Its southern portion contains the Manawatāwhi / Three Kings Islands which have biological significance as they are host to unique species and important marine ecosystems.

[6] However, there is a distinct age difference between the 25 million years ago dates of the southern part of the ridge eruptives and the nearest North Island volcanics.

[3] There was a pulse of voluminous late Oligocene to early Miocene (25 to 22 million years ago) volcanic activity within the Cook Fracture Zone and the northern portions of the ridge that now dominate.

This collision as the continental crust of the ridge moved southeast about 25.5–22 million years ago would have been had to have been associated with a subduction flip in the postulated model.

These are separated from the New Zealand North Island by a 8 km (5.0 mi) wide submarine trough that is at least 200 m (660 ft) deep and may be associated with the Vening Meinesz Fault Zone.