Plate Tectonics and Layers of the Earth Ch p. 270 – Earth Standards: S6C1:PO2, PO3, PO4 S6C2: PO3, PO4, PO5

Plate Tectonics Launch Lab! You will be working with the person sitting next to you. I will pass out a picture to you and your partner. Make sure no one other than the two of you sees which picture you received. You need to cut the picture up into pieces. Make sure that each piece has a shaped edge…you cannot just cut it into squares. Once you have cut your picture into pieces, trade with the other group at your table. Complete the puzzle using different strategies. Be ready to explain which strategies you used to solve the puzzle.

What I think I know About plate Tectonics, Earthquakes and Volcanoes: Facts (what I definitely know) about plate tectonics, Earthquakes and volcanoes: New information About plate tectonics, Earthquakes and volcanoes:

Background Information: Layers of the Earth The Earth is made up of several layers that have different properties and compositions. There are three main layers: –Crust –Mantle –Core (inner and outer) The lighter materials are the outermost layer, and the heavier materials are the inner, deeper layers.

1) Crust: - Outermost layer - Floats on top of the mantle - Less than 1% of the Earth’s mass - Ranges from 5 to 60 km thick – thinnest layer - We know most about this layer. Why? Two types of crust on Earth: Continental Crust - Similar to granite - Between 20 – 60 km thick Oceanic Crust - Similar to basalt – more dense than granite - Between 5 – 8 km thick Both types of crust contain many tectonic plates that float on top of mantle

2) Mantle: –Layer between the crust and the core –About 67% of the Earth’s mass –2,885 km thick –No one has seen mantle layer – too deep to drill to get sample –Some places on Earth, mantle rock has been pushed through surface Molten rock from mantle layer flow from volcanoes on ocean floor –Made up of mostly iron (Fe) and magnesium (Mg) Mantle contains 2 main layers: –Upper Mantle Base of crust to depth of 660 km –Lower Mantle Depth of 660 km to 2225 km Crust and top of Upper Mantle together are called the Lithosphere About 100 km thick Contains area of earthquakes, mountain building, volcanoes and continental drift Just below Lithosphere is area called Asthenosphere –About 100 – 200 km thick

3) Core: - About 33% of Earth’s mass - 6,972 km in diameter - Made up of mostly iron (Fe) and nickel (Ni) - Contains 2 layers: - Inner Core – center of Earth - Solid - Outer Core - Liquid - Surrounds Inner Core The planet Mars is actually smaller than the core of Earth (Mars = 6,787 km)

Continental Drift : hypothesis that states that the continents have moved slowly to their current locations on Earth In 1912, Arthur Wegener suggested that all the continents were connected as one land mass Large land mass of all the connected continents was called: Pangaea = “ all land” Suggested Pangaea broke apart about 200 million years ago Hypothesis wasn’t accepted until after Wegener died in 1930 Puzzlelike fit of continents was Wegener’s first evidence for Continental Drift

Fossil Evidence of Continental Drift: - Fossils from the reptile Mesosaurus were found in South America and Africa - Unlikely to swim between continents - Wegener thought reptile covered both continents during Pangaea period - Fossils from fernlike plant Glossopteris - Found in Africa, Australia, South America and Antarctica -Wegener thought this showed continents had to be connected at one point in time = Pangaea Climate Evidence of Continental Drift: - Fossils of warm weather plants were found on island in Arctic Ocean - Wegener thought island drifted from tropic regions - Glacial deposits and grooved bedrock on South America, Africa, India, and Australia - Shows they were once covered with glaciers - No glaciers exist in those areas today Wegener thought they were all connected near the Earth’s south pole at one time

Rock Evidence of Continental Drift: –If continents were connected as Pangaea, shouldn’t rocks be similar on different continents?… YES! –Similar rock structures and types of rocks are found on different continents –Appalachian Mountains (below left) in eastern United States are similar to mountains in Greenland and Western Europe (below right) –South America and western Africa have similar rock structures

- Wegener had some good evidence for Continental Drift… But… the big questions of how, exactly when or why this happened still weren’t answered. - Most people rejected his idea of Continental Drift - After Wegener’s death, more clues were found to support Continental Drift. - New idea… SeaFloor Spreading, helped explain how the continents could move. - Proposed by Harry Hess in 1960’s - SeaFloor Spreading : as hot, less dense material is forced up through the Earth’s crust in an opening called a mid-ocean ridge, it turns and flows sideways, carrying the seafloor away from the ridge in both directions This would cause continents to move away from each other

Evidence for SeaFloor Spreading: Movement of sea floor –Process of seafloor spreading… Age evidence: –1968 – research ship – Glomar Challenger – gathered samples of sea floor rocks –Checked age of rocks –Rocks on sea floor – near mid-ocean ridge – were 180 million years old or younger –Rocks away from mid-ocean ridge – near continents – some were almost 4 billion years old –WHY?

Magnetic Clues: - Magnetic field of Earth has a North and South pole - Magnetic force leave at the south pole and enter at the north pole - During a magnetic reversal – the magnetic forces run in opposite way - Reversal has happened many times in past - Iron bearing minerals – magnetite, which is in basalt, record Earth’s magnetic field direction - Rocks show the effects of the reversal – new iron minerals are formed - Magnetometer records magnetic data - Magnetic alignment in the rocks reverses back and forth over time – these match and are parallel with mid-ocean ridges Why is this Important? – it shows new rock was being formed at the mid- ocean ridges

Plate Tectonics: (pg. 280) Seafloor spreading let scientists know what was happening with the crust and upper mantle It also showed that there was more than just continents moving… –Larger sections were moving 1960 – scientists developed a new theory that put continental drift together with seafloor spreading Theory of Plate Tectonics: Earth’s crust and upper mantle are broken into sections… theses sections – called plates, move around on a layer of the mantle Which layer are the plates a part of?

What causes Plate Tectonics? - Process of heating and cooling, which causes movement of particles is called convection current - Hot particles rise, cool particles lower… - Continuous process keeps particles moving… creates energy - These convection currents provide energy that moves plates Effects of Plate Tectonics: Plates are constantly interacting with other plates… What does this do to the Earth? - Forms mountain ranges, volcanoes, faults, rift valleys

Three types of plate boundaries: (pg. 281) 1) Boundary between plates that are moving apart = divergent boundary 2) Boundary between plates that are moving together = convergent boundary. - Area where one plate goes down into the mantle is called the subduction zone. - Volcanoes usually form near convergent boundaries when the rock melts or mountains can form when two plates collide and crumple up. 3) Boundary where plates are sliding past each other = transform boundary