Good Afternoon! Please get your science notebook and get out your plate boundaries map and worksheet from Friday.

Chapter 9: Plate Tectonics Review

Layers of the Earth

From the Earth’s Crust to the Inner Core: Depth Increases Pressure Increases Temperature Increases Layers of the Earth Temp. (°C) Elements Crust 0- 860 Oxygen, silicon Mantle 870 Iron, magnesium Outer Core 2200 Iron, nickel Inner 5000 iron

Lithosphere The cool, rigid layer of the crust and upper most solid mantle. This layer is broken down into several large tectonic plates.

Asthenosphere The asthenosphere is the semi-rigid part of the middle mantle that flows like hot asphalt under a heavy weight. The tectonic plates float on this semi-liquid layer.

Lithosphere vs. Asthenosphere Lithosphere= rigid Asthenosphere= semi-soft

Convection Currents in the Mantle According to scientists, convection currents is the driving force behind the movement of the Earth’s plates.

Convection Heated water is less dense therefore rises while cooled water is more dense, which sinks. This is also true with air and other fluids.

Alfred Wegener’s hypothesis on Continental Drift All the continents had once been joined in a single landmass, called Pangaea, and have since drifted apart. Evidence from Landform Evidence from Fossils Evidence from Climate

Evidence of Continental Drift A mountain range lines up between Argentina in South America and Africa. Fossils of the reptiles Mesosaurus and Lystrosaurus have been found in places now separated by oceans. Fossils of the fernlike plant, Glossopteris, have been found in rocks in Africa, South America, Australia, India, & Antarctica. Deep scratches in rocks show that continental glaciers once covered South Africa.

Pangaea A supercontinent, meaning “all lands”, that existed about 300 million years ago.

Sea-Floor Spreading Theory As the plates diverge, molten material rises from the mantle and erupts along the mid-ocean ridge. Image: A diver swims between the Eurasian and North American plates in Thingvellir lake, Thingvellir National Park, Iceland. Iceland is one place where a mid-ocean ridge can be seen on land and in shallow waters.(credit: Wild Wonders of Europe/Lundgre http://www.bbc.co.uk/science/earth/surface_and_interior/mid_ocean_ridge

Plate Tectonics Theory Geological theory that states that pieces of Earth's lithosphere are in constant, slow motion

Divergent Boundaries Plate boundary where 2 plates move away from each other. Is the result of new ocean floor, such as the mid-ocean ridge and rift valley’s on land.

Convergent Boundaries Two plates move towards each other and collide. The result can be an ocean trench, volcanic island arc, volcanoes, and folded mountains.

Cause of Deep Ocean Trenches When an ocean plate collides with a continental plate, the plate is subducted under the continent. Subduction – when one tectonic plate (oceanic) is pushed underneath another tectonic plate.

Folded Mountains When 2 continental plates collide, folding mountains occur Himalayans from space

Transform Boundaries Plate boundary where two plates slip past each other, moving in opposite directions. Earthquakes frequently occur along these boundaries. Creates a fault

Earthquakes Occur usually when 2 plates slide past each other, however, can happen at all plate boundaries. Release of energy when the lithosphere suddenly breaks and slides

Ring of Fire Volcanoes form where tectonic plates meet other plates.