Seafloor Spreading Hypothesis

A scientist named Harry Hess studied the ocean floor and discovered a massive mountain range running through the middle of the ocean. This is called the mid-ocean ridge, where new seafloor forms.

Hess proposed that hot magma rises from deep inside the Earth at these ridges. When it reaches the surface, it cools and forms new seafloor.

As more magma erupts, it pushes the older seafloor away from the ridge, making the ocean floor spread like a conveyor belt.

Scientists discovered that the seafloor contains stripes of magnetic polarity, showing how Earth’s magnetic field has reversed many times.

The youngest seafloor is at the mid-ocean ridge, while the oldest seafloor is farther away. Even the oldest seafloor is much younger than the continents.

This movement is driven by mantle convection, where hot material rises and cooler material sinks, creating currents that pull and push the seafloor.

Eventually, as the moving seafloor reaches deep ocean trenches, it sinks back into the mantle, recycling Earth’s crust.

This process of seafloor spreading explains how continents move.