Several of the Cook Islands are located on the southern part: Pukapuka, Nassau, Suwarrow, Rakahanga, and Manihiki.

The south-eastern High Plateau is the shallowest and flattest; its basement is covered by up to a kilometre of pelagic sedimentary rock.

The formation of the plateau is related to the intense volcanism of the Early Cretaceous and mid-ocean ridge jumps.

A hotspot and several mantle sources were involved in the formation of the Manihiki large igneous province (LIP).

[6] Other Cretaceous LIPs in the Pacific, except Ontong Java and Hikurangi, include the Hess, Shatsky and Magellan rises.