page_title: Savaiʻi
section_title: Geology
hierarchical_section_title: Savaiʻi / Geography / Geology
caption_attribution_description: English: Mt Matavanu volcanic eruption, Savai'i island in Samoa, 1905. Gagana Samoa: Matavanu, mauga afi i Savai'i, 1905. Français&#160;: Mont Matavanu éruption volcanique sur l'île de Savai'i, 1905. Русский: Гора Matavanu извержения вулкана на острове Савайи, 1905. Deutsch: Matavanu Vulkanausbruch auf Insel Savaii, 1905.
context_page_description: Savaiʻi is the largest and highest island in Samoa and the Samoan Islands chain. The island is the sixth largest in Polynesia, behind the three main islands of New Zealand and the Hawaiian Islands of Hawaii and Maui.
  The island of Savaiʻi is also referred to by Samoans as Salafai, a classical Samoan term used in oratory and prose. The island is home to 43,142 people who make up 24% of the country's population.
  The only township and ferry terminal is Salelologa, the main entry point to the island, situated at the east end of Savaiʻi. A tar sealed road serves as the one main highway, connecting most of the villages with local buses reaching most settlements.
  Savaiʻi is made up of six itūmālō. Each district is made up of villages with strong traditional ties of kinship, history, land and matai chief titles. There is also some limited ecotourism development which operates mostly within the villages. The Mau, Samoa's non-violent movement for political independence during colonialism in the early 1900s, had its beginnings on Savaiʻi with the Mau a Pule movement.
  The island is the largest shield volcano in the South Pacific with recent eruptions in the early 1900s.
context_section_description: Savaiʻi is the largest shield volcano in the South Pacific  and only 3% is above water.
  It is an active volcano, which last erupted in 1905-1911 with lava flows that destroyed villages on the central north coast. The island is formed by a massive basaltic shield volcano which rises from the seafloor of the western Pacific Ocean. A possible model for the formation of the volcanic Samoa island chain is explained by the Samoa hotspot situated at the east end of the Samoa Islands. In theory, the Samoa hotspot is a result of the Pacific Tectonic Plate moving over a 'fixed' deep and narrow mantle plume spewing up through the Earth's crust. The Samoa islands generally lie in a straight line, east to west, in the same direction the Plate is moving. In the classic hotspot model, primarily based on studies of the Hawaii hotspot, the volcanic islands and seamounts further away from the Samoa hotspot should be progressively older. However, Savaiʻi, the most western of the Samoa island chain, and Taʻu Island, the most eastern of the Samoa islands, both erupted in the 20th century, data which is an enigma for scientists. Taʻu last erupted in 1866. Another discrepancy in the data from the Samoa islands is that subaerial rock samples from Savaiʻi were too young by several million years to fit the classic hotspot model of age progression in an island chain, raising arguments among scientists that the Samoa islands does not have a plume origin. The nearness of Savaiʻi and the Samoa island chain to the Tonga Trench at the south became a possible explanation for these discrepancies as well as the possibility that the islands were formed by magma seeping through cracks in stressed fracture zones. However, in 2005, an international team gathered further submarine samples from the deep flanks and rifts of Savaiʻi. Tests on these later samples showed much older ages, about five million years old, that fit the hotspot model. The discovery in 1975 of Vailuluʻu Seamount 45 km east of Taʻu in American Samoa has since been studied by an international team of scientists and contribute towards understanding of the Earth's fundamental processes.
  Pre-historic geological formations on SavaiʻI have created natural sites such as the Alofaʻaga Blowholes and Moso's Footprint. The Peʻapeʻa Cave, named after the swallows that inhabit it, is a lava tube one kilometre in length, formed during the Mt Matavanu eruptions.
caption: Mt Matavanu eruption, 1905
exif: {"Image ImageDescription": "Volcanic eruption at Savaii, 1905 - Steam plumes rising from lava entering the sea. Probably the 1905 erruption of the Matavanu volcano photographed by Alfred James Tattersall.", "Image Make": "Mount Matavanu", "Image Model": "National Library of New Zealand", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72009/1000", "Image YResolution": "72009/1000", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop", "Image DateTime": "2012:08:07 02:58:31", "Image Artist": "Alfred John Tattersall (1861 - 1951)", "Image Copyright": "http://mp.natlib.govt.nz/detail/?id=16687&l=en", "Image ExifOffset": "522", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "EXIF DateTimeOriginal": "1905", "EXIF ColorSpace": "Uncalibrated", "EXIF ExifImageWidth": "3310", "EXIF ExifImageLength": "2602"}