Geological Foundations of Environmental Science Midterm Study Questions Week 1 1. How old are the universe, the solar system, and the earth? How did each form? ● ● ● Universe: ○ 15 billion years ○ Big Bang Solar System: ○ 4.56 billion years ○ Solar Nebula Hypothesis: Earth: ○ ○ 4.6 billion years Solar Nebula 2. Where is the majority of the mass of the solar system? ● 99.85% of the mass of the solar system resides in the sun 3. What, if any, systematic variations are there across our solar system? Why do these variations exist? ● ● Inner Planets (rocky): ○ Small ○ Heavy elements (Fe, Ca, Al) Outer Planets (gaseous): ○ Large ○ Light elements (H, C, N) 4. How and when did the moon form? ● ● ● ● Co-accretion: moon formed from solar nebula at the same time and they have evolved as a pair Capture: maverick moon comes close to earth and is trapped by earth’s gravitational field Fission: moon spins off from earth due to rapid rotation rate Giant Impact Hypothesis: Mars-sized body slammed into the Earth twice 4.6 billion years ago. ○ Impactor compositionally zoned internally ○ Explains: ■ Rapid rotation of the Earth ■ Depletion of lunar volatiles ■ Iron depletion of the Moon ■ ■ Oxygen isotope record of Earth and Moon match Allows for a magma ocean 5. What is the composition of the moon? ● Moon’s composition is similar to Earth’s mantle Week 2 1. What is the overall structure of the earth? (be able to draw a cross-section of the earth and label its constituent parts; both compositional layers and rheological layers – know the difference). How does this relate to variations that are seen in the solar system? How did the earth obtain this structure? ● How did the Earth obtain its structure: ○ Inhomogeneous or heterogeneous accretion: ■ Formed from the inside out: dense material present first and less dense material added to outside over time ○ Homogeneous accretion: ■ Formed from a homogeneous mixture; differentiation of materials based on density occurred in molten phase leading to compositionally zoned planet 2. How do we know the internal structure of the earth? ● Seismologists and geophysicists study propagation of seismic waves through the Earth to determine the internal structure of the planet 3. What is a P-wave? What is an S-wave? Know the characteristics of each type of seismic wave. ● ● P-wave (Primary): ○ Push-pull (compress and expand) motion, changing the volume of the material ○ Travel through solids, liquids, gases S-wave (Secondary): ○ Shear wave; shaking motion at right angles to their travel direction ○ Travel only through solids ○ Slower velocity than P waves 4. What are the two different types of crust? Know their composition and density. ● ● Continental: ○ Density: 2.7 g/cc ○ Felsic/Granitic ○ Thick: 35-40 km Oceanic: ○ Density: 2.9 g/cc ○ Mafic/Basaltic ○ Thin: 5-10 km 5. What are the compositions of the mantle and the core? ● ● Mantle: ○ Upper: Iron and Magnesium silicates. ■ olivine, pyroxene, garnet, amphibole ○ Lower: different Iron and Magnesium silicates; oxides Core: ○ Densest layer: 10-13 g/cc ○ Iron and nickel ○ Outer core is liquid ○ Inner core is solid 6. What is continental drift? ● ● Precursor theory to plate tectonics Theory that continents moved around the surface of the Earth over time 7. What is the theory of plate tectonics? What data is used to support this theory? ● Data ○ ○ ○ ○ ○ ○ ○ ○ ○ Jigsaw fit of continents Distribution of rock types, fossils Absolute rock ages Distribution of mountain ranges Hot spots Paleoclimate record Evidence of glaciers at low latitudes Paleomagnetism ■ Polar wandering curves ■ Seafloor magnetic stripes Seafloor sediment thickness 8. How are plate boundaries defined? ● Areas of concentrated seismic activity 9. What are the three different types of plate boundaries? What processes occur at each type of plate boundary? Know where you might find each of these different types of boundaries on the earth’s surface. ● ● Divergent ○ Mid-oceanic ○ Continental Convergent ○ Ocean-Ocean: subduction zone, deep sea trench ○ Ocean-Continent: subduction zone, deep sea trench ● ○ Continent-Continent: suture zone, mountain ranges Transform 10. What drives plate tectonics? ● ● ● Mantle convection Slab pull Ridge push Week 3 1. What is a mineral? ● ● ● ● ● Naturally occurring Inorganic Homogeneous solid Definite but not fixed chemical composition Ordered atomic structure 2. Understand compositional variations in minerals and the concept of polymorphism. ● ● Cation Substitution: same crystal structure, different chemical composition ○ Cations of similar size tend to substitute for one another Polymorphism: different crystal structure, same chemical composition ○ Structure a function of conditions of formation (P, T) 3. What properties are used to identify minerals? ● ● Color ○ ○ Luster ○ ○ Unreliable for mineral identification Highly variable due to slight changes in mineral chemistry ■ Gemstones: exotic coloration of some minerals Appearance of a mineral in reflected light Two basic categories ■ Metallic: Strong reflections produced by opaque substances ■ Nonmetallic ● ● ● ● ● ● ● ● ● ● ● Vitreous: Bright, as in glass Resinous: Characteristic of resins, such as amber Greasy: Appears to be coated with an oily substance Pearly: Whitish iridescence of pearl Silky: Sheen of fibrous materials like silk Adamantine: Brilliant luster of diamond Streak ○ Color of a mineral in its powdered form Hardness ○ Resistance to abrasion or scratching ○ Mohs Hardness Scale Cleavage and Fracture ○ Cleavage ■ Tendency to break along planes of weak bonding ■ Described by resulting geometric shapes ● Number of parallel planes ● Angles between adjacent planes ○ Fracture ■ Tendency to break along irregular, non-planar surfaces known as fractures Density Special properties ○ Magnetism ○ Reaction to hydrochloric acid ○ Malleability ○ Double refraction ○ Taste ○ ○ Smell Elasticity 4. Be familiar with the different types of silicates and how this might impact crystal habit. ● ● Silicates ○ Most important mineral group; comprise most rock-forming minerals ○ Abundant due to large percent of silicon and oxygen in Earth’s crust ○ Silicon-oxygen tetrahedron ■ Fundamental building block ■ Four oxygen ions surrounding a much smaller silicon ion Types and Cleavage ○ Isolated tetrahedra: none ○ Single-chain: two planes at right angles ○ Double-chain: two planes at 60 and 120 degrees ○ Sheet: one plane ○ Frameworks: two planes at 90 degrees 5. What is a rock? ● An aggregate of minerals 6. What are the three basic rock types? How do we tell them apart? ● Rock Types ○ Igneous ■ Well-formed crystals ■ Very different colors due to different compositions ○ Sedimentary ■ Made up of abraded particles transported at the surface of the Earth ○ Metamorphic ■ Compositionally layered 7. How do these rock types form? Be familiar with the rock cycle. 8. Know the textural terms for the igneous rocks and what significance they have? ● ● Intrusive: coarsely crystalline Extrusive: finely crystalline 9. What do grain size and composition of sedimentary rocks tell us of their history? ● ● ● Types ○ Detrital ○ Chemical ○ Biochemical Grain size: reveals information about the energy of the system at the time of deposition Composition: provides information about the source area of the parent rock 10. What is a metamorphic foliation? How does it differ from layering in sedimentary rocks? ● Foliation: platy, wavy, leafy structure imparted to the rock by the parallel alignment of minerals ○ Common in regionally metamorphosed rocks ○ Sedimentary layering is not due to the parallel alignment of crystals 11. What are the two main types of metamorphism? ● ● Regional metamorphism: takes place over broad areas under high pressure and/or temperature conditions Contact metamorphism: impacts or changes rocks more locally and is generally associated with alteration of rocks surrounding igneous bodies 12. Have a grasp on the relationship between tectonics and rock types. Week 4 1. What are the compositional and textural categories used to describe igneous rocks? Be able to apply them. 2. Understand the differences between intrusive and extrusive igneous rocks and how this is manifested in rock texture. ● ● Intrusive ○ Phaneritic: coarsely crystalline ■ Light in color ■ Minerals ● Quartz ● Orthoclase ● Biotite ■ Felsic: rich in feldspar and silica ■ Density relatively low ○ Porphyritic: two distinctly different crystal size populations ■ Porphyritic-phaneritic: ■ Porphyritic-aphanitic: Extrusive ○ Aphanitic: finely crystalline ■ Dark in color ■ Mafic: rich in magnesium and iron ■ Density: relatively high ○ Glassy: non-crystalline solid ■ quenched/supercooled 3. Be able to identify different types of igneous intrusions (dikes, sills, etc.) 4. Have a grasp of where you might find igneous rocks of different compositions. 5. Understand Bowen’s Reaction Series. Week 5 1. How much of Earth’s surface is covered by sediments or sedimentary rocks? ● 75% 2. How are sediments moved? ● ● ● Water Wind Ice 3. What are two types of weathering? What are examples of each types of weathering? What conditions favor each type of weathering? ● ● Mechanical: breaks rocks into smaller pieces. Increases surface area for chemical weathering ○ Freeze-thaw ○ Stress-release ○ Organic activity ○ Root wedging ○ Insolation Chemical: composition of rocks change as minerals are dissolved, altered, or replaced ○ Congruent ■ Dissolution ■ No solid by-product ○ Incongruent ■ Hydrolysis - reaction with water ■ Solid by-products remain ● Clay minerals ■ Oxidation ■ Spheroidal weathering 4. What are two types of chemical weathering? What controls the type of chemical weathering that occurs? 5. What do sediments reveal? 6. Other than weathering, are they other ways to produce sediments? What are they? ● ● Biological activity Chemical precipitation 7. What is a soil? What do soils tell us about climate? ● In situ material formed from mechanical and chemical breakdown of parent material ○ Caliche: soils rich in calcium carbonate = warm and dry ○ Laterites: soils rich in aluminum and iron oxides = warm and wet 8. How are sedimentary rocks classified? ● ● Detrital ○ Clastic: constructed from solid debris generated by weathering and erosional processes ■ Mostly silicate minerals: bulk of Earth’s crust consists of silicate rocks = siliciclastic ● Extrabasinal: produced outside the basin of deposition ● Silicate clay>quartz>feldspars>micas>etc... ■ Identify by grain size and composition Chemical/Biochemical ○ Intrabasinal: form onsite via chemical or biochemical precipitation ■ Water chemistry at time of deposition can be worked out from minerals present ■ Calcium carbonate ● Limestone ○ Coquina ○ Oolite ○ Chalk ● Evaporites ○ Halite 9. Know the relative sizes of different sedimentary particles. 10. How do we name sedimentary rocks? 11. Be able to identify sedimentary rocks discussed in the slide show. Be able to interpret the energy associated with deposition of different sediments and sedimentary rocks. ● ● Coarser-grained sediments accumulate under relatively high-energy conditions Finer-grained sediments accumulate under relatively low-energy conditions 12. What is diagenesis? ● All of the processes that happen to a sediment from the time of deposition until the metamorphic realm (approx 200 degrees C) is reached 13. What processes comprise diagenesis? ● ● Compaction ○ Reorientation and repacking of individual sedimentary particles Cementation ● ● ○ Processes of gluing together sedimentary particles and turning them into rock Dissolution/reprecipitation: ○ In contact with appropriate fluids, materials that are present at the surface of the sedimentary particles may be dissolved as these fluids pass through them. This material is often not carried out of the sediment and will reprecipitate fairly close to where it was added into the system Recrystallization ○ One crystalline form is changed to another ■ Aragonite to calcite 14. What are different types of sediment transport? Be able to give an example of each and explain the processes associated with each type of sediment transport. ● ● ● Non-fluid assisted ○ Rockfalls and rockslides Fluid-assisted ○ Grain flows ■ Aeolian: sediments suspended on a cushion of air move en masse in a downslope direction ○ Sediment-gravity flows: cement-like slurries of sediment and water that travel rapidly down slope ■ Mudflows: fine-grained slurry ■ Debris flows: coarse-grained slurry Directly flow related: most common 15. Laminar and turbulent flow. Know conditions associated with each type of flow. ● ● Laminar flow ○ Low velocity ○ High viscosity ○ Low Reynold’s number ○ Examples: Ice and Mud-supported gravity flows Turbulent flow: describes most natural flow ○ High velocity ○ Low viscosity ○ High Reynold’s number 16. What is the Reynold’s number? What is Froude number? Why are they important? ● Reynold’s number ○ Measure of fluid inertial forces relative to fluid viscous forces ○ Critical boundary 500-2000 ● Froude number ○ Measure of fluid inertial forces relative to gravitational forces in the flow. ○ Critical boundary at 1 17. Sediment transport. Know the difference between bed load and suspended load. What sediment sizes are associated with each type of load? What are the processes of movement associated with bed load? ● ● Bed load: transport occurs close to the sediment bed and sediments make contact with the sediment bed ○ Coarse fraction ○ Rolling and sliding along the surface ○ Saltation: bouncing along the surface Suspended load: sediment moves through the water column without making contact with the sediment bed ○ Fine -grained fraction ○ Sediments kept i suspension by turbulence in the flow 18. How does Froude number relate to flow regime? What is the relationship between fluid surface and sediment surface for upper versus lower flow regime? Why is this important? 19. Understand sedimentary structures and their relationship to grain size. 20. Understand sedimentary structures and their significance. ● ● Depositional: form during accumulation of sediments Post-depositional: form after deposition of the sediments 21. What is a ripple? How does fluid move over a ripple? What are the internal characteristics of a ripple? Give a ripple bedform can you determine the direction(s) of fluid flow? How do ripples migrate? ● ● ● Ripples are periodic highs and lows that form from loose sand-sized material under subcritical (lower flow regime) conditions Steep side is the downstream side (lee side) Migrate downstream through lee face avalanches 22. Be able to determine flow direction by looking at cross-beds in sedimentary rocks. This is important in the interpretation of sedimentary environments. 23. What processes cause sediment deposition? ● ● ● ● Flow expansion ○ Increase flow cross-section ○ Decrease flow velocity ○ Decrease flow competence Decrease in slope ○ Decrease flow velocity ○ Decrease flow competence Ponding ○ Flow into closed basin or standing water body ○ Decrease flow velocity ○ Decrease flow competence Frictional dissipation ○ Kinetic energy of motion ------ heat energy ○ Stops mass movements 24. What is a graded bed? How do they form? ● Consistent change in sediment size from bottom to top of the layer ○ Normal: fine upward ○ Reverse: coarsen upward 25. How do tracks and trails form? ● ● Organisms produce tracks and trails as they sit or move about on exposed sediment surface Form after sediments are deposited and before they are buried and lithified 26. How do burrows form? How can you tell a burrow from a mudcrack (desiccation crack)? ● ● Organisms burrow into the subsurface ○ High energy environment = vertical and deeper burrow ○ Low energy environment = shallow and more horizontal burrow Burrows have rounded base while cracks have v-shaped base; also, burrows have individual rounded hole at surface 27. How do desiccation cracks form? What do they look like in plan view and in cross section? ● ● ● Form from the drying of muddy sediments that are subaerially exposed. Mud dries and shrinks Polygonal networks of cracks form on sediment surface 28. What is a sedimentary environment? ● ● Geomorphic entities that are physically, chemically, and biologically distinct Includes lakes, rivers and streams, glacial environments, alluvial fans, dunes, oceans, etc. 29. What does study of sedimentary rocks and paleoenvironments reveal? ● ● Present is the key to the past Data acquired from different sedimentary environments so that a generalized model of sedimentary processes and deposits can be produced 30. What is Walther’s Law? ● ● Sediments that accumulate in laterally adjacent sedimentary environments will stack conformably one on top of the next If you understand the distribution of modern depositional environments in space, you can interpret them in time 31. Understand distribution of sediments and sedimentary subenvironments in continental environments such as lakes, glacial environments, deserts and arid environments (alluvial fans, playa lakes and dunes), humid environments (meandering streams, braided streams and perennials lakes). ● ● ● ● Glacial Environment ○ Glacial striations ○ Tills/tillites ○ Moraines ○ Glacial lake sediments - Varves ○ Dropstones Deserts and Arid Environments ○ Alluvial Fans ○ Playa lakes ○ Dunes Humid Environments ○ Freshwater lakes ○ Fluvial environments ■ Braided streams ■ Meandering streams Marine Environments ○ Deltas (mixed marine and nonmarine environments) ○ Barrier islands ○ Tidal flats ○ Open shelf ○ Reefs and carbonate platforms ○ Deep sea environments 32. What does the succession of sediments look like from these different environments? How are they similar? How are they different? 33. Understand marine depositional environments—processes and products of sedimentation—deltas, barrier islands, tidal flats, open shelf, reefs and carbonate platforms and deep sea environments. What do the successions of different marine depositional environments look like? How can you distinguish between them? Week 6 1. What is metamorphism? ● ● ● ● ● Crustal rocks buried in the crust Subjected to elevated pressures and temperatures Mineral assemblages stable on the surface become unstable and are recrystallized in the solid state to form a stable new mineral assemblage Original rock texture partially or completely obliterated Chemical composition of rock changes very little 2. What is foliation? How and where does it form? ● ● ● Parallel alignment of all of the platy or sheet-like crystals in the rock Takes place when metamorphism involves shear stress Lineation: parallel alignment of a number of linear elements ○ Parallel array of one or more of: ■ Long thin prismatic crystals (amphiboles) ■ Fold hinge lines ■ Lines of intersection between cleavage produced during two different deformations 3. Describe the progressive metamorphism of shale. 4. Compare and contrast regional and contact/thermal metamorphism. ● ● Regional ○ Impacts tens of thousands of square km ○ Associated with mountain building and collision of lithospheric plates ○ Metamorphic grade reflected in the mineral composition and crystal size Contact/thermal ○ Occurs adjacent to igneous intrusions/bodies ○ Intensity of metamorphism decreases away from the heat source ○ Intensity also varies as a function of the size of the intrusion ○ Metamorphic aureole ○ Small intrusions cause fine-grained metamorphic rocks with uniformly sized crystals = hornfels ○ Larger intrusion produces coarser grained metamorphic rocks 5. What are index minerals? Know the different index minerals and their associated metamorphic grade. ● Used to determine degree of metamorphism a rock has experienced 6. Know metamorphic environments (with respect to P and T variations) associated with mountain building. What metamorphic facies are associated with the different environments? 7. Understand P, S, Love and Rayleigh waves. Be able to identify them on a seismogram. 8. Be prepared to determine the distance to an epicenter and the location of an earthquake.
