Transcript Chapter 10
Plate Tectonics Evolution of the Earth This Powerpoint is hosted on www.worldofteaching.com Please visit for 100’s more free powerpoints How do we know anything about the Earth Page 20,22: Pg. 20 3 Column Vocab 1. Mid ocean Ridge 2. Sea floor spreading 3. Plate Tectonics 4. Asthenosphere 5. Lithosphere 6. Convection cell 7. Pangaea Pg. 22 8. Subduction zone 9. Rifting 10. Divergent boundary 11. Convergent boundary 12. Transform boundary **Not all terms are in glossary—some are italicized within the chapter How to do 3 column vocab. Word Definition Picture Page 16 How are scientists able to study the composition and size of the interior layers of the Earth? a. By direct observation b. By analyzing surface rock samples c. By using seismic waves d. By deep drilling into the interior layers Page 16 • Which statement BEST describes how new scientific views become accepted? a) A group of scientists come to common agreement over an idea at the same time. b) New ideas become a theory when hypotheses are proven to be correct. c) When a theory gains so much support it becomes a scientific law. d) When observations of our natural world produce plausible explanations. In: pg 18,19 • Watch the movie clip “ The Earth’s Interior” and write down 15 facts. 1. 2. 3. 4. 5. Use the diagrams below to answer the question. Page 16 • Which type of plate boundary is shown in the diagram? a. Divergent b. Transform c. Convergent d. Universal Page 16 • Prior to Alfred Wegener’s theory of continental drift geologists thought continents were fixed in their locations. In developing his theory which of the following evidence was NOT used by Wegener? a) Fossil similarities between southern continents. b) Evidence of polarity change in found along the MidAtlantic Ridge. c) Similarities in the paleoclimates of South America and Africa. d) The apparent fact the South America and Africa seemed to fit together. 20 Warm up Wrap up 21,23,25 Earth’s interior Chapter 10 Interior Interior Thru 1: Pg 21 The Earth’s Interior Questions • Read the front and complete the questions on the back. • Tape in as a flap Thru 1: pg. 21 Please copy this concept map and then complete it by filling in one appropriate descriptor at the end of each arrow. Use pages 239-241 in the textbook. When discovered Scientist Definition Theory of Continental Drift What is missing? Continents Supporting Evidence Fossils Rock Climatic Formations Quiz #1 Sep. Sheet 1. 2. 3. 4. 5. 6. 7. Pg. 25 What is the title of Ch. 10? Pg. 27 What is the answer to #2? Pg. 27 What is the answer to #10? Pg. 27 How thick is the core? Pg. 29 What is the answer to #5? Pg. 29 What is the answer to #10? Pg. 31 What was the name of the scientist who came up with the Theory of Continental Drift? 8. Pg. 31 The Theory of Continental Drift says that the continents are___________. Thru 2 Pg. 23-use the supercontinent on pg. 33 and the book to answer these questions. Analysis Questions: 1. What are 3 pieces of evidence you used to fit together the continents? 2. Why is this called a supercontinent? 3. How does this model help support the Theory of Continental Drift? 4. Why aren’t the continents still in this location today? Pg. 25 Supercontinent Cutout. Cutout the continents and fit them together to make the supercontinent that Wegener proposed. Glue them on this page. Alfred Wegener Theory of continental drift • Harry Hammond Hess Harry Hess commanding the USS Cape Johnson. • Born May 24, 1906 Died August 25, 1969 Suggested that the convection of the Earth's mantle was the driving force behind plate tectonics. . Tectonic Plates Today plate boundaries are determined by examining the location of volcanoes and earthquakes. Volcanoes result from the friction (heat) of the plates motion. Earthquakes occur where plate rub against one another Tectonic Plates Tectonic Plates Tectonic Plates Tectonic Plates Evidence of Continental Drift Pangea • What is Pangaea? • Pangaea was a super continent at one time. • Scientists use the similarity of rock types and fossil types that date to the same age to support their theory that the continents were connected to form a super continent. • The map below give just one example of areas on different continents that show the same fossils and rock types. Pangea • Pangea Tectonic Plates Evidence Our first evidence of tectonic motion is based on similar fossils and rock types on opposing sides of the ocean Tectonic Plates Tectonic Plates Radioactive Dating Another source of evidence is based on seafloor ages which get younger as we approach sea floor ridges Tectonic Plates Our final piece of evidence is the magnetic record of the ocean floor. This shows the pattern of reversal and we find a near perfect mirror image on opposing sides of the ridge Where are we going? We appear to be headed for another super continent as North America, South America, Asia and Australia converge in the ever shrinking Pacific Ocean Composition vs. Motion We can look at the interior of the Earth based on the composition of the rocks or based on the movement Based on Composition • Crust – solid, relatively low density silicate rock • Mantle – Semi fluid, denser, mafic (iron and magnesium bearing) rocks • Core – Liquid then solid iron and nickel with traces of heavier elements Based on Motion • It turns out that the upper section of the mantle is adhered (stuck to the underside side of the crust to form what we call tectonic plates Plate Types • Oceanic plates: basalt – Dark (black) and dense rock type composed of silicates, iron and magnesium • Continental plates – granite and andesite – Light colored (pink, white and gray) and low density rock type composed almost entirely of silicates. Plate Boundaries • Convergent – plates move toward one another • Divergent – plates move away from each other • Transform – plate moves sideways from each other Plate Boundaries Convergent Plates Convergent Plates Convergent Plates The only subduction zone in the Atlantic Convergent Plates Black arrows show subduction zones and the direction of plate movement • Subduction.swf ocean-con ocean-ocean con-con Divergent Plates • Divergent • sfloorspreading.swf Divergent Plates Divergent Plates Divergent Plates Transform Plates • Trboundary.swf Transform Plates San Andreas Fault Mid-Plate Hotspots Mid-Plate Hotspots Mid-Plate Hotspots Mid-Plate Hotspots Hotspotvol.swf Why do the Plates Move? Why do the Plates Move? • No single idea explains everything but we can identify several forces that contribute to the movement of the plates. – Slab pull • The sinking of the cooled dense oceanic plates pulls on the rest of the plate – Ridge rises • The material deposited on the top of the ridge slides downs from the rise pushing on the plate – Convection • Movement within the mantle could be part of the driving force behind the motion of the plates. The Big Picture Volcanoes • Volcanoes are the result of hot spots within the crust or mantle of the earth. • The hot, liquid rock will break through weak spots in the surface and form volcanoes or flood basalts. • Many volcanoes do not release lava, instead they spit ash and small bits of lava called lapilli. • Some eruptions are quiet with very fluid (low viscosity) lava flows while others are explosive Volcanoes Quiet lava flows Volcanoes Mt. St. Helen before the explosive eruption Volcanoes Volcanoes Time lapse of the eruption Volcanoes Mt. St. Helen after the eruption Volcanoes Earthquakes Tidal waves or Tsunamis result when the low amplitude long wavelength waves reach the shallow shoreline and begin to feel the bottom of the sea floor. This Shortens the wavelength and increase the amplitude (height). Earthquakes Location of worldwide earthquakes Tsunami Ch. 10 Plate Tectonics Thru 1: pg 35 Cornell Notes The Theory of Continental Drift • Continents were once in a single landmass or supercontinent that drifted apart into the continents we see today. – Supercontinent was called Pangaea • Alfred Wegener came up with the Theory of Continental Drift in 1911. • Used the shape of continents, distribution of fossils and rock formations to hypothesize that the continents were at one time all together. • No mechanism until 30 years later. The Supercontinent Mid-ocean Ridges • Undersea chains of volcanic mountains that run along the ocean floor. • Have deep valleys in the center where magma comes up. Sea Floor Spreading • The ocean floor is moving outward from the mid-ocean ridges. – The rock closer to the ridges is younger than the rock far from the ridges – Oceanic rock is much younger than continental rock. – Explains how the continents move. • Magma rises to the surface and solidifies and new crust forms • Older Crust is pushed farther away from the ridge Sea Floor Spreading Animation Lithosphere and Asthenosphere • Lithosphere is the rigid outer layer of the Earth. • Made of the crust and the solid outer layer of mantle. • Asthenosphere is the layer of “plastic” rock in the lower mantle. • Flows like a very thick liquid. Lithospheric Plates • Lithospheric Plates-The rigid lithosphere is broken into blocks or plates – Also called Tectonic Plates. – Float on the semi rigid, moving asthenosphere. Tectonic Plates Theory of Plate Tectonics • Theory of Plate Tectonics explains how the lithospheric plates move. Convection Currents HOT!!!! Convection currents caused by the very hot material at the deepest part of the mantle rising, then cooling and sinking again --repeating this cycle over and over. ***Remember…this heat is generated by the core!! How Plates Tectonic Works As magma heats up and rises, it exits through the rift in the middle of the mid-ocean ridge. It cools and pushes the plates apart. The Asthenosphere is also moving in convection currents(created by unequal heating), carrying the plates Now! • Write 3 questions in the left hand column and a 3 sentence summary at the bottom. Out Tent Paragraph-use the following words correctly in a paragraph. Highlight the words within the paragraph. • Lithosphere • Asthenosphere • Tectonic plate • Convection cell • The movement of tectonic plates is inferred by many scientists to be driven by a. tidal motions in the hydrosphere. b. density differences in the troposphere. c. convection currents in the asthenosphere. d. solidification in the lithosphere. In: pg. 38 • Use your notes on pg. 35 to answer these questions: 1. Who came up with the Theory of Continental Drift? 2. _______ are undersea chains of volcanic mountains that run along the ocean floor. 3. ________ spreading explains that the ocean floor is moving outward from the mid-ocean ridges. 4. The ______is the rigid outer layer of the Earth. 5. The ______ is the layer of the lower mantle that flows like a thick liquid. 6. The lithosphere is broken into _____ plates. 7. The Theory of ______ ______ explains how the plates move. 8. The mantle moves in _________ currents created by the unequal heating of mantle material. Thru 1: Pg. 39 Plate Boundaries Diagrams http://geology.com/nsta/ Plate boundaries Different Types of Boundaries http://pubs.usgs.gov/gip/dynamic/understanding.html Divergent Boundary – Arabian and African Plates Convergent Boundary – Indian and Eurasian Plates Convergent Boundary – Oceanic & Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com Convergent Boundary – Oceanic & Oceanic http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com Convergent Boundaries - Continental http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com Transform Boundary – San Andreas Fault www.geology.com Out When 2 plates converge, one plate will normally subduct. • What does the word “subduct” mean? • What is a subduction zone? • What determines which plate will subduct? Wed. 2/27 and Thurs. 2/28 In: pg. 40 • Match the type of boundary with the structure that will form. 1. Oceanic/oceanic 2. Oceanic/continental 3. Continental/continental A. Mountain ranges. B. Trenches and island arcs C. Trenches and volcanic arcs Thru 1: pg. 41 • Tectonic Plates Map Worksheet. – Complete the questions and tape in the worksheet. Out • A friend tells you that California is going to fall off and Nevada will one day be waterfront property. Please explain what is wrong about this statement. In: pg. 34 • Take the cup at your table to the sink and fill it about ½ full of water. Return to your table and drop the colored ice cube in the cup. Watch the water that melts off of the ice cube and draw what you see. Use arrows to represent the movement of the red water. 1. Did the cold water coming off of the ice cube sink or float? 2. Which is more densecold or warm water? Convection • When a substance is heated it becomes less dense and rises. • When a substance cools, it becomes more dense and sinks. • This creates a circular movement in the material called a convection cell or current.