Continental Drift 1912 – German Scientist Alfred Wegener Proposed that the world’s landmasses were once joined together There was once a supercontinent he named Pangaea

Theory of Plate Tectonics Lithosphere divided into plates & their movement produces changes in Earth’s surface Evidence to support the theory of Continental Drift Shape of the continents Mountain ranges Similarity of rocks Similarity of fossils

World Plates

What are tectonic plates made of? Plates are made up of the rigid lithosphere

What lies beneath the tectonic plates? The asthenosphere – liquid part of the mantle

Plate Movement Plates moved around by convection cells in the underlying hot mantle

Plate Boundaries The interface at which the plates interact The site of most of the major events involving Earth’s crust Mt. Building, Earthquakes, Volcanic Eruptions 3 major types: Convergent Divergent Transform

Plate boundaries

Convergent Plate Boundaries Plates come together Subduction The more dense plate goes under the less dense plate Trenches – deepest parts of the ocean Collision Two low density plates collide

Himalayas

Divergent Plate Boundaries Plates spread apart As plates move apart new material is erupted to fill the gap Occurs at mid-ocean ridges – Rift Valleys Sea Floor Spreading

Iceland Iceland has a divergent plate boundary running through its middle

Divergent Boundaries

Transform Plate Boundaries Plates slide past one another Ex. San Andreas Fault

Ocean Evidence Discovered in the 1950’s Oceanic crust age Heat Flow Increases as you move away from the ridges Rocks equidistant from the mid-ocean ridge in opposite directions are the same age Heat Flow Heat decreases as distance from ridges increases

Magnetic Reversals Earth has a magnetic field The field has a North & South Pole The position of these poles has reversed many times in the past

Magnetic Reversals

Visible Effects of Plate Tectonics Earthquakes Mountain Building Hot Spots Tsunamis Volcanoes

Hot Spots A location where hot plumes of magma flow out of the crust Located in the interior parts of plates Due to plate movement, this can create island chains Hawaii

Tsunami Large ocean wave Caused by a disruption of the ocean floor Earthquake Underwater volcano Underwater landslide

2004 Tsunami

Volcanoes Mountains composed of extrusive igneous rocks

Ring of Fire Region surrounding the Pacific Ocean