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Transcript
Earth Science Chapter 5 Plate Tectonics Big Ideas • Earth’s Interior • Convection and the Mantle • Drifting continents • Sea-floor Spreading • Plate Tectonics Earth’s Interior •How far do you think it is to the center of the Earth? •Almost 4,000 miles! •The deepest mine in the world is only 2 miles • How do you think scientists know about the center of the Earth? • Geologists use 2 main types of evidence to learn about Earth’s interior: –Direct Evidence from rock samples –Indirect evidence from Evidence from Rocks • Humans have drilled holes and extracted rock from depths of 12 miles • Blasts from the Earth have brought rocks from 100 ft to the surface Evidence from Seismic Waves • Earthquakes produce seismic waves • The speed of seismic waves and the path they take show the structure of the planet Three main layers • The three main layers of Earth are the crust, mantle, and the core • These layers differ in size, composition, temperature, and pressure Temperature • The first 20 meters beneath Earth’s crust is cool • After this depth, temperature rises 1 degree Celsius per 40 meters • Heat comes from the molten layer and radioactive substances Pressure •The deeper you go, the higher the pressure •This pressure is equal to that of a swimming pool Pressure Lab Skills Activity • Work with a partner, • Read the directions to the Lab Zone Skills Activity • Create the Data Table on page 129 Crust • Crust is a layer of rock that forms Earth’s outer skin • Crust includes both dry land and ocean floor • Crust is very thin compared to the other layers of Earth, only 5-70 km thick Crust Crust • The crust beneath the ocean is oceanic crust and usually made of basalt • Continental crust consists of rocks such as granite • I was very disappointed in the behavior of some of you on Friday. • That was extremely disrespectful of you to run from the classroom when the bell rang. • You need to remember that I dismiss you and not the bell. • Please take your seat and sit quietly while you wait for class to begin Mantle • The mantle is about 40 km below the surface • It consists of a hot, solid rock • It can be divided into layers • The mantle is about 3000 km thick Mantle Lithosphere • The crust and the uppermost part of the mantle form the lithosphere • It is about 100 km thick • Lithos means “stone” in Greek Lithosphere Asthenosphere • Under increase heat and pressure • Less rigid-soft like tar, but still solid • Asthenes means “weak” in Greek The Lower Mantle • Beneath the asthenosphere the mantle is solid • This material extends to the Earth’s core Lower Mantle The Core • Consists of mostly nickel and iron • Made of two parts, a liquid outer core and solid inner core • Together it is about 3486 km thick • Despite extreme pressure, the outer core is molten surrounding a dense, solid inner core • Evidence suggests that the extreme pressure in the inner core will not allow the solid metal to spread and become liquid Core Core and Magnetic field • Scientists think that movements in Earth’s liquid outer core create Earth’s magnetic field. • This magnetism is what attracts a compass’ needle towards north (it aligns with Earth’s magnetic field) Individually • Complete the section 1 assessment on page 131, including the “writing in science” assignment. If you do not complete these in class, they will become your homework and will be due tomorrow. Make a Chart Types of Heat Transfer Radiation Explanation/definition Conduction Explanation/Definition Convection Explanation/Definition When you complete the chart • Read the sections “Convection Currents”, and “Convection Currents in Earth.” • 1. Define Convection Currents • 2. Explain how convection currents work, using a real example • 3. Create an illustration of a convection current Bellwork • What are the three types of heat transfer and give an example of one that is not in your book! Drifting Continents • http://www.youtube.com/watch?v=WaUk94A dXPA Continental Drift • Prior to Columbus, mapmakers did not know about the new worlds • Shortly after they began to notice how the coastlines of several countries seemed to fit together like a puzzle Continental drift • Early 1900s German Scientist Alfred Wegener made a hypothesis: • All of the continents were once joined together in a single land mass and have since drifted apart. The Origin of Continents and Oceans • Wegener gathered evidence from different scientific fields to support his ideas about continental drift. • He studied land features, fossils, and evidence of climate change Write a Book! • Make your own version of Wegner’s book • Use the same title as he did • Read pages 138-138 about the evidence he found • Create a page for each type of evidence • Explain how the evidence supports his hypothesis and include illustrations if appropriate. The Origin of Continents and Oceans • Page 1: Title • Page 2: Evidence from land features • Page 3: Evidence from fossils • Page 4: Evidence from climate • Page 5: Conclusion WHAT DID YOU FIND? Sea-Floor Spreading • http://www.youtube.com/watch?v=p0dWF_3 PYh4 Mid Ocean Ridges Mid Ocean Ridge • Curve like seams through Earth’s oceans • Most mountains are under water, except Iceland! Iceland Hess and Sea-floor spreading • Harry Hess in 1960 realized that Wegener was right and the continents were being moved by sea-floor spreading: –The sea floor spreads apart along both sides of a mid-ocean ridge as new crust is added –The ocean floors act like conveyor belts carrying the continents along with them Read pages 144-145 Editorial • You are Harry Hess! (or Harriet Hess) • You have just concluded your research about sea-floor spreading • Prepare a speech for your science conference in which you will share your findings • Include your theory, the evidence that supports if from molten material, magnetic stripes, and drilling samples, and end with a conclusive argument! • http://earthguide.ucsd.edu/eoc/teachers/t_te ctonics/p_seafloorspreading.html • http://serc.carleton.edu/files/introgeo/model s/mathematical/examples/SeaFlrSpreadIpdf.p df • http://www.montereyinstitute.org/noaa/lesso n02/l2la1.htm Bellwork • What were the three types of evidence Harry Hess used to support his theory of sea floor spreading? • http://www.youtube.com/watch?v=q_IYQdKk WsU • http://www.youtube.com/watch?v=6CsTTmvX 6mc • http://maccallum.wikispaces.com/Lesson+15+AN D+16+Continenetal+Drift+and+Sea+floor+spreadi ng • http://www.westerville.k12.oh.us/userfiles/4161 /Classes/9094/Sea%20floor%20spreading%20wo rksheet.pdf • http://science.berlinwall.org/files/bhs_science/C ontinental%20Drift,%20sea%20floor%20spreadin g%20and%20plate%20tectonics%20PDF.pdf 11-19 Activity • Open your books to page 148 • We will be completing this lab activity in class today • Everyone needs to complete their own seafloor spreading model • When you complete the model you will answer the Analyze and Conclude questions • You may talk to students near your desk about the questions 1-6 • When you complete the activity, • Come up with two original questions from each of the four sections in this chapter (make sure you can answer your question) • I will combine these questions for your review session tomorrow! Subduction at Trenches • Deep-ocean trenches: deep underwater canyons. • At deep-ocean trenches the oceanic crust bends down and sinks beneath the continental crust. Subduction • Subduction: the process by which ocean floor sinks beneath the deep ocean trench and back into the mantle • http://www.youtube.com/watch?v=K8J7t3KYr 9c • http://www.youtube.com/watch?v=wkc4lbhh SRs Process of Subduction • As the older rock is subducted, younger rock moves away from the mid-ocean ridge • New rock is hot, but it cools and becomes more dense as it ages Old rock, New Rock, Red Rock, Green Rock Process Continued • Eventually gravity pulls the older, denser rock down at the trenches Subduction and Earth’s Oceans • Subduction and seafloor spreading can change the size and shape of the oceans • Ocean floor is renewed about every 200 million years • The Pacific’s trenches are eating more crust than the ridges can make • In the Atlantic the opposite is the case • http://www.youtube.com/watch?v=hSdlQ8x7 cuk Review • http://www.youtube.com/watch?v=_5q8hzF9 VVE