Chapter 4 Section 3 Theory of Plate Tectonics
Language of the discipline lithospheric plate: a large brittle piece of Earth’s outer shell plate tectonics: theory that explains how lithospheric plate move and cause major geologic features and events on Earth’s surface ocean trench: long, deep parts of the seafloor Slab: plate that sinks back into the mantle Global Positioning System (GPS): a network of satellites used to determine locations on Earth
Language of the discipline continue…… • Convection: heat transfer by the movement of matter from one place to another • Define: to fix or mark the limits of
Earth’s Plates • Lithospheric platesare large brittle pieces of Earth’s outer shell. • The theory ofplate tectonicsexplains the movement of lithospheric plates.
Boundaries of Lithospheric Plates • Mid-ocean ridges show boundaries of some lithospheric plates . • Earthquakes and volcanoesoccur where the edges of plates are pushed together, pulled apart, or slide horizontally. • Ocean trenchesare the deep parts of the seafloor where numerous earthquakes and volcanoes occur. • Seafloor is formed at ridges and destroyed at ocean trenches.
Types of Lithosphere • Oceanic Crust: thinner than continental, made of dense igneous rock covered by a thin layer of sediment (sand & dirt) • Continental Crust: thicker than oceanic; made of igneous and metamorphic rock covered by sedimentary rock
What controls plate movement? • Some scientists believe that convection controls the movement of plates.
What controls plate movement? (cont.) • Temperature increases with increasing depth. • Radioactive decay is one important source of internal heat. • Heat increases the temperature of rock which decreases the density.
Plate Movement and Convection • Slabs are cooler, denser lithospheric plates that sink down into the mantle. • They bend and break as they sink down into the mantle, causing earthquakes.
Ridge Push and Slab Pull • Convection: Cooler, denser masses of rock sink, bringing plates with them. Less-dense rock is brought to the surface at mid-ocean ridges. • Ridge Push: The force of gravity moves the plate downward and away from the mid-ocean ridges. • Slab Pull: Gravity acts on denser plates, pulling them into the mantle.
Plate Movement • Global Positioning System (GPS)is a network of satellites using radio waves to determine locations on Earth. • Measures the movement of plates • Using GPS and satellite laser ranging (SLR), plate movement has been estimated at a few centimeters per year.
GPS & Satellite Laser Ranging in Plate Tectonics • GPS (Global Positioning System) is a network of satellites that uses radio waves to measure the direction and speed of plates as they move along Earth’s surface. • Satellite Laser Ranging (SLR) uses laser beams to measure the distances of plate movements.
Checking for Understanding • 1. What does the theory of plate tectonics explain? • 2. What two types of lithosphere make up Earth’s surface ? • 3. Why does the density of the surrounding rock decrease (Think slabs?) • 4. What are GPS? • 5. Use the term slab and ocean trench in a sentence. • 6. A method used to determine the rate of plate movement is ______. • 7. On the back of your paper draw a compare and contrasting thinking map of the following: Convection, Ridge Push, and Slab Pull.