Midoceanic rises can be divided into two categories: rifted and nonrifted. Rifted rises are characterized by a median valley, high relief, a thick second layer, and the presence of metamorphic and deep intrusive rocks. Rifted rises are believed to have slow spreading rates of less than 2 cm/year....
van Andel, Tjeerd H.. 1968. "The structure and development of rifted midoceanic rises." Journal of Marine Research 26, (2). https://elischolar.library.yale.edu/journal_of_marine_research/1123