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The 'Ontong Java Plateau' is a huge oceanic plateau located in the Pacific Ocean, lying north of the Solomon Islands. The plateau covers an area of approximately 2,000,000 km², or roughly the size of Alaska, and reaches a thickness of up to 30 km. The plateau is of volcanic origin, composed mostly of flood basalts. Although they are now separated by thousands of kilometres, Manikihi Plateau and Hikurangi Plateau were then part of the same large igneous province, forming the world's largest oceanic plateau. It extruded some 100 million km³ of magma, covering approximately 1% of the Earth's surface, in the largest volcanic event on Earth in at least the last 200 million years.^[1][2] Most of the rocks that make up the plateaus have been dated to 119-125 million years ago, with some secondary volcanism occurring 20-40 million years later.
These plateaus were formed under the Pacific, and mostly still lie under the sea, although the collision of the Solomon Islands with the Ontong Java Plateau has lifted some of this plateau above sea level on the islands of Makira, Malaita and the northern half of Santa Isabel, along with the smaller islands of Ramos and Ulawa. Several large seamounts arise from the plateau, including the one capped by Ontong Java Atoll.

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Notes

1. "the Manihiki and Hikurangi Plateaus [...] we interpret as remnants of a formerly contiguous Ontong Java–Manihiki–Hikurangi large igneous province". Osbourn Trough: Structure, geochemistry and implications of a mid-Cretaceous paleospreading ridge in the South Pacific, Tim J. Worthington, , , Earth and Planetary Science Letters,
2. The single largest oceanic plateau: Ontong Java-Manihiki-Hikurangi, Brian Taylor, , , Earth and Planetary Science Letters, Summary.

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