An
oceanic core complex (OCC), or
megamullion, is a seabed
geologic feature that forms a long ridge perpendicular to a
mid-ocean ridge. It contains smooth domes that are lined with transverse ridges like a corrugated roof. They can vary in size from 10 to 150 km in length, 5 to 15 km in width, and 500 to 1500 m in height.