Sea-Floor Spreading

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Henry Hess studied the ages of rocks on the Atlantic Ocean seabed and discovered that rocks were youngest at the Mid-Atlantic Ridge, becoming older further from the ridge. This indicated that new volcanic rock at the ridge pushed older rocks apart, widening the sea floor and causing North and South America to drift away from Europe and Africa.

The sea-floor spreading theory explains how new oceanic crust is formed at mid-ocean ridges and gradually moves away from them.

Mid-Ocean Ridges: These are underwater mountain ranges where new oceanic crust is created. The Mid-Atlantic Ridge is one example.
Formation of New Crust: Magma from the Earth's mantle rises up through cracks in the ocean floor at the mid-ocean ridges. When this magma reaches the surface, it cools and solidifies to form new crust.

Spreading of the Sea Floor: As more magma continues to rise and solidify, it pushes the newly formed crust away from the ridge on both sides. This creates a continuous conveyor belt-like movement.
Age of Rocks: The rocks closest to the mid-ocean ridge are the youngest. As you move further away from the ridge, the rocks get progressively older.

Movement of Continents: The sea-floor spreading causes the ocean floor to widen. As the oceanic crust moves, it carries the continents with it. This is why continents like North and South America are slowly drifting away from Europe and Africa.

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In 1948, the Mid-Atlantic Ridge was discovered. This is a huge mountain range that runs roughly north-south along the floor of the Atlantic Ocean. The Mid-Atlantic Ridge consists of volcanic rock that emerged from the Earth's mantle.

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Proof of Sea-Floor Spreading Theory

Youngest Crust at Mid-Atlantic Ridge: Rock samples show the crust is youngest (10 million years) where magma cools at the Mid-Atlantic Ridge.
Older Crust Near Continents: The crust gets progressively older (up to 200 million years) as you move towards the continents.

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