Presentation on theme: "Plate tectonics Notes. Drilling into the mantel: NPR article Radio program Drilling-To-The-Mantle-Of-The-Earth."— Presentation transcript:
Plate tectonics Notes
Drilling into the mantel: NPR article Radio program Drilling-To-The-Mantle-Of-The-Earth Drilling-To-The-Mantle-Of-The-Earth Video: hives/ hives/
Structure of the Earth The Earth is made up of 3 main layers: Core Mantle Crust Inner core Outer core Mantle Crust
Inner Core center of the Earth made of iron and nickel that is in a solid state, 1200 km thick
Outer Core Surrounds the inner core liquid iron and nickel 2270 km thick Liquid is in constant motion Moving electric charge creates the Earth’s magnetic field oceanexplorer.noaa.gov/explorations/05galapagos/logs/dec22/media/magfield_600.gif
Mantle between the outer core and crust Mafic composition: means made of heavy elements like iron, magnesium, and silicon (ex: basalt rock) 2900 km thick. The asthenosphere is the layer of the upper mantle that is made of rock that is partially melted.
Crust outermost layer of the earth Felsic composition: means made of lighter elements (example: granite rock) 10 km at ocean basins, and 65 km thick below the continents. Lithosphere is made of the upper part of the mantle and the crust. The lithosphere is a solid that is broken in pieces (tectonic plates).
Cross Section of the Earth
Alfred Wegener: German Scientist who proposed the theory of continental drift. Continental Drift: All continents were once a part of a single supercontinent and they’ve moved Wegener 1930 launching weather balloon in the arctic. media.org/resource/ess 05.sci.ess.earthsys.weg ener1/plate-tectonics- the-scientist-behind- the-theory/http://www.pbslearning media.org/resource/ess 05.sci.ess.earthsys.weg ener1/plate-tectonics- the-scientist-behind- the-theory/ video about Wegner 4 minutes
1. The shapes of many continents look like they are separated pieces of a jig-saw puzzle. Picture above from this website to visit: zzle/puzzle_together.html zzle/puzzle_together.html Evidence to support theory of continental drift
2. the rock types and fossils found on multiple continents match suggesting the populations once lived on a continuous land mass Website to visit:
Continental Drift was not quickly accepted by scientists because: Wegner did not have a supported explanation for how the continents move and what provided the energy source to move them.
Answers to Wegener’s opponents lead to Theory of Plate Tectonics The plates move because the crust is divided into separate pieces: tectonic plates also called lithospheric plates These plates are in motion over the liquid-like asthenosphere. The asthenosphere moves due to convection currents in the lower mantle
Cold rock is brittle Hot rock is plastic Very Hot rock is Melted
What’s happening in the asthenosphere? Convection currents and they are moving the lithosphere above!
Convection currents & plate movement “Plates” of lithosphere are moved around by convection currents in the underlying hot mantle Movement
Extra diagrams Sea Floor and Convection Currents
Convection inside the mantle The source of heat driving the convection currents is radioactivity deep in the Earth’s mantle. PROCESS Heated asthenosphere is less dense then its surroundings so it rises. Once it gets close to the earth’s surface it cools, becomes more dense so it sinks.The more dense material then sinks The process continues forming a circular pattern called a CONVECTION CURRENT
Convection current definition PROCESS Heated asthenosphere is less dense then its surroundings so it rises. Once it gets close to the earth’s surface it cools, becomes more dense so it sinks. The process continues forming a circular pattern called a CONVECTION CURRENT
Convection current simulations onvection.htm onvection.htm simulation of convection in the mantle: ence/terc/content/visualizations/es0805/es 0805page01.cfm?chapter_no=visualizatio n ence/terc/content/visualizations/es0805/es 0805page01.cfm?chapter_no=visualizatio n ectonics/p_convection2.html ectonics/p_convection2.html Observe an animation of convection in the mantle.
Good web site not yet used p13.htm
How do we know that tectonic plates are moving due to convection currents in the asthenosphere? One piece of evidence is preserved in rocks of the ocean floor!
The ocean floor Draining the oceans simulation: ence/terc/content/investigations/es2301/es 2301page03.cfm ence/terc/content/investigations/es2301/es 2301page03.cfm
Features on the Ocean Floor Henry Hess and Graphing activity
WHAT DOES A COMPASS DO WHEN PUT CLOSE TO A PIECE OF ROCK THAT CONTAINS A LOT OF IRON? Demonstration to do before sea floor spreading lab
Magnetic rock contains iron atoms. Iron will freely rotate when it is magma. Each atom acts like a tiny magnet aligning itself north and south with the earth’s magnetic field. When the magma cools it preserves a record of the earth’s magnetic field at the time the rock was formed Explain how igneous rock can record information regarding the direction of the Earth’s magnetic field.
Magnetic reversals Earth’s magnetic poles have reversed several times in the past. Evidence for this is seen in bands of igneous rock on the ocean floor.
Sea floor spreading lab video 2 minutes video 2 minutes share.com/media.php?id=1325 moving animation of sea floor spreading with compass share.com/media.php?id=1325
Convection currents cause sea floor spreading
Sea floor spreading Magma rises along a rift valley in the ocean floor where 2 oceanic plates are diverging from one another. The magma forms new igneous rock. Magnetic minerals in the rock record the magnetic field at the time it was formed. Bands of magnetic rock along the mid ocean ridge show an alternating pattern of magnetic poles indicating new rock has been formed as the earth’s magnetic field has changed.
Earth’s magnetic field: What’s happening in the core? The moving metal core creates the earth’s magnetic field
Earth’s magnetic field Movement of molten iron and nickel in the Earth’s core generates electrical and magnetic fields that produce Earth's magnetism. The movement of the metal and therefore magnetic field has changed. Electricity and magnetism review
Background for seafloor spreading: Earth’s magnetic field Electricity charge, magnetism powerpoint Earth's Inconstant Magnetic Field radio article news/science-at- nasa/2003/29dec_magneticfield/ Magnetic storm video
Electric Charge Magnetic fields Electromagnetic Forces
An objects electric charge depends on the imbalance of its protons and electrons Negatively charged objects: more electrons than protons. Positively charged objects: more protons then electrons Electricity and magnetism review Protons and neutrons normally remain in the nucleus Electrons are easily transferred from one atom to another The direction in which electrons are transferred depends on the materials
Ion (has to do with electrons) Example: Lithium 3 (+) protons and 3 (-) electrons Neutral – no charge 3 (+) protons and 2 (-) electrons +1 charge – positive ion Ion: An atom that has an unequal number of protons and electrons. Ions have a positive or negative charge Atoms that have a neutral charge are not ions
Like charges repel ( +,+ or-, -) Opposite charges attract (+, -) Electricity and magnetism review
Demonstration: Rub balloon on hair Compare the charge of a balloon and hair Like charges or opposite charges? How do you know? Compare the charge of two balloons Like charges or opposite charges? How do you know? Electricity and magnetism review
Charged particles produce an electric field in the space around it. Electricity and magnetism review
Electric field between two charges Electricity and magnetism review
The strength of the electric force depends on two factors The distance between charged objects As distance decreases force increases The amount of charge of the objects The greater the charge the greater the electric force Electricity and magnetism review
All magnetic fields are the result of moving electric charges. The Invisible World of Magnetic Fields Electricity and magnetism review
Magnets are sources of magnetic fields. The forces can be illustrated with magnetic field lines. Demonstration of field lines with iron fillings on magnet Electricity and magnetism review
Bar magnet with iron fillings Electricity and magnetism review
The force of magnetism coming from the magnet is called the "magnetic field", and is illustrated by lines. The magnetic field is strongest where the lines of force come together (and turn red), and is weakest when the lines of force are far apart (and turn blue). Electricity and magnetism review
Demonstration with iron fillings in cylinder Electricity and magnetism review
Geographic north vs Magnetic North Earth's magnetic field is slightly tilted with respect to the planet's spin axis; there is currently a difference of about 11° between the two.
Electromagnet Directions: 1. Wind the wire around the nail. Hold insulated wire with the ends against the batter terminals 2. Move compass/or paperclip toward the nail to determine whether the nail is magnetized. 3. Switch connections to the battery so the current is reversed. Bring the compass/or paperclip toward the same part of the nail. Electricity and magnetism review Video about electromagnetic crane: QkMpY
Earth as an electromagnet Moving electric charge creates a magnetic field. A battery can cause a moving electric charge in a metal wire wrapped around a nail. This creates a magnetic field around the nail. The moving metal in the earth’s core causes moving electric charge that creates a magnetic field around the earth. Electricity and magnetism review
Extra slides When two magnets are brought together, the force will attract the two magnets together if the poles are opposite, that is if the pole of the first magnet is positive and the pole of the second magnet is negative. If that condition is true, the two magnets will be "forced" to stick together. If two magnets of the same polarity are brought together, the force of magnetism will repel the two magnets from each other, and they cannot be made to stick together. Electricity and magnetism review
(Background information) Magnetic field’s importance to humans: Earth’s magnetic field deflects some of the harmful radiation from the sun (solar winds) Electricity and magnetism review
Notes of the Earth’s Magnetism The Earth’s magnetic pole and geographic pole are 2 different places. The geographic pole is the axis for the rotation of the planet. The Earth’s magnetic pole changes. It is currently in Northern Canada. It has completely reversed at different times in the Earth’s history. The magnetic pole is caused by the movement of the liquid metallic outer core. The Earth’s inner core is a solid ball of iron and nickel that spins faster then the planet itself. The Earth’s outer core is a “ocean” of liquid metal that moves and even has swirling sections, similar to a hurricane
Theory of Plate Tectonics The Earth’s crust is divided into 12 major plates which are moved in various directions.
Evidence to support the Theory of Plate Tectonics 1. The shapes of many continents fit like puzzle 2. Fossil evidence 3. Seafloor spreading showing magnetic reversals 4. Location earthquakes and volcanoes
4. There are a large amount of earthquakes & volcanoes along the plate boundaries.
Volcanism is mostly focused at plate margins Pacific Ring of Fire
Plate Tectonics This plate motion causes them to collide, pull apart, or scrape against each other. Each type of interaction causes a characteristic set of Earth structures or “tectonic” features.
TYPES OF PLATE MOVEMENT & FEATURES THEY CREATE
Divergent Convergent Transform Three types of plate boundary 14
Website simulation of Plate movement Plate Tectonics: The Scientist Behind the Theory tectonics-the-scientist-behind-the-theory/ Plate Tectonics: An Introduction tectonics-an-introduction/ Plate Tectonics: Further Evidence tectonics-further-evidence/http://www.pbslearningmedia.org/resource/ess05.sci.ess.earthsys.wegener2/plate- tectonics-further-evidence/ Mountain Maker, Earth Shaker maker-earth-shaker/ 0804page01.cfm?chapter_no=visualizationb 0804page01.cfm?chapter_no=visualizationb
________ 1. What kind of boundary is this? __divergent__________ boundary 2. What is being formed on the earth’s surface at this plate boundary? New crust is being formed called mid ocean ridge mountains. 3. What is the deep crack called? rift____ ____Valley_________ ______________ __
1.What kind of boundary is this? ________________ Boundary 2. What type of plates are interacting here? 3. How does the density of the ocean plate compare to the continental plate? 4. Which plate subducts? 5. What happens to the sinking plate as pressure increases and temperatures rise? ______________ __
1.What kind of boundary is this? _______________ boundary 2. What type of plates are interacting here? ____________- ____________________ 3. How does the density of the two plates compare? 4.. Why doesn’t one plate subduct underneath the other? 5. What kind of surface feature is formed at this boundary? _______________ _
1.What kind of boundary is this? _______________ boundary 2. When the movement does not happen smoothly what happens?
Spreading ridges As plates move apart new material is erupted to fill the gap Divergent Boundaries 15
Iceland has a divergent plate boundary running through its middle Iceland: An example of continental rifting
Information about Iceland iceland.asp iceland.asp 10.asp Surtsey Island 10.asp
There are three styles of convergent plate boundaries Continent-continent collision Continent-oceanic crust collision Ocean-ocean collision Convergent Boundaries
2 plates of similar density. Forms mountains, as the edges of each plate push together and rock accumulates in the middles. e.g. European Alps, Himalayas Continent-Continent Collision
Called SUBDUCTION Continental plate less dense, oceanic plate more dense Continent-Oceanic Crust Collision
Oceanic plate subducts underneath the continental plate forming a trench where they meet. Oceanic plate heats up and dehydrates as it goes down The melted rock rises through the continental plate forming volcanoes Example: The Andes mountains Subduction
When two oceanic plates collide, one runs over the other which causes it to sink into the mantle forming a subduction zone. The subducting plate is bent downward to form a very deep depression in the ocean floor called a trench. The worlds deepest parts of the ocean are found along trenches. E.g. The Mariana Trench is 11 km deep! Ocean-Ocean Plate Collision
Where plates slide past each other Often cause earthquakes, Surface features: sometimes form long linear features like gulley’s Transform Boundaries Above: View of the San Andreas transform fault
Plate Tectonics Summary The Earth is made up of 3 main layers (core, mantle, crust) On the surface of the Earth are tectonic plates that slowly move around the globe Plates are made of crust and upper mantle (lithosphere) There are 2 types of plates (oceanic, continental) There are 3 types of plate boundaries Volcanoes and Earthquakes are closely linked to the margins of the tectonic plates
EXTRA SLIDES NOT USED
Plate boundaries quiz ( white text) 1. Which diagram shows a convergent boundary? 2. Which is a divergent boundary? 3. Which is a transform boundary? x/student/chapter8/08f21.html ABC
4. Which forms trenches? B 5. Which forms a spreading ridge? A 6. Which form volcanic mountain ranges? B 7. Which show subduction? B 8. Which show new rock being formed? 9. Which form a rift valley? _____ A ABC ABC
Pg 235 Questions 1. What is Plate Tectonics? a. What is plate tectonics? The study of the formation and movement of the plates that make up the lithosphere. b. Identify the plates that are moving apart: RIDGE with a RIFT VALLEY (African plate and South American) (North American and the Eurasian plate) moving together or colliding: TRENCH (Nazca plate and South American plate) sliding past each other: FAULT (Pacific and North American)
2. a. Describe the structure and properties of the lithosphere. The lithosphere is made of solid rock. It makes up the crust. b. How are the composition and density of continental crust different from that of the rest of the lithosphere? The continental crust is made of mostly granite and is less dense then the oceanic crust which is made of mostly basalt.
3. a. Where is the asthenosphere? The upper mantle / below the solid lithosphere. A layer within the mantle that is thought to cause plate movement. b. What is the major property of the asthenosphere? It can move very slowly because it is “partially melted”. c. How do the lithospheric plates move where convection currents are rising? Apart, new material comes to surface. d. How do the plates move where convection currents are sinking? Together
Geohazards and plate boundaries LocationEarthquakesVolcanoesBoundary type Conclusion Peru Convergent with subduction Kuril Islands near Japan Convergent with subduction San Andreas Fault near San Francisco +++++Transform Iceland++++++Divergent Aleutian Islands Convergent Himalayan Range Convergent Contients New Zealand++++ Transform