The Ontong Java Plateau
Location of the Ontong Java Plateau
The Ontong Java Plateau is a huge oceanic lava plateau in the Pacific Ocean north of the Solomon Islands. It covers approx. 2 million, about the same area as Alaska, and consists of up to 30 km layers of basalt lava.
Tectonic setting of the Ontong Java Plateau (from Pettersen et al, 1999)
The plateau was produced 125–120 million years ago by a flood-basalt eruption of a large mantle plume. It represents one of the largest lava eruptions on earth during the past 300 million years.
The eruption produced about 100 million cubic kilometers of basalt (i.e. 100 MILLION times more magma than Mt St. Helens in 1980) and covered about 1% of the earth's surface, creating the largest oceanic plateau. Tectonic movements split the original plateau into present-day's Onto Java Plateau, the Manihiki Plateau east of Samoa and the Hikurangi Plateau east of New Zealand's North Island.
The mantle plume that produced the Ontong Java Plateau is called the Louisville hotspot. A secondary phase of lava eruptions occurred 20-40 million years later (100-80 million years ago).
Most of the plateau was formed under water and is submerged, but tectonic collision with the Solomon Island Block has caused parts of the Ontong Java Plateau to be uplifted above sea level. This includes the islands of Makira, Malaita and the northern half of Santa Isabel, as well as the smaller islands of Ramos and Ulawa. Several large volcanic seamounts arise from the plateau, including the one capped by Ontong Java Atoll (which gave the name to the lava plateau).
References:- J. G. Fitton et al, eds (2004). "Origin & Evolution of the Ontong Java Plateau", Special Publication 229, Geological Society
- M.G. Petterson et (1999) "Geological–tectonic framework of Solomon Islands, SW Pacific: crustal accretion and growth within an intra-oceanic setting", Tectonophysics, v. 301, pp. 35-60