# 4.9: What drives plate motions?

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## What drives plate motions?

• Researchers agree that convective flow in the mantle is the basic driving force of plate tectonics (Figure 4.28).

Figure 4.28. Mantle convection is the driving force of motion of lithospheric plates. Much of the convection motion may be in the upper mantle, but it is likely to extend deep into the earth's molten outer core.

Forces that drive plate motion:
Slab-pull - the slow pull of mantle material where is moves from a rising location to a sinking location.
• Slab-suction - The high density of cold ocean crust sinking into the mantle pulls crust with it.
Ridge-push - new ocean crust is warm and tends to rise above the ocean floor, pushing older cooler crust away

Plate tectonics model explains many aspects of the geometry of continents and ocean basins and the processes creating new oceanic and continental crust. Material that does not become incorporated into the lithosphere sinks and becomes incorporated back into the mantle.

Importance of plate tectonics
• The theory provides explanations for many of earth’s major processes
• Explains the geologic distribution of earthquakes, volcanoes, and mountains
• Explains the distribution of ancient organisms and mineral deposits
• Plate tectonics are responsible large volumes of oil and gas deposits we enjoy today. Think about how your life and society would be different if we only had a mere fraction of the hydrocarbons we currently have and use.

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