1 Journal Question: If your finger nails grow at about a two inches per year, how long would it take for them to grow to be a mile? (hints: 12 inches in a foot, 5,280 feet in a mile) Answer: A nail will grow 1 foot in 6 years. 6 years multiplied by 5,280 feet is how long it will take to grow a mile… 6 x 5,280 = 31,680 years to grow a mile

2 CONTINENTAL DRIFT & PANGEA In 1912, Alfred Wegener proposed Pangea- long time ago all continents were one land mass His evidence: 1. Continent’s fit together like a puzzle 2. rocks and fossils on different continents matched Continental Drift –Wegener’s theory of how continents moved apart

3 1. Crust – solid, rocky outermost surface 2. Upper Mantle – Lithosphere: solid Asthenosphere: Syrup 3. Lower Mantle – Mesosphere: solid due to intense pressure 4. Outer core: Hot Liquid metal 5. Inner Core: Hot solid metal – hotter than surface of sun

4 1960s – Seafloor Spreading – theory proposed that new ocean crust forms at ocean floor as plates are pushed apart, and causes continental drift. -Powered by the convection currents of magma in the mantle Theory of Seafloor Spreading Link

5 Subduction Zone – Area where Lithospheric Plate descents into Asthenosphere. (think about it: if plates are spreading in one area, they must be coming together in another) Seafloor Spreading Link

6 Tectonic Plate Boundaries and Movement

7 JQ: Explain how the Theory of Plate Tectonics, Continental Drift, and Seafloor Spreading relate to one another.

8 1. Age of Sea floor crust – The crust near a spreading ridge is under 200 Million Years old, and gets older as you move farther away from the ridge (continental crust is 4.6 Billion years old) Evidence for Plate Movement

9 2. Magnetic Strips of Rock– The positions of the north pole switches over thousands of years. Ocean floor rock contains metal particles that show stripes of sea floor crust that alternate north and south direction. Layers formed vertically, not horizontally, like continental crust Evidence for Plate Movement

10 These are the major plates: North American, South American, Pacific, Eurasian, African, Nazca, Indo-Australian, and the Antarctic plate.

11 3. Hot Spots– Areas in Earth’s mantle that are hotter – can lead to chain of islands; as plate moves over hot spot, volcanic islands can be formed (ex: Hawaii) Evidence for Plate Movement Link The position of the hot spot in the mantel doesn’t change.

12 3Types of Plate Boundaries DescriptionExample? Where two plates move apart Where two plates are pushed together Where two plates move past one another Ridges Trenches San Andreas fault line in Cali

13 71% Abyssal Plain Atlantic Ocean Convection Currents Hot Spots Continental Drift Continental Margin Continental Rise Continental Shelf Continental Slope Alfred Wegener Subduction Guyot Ice comets & volcanoes Pangea Asthenosphere Lithosphere Major Ocean Basins Mantle Divergent Near Mid-Ocean Ridges Oceanic Ridge Older On Continents Pacific Ocean Recycled Sea Floor Spreading Continental Drift SONAR Southern Ocean Thinner Trench Hawaiian islands Volcanoes & Earthquakes Younger

14 By looking at seismic and volcanic activity around the world, scientists can identify the plate boundaries.

15 MORE EVIDENCE FOR PLATE TECTONICS Pattern of reverse & normal polarity in ocean floor rocks As seafloor cools – the minerals in the magma align with the current magnetic field Bands of seafloor rock alternating between normal and reverse polarity parallel MORs and are mirror images of each other

16 MORE EVIDENCE FOR PLATE MOVEMENT Oldest continental crust is 4.6 billion years old Oldest oceanic crust is 200 million years old and gets older away from MOR Why the difference? New seafloor is created at MORs and destroyed at trenches

17 MORE EVIDENCE FOR PLATE MOVEMENT HOT SPOTS Plumes of molten rock well up from deep within the mantle and forces its way up through the lithosphere to erupt in a volcano The plate moves over the hot spot creating a new volcanic island As the plate moves, old volcanoes are eroded, new volcanoes form

18 EMPEROR SEAMOUNT CHAIN

19 FOUR TYPES OF PLATE BOUNDARIES 1. Oceanic-Oceanic Boundary - divergent, meaning to move apart a. both plates are composed of basalt - the primary type of ocean floor rock (iron, magnesium and silicon ) b. both plates have the same higher density rock c. the result is a spreading center where new ocean floor is created ex: Mid-Ocean Ridge (MOR) This same ridge is 40,000 miles long and is found in many places in addition to the middle of the Atlantic Ocean.

20 2. Continental-Continental Boundary - divergent, meaning to move apart a. both plates are granitic - a type of igneous rock b. plates have the same lower density rocks c. The result is that continent is pulled apart and a rift valley forms – eventually becoming a new ocean ex: East Africa Rift Zone NASA

21 3. Continental-Continental Boundary - convergent, meaning to come together a. both plates are granitic - a type of igneous rock that is the basis of the rock cycle (silicon and aluminum) b. plates have the same lower density rocks c. The result is that edges are forced up into mountains. ex: Himalayas, Atlas Mountains NASA

22 4. Oceanic-Continental or Oceanic-Oceanic Boundary - a subduction zone where one plate overrides and the other is forced down into the mantle (convergent) a. lighter continental plate or oceanic plate overrides the denser oceanic plate b. oceanic plate edge is subducted down into the asthenosphere and remelted c. The result is a trench ex: Peru/Chile Trench USGS Chile Trench