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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

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CONTINENTAL DRIFT & PANGEAIn 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

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Layers of Earth/Composition

1. Crust – solid, rocky outermost surface

2. Upper Mantle – Lithosphere: solidAsthenosphere: 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

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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

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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

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Tectonic Plate Boundaries and Movement

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JQ: Explain how the Theory of Plate Tectonics, Continental Drift, and Seafloor

Spreading relate to one another.

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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

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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

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

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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.

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3Types of Plate Boundaries

Description Example?

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

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71%Abyssal PlainAtlantic OceanConvection CurrentsHot SpotsContinental DriftContinental MarginContinental RiseContinental ShelfContinental SlopeAlfred WegenerSubductionGuyotIce comets & volcanoesPangeaAsthenosphereLithosphere

Major Ocean BasinsMantleDivergentNear Mid-Ocean RidgesOceanic RidgeOlderOlderOn ContinentsPacific OceanRecycledSea Floor SpreadingContinental DriftSONARSouthern OceanThinnerTrenchHawaiian islandsVolcanoes & EarthquakesYounger

Set Up Your Marinego Board-YOU MUST GET 6 in a row

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

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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

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MORE EVIDENCE FOR PLATE MOVEMENT

Oldest continental crust is 4.6 billion years oldOldest 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

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MORE EVIDENCE FOR PLATE MOVEMENT

HOT SPOTSPlumes 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

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EMPEROR SEAMOUNT CHAIN

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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 createdex: 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.

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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

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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 MountainsNASA

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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 trenchex: Peru/Chile Trench

USGS

Chile Trench