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 kmē, or roughly the size of Alaska, and it 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, Manihiki 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.
Encyclopedia
top
