GSA Today Zealandia: Earth’s Hidden Continent Cover Image 2 GNS Science, P.O. Box 30368, Lower Hutt 5040, New Zealand 3 SGEES, Victoria University of Wellington, P.O. Box 600, Wellington 6140, New Zealand 4 Service Géologique de Nouvelle Calédonie, B.P. 465, Nouméa 98845, New Caledonia 5 School of Geosciences, University of Sydney, NSW 2006, Australia Abstract A 4.9 Mkm 2 region of the southwest Pacific Ocean is made up of continental crust. The region has elevated bathymetry relative to surrounding oceanic crust, diverse and silica-rich rocks, and relatively thick and low-velocity crustal structure. Its isolation from Australia and large area support its definition as a continent—Zealandia. Zealandia was formerly part of Gondwana. Today it is 94% submerged, mainly as a result of widespread Late Cretaceous crustal thinning preceding supercontinent breakup and consequent isostatic balance. The identification of Zealandia as a geological continent, rather than a collection of continental islands, fragments, and slices, more correctly represents the geology of this part of Earth. Zealandia provides a fresh context in which to investigate processes of continental rifting, thinning, and breakup.