Presentation on theme: "SECTION 17.4 CAUSES OF PLATE MOTION Earth Science 1."— Presentation transcript:
SECTION 17.4 CAUSES OF PLATE MOTION Earth Science 1
Objectives Explain the process of convection. Summarize how convection in the mantle is related to the movements of tectonic plates. Compare and contrast the processes of ridge push and slab pull. 2
Main Idea 3 Convection currents in the mantle cause plate motions. Convection is the transfer of energy via the movement of heated matter.
Vocabulary ridge push slab pull convection 4
Convection Many scientists now think that: large-scale motion in the mantle (Earth’s interior between the crust and the core) drives the movement of tectonic plates. Convection - the transfer of thermal energy by the movement of heated material from one place to another. 5
Convection 6 The cooling of matter causes it to: contract slightly and increase in density. The cooled matter then sinks as a result of gravity. Warmed matter is then displaced and forced to rise. This up-and-down flow produces a pattern of motion called A convection current.
Convection Currents 7
Convection in the Mantle Convection currents develop in the mantle move the crust move outermost part of the mantle transfer thermal energy from Earth’s interior to its exterior. 8
Convection in the Mantle The rising material in a convection current spreads out as it reaches the upper mantle causes both upward and sideways forces These forces lift the crust split the crust at divergent plate boundaries. 9
Convection in the Mantle 10 The downward part of a convection current occurs where A sinking force pulls tectonic plates downward Occurs at convergent boundaries.
Ridge Push Ridge push is the tectonic process associated with convection currents in Earth’s mantle that occurs when the weight of an elevated ridge pushes oceanic plates The force of the magma moving upward pushes oceanic plates the plates move toward a subduction zone. 11
Slab Pull 12 Slab pull is the tectonic process associated with convection currents in Earth’s mantle that occurs as the weight of the subducting plate pulls the trailing crust The plate is pulled into a subduction zone.
The Result 13 The convection currents in the mantle, in combination with ridge push and slab pull: Move the tectonic plates Causing Continental Drift Wegener was correct!!!!!