Plate Tectonics EQ: How do lithospheric plates move and how do they affect the Earth’s surface?

An Idea Before its Time In 1912, Alfred Wegener proposed the idea of Continental Drift He suggested that all of the continents were once joined together to form a supercontinent

Pangaea Wegener called this super landmass Pangaea and believed that it broke apart 200 million years ago Pangaea means “all land” At first, his theory was not accepted Unable to explain how the continents drifted apart

Evidence down the Road Years later came important observations that supported Continental Drift Fossil Clues- similar fossils found in South America and Africa and others found in Africa, Australia, India, South America, and Antarctica.

Evidence down the Road Rock evidence- similar rock structures are found on different continents, such as this mountain belt that end at one coastline, only to reappear on a landmass across the ocean.

Evidence down the Road Climate Clues- glacier deposits and rock surfaces shows that parts of South America, Africa, India, and Australia were once covered with glaciers

Quick Check: What is Continental Drift? What 3 pieces of evidence support the idea of Pangaea? The idea that all of the continents were once joined together Fossils, Rock Clues (Mountains), and Glaciers

A New Theory Emerges Wegener could not provide an explanation of exactly what made the continents move. New technology lead to findings which then lead to a new theory called plate tectonics

This New Evidence… With new technologies, scientists discovered a mountain chain on the ocean floor known as the Mid-Ocean Ridge Mid-ocean ridges are underwater chains that run through Earth’s ocean basin The Mid-Atlantic Ridge, the longest mountain chain in the world

Seafloor Spreading Mid-ocean ridges are places where the sea-floor spreads As tectonic plates move away from each other, the seafloor spreads apart and magma rises to fill in the gaps The hot magma contacts ocean water, cools and hardens becoming new rock This process is known as Seafloor Spreading

Plate Tectonics The Theory of Plate Tectonics was developed in 1960s and combines the theories of Continental Drift and Sea-Floor Spreading. Scientist believe the Earth’s crust and part of the upper mantle is broken into 12 sections that make up the plates which move on top of the asthenosphere

Convection Currents Convection currents, originating deep within the mantle, provides the energy that drives plate tectonic These currents rotate in circular patterns, carrying heat upward http://www.absorblearning.com/media/attachment.action?quick=12p&att=2775

Plate Boundaries Divergent boundaries are the place where two plates move apart. Convergent boundaries form where two plates move together. Transform fault boundaries are where two plates slide past each other without the production or destruction of the lithosphere.

Convergent Boundary

Divergent Boundary

Plate Tectonic Discussion Questions: Explain why Wegener’s theory of Continental Drift was not accepted at first. Explain what is Plate Tectonics and what causes the movement of plate tectonics. What are the 3 plate boundaries and describe them.