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INSIDE EARTH Big Idea: Students will understand Earth's internal structure and the dynamic nature of the tectonic plates that form its surface. Objective 1: Evaluate the source of Earth's internal heat and the evidence of Earth's internal structure. Objective 2: Describe the development of the current theory of plate tectonics and the evidence that supports this theory. Objective 3: Demonstrate how the motion of tectonic plates affects Earth and living things. Earth’s Internal Heat Earth is HOT, temperature increases 25◦ C per km of depth Core temperature 6,000◦ C (about 10,800◦ F) Why is this heat important? Powers most geological processes Drive plate tectonics Source of Earth’s Heat Heat of formation Energy of Earth’s formation converted into heat energy e.g. kinetic energy of impacts Radioactive decay Heat is a by product of radioactive decay Slows down Earth’s cooling – almost at a steady temperature Earth’s Layers Earth is layered, it is not the same throughout How did the layers form? ??? Layers defined by composition or physical properties Compositional Layers Compositional Layers Core Metallic, extremely dense Solid iron inner core Liquid nickel-iron alloy outer core Makes Earth’s magnetic field 3,500 km thick ~ 4,400-6,000◦ C Compositional Layers Mantle Silicate rocks rich in magnesium and iron Dense, semi-solid 2,900 km thick ~ 500-4,400◦ C Compositional Layers Crust Variety of igneous, metamorphic and sedimentary rocks Solid low-density plates, float on mantle 5-70 km thick < 0-500◦ C Evidence of Earth’s Structure Seismic studies (seismology) The scientific study of earthquakes and seismic waves as they move through and around the Earth Seismograph / seismometer Instrument that measures motions of the ground Evidence of Earth’s Structure Seismic waves Waves of energy caused by the sudden breaking of rock within the Earth P-waves (primary) Fastest body wave Can move through liquid and solid S-wave (secondary) Slower body wave Can only move through solids Evidence of Earth’s Structure P-waves Bend at core Speed up at inner core Outer core must be liquid Inner core is solid S-waves Move through the mantle Mantle must be solid Do not pass through the core Core must have a liquid layer Evidence of Earth’s Structure Composition of meteorites Similar in composition to Earth’s interior Iron meteorites = core Stony iron meteorites = deep mantle Stony meteorites = crust and upper mantle Evidence of Earth’s Structure Samples of the crust and mantle Scientists drill and take samples of the crust Currently trying to drill to the mantle Can’t drill to mantle, but it is exposed in some places Volcanic eruptions Layers Based on Physical Properties Lithosphere Crust and uppermost rigid mantle Hard and rigid Divided into plates Can break = ? Earthquake Layers Based on Physical Properties Asthenosphere Hot, mobile part of upper mantle Semi-solid = plastic A solid that can flow e.g. silly putty Lithosphere floats on top Source of most magma Layers Based on Physical Properties Mesosphere Dense, solid rock Hotter than upper mantle, but pressure is greater so it is rigid Layers Based on Physical Properties Outer core Dense, liquid metal Flow creates magnetic field Inner Core Extremely dense, solid metal Pressure keeps solid Evidence of Physical Layers Seismic waves Can also detect boundaries between layers Speed matters! E.g. waves slow in asthenosphere = semi-solid Density Magnetic field Based on comparisons to Earth’s average density and meteorite density Evidence of flow in outer core Observations and experimentation! Movement of Earth’s Heat Conduction Direct transfer of heat through molecules Convection Transfer of heat through movement Majority of heat transfer http://earthguide.ucsd.e du/eoc/teachers/t_tecto nics/p_convection2.html INSIDE EARTH Big Idea: Students will understand Earth's internal structure and the dynamic nature of the tectonic plates that form its surface. Objective 1: Evaluate the source of Earth's internal heat and the evidence of Earth's internal structure. Objective 2: Describe the development of the current theory of plate tectonics and the evidence that supports this theory. Objective 3: Demonstrate how the motion of tectonic plates affects Earth and living things. Continental Drift Alfred Wegener Continental Drift Hypothesis German scientist that proposed the Continental drift hypothesis in 1912 The continents once were a single landmass before breaking apart and drifting to their present locations Single landmass was later named Pangaea https://www.youtube.com/watch?v=T1-cES1Ekto Evidence Fossil record Ancient fossils of extinct plants and animals found in rocks of the same age on different continents Mesosaurus: extinct land reptile fossil found in E. South America & W. Africa Ancient climates Warm climates show deposits from ancient glaciers Cold climates containing ancient coral reefs and coal deposits (from warm tropical swamps) http://www.geo.arizona.edu/~r ees/atlanticcontinentsrev.mov Evidence Geometric fit of continents Geologic record Identical rocks of the same type and age on different continents Mountain ranges with the same rock types, structure and ages on opposite sides of the Atlantic Problems with Continental Drift Wegener could not explain HOW the continents moved Seafloor Spreading In 1960, Harry Hess, a Princeton geologist, proposed the “HOW” of Continental Drift Seafloor spreading A process that occurs at mid-ocean ridges, where new oceanic crust is formed through volcanic activity and then gradually moves away from the ridge. It ultimately subducts back into the mantle at oceanic trenches. https://www.youtube.com/watch?v=GyMLlLxbfa4 Evidence of Seafloor Spreading Mid-ocean ridges Underwater mountains where magma rises up and pushes the seafloor outward The lava cools and becomes new oceanic crust Youngest, hottest part of the seafloor Oceanic trenches (deep-sea) Long, narrow depressions on the seafloor Occur where two plates converge (meet) and one subducts under the other Oldest, deepest, coolest part of the seafloor Evidence of Seafloor Spreading Magnetic striping Ancient magnetism shows reversal of Earth’s magnetic field (flips from N to S) Occurs on average every 500,000 years As lava at a mid-ocean ridge cools, magnetite crystals line up in the magnetic field like magnets (pointing N) This is recorded on the ocean floor as stripes, with mirror images on either side of a midocean ridge https://www.youtube.com/watch?v=BCzCmldiaWQ&list=PLRDOLHrgGYUvmqLQhZ5jG1QdrMJibRAD Evidence of Seafloor Spreading Age of the seafloor Seafloor is youngest at the mid-ocean ridges and becomes progressively older with distance from the ridges Theory of Plate Tectonics The Earth’s surface is divided into several moving, crustal plates composed of oceanic lithosphere and thicker continental lithosphere, each with its own kind of crust Types of crust Oceanic- younger, thinner, 5 miles thick (oldest 200 million years old) Continental- older, thicker, up to 60 miles thick (oldest 4 billion years old) Evidence for Plate Tectonics Distribution of earthquakes and volcanos Both occur at plate boundaries Evidence for Plate Tectonics Hot spots (mantle plumes) Volcanic regions fed by spots of mantle upwelling Plates move over these spots, creating volcanic island chains Show rate and direction of plate movement e.g. Hawaiian Islands INSIDE EARTH Big Idea: Students will understand Earth's internal structure and the dynamic nature of the tectonic plates that form its surface. Objective 1: Evaluate the source of Earth's internal heat and the evidence of Earth's internal structure. Objective 2: Describe the development of the current theory of plate tectonics and the evidence that supports this theory. Objective 3: Demonstrate how the motion of tectonic plates affects Earth and living things. Lithospheric Plates Plates are made of crust and rigid upper mantle Float on top of the asthenosphere Move at a rate of a few centimeters a year 2 types Continental plates – granitic rocks, less dense, older Oceanic plates – basaltic rocks, denser, younger Major Plates https://www.youtube.com/watch? v=uGcDed4xVD4 7 major plates 1. 2. 3. 4. 5. 6. 7. African Plate Antarctic Plate Eurasian Plate Indo-Australian Plate North American Plate Pacific Plate South American Plate Plate boundaries The border between adjacent plates where they interact Convergent Boundaries 2 plates are colliding and one plate subducts into the mantle under the other a) b) c) Continental/Oceanic produce a trench and volcanic mountains Oceanic/Oceanic produce a trench and an island arc Continental/Continental produce folded mountains Divergent Boundaries 2 plates are moving apart The asthenosphere moves up to fill in the space Ocean: produces underwater mountains (midocean ridges & seamounts), rift valleys, & islands Land: produces rift valleys, rift lakes & fault block mountains Transform Boundaries 2 plates slide past each other or move the same direction, just at different speeds Produce transform faults. e.g. San Andreas Fault Causes of Plate Movement Gravity Ridge-push: plates are at higher elevations at mid-ocean ridges and are pulled down and away from the ridge by gravity Slab-pull: as plates are subducted, gravity pulls the plate down into the mantle and the plate moves behind Density Less dense lithosphere floats on denser asthenosphere, allowing movement Differences in density allow plates to subduct beneath one another Causes of Plate Movement Convection Currents As material warms, it becomes less dense so it rises and spreads out. As it spreads out, it cools and sinks, only to be heated and rise again. Plates may be dragged along on the current http://earthguide.uc sd.edu/eoc/teacher s/t_tectonics/p_conv ection2.html https://www.youtube.c om/watch?v=ryrXAGY 1dmE#t=37 Map Assignment: draw in plate boundaries color the plates different colors write in name of plate and draw in arrows to show direction of movement. Earthquakes Earthquakes transfer energy from the Earth’s interior to the surface as seismic waves (mechanical energy) Rayleigh surface waves do the most damage Pacific Ring of Fire – 90% of world’s earthquakes occur in this belt Fault zones – fractures in rock, due to tectonic stresses e.g. San Andreas fault Not always at boundaries (e.g. Wasatch fault) https://www.youtube.com/watch?v=R8 oXqU6ccsY Volcanos Hot, less dense magma rises due to density and erupts, transferring: Heat as flowing magma Energy as explosions (mechanical energy) Subduction zone Subducting plate melts, the water in it melts surrounding magma, which rises and erupts Credits http://www.livescience.com/29054-earth-core-hotter.html http://www.soest.hawaii.edu/GG/FACULTY/POPP/Oct07_Ch_12.pdf http://www.geology.sdsu.edu/how_volcanoes_work/Heat.html http://geology.com/meteorites/meteorite-types-and-classification.shtml http://www.sciencephoto.com/ http://scienceline.ucsb.edu/getkey.php?key=3665 http://commons.wvc.edu/rdawes/G101OCL/Basics/earthinterior.html http://faculty.icc.edu/easc111lab/labs/labi/prelab_i.html http://www.columbia.edu/itc/ldeo/v1011x-1/jcm/Topic3/Topic3.html http://www.dailymail.co.uk/sciencetech/article-2297050/Massive-volcaniceruptions-wiped-HALF-life-Earth-200-million-years-ago.html http://www.huffingtonpost.com/2013/09/20/photos-oflava_n_3950497.html http://earthsky.org/earth/what-is-the-source-of-the-heat-in-the-earths-interior http://www4.uwsp.edu/geo/faculty/ozsvath/lectures/Continental_Drift.htm http://www.geology.sdsu.edu/how_volcanoes_work/Heat.html http://www.nature.nps.gov/geology/usgsnps/animate/pltecan.html https://geoinfo.nmt.edu/resources/uranium/basics.html http://mail.colonial.net/~hkaiter/ContinentalDrift.html http://astrobioloblog.wordpress.com/2011/10/10/how-the-earth-was-born/ http://facweb.bhc.edu/academics/science/harwoodr/geol102/Study/origin. htm http://www.sciencedaily.com/articles/o/oceanic_trench.htm http://www.space.com/17777-what-is-earth-made-of.html http://www.sanandreasfault.org/Tectonics.html http://pubs.usgs.gov/gip/dynamic/inside.html http://www.pbs.org/wgbh/nova/education/activities/2515_vesuvius.html http://www.merriam-webster.com/concise-images/73583.htm http://www.divediscover.whoi.edu/tectonics/tectonics-subduct.html http://maggiesscienceconnection.weebly.com/layers-of-the-earth.html http://www.columbia.edu/~vjd1/driving_forces_basic.htm http://www.geo.mtu.edu/UPSeis/studying.html http://web.ics.purdue.edu/~braile/edumod/waves/WaveDemo.htm http://www.geo.mtu.edu/UPSeis/waves.html http://www.cyberphysics.co.uk/topics/earth/geophysics/Seismic%20Waves% 20Reading.htm http://www.awi.de/en/news/focus/2012/the_100th_anniversary_of_alfred_ wegeners_continental_drift_theory/picture_gallery/