Sea-Floor Spreading

Science, Grade 6


Table Of Contents: Sea-Floor Spreading

1. Mid-Ocean Ridges
In the middle of the Atlantic ocean is a submerged mountain range called a mid-ocean ridge. It is part of a worldwide system of mid-ocean ridges formed by sea-floor spreading.
2. How Sea-Floor Spreading Occurs
Sea-floor spreading occurs when two tectonic plates pull away from each other, and a crack forms in the ocean floor. Magma from the Earth's mantle pours onto the ocean floor through the crack and creates new oceanic crust.
3. New and Old Oceanic Crust
A mid-ocean ridge is formed along the crack where magma is emerging. As the sea floor spreads, new oceanic crust pushes the older crust away from the ridge.
4. Supports Plate Tectonics Theory
Sea-floor spreading is part of the plate tectonics theory. In the Atlantic, the plates move away from the mid-ocean ridge at a rate of about one centimeter per year. As the sea floor spreads, the Earth's crust is changing and moving the continents as well.