CHAPTER TEN PLATE TECTONICS

Background Information  The Earth is made up of several layers that have different properties and compositions.  There are three main layers:  Crust  Mantle  Core (inner and outer) Layers of Earth

Section 1: Continental Drift  Alfred Wegener (German meteorologist)  Suggested that all the continents were joined together at some times in the past  1912: he proposed the hypothesis of the continental drift which explains that continents have moved slowly to their current locations over time  Pangaea (“all land”) is the name he gave to the large land mass that he believes existed over 200 million years ago Evidence of Continental Drift

Section 1: Continental Drift Evidence of Continental Drift

Section 1: Continental Drift  Evidence of Continental Drift  Fossil The reptile Mesosaurus was found in South America and Africa Fossils from a fernlike plant Glossopteris was found in Africa, Australia, South America and Antarctica  Climate Fossils of warm weather plants were found on an island in Arctic Ocean Glacial deposits and grooved bedrock were found on South America, Africa, India, and Australia Evidence of Continental Drift

Section 1: Continental Drift  Rock Similar rock structures and types of rocks are found on different continents Appalachian Mountains (below left) in eastern United States are similar to mountains in Greenland and Western Europe (below right) South America and western Africa have similar rock structures Evidence of Continental Drift

Section 2: Seafloor Spreading  Harry Hess (1960 )  Proposed the new idea of seafloor spreading to explain how the continents could move.  Seafloor spreading is when a hot, less dense material is forced up through the Earth’s crust in an opening called a mid-ocean ridge, it turns and flows sideways, carrying the seafloor away from the ridge in both directions. Mapping the Ocean Floor

Section 2: Seafloor Spreading  Evidence for Seafloor Spreading :  Age evidence: Rocks on sea floor – near mid-ocean ridge – were 180 million years old or younger Rocks away from mid-ocean ridge – near continents – some were almost 4 billion years old  Magnetic evidence: Scientists found that rocks on the ocean floor show many periods of magnetic reversal. Mapping the Ocean Floor

Section 3: Theory of Plate Tectonics  Seafloor spreading let scientists know what was happening with the crust and upper mantle.  1960 – scientists developed a new theory that put continental drift together with seafloor spreading.  Theory of Plate Tectonics: Earth’s crust and upper mantle are broken into sections. Theses sections – called plates, move around on a layer of the mantle. Plate Tectonics

Section 3: Theory of Plate Tectonics  Plates are made of the crust and a part of the upper mantle.  The lithosphere is a rigid layer that is generally less dense than material that is underneath.  The plastic-like layer below the lithosphere is called the asthenosphere. Plate Tectonics

Section 3: Theory of Plate Tectonics  3 kinds of plate boundaries:  Divergent Boundary: boundary between plates that are moving apart Plate Boundaries

Section 3: Theory of Plate Tectonics  3 kinds of plate boundaries:  Convergent Boundary: Boundary between plates that are moving together Area where one plate goes down into the mantle is called the sub-duction zone. Volcanoes usually form near convergent boundaries when the rock melts or mountains can form when two plates collide and crumple up. Plate Boundaries

Section 3: Theory of Plate Tectonics  3 kinds of plate boundaries:  Transform Boundary: boundary where plates are sliding past each other. Plate Boundaries

Section 3: Theory of Plate Tectonics  Process of heating and cooling, which causes movement of particles is called convection current.  Effects of Plate Tectonics:  Plates are constantly interacting with other plates.  Forms mountain ranges, volcanoes, faults, rift valleys Causes of Plate Tectonics