Continental Drift Pangaea super to Continental Drift name

Continental Drift • Pangaea super to • Continental Drift – name given to a continent that began break apart approximately 200 million years ago – Wegner’s hypothesis that suggests the continents are in constant motion on Earth’s surface

A Plate Tectonics Puzzle Solve the puzzle to discover what the Earth looked like 220 million years ago. 1. What’s the code? Use the legend to identify the symbols on each island or continent. 2. Puzzle me this. Look at the shapes of continents and islands. What landmasses seem to fit together? 3. Let’s rock! Examine the evidence and try to match up landmass boundaries that show similar rock strata, fossilized desert belts, and dinosaur fossils. 4. Hold that Pose. Look over the arrangement of the continents and islands and decide if the position of any of them should change. When you are satisfied with your map of Pangaea, tape or glue it down on the world map.

Drifting Continents Did Pangea Exist?

Alfred Wegner developed the hypothesis of Continental Drift using fossils, rocks and climate clues, but could not explain why the continents moved.

The Theory of Continental Drift • A German scientist named Alfred Wegener formed the hypothesis that the continents had moved! • In 1914 he proposed that all the continents had once been joined together in a single landmass and have since drifted apart.

The Theory of Continental Drift • Wegener’s idea that the continents slowly moved over the earth became known as continental drift. • Unfortunately Wegener could not provide a satisfactory explanation for the force that pushed or pull the continents. Therefore most geologists rejected his idea.

Evidence of Continental Drift • Evidence from landforms • Mountain ranges and other features on the continents provided evidence for continental drift. • Mountain ranges in South Africa line up with mountain ranges in Argentina.

Continents Fit Together Matching rock formations along the coasts Continents appear to fit together

Evidence for Continental Drift • Evidence from fossils • A fossil is any trace of an ancient organism that has been preserved in rock. • Glossopteris fossils have been found in rocks in Africa, South America, Australia, India, and Antarctica.

Fossil Patterns Across Continents

Fossil Patterns Across Continents

Evidence for Continental Drift • Evidence from climate • Fossils of tropical plants have been found too far south to have survived. • Glacier deposits are found too far north to have existed. • These clues provide evidence that continental drift really happened.

Glacial Continuity Across Continents Glacial Scratches on Bedrock

Rejection!! Even with the evidence, most scientists rejected Alfred Wegener’s theory for about a half a century, from the 1920 s to the 1960 s.

• Wegener’s hypothesis of Continental Drift was generally abandoned by the 1940 s because the movement of an entire continent seemed to be physically impossible • There Is No Mechanism for Continental Drift! • It was revived in the 1950 s because of accidental discoveries made during and after World War II

Ticket Out the Door • In 5 sentences – Explain what theory of Continental Drift is, what are the clues that lead Wegener to this theory and why it was rejected.

New Evidence Bathymetry of the Deep Ocean Floors Polar Wandering Magnetic Field Reversals Seismic Imaging

Read Pages 16 -24 • Read through the pages once • The second time you read through it you will be looking for questions that you have ask. • There are 4 types of questions you will develop 1. Right there – the answer is 100% in the text, the answer is easy to find, and it usually comes from one sentence in the text 2. Think and Search – the answer is in the text. It usually comes from different parts of the text, it maybe in a different sentence or even a different paragraph or page. You have to put information together in order to find the answer to the question. 3. Author and Me – The answer comes from the thinking about what you already know, thinking about what the author said, and thinking about how those 2 things go together 4. On My Own – Everyone who reads the text may have a different answer. Your answer comes from the opinion you have formed after reading the text; it is your judgment. The answer is not in the text.

The Earth is divided into 4 layers.

CRUST MANTLE INNER CORE OUTER CORE

The Crust • Layer of rock that forms Earths outer skin • Solid rock included both dry land ocean floor (rocks, mountains, soils, water) • Thin layer (similar to paper thin layer of an onion) • Ranges from 5 -40 km thick (70 km underneath mountains) • Basalt = oceanic crust • Granite = continental crust

Crust • The plates move along smoothly but sometimes they get stuck and pressure builds up.

Mantle • Rock that is very hot but solid at the same time. • Solid upper mantle and crust = lithosphere (100 km thick) • Under lithosphere = asthenosphere – So hot that it behaves like a plastic material; it flows

Mantle • The movement of the mantle create the movement of the Earth’s plates.

Outer Core • Liquid layer of iron and nickel • LOTS of pressure Inner Core • Dense solid metal • Extreme pressure (squeezes that atoms of iron and nickel so much they can’t spread out and become liquid)

Earth’s Magnetic Field • Currents in the liquid outer core force the solid inner core to spin. The inner core spins at a slightly faster rate than the earth’s rotation. Because of this movement, it causes Earth to act like a giant bar magnetic. The magnetic field protects us from the sun’s damaging UV rays.

Convection Currents • As liquid heats up, it becomes less dense and rises. When it is away from the heat source, it cools down and becomes more dense and sinks. Heat from the lower mantle and the cores (inner and outer) cause convection currents in the asthenosphere. Moves up Cools Down Heats Up Moves down Heat source

Writing Activity • Write a paragraph about the earth’s layers. Include facts from your notes. • 8 -11 sentences

Seafloor Spreading Notes *What is seafloor spreading? *What evidence is used to support seafloor spreading? • mid-ocean ridge • seafloor spreading • magnetic reversal • normal polarity • reversed polarity

Seafloor Spreading Notes *What is seafloor spreading? *What evidence is used to support seafloor spreading? • mid-ocean ridge • seafloor spreading • magnetic reversal • normal polarity • reversed polarity - mountain range located on the seafloor in the middle of the ocean - new oceanic crust forms at a mid-ocean ridge as - old oceanic crust moves away from the ridge - event in which the magnetic field reverses direction - today’s magnetic field; magnets orient themselves to point north - magnetic field in - which magnets orient themselves to point south

Draw and label the diagram representing seafloor spreading and subduction zones • Basalt • Granite • Oceanic crust • Continental crust • Divergent boundary • Convergent boundary • Mid-ocean ridge • • • Trench Volcanic arc Oldest rock Newest rock Seafloor spreading Subduction zone Convection currents Mantle Magma

Draw and label the diagram representing seafloor spreading and subduction zones • Basalt • Granite • Oceanic crust • Continental crust • • Divergent boundary Convergent boundary Mid-ocean ridge Trench Volcanic arc Oldest rock Newest rock • • Seafloor spreading Subduction zone Convection currents Mantle

Seafloor Spreading Cut and paste the diagram representing seafloor spreading and subduction zones Basalt Granite Oceanic crust Continental crust Divergent boundary Convergent boundary Mid-ocean ridge Trench Volcanic arc Oldest rock Newest rock Seafloor spreading Subduction zone Convection currents Mantle

Process of Seafloor Spreading 1. At the mid ocean ridge molten material comes up from the mantle, cools, hardens and becomes new crust 2. The new crust spreads out and pushes the old rock to the sides in a continuous process 3. When older oceanic crust reaches a continental crust the more dense oceanic plate is subducted down and forms a trench on the surface. 4. The older crust melts back into the mantle and is recycled by convection currents

What are the 4 steps in sea floor spreading?

The Rock Cycle

Earth’s Magnetic Field • Earth is a gigantic magnet surrounded by a magnetic field • Dipole (bar magnet) • Source is the liquid outer core – Molten iron in the liquid outer core flows around the solid inner core • Unlike bar magnet the Earth’s field changes over time

Plate Tectonics • The technologies developed as a result of World War II lead to the hypothesis of plate tectonics and an explanation of how they move • Wegener was right the continents do move

Plate Tectonics • Plate Tectonics was accepted in the scientific world 1965 -1967 • It is a young scientific theory less than 50 years old!

Plate tectonics – theory that states that pieces of the lithosphere are in constant slow motion driven by convection currents in the mantle

Convergent Boundaries • Two plates collide • The denser plate sinks below the more buoyant plate in a process called subduction. Examples – Ocean-Continent: Cascade Mountains (Mt. St. Helens, Mt. Rainier), Andes Mountains – Continent-Continent: Himalayan Mts. – Ocean-Ocean: Lesser Antilles

Divergent Boundaries • Two plates separating Examples – Ocean-Ocean: Mid-Ocean Ridge – Continent-Continent: Eurasian Plate, African Rift Valley

Transform Boundaries • Two plates slide horizontally past one another Examples – Continent-Continent: San Andres Fault – Ocean-Ocean: East Pacific Rise

Plate Boundaries Foldable

Forces That Shape the Earth pg 222 -228 *How do continents move *What forces can change rocks *How does plate motion affect the rock cycle? • Isostasy • Subsidence • Uplift • Compression • Tension • Shear • strain

Rocks Climate Clues Fossils

What is Plate Tectonics? • Continental Drift – Tell me about them - 3 types of clues (fossils, rocks, climate clues) • Interior of the Earth (layers) • Seafloor spreading • Plate boundaries – Where they are – How they move

• In the early 1900 s Alfred Wegener set forth his continental drift hypothesis. One of its major tenets was that a supercontinent called Pangaea began breaking apart into smaller continents about 200 million years ago. The smaller continental fragments then "drifted" to their present positions. To support the claim that the now-separate continents were once joined, Wegener and others used the fit of South America and Africa, distribution of ancient climates, fossil evidence, and rock structures. • One of the main objections to the continental drift hypothesis was its inability to provide an acceptable mechanism for the movement of continents. • The theory of plate tectonics, a far more encompassing theory than continental drift, holds that Earth's rigid outer shell, called the lithosphere, consists of seven large and numerous smaller segments called plates that are in motion relative to each other. Most of Earth's seismic activity, volcanism, and mountain building occur along the dynamic margins of these plates. • A major departure of the plate tectonics theory from the continental drift hypothesis is that large plates contain both continental and ocean crust and the entire plate moves. By contrast, in continental drift, Wegener proposed that the sturdier continents "drifted" by breaking through the oceanic crust, much like ice breakers cut through ice.

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