The island of Savaii (1,709 sq km (659 sq mi)) is the biggest island of the Samoan Archipelago, it lies just 20 km northwest of Upolu across the Apolima Strait in the Pacific Ocean. The island is of volcanic origin and is covered by dense forests, at the center of the island is Mount Silisili (1.858 meters), the highest peak of the Samoa Islands. Savaii had its last eruption between 1905 and 1911 when, in the north of the island, Mount Matavanu (402 meters) erupted dramatically transforming the landscape with lava fields that came up to the sea.