There are fewer seamounts in the Indian Ocean than in the Atlantic and Pacific. These are typically deeper than and located north of 55°S and west of 80°E. Most originated at spreading ridges but some are now located in basins far away from these ridges. The ridges of the Indian Ocean form ranges of seamounts, sometimes very long, including the Carlsberg Ridge, Madagascar Ridge, Central Indian Ridge, Southwest Indian Ridge, Chagos-Laccadive Ridge, 85°E Ridge, 90°E Ridge, Southeast Indian Ridge, Broken Ridge, and East Indiaman Ridge. The Agulhas Plateau and Mascarene Plateau are the two major shallow areas.