Continental Drift Theory Weatherman Scientist Researcher Professor Crazy Person? Geophysicist Alfred Wegener (1880-1930)

Sea-floor spreading responsible for driving continents apart, as well as convection currents. Newer rocks found on the ocean floor near these ridges than the continents. Harry Hess scientist who explaned sea floor spreading During WWII, submarines were used to explore the ocean floor in order to patrol for underwater missile strikes.

Do demo of continental drift The Earth’s upper mantle is where convention currents cause tectonic plates to move.

Convection currents drive continental plates to move Convection currents drive continental plates to move. Heat pushes the hot liquid mantle away from the Earth’s core towards the crust. As it cools, the liquid becomes denser, and sinks again, causing convection loops.

Major tectonic plates and the directions they are moving. By 1968 American geologists suggested solid plates move because they float on the liquid mantle beneath them. Forming Plate Tectonic Theory. Plates are composed of the lithosphere, the crust and top part of the mantle that is cooler and more rigid. Major tectonic plates and the directions they are moving. The plates move at the rate of your fingernails grow ing at 2.5 cm/year!

Challenge: Can you review the evidence of continental drift to predict what the Earth looked like 200 million years ago? With a partner… -Listen to the clues found in fossil records, rocks, landforms, plant/animal evidence to arrange the continents how they might have looked 200 mya -Consider if “Pangaea” or supercontinent theory has merit. What would it have looked like?

Continental “CLUES” Glossopteris fossils, an extinct seed fern, are found throughout India, South America, southern Africa, Australia, and Antarctica. Rocks in Europe and North America are the same age, and get progressively older as you move away from the ocean. Fossils of Lystrosaurus, a mammal-like reptile, have been found in Antarctica, India, and Africa. Mountains in Greenland and Norway have similar rock types and structure. The mountains of Scotland and the Appalachian mountains of North America are made of the same kind of rock

Continental “CLUES” cont’d Glacial scratches and varves (layered sediment deposits) from up to 200 mya, which are signs of how far a glacier extended, exist on every continent except Antarctica. Mesosaurus, fossils one of the first aquatic reptiles, have been found in South Africa and South America The geology of southern Senegal and the Amazon Basin are almost identical The paleomagnetic stipes or iron crystal patterns in the rocks of northern Brazil and central Africa are mirror images of each other. What other clues do you see? Think about what happens when plates collide. Camel fossils were found in North and South America, but living camels are only found in Asia, Africa, and the Middle East There are tropical plant fossils found at the poles

Fossil records and geologic similarities helped scientists piece together the continents’ position over 200 million years ago.

Pangaea Lives! I told you so! Ask kids how their supercontinent compares to Pangaea’s arrangment. Pangaea Lives!

Final Thoughts… Green Sea Turtles, some of the oldest reptiles in the world, spend their whole lives in the waters off the coast of Brazil, except to lay their eggs. Females travel 1,250 miles to make nests on a tiny island in the middle of the Atlantic Ocean, as their ancestors have been doing for millions of years. Can you explain how this behavior of the green sea turtles supports Continental Drift Theory? Above: Ascension Island off the coast of Brazil. Below: A Green Sea Turtle

When Plates Collide: Earthquakes What Happens? Where Can We See This? A building falls over during a Taiwan earthquake in 1999

When Plates Collide: Seafloor Spreading What Happens? Where Can We See This? The Mid-Atlantic Ridge runs north and south, separating North and South America from Europe and Africa and is over 10,000 mi long!

When Plates Collide: Island Arcs What Happens? Where Can We See This? Above Right: The Aleutian Islands in Alaska. Below Right: Hawaii

Plate Tectonics Time Lapse