INTRO TO CONTINENTAL DRIFT…SORT OF  https://www.youtube.com/watch?v=TzzGPfVx32M (2.5 min)

Plate Tectonics, part III Pangea Continental Drift Seafloor Spreading Magnetic Reversals Hot spots Sinkholes

PANGAEA Scientist Alfred Wegener noticed that Earth’s continents seemed to fit together like a puzzle, so he hypothesized that they were once joined in a single “super continent” called Pangaea

255 MILLION YEARS AGO

152 MILLION YEARS AGO

66 MILLION YEARS AGO THE EXTINCTION OF THE DINOSAURS

PRESENT DAY POSITION

50 MILLION YEARS FROM NOW

150 MILLION YEARS FROM NOW

250 MILLION YEARS FROM NOW

CONTINENTAL DRIFT This led to his Theory of Continental Drift – that although the continents were once joined, they slowly drifted apart! But nobody believed him  Wegener’s Evidence: 1. Matching rock layers on different continents 2. Matching fossils on different continents 3. Evidence of climate change – tropical plant fossils in cold places, ice scratches in warm places

SEA-FLOOR SPREADING http://www.youtube.com/watch?v=GyMLlLxbfa4 (4 min) Harry Hess’ discovery turned the Theory of Continental Drift into the Theory of Plate Tectonics!

SEA FLOOR SPREADING The sea floor spreads apart at divergent boundaries allowing new crust to form…this new crust builds Mid-Ocean ridges The crust closest to the crack is the youngest while the crust further from the crack is older This led to the development and understanding of plate tectonics!

MAGNETIC REVERSALS Minerals in the magma that rise through the cracks in the sea floor align themselves with Earth’s magnetic poles (North and South) As the rock cools, the minerals stay fixed in this position, like a compass Earth’s poles periodically reverse. The “stripes” of rock along the ocean floor record these reversals.

QUICK REVIEW What is the former “supercontinent” called? The idea that the continents had slowly moved is called…? Who was the scientist that proposed the idea of Continental Drift? What did he use as evidence to prove his theory? What LAND FORM was later discovered on the ocean floor that supported his theory?

QUICK REVIEW How is this land form created? This discovery turned the Theory of Continental Drift into the Theory of…? We further discovered that the oldest crust was located…? And the youngest crust was located…? Not only were there age patterns, but patterns of what else? Which scientist is responsible for the discovery of the Mid-Ocean Ridge & Sea-Floor Spreading?

REMEMBER… It is the movement of the tectonic plates that cause the majority of changes on Earth. Some changes happen quickly, while others happen slowly, but none have been more Earth changing than this… HOW?

HOT SPOTS!

HOT SPOT VIDEOS How was Hawaii formed? (history.com) (3min) http://www.history.com/topics/us-states/hawaii/videos/how-was-hawaii-formed Hawaii’s Hotspot (3 min) https://www.youtube.com/watch?v=bYv6V5EJAKc Underwater volcano eruption (2 min) http://www.youtube.com/watch?v=HrKTuCDierM

HOT SPOTS Hot spots occur far from plate boundaries. Magma rises and eventually melts through the crust above it. The plate moves, but the hot spot stays in the same place - creates a series of volcanic islands or volcanoes. Hot spots help measure plate movement.

HOT SPOTS! – Review What is the Earth’s lithosphere made up of? Where can a volcano form? What plate are the Hawaiian Islands on? Are they at a plate boundary or a hot spot? What is a hot spot? Does a hot spot move? So what is moving? How many islands has this hot spot formed to make the Hawaiian Island chain? Where are there other hot spots?

Plate tectonics & Hot spots – Review Explain the difference between continental drift and seafloor spreading? CD—comes from looking at the shape of continents and how they fit together SS—comes from sonar readings and learning about the mid-ocean ridges What are hotspots? Weaknesses in the crust where magma plumes rise up and cause volcanic activity, sometimes even islands.

SINKHOLES http://www.youtube.com/watch?v=RUjo3K_00tY (3:43 min) Would you categorize them as a fast change, a slow change, or both? They seem to be getting more common…WHY?

KEY VOCABULARY TERMS Crust Mantle Outer Core Inner Core Lithosphere Asthenosphere Convection Current Magma/Lava Law of Uniformitarianism Tectonic Plates Subduction Divergent Boundary Convergent Boundary Transform Boundary Mid-Ocean Ridge Rift Valley Deep-ocean Trench Pangaea Continental Drift Sea floor Spreading Magnetic Reversal Hot Spot

“CONTINENTS ADRIFT” Conclusion Plate Tectonics & Continental Drift (26 min) http://www.youtube.com/watch?v=HrKTuCDierM

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