Solid Earth Science Review Session 1 PDF

Review Session 1 Solid Earth Science  Global scale: How does the interior of the earth work? Hot plumes (red) rise from the core-mantle boundary to feed volcanoes in Hawaii and Iceland French & Romanowicz  Plate scale: How does a plate subduct (sink)?...

Review Session 1 Solid Earth Science  Global scale: How does the interior of the earth work? Hot plumes (red) rise from the core-mantle boundary to feed volcanoes in Hawaii and Iceland French & Romanowicz  Plate scale: How does a plate subduct (sink)? The cold Pacific plate (blue) subducts into the viscous mantle along the Tonga Trench Fukao & Obayashi Earth’s deep material cycle Basin scale: Where are the faults? Stripes are rock layers and faults Han et al. [IRIS] Mountain scale: Where is magma beneath volcanoes? Bathymetry: red stripe is the mid-ocean ridge Bright spots indicate magma – active volcanoes Carbotte et al. What drives plate tectonics?  Earth Energy Sources Short-wavelength re- External radiation * Human energy use** ~ 1.6 x 1013 watts Internal base figure © 1995 John Wiley & Sons * Absorbed energy radiated back as long-wavelength radiation ** data estimate from about 2005  Heat Transfer Radiation – heat travels as electromagnetic radiation Conduction – heat moves through a material Convection – heat is entrained in and moves with a material Temperature Composition Core Core Geological time scale: A. McNamara © 2005 Brooks/Cole millions of years @ EES, MSU  Subduction volcanoes Intraplate volcanoes Mid-ocean ridge volcanoes Subduction volcanoes  Differences between oceans and continents Ocean Continent Crust is 4-7 km thick Crust is 20-70 km think Crust mainly consists of igneous rocks: Crust mainly consists of basalts and other mafic (Mg-rich, Fe-rich) sedimentary/metamorphic/igneous rocks, rocks granites and other felsic (Si-rich) rocks Crust is denser Crust is less dense Crust is younger (0 – 180 million years) Crust is older (up to 4 billion years) Lithosphere is ~75 km thick Lithosphere is ~125 km thick Lithosphere gets recycled (created at mid- Lithosphere is stable ocean ridges, subducts into the deeper Earth along oceanic trenches) Covered by water – ocean basins Usually above the sea level, but also can be covered by water – continental margin © 2005 Brooks/Cole [Harris et al., 2014] Lecture 5 Class code: 398661  “Slab-pull” The oceanic plate cools, Plates with becomes thicker/denser, more and eventually “sinks” subducting (subduction) because it is lithosphere attached move more dense faster The slab pulls the plate (“sinking towel”) behind it Wyllie (1976) Forsyth and Uyeda (1975) © 2001 W. W. Norton  Ridge “push”? The plate “slides” off of the elevated ridge, pushing the plate in front? HOT © 2001 W. W. Norton [The MELT team led by Forsyth, [Shen & 1998, Forsyth, Science] 1995]  The Plates May Drive the Mantle Thermal convection must occur due to radioactive decay in the mantle But convection can be driven by cooling at the TOP, not always heating at the bottom Ridges are passively pulled apart; cold slabs pull the plate down “Slab-pull” drives the mantle convection – NOT the other way around Plate motion is just one part of the mantle convection © 2001 W. W. Norton Lecture 5 Class code: 398661 [Voosen, 2022, Science]  The inner core was formed about 565 million years ago: very young compared to the Earth (4.6 billion years). The birth of the inner core coincides with the strengthening of the Earth’s magnetic filed and the Cambrian explosion. [Driscoll, 2019, Nature Geo.]  [Voosen, 2022, Science] [Yang & Song, 2023, Nature Geo.]  Reading assignments Chapter 3: pages 35-44 (5th edition) Due Thursday, Feb. 6  Exam 1 Time: Tuesday, Feb. 4 at 8:30-9:30 am Location: South Kedzie S107 Multiple-choice and short-answer questions Review session this Thursday The slides of the review session will be posted online as a study guide We will use scantron sheets. Bring your pencil and eraser  Exams (60%) There will be 4 exams: 3 exams during the semester and 1 final Your 3 best exams will be used to calculate: 20% each You may drop or miss any one of the first 3 exams without impacting your grade. This also means there will be no make-up exams except for reasons related to religious observances. The final grades may be curved More details on the D2L syllabus. For any reason, documentation is always required.  RCPD VISA holders If you have talked to me before, please send me an email to summarize what we discussed and our agreement on accommodating your needs. I don’t necessarily remember every word I said. I will only follow the written records. If you haven’t talked to me yet, please reach out to me as soon as possible. How Science (is supposed to) Works Work with testable hypotheses Predictions: If a theory (or hypothesis) is true, then _____ should happen Theories: tested explanations (by multiple scientists) of data or relationships (why things work). Laws: generalization of patterns (usually very specific relationships) in nature (may have conditions) Hypothesis: Something that looks like it might explain the data from which predictions can be made and tested Data/facts/observations – but you might not know what you are or should be observing All theories must be falsifiable if new data arise “The Tao (principle of the universe), that can be described, is not the true Tao.” – Taoism is not science. Do the costs of natural hazards increase every year? Why? [Hyndman & Hyndman, 2016] What are the differences between hazard prediction and hazard assessment? Predictions generally rely on projections based on frequency and pattern of past occurrences (weather, stock market, sports, etc…). Precise predictions of when natural events will occur are usually impossible …. BUT predicting the scale of damage from a particular hazard is often possible, based on past events – hazard assessment. Prediction Assessment  What are rocks and what are minerals? Rocks Rocks are naturally-occurring aggregates of minerals (and, by definition, glass* and coal**) Texture and composition can tell us a lot about the history of the rock Examples: granite, shale, marble Minerals A mineral is a naturally occurring chemical compound, usually of crystalline form and not produced by life processes. A mineral has one specific chemical composition Examples: quartz, olivine, diamond Minerals Rock  What are the three major types of rocks? Any kind of rock can turn into any other kind of rock © 1995 W. C. Brown  How can we date rocks? “Absolute” dating When did something happen? Isotope Geochemistry (radioactivity) Uranium-lead, 14C, etc. Only related to chemical changes Relative dating What happened first, what happened next Stratigraphy & Structural Geology Caused by rock deformations – usually related to natural hazards Correlation © 2005 Brooks/Cole Identifying rock layers of the same age from place to place and across or between continents over short distances, correlations can/are usually be performed © 1993 W. C. Brown by rock type Law of Faunal Succession - life changes with time Need to use index fossils or assemblages: Wide range in space and short duration in time.  Cross-cutting relationships (something that cross-cuts another rock is younger) © 2005 Brooks/Cole Igneous intrusions are younger © 2005 Brooks/Cole than the rocks they intrude Faults cut pre-existing rocks Highway 49 near Merced River, California - K. Fujita San Andreas Fault, southern California - USGS How did the theory of plate tectonics evolve? The first to make a serious scientific study of this pattern was German scientist Alfred Wegener (1880-1930)  AFRICA Wegener’s evidence included similar rock types of the same SOUTH geologic age along the edges AMERICA of continents that had once been joined together Wegener also looked at the distribution of certain fossil plants and animals, which makes much more sense if the continents were joined together at the time these animals were living.  Seafloor Age [NOAA] Seafloor age no more than 180 million years: youngest at the ridges [red], oldest at the edges [blue and purple] On continents: Oldest rocks on Earth > 4 BILLION years old! Stage 4: THEORY of Plate Tectonics Big Year: 1967! Princeton group (Morgan) and Scripps group (McKenzie & Parker) independently developed mathematical models to define the plate motions Dan McKenzie (1942 - ) W. Jason Morgan (1935 - ) Robert Parker What are three types of plate boundaries? [Hyndman & Hyndman, 2016]  Where does seafloor form? And where does seafloor disappear? Divergent Convergent create new – collision (if two continents) oceanic lithosphere – “recycle” old oceanic lithosphere Sea-floor – Subduction spreading What is subduction? © 2005 Brooks/Cole  How fast do plates move? Red: the Earth’s interior as reference Blue: relative motion (a few cm/year) http://geologylearn.blogspot.com/2016/02/what-drives-plate-motion-and-how-fast.html  What are the major layers in the solid Earth? © 2003 McGraw-Hill Seismic/Chemical Rheologic (material behavior) Crust (0 to 6-40 km): silicate and other minerals Lithosphere (rigid; 0 to 70-150 km)* Mantle (40 to 2886 km): silicates Asthenosphere (“mushy”, 70-150 to 200-250 km) Core: iron and nickel Regular mantle - Outer (Fluid; 2886 to 5156 km) - Inner (Solid; 5156 to 6371 km) * note: includes crust and uppermost mantle How do these concepts differ from each other: lithosphere, tectonic plate, crust, mantle, asthenosphere? Wrong Correct The Earth’s interior is hollow (air, cracks) High pressure in the Earth’s interior Mantle is liquid Mantle is solid Crust moves over mantle Lithosphere moves over asthenosphere (part of mantle) Plate = Crust Plate = Lithosphere = Crust + Uppermost (50-90 km thick) mantle Only the crust is brittle The lithosphere is brittle The lithospheric mantle is compositionally No significant difference in composition different from the asthenosphere between the lithospheric mantle and asthenosphere [Hyndman & Hyndman, 2016] © 2005 Brooks/Cole What are the differences between oceanic and continental plates? Ocean Continent Crust is 4-7 km thick Crust is 20-70 km think Crust mainly consists of igneous rocks: Crust mainly consists of basalts and other mafic (Mg-rich) rocks sedimentary/metamorphic/igneous rocks, granites and other felsic (Si-rich) rocks Crust is denser Crust is less dense Crust is younger (0 – 180 million years) Crust is older (up to 4 billion years) Lithosphere is ~75 km thick Lithosphere is ~125 km thick Lithosphere gets recycled (created at mid- Lithosphere is stable ocean ridges, subducts into the deeper Earth along oceanic trenches) Covered by water – ocean basins Usually above the sea level, but also can be covered by water – continental margin © 2005 Brooks/Cole [Harris et al., 2014]  What is the driving force of plate motions? Heat Transfer Radiation – heat travels as electromagnetic radiation Conduction – heat moves through a material Convection – heat is entrained in and moves with a material Temperature Composition Core Core Mantle convection driven by A. McNamara © 2005 Brooks/Cole radioactive decay: millions of years @ EES, MSU  The Plates May Drive the Mantle Thermal convection must occur due to radioactive decay in the mantle But convection can be driven by cooling at the TOP, not always heating at the bottom Ridges are passively pulled apart; cold slabs pull the plate down “Slab-pull” drives the mantle convection – NOT the other way around Plate motion is just one part of the mantle convection © 2001 W. W. Norton