SECTION 17.4 CAUSES OF PLATE MOTION Earth Science 1.

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SECTION 17 .4CAUSES OF PLATE MOTION

Earth Science

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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.

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Main Idea

Convection currents in the mantle cause plate motions.

Convection is the transfer of energy via the movement of heated matter.

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Vocabulary

ridge push

slab pull

convection

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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.

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Convection

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.

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Convection Currents

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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.

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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.

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Convection in the Mantle

The downward part of a convection current occurs where A sinking force pulls

tectonic plates downward

Occurs at convergent boundaries.

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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.

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Slab Pull

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.

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The Result

The convection currents in the mantle, in combination with ridge push and slab pull:Move the tectonic platesCausing Continental DriftWegener was correct!!!!!