How quickly can seafloor spreading occur at different oceanic ridges?

Seafloor spreading rates vary significantly across different oceanic ridges, ranging globally from 10 mm (0.4 inch) per year or less up to 160 mm (6.3 inches) per year. These rates are determined by analyzing the age of the oceanic crust as it moves away from spreading centres.12

Oceanic ridges are classified into three categories based on these spreading rates:

• Slow-spreading ridges: Up to 50 mm (about 2 inches) per year. These are often characterized by a rift valley at the crest and rough, faulted topography on their flanks, such as the Mid-Atlantic Ridge.1
• Intermediate-spreading ridges: Up to 90 mm (about 3.5 inches) per year. The crests of these ridges are typically broad highs with occasional small, fault-bounded valleys.1
• Fast-spreading ridges: Up to 160 mm (about 6.3 inches) per year. These ridges lack rift valleys and instead feature an axial high at the crest, with much smoother flanks, such as the East Pacific Rise.1

Spreading rates are generally more rapid in the Pacific Ocean compared to the Atlantic and Indian oceans.2