Ridge Classification

Rate Full Rate Example Rift Valley
Slow 10-50 mm/yr Mid-Atlantic Ridge  Axial zone with well developed median rift valley; 30-50 km wide; 1.5-3 km deep; rugged topography; Steep walls  (shows up well in global topography)
Intermediate 50-90 mm/yr Northern East Pacific Rise  Axial zone with small median rift only 50-200 m deep; smooth topography
Fast  >90 mm/yr Southern East Pacific Rise No median rift in axial zone; very smooth topography