives you reach the upper limit of dating (i.e,,, C-l4 has a half-life of 5730 yrs, The upper limit of dating is 57300 yrs”) ~What our the assumptions of radiometric dating (e.g,., closed system, measure N and D atoms accurately, etc)? -Understand the isotopic systems we discussed in class (K-Ar, Fission Track, Radiocarbon). 13. Deformation -What are the three types of defr'omation? What are the controlling factors of defbrmation (temp, confining pressure, time, rock type, strain rate). -Brittle Fracture (classifying faults— normal, reversed, and strike—slip), —Ductile Deformation [measurine fOIded rock (strike and dip), classifying folds. 14. Metamorphism and Metamorphic Rocks 15. Seismology, Earthquakes and Tectonic Hazards -Earthquakes; (What are they?) P vs S waves; Location of epicenter; magnitude vs intensity Earthquakes and plate tectonics (EQ’s and plate boundaries — Earthquake damage, Prediction and Prevention @Oi637 /Of 4 4‘. The aesthenosphere is composed of rock rich in: a./ quartz and olivine b. gabbro peridotite (>90% olivine) a basalt -- \om “we: grow Wet WH‘t Let, amphibole and pyroxene 5. As a granitic magma (wet melt) rises toward the surface: a a. its melting temperature will increase. be. its melting temperature will decrease c. it will tend to crystallize before it reaches the surface nswers a and c are both correct . answers b and c are both correct 6.. A partial melt of the asthenosphere will tend to rise toward the surface because 6 . a. because of centrifugel forces b. earth's magnetic field c. convection cells in the outer core -._ d. of gas bubbles within the magma he melt is less dense than the surrounding rock V 7. Pillow basalts form r. ' a, when basalt is extuded thr0ugh a narrow opening. b. when a basalt flow is blocked and the flow piles up in pillow stnrcturesr. c. when the basalt flow is erupted onto land and chilled quickly @when the basalt flow is erupted into water e.. none of the above are correct 8,. When two ocean plates converge B a. the younger plate Will be subducted Q the older plate will be subducted c. the plate closest to ocean water will be subducted d. a collision mountain belt will form e. none of the above are correct 9. The most widely accepted explanatibn for the earth's magnetic field is Q . '@ movement of electrons in the molten iron of its outer core w b.. movement of electrons in the molten iron of its inner core c. small magnetic mineral present in its crust d. the earth does not have a magnetic field er. none of the above are correct 10:. What kind of plate margin existed when the Appalachian Mountains formed during the Paieozoic Era? a. divergent margin ‘v' b. convergent margin (ocean-continental collision) cl. convergent margin (ocean-ocean collision) d. transform margin collision margin (continent-continent) 15. Diamond is harder than graphite because: C a. diamonds have covalent bonds between atoms while graphite has metallic bonds between its atoms. ‘b\diamonds and graphite have the same bonds, but diamonds are composed of a harder ment than graphite. r iamonds have covalent bonds between its constituent atoms while graphite has vanderwahl nds. \diamond and graphite have the same hardness except graphite is composed of a powdered form. e. none of the above answers are correct 16. The silicate tetrahedron (Sio4)? has a net charge of E a. +4 - @34- c, -3 d. +2 e. 0 (rt is balanced) 18. Why do the terrestrial planets have so little molecular (gaseous) hydrogen? a. Hydrogen was a very rare component of the primordial dust from which the planets formed. b. The terrestrial planets have a large component of molecular hydrogen in their interiors. ©The terrestrial planets are close to the sun and the low density hydrogen was lost to space. d. HydrOgen is only present as water in all planets. e. none of the above are correct 22.. Why does the topographic expression of the Hawaiian island become progressively lower from the Big Island to l the island lying northwest? a. the topographic expression of all the Hawaiian Islands is the same b. the ocean lithosphere is less dense to the northwest and it floats higher 0. there is a subductiOn zone to the northwest drawing the ocean crust downward d. the Big island has a segment of continental crust within its interior @the ocean lithosphere is lighter over the hotspot and it floats higher 23. Anange the compositional zones of the earth according to their respective density (densest to lightest). a. a. mantle, outer core, inner core, continental crust, ocean crust b. inner core, outer core, mantle, continental crust, ocean crust c. inner core, outer core, mantle, continental crust, ocean crust d. outer core, mantle, ocean cmst, continental crust, inner core .. @nner core, outer core, mantle, ocean crust, continental crust 24.. What kind of plate margin is represented by the Andes Mountains? a. divergent margin convergent margin (ocean-continental subduction) ., convergent margin (ocean-ocean subduction) d. transform margin e. collision margin (continent-continent) 25.. Meteorites are thought to be composed of C ? a. materials mainly comprising the sun . ~— b. materials very different from the original material comprising the Earth ©naterials that are similar in composition to those found in the solid earth d. mainly organic components e. mainly materials found only in continental crust 26‘, Which zone of the earth is also described as the “low velocity zone?” a. outer core inner core sthenosphere d. lithosphere e. mesosphere 27. The melting temperature of Q must be reached in order for the earth to become compositionally zone: a. silicon b. Fe-Mg silicate minerals @atamc Fe and Ni i. water e.. crustal rocks 29. Transform plate boundaries are typically associated with C ., a. convergent margins where the descending piates slows down during subduction b. convergent margins where the descending plates speeds up during subduction @divergent margins where the rate of spreading is different along segments of the spreading ridge ' > d. divergent margins where the rate of spreading is the same along segments of the spreading ndge e.. none of the above answers are correct. 32. What is the significance of the change in direction of the Hawaiian island chain and the Emperor’Seamount hain? the tectonic plate on which both island chains sit changed directions . each island chain formed from two different hot spots. c. a single hot spot moved beneath the tectonic plate \ d. the Hawaiian islands formed over a hot spot volcanism While Emperor Seamounts are part of a mid-ocean spreading ridge e. none of the above answers are correct 33. Which tectonic margin would tend to have deep and shallow focused earthquakes? 4 g a. divergent b. transform @onvergent . all of the above answers are correct e. only answers a and b are correct 3:15. S—waves 0x @are absorbed bi. decelerate c., accelerate (1. reverse e. rebound 45,. Why is there a low velocity zone for seismic waves entering the asthenosphere? 0‘ a. the asthenosphere is considerably less dense than the overlying continental crust b” the asthenosphere is considerably more dense than the underlying continental crust“ c. there is not a low velocity zone in the asthenosphere @the asthenosphere is a partiai melt and seismic wave decelerate as they enter the phase ange er. none of the above are the correct answer as they travel through the outer core. ...
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Geology 101 - Review for Midterm and Final - Swanson_ -...

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