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How fast can oceanic crust spread away from a mid-ocean ridge?
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oceanic crust
A cross section of Earth's outer layers, from the crust through the lower mantle.
Oceanic crust spreads away from mid-ocean ridges at varying speeds, a process fundamental to the theory of plate tectonics. Global spreading rates range from as little as 10 mm (0.4 inch) per year up to 160 mm (6.3 inches) per year.21
Geologists classify these ridges based on their spreading rates:
- Slow-spreading ridges: Up to 50 mm (about 2 inches) per year, such as the Mid-Atlantic Ridge.23
- Intermediate-spreading ridges: Up to 90 mm (about 3.5 inches) per year.2
- Fast-spreading ridges: Up to 160 mm (about 6.3 inches) per year, such as the East Pacific Rise.2
These rates are determined by analyzing the age of the oceanic crust at varying distances from the spreading centre. Faster-spreading ridges generally exhibit smoother topography and lack the deep rift valleys characteristic of slower-spreading ridges.12