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

CONTINENTAL DRIFT & PANGAEA In 1912, Alfred Wegener proposed Pangaea- long time ago all continents were one land mass His evidence: 1. Continent’s fit together like a puzzle 2. rocks and fossils, mountain chains, and glacial marks on different continents matched Continental Drift –Wegener’s theory that the continents were once joined together in a supercontinent call Pangaea that has since moved apart His Theory of Continental Drift was dismissed because he could not explain how or why the plates moved. As a German meteorologist, he lacked credentials, and he couldn’t explain how huge continents could move.

Layers of Earth Compositional Properties: 1. Crust – solid, rocky outermost surface 2. Mantle – plastic-like (deforms) Mg & Si 3. Outer Core – hot, liquid Fe & Ni 4. Inner Core – hot (hotter than the surface of the sun), solid Fe & Ni Physical Properties: 1. Lithosphere – rigid, crust & upper mantle 2. Asthenosphere – asphalt-like upper mantle (flows)

In the early ’60’s, Harry Hess and J In the early ’60’s, Harry Hess and J. Wilson, proposed a mechanism for continental movement, which eventually became known as Seafloor Spreading 1969 - The Glomar Challenger drilled a series of holes in the Mid-Atlantic ridge. What they found revolutionized geology and oceanography! NOAA

Continental rocks date the Earth at about 4. 6 billion years old Continental rocks date the Earth at about 4.6 billion years old. Since the ocean floor is lower in the lithosphere, scientists expected to find older rocks at those depths. Continental geology’s Law of Superposition states that oldest rocks are laid down first and should be found horizontally lowest in a bed unless uplifted.

Instead, they found no rock older than 200 million years old and most were much younger. How could the ocean floor be younger than the continents riding on it? The Deep Sea Drilling Project showed that rocks became older as they moved away from the Mid Ocean Ridge (MOR). Oceanic geology showed rock layers are created vertically - not according to the Law of Superposition.

Theory of Seafloor Spreading 1960s – Seafloor Spreading – theory proposed that new ocean crust forms at ocean floor as plates move apart, and causes continents to move. Powered by the convection currents of magma in the mantle Link

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

The MOR seemed to be a parallel distance from continents on either side. Core samples revealed matching magnetic stripes in rocks on both sides of MOR. In 1977, Project FAMOUS, using Alvin, photographed magma squeezing out of the MOR and creating new ocean floor. Scientists, Vine and Matthews, now had the data for a cohesive theory on plate tectonics. The sea floor was spreading - moving the continents with it. The theory of sea floor spreading explained continental drift. Wegener was right.

PLATE TECTONICS - TO BUILD Earth’s lithospheric crust: - is divided into large and small plates - makes up the ocean crust AND the continental crust, along with the upper mantle - these plates move THEORY OF PLATE TECTONICS – Earth’s crust and upper mantle is broken up into lithospheric plates that move relative to each other The oceanic crust averages 5 km (3 mi) thick The continental crust averages 20-50 km (12-30 mi) thick Both are relatively thin

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

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

Tectonic Plate Boundaries and Movement These are the major plates: North American, South American, Pacific, Eurasian, African, Nazca, Indo-Australian, and Antarctic

Tectonic Plate Boundaries and Movement

Evidence for Plate Movement Age of Sea Floor Crust – The crust near a MOR is the youngest and gets older as you move farther away from the ridge - the oldest seafloor is about 260 million years (the oldest continental crust is 4.4 billion years old)

EVIDENCE FOR PLATE MOVEMENT – SEA FLOOR CRUST Oldest continental crust is 4.4 billion years old Oldest oceanic crust is 260 million years old and gets older away from MOR Why the difference? New seafloor is created at MORs and destroyed at trenches

Evidence for Plate Movement 2. Magnetic Strips of Rock– The positions of the north pole switches every 5 million years or so (recently every 200-300K years).

EVIDENCE FOR PLATE TECTONICS – MAGNETIC PATTERNS Pattern of reverse & normal polarity in ocean floor rocks As seafloor cools – the iron 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

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

EMPEROR SEAMOUNT CHAIN – YELLOW ARROWS SHOW PLATE MOVEMENT

Types of Plate Boundaries Description Example? Where two plates move apart Oceanic Ridges Continental Rifts Where two plates are pushed together Oceanic Trenches Continental Mountains Where two plates move past one another San Andreas Fault in California

TYPES OF PLATE BOUNDARIES 1. Oceanic-Oceanic Divergent Boundary - 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.

2. Continental-Continental 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

c. The result is that edges are forced up into mountains. 3. Continental-Continental Convergent Boundary - meaning to come together a. both plates are granitic - a type of igneous rock (silicon and aluminum) b. plates have the same lower density rocks – so neither plate will subduct c. The result is that edges are forced up into mountains. ex: Himalayas, Atlas Mountains, Appalachians NASA

4. Oceanic-Continental or Oceanic-Oceanic Convergent Boundary - a subduction zone where one plate overrides and the other is forced down into the mantle 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

Set Up Your Marinego Board -YOU MUST GET 6 in a row 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 SONAR Southern Ocean Thinner Trench Hawaiian islands Volcanoes & Earthquakes Younger