The Theory of Plate Tectonics Chapter 7 Section 3

A. The Theory of Plate Tectonics The Earth’s lithosphere (crust and upper mantle) is divided into tectonic plates. These plates move on top of the asthenosphere. We know that these plates move in different ways.

Tectonic Plates

B. Tectonic Plate Boundaries 1.A boundary is a place where tectonic plates touch. There are 3 types of tectonic plate boundaries: Convergent- move toward each other Divergent- move away from each other Transform- move past each other

The numbers on the map represent the rate at which plates are moving in centimeters.

Plate Movement

C. Convergent Boundary When two plates collide, or move toward each other, the boundary is called convergent There are 3 types of convergent boundaries, depending on what type of crust comes together. Continental-continental-mountains form Continental-oceanic- subduction zone-volcanoes Oceanic-oceanic- subduction zone- volcanoes

D. What forms at a Convergent Boundary? 1. Continental meets continental 2. MOUNTAIN RANGES form

E. What forms at a Convergent Boundary? oceanic crust sinks below the continental crust and sinks or oceanic plate sinks below another oceanic plate. 2. This is a subduction zone/volcano forms

F. What forms at a Divergent Boundary Two tectonic plates move away from each other. On the sea floor at the mid-ocean ridge this is called sea floor spreading. As the plates move apart, magma rises to fill the gaps. The magma is cooled and forms new ocean floor. The volcanic country of Iceland, which straddles the Mid-Atlantic Ridge, offers scientists a natural laboratory for studying on land the processes also occurring along the submerged parts of a spreading ridge. Iceland is splitting along the spreading center between the North American and Eurasian Plates, as North America moves westward relative to Eurasia.

Mid Ocean Ridge- Atlantic Ocean

Divergent Boundary Sea Floor Spreading On-land exposure of the Mid-Atlantic Ridge in Iceland. Sea Floor Spreading

G.What forms at a Transform Boundary? Two tectonic plates move past one another. As they grind together and jerk, they slide past each other creating earthquakes. EX: San Andreas Fault

Transform Boundary

H.Possible Causes of Plate Movement Convection Currents: hot rock deep in the Earth rises, cooler rock sinks. The rising and sinking of magma pushes and pulls on plates causing them to move. http://my.hrw.com/sh/hz5/0030289211/student/ch07/sec03/qc01/hz507_03_q01fs.htm

Tracking Tectonic Plate Movement Plates move very slowly, centimeters to inches a year. GPS, Global Positioning System, measures the rate of movement. Radio signals beam continuously from satellites to the Earth. By recording the time it takes for the Ground station to move a given distance, scientists can measure the speed at which plates move. Plate Boundary Animation http://www.classzone.com/books/earth_science/terc/content/visualizations/es0804/es0804page01.cfm?chapter_no=visualization http://wwnorton.com/college/geo/earth4/animations.aspx