Mantle convection drives seafloor spreading by causing hot mantle rock to rise, thin the lithosphere, and create cracks where magma erupts, pushing the seafloor apart.
The Process Explained:
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Mantle Convection: The Earth's mantle isn't solid; it's more like a very viscous fluid. Heat from the Earth's core and radioactive decay within the mantle causes convection currents – hot, less dense rock rises, while cooler, denser rock sinks.
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Rising Mantle Plumes: In certain areas, particularly at mid-ocean ridges, hot mantle plumes rise towards the surface.
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Lithospheric Thinning: As the hot mantle plume ascends, it heats the overlying lithosphere (the Earth's crust and the uppermost part of the mantle). This heat causes the lithosphere to thin and weaken.
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Cracking and Magma Eruption: The thinning and weakening of the lithosphere create cracks and fissures. The pressure from the rising mantle plume, combined with the weakened crust, allows magma (molten rock) to escape from the mantle into these cracks.
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Seafloor Spreading: The erupting magma solidifies, forming new oceanic crust. This newly formed crust pushes the existing crust aside, causing the seafloor to spread apart. This process occurs continuously over millions of years.
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Formation of Mid-Ocean Ridges: The continuous eruption of magma along the cracks creates elevated underwater mountain ranges known as mid-ocean ridges. These ridges mark the boundaries between tectonic plates that are diverging.
In Summary:
| Stage | Description |
|---|---|
| 1. Convection | Heat from the Earth's core drives convection currents in the mantle. |
| 2. Rising Plume | Hot mantle rock rises as a plume towards the lithosphere. |
| 3. Thinning | The hot plume thins and weakens the lithosphere above it. |
| 4. Cracking | Cracks form in the weakened lithosphere. |
| 5. Eruption | Magma erupts through the cracks, solidifying into new oceanic crust. |
| 6. Spreading | The new crust pushes the existing crust apart, causing seafloor spreading. |
In essence, mantle convection provides the driving force for seafloor spreading by delivering heat and magma to the lithosphere, causing it to crack and separate, leading to the continuous creation of new oceanic crust.
