Solomon Sea
The Solomon archipelago was formed by the convergence of the Indo-Australian and Pacific Plates. The Indo-Australian Plate and the smaller Solomon Sea Plate are subducting beneath the Pacific Plate along the New Britain–San Cristobal oceanic trench, which runs south of and parallel to the archipelago in the Solomon Sea. The surface geology of the islands is mostly igneous rocks, outcrops of metamorphic rocks, alluvial lowlands, and uplifted coral islands. Areas of ancient coralline limestone are found on Bougainville.