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Ofu-Olosega from Space Shuttle.
Elevation 639 m (2,096 ft)
Prominence 639 m (2,096 ft)
Location American Samoa
Coordinates 14°10′30″S 169°37′05″W / 14.175°S 169.618°W / -14.175; -169.618Coordinates: 14°10′30″S 169°37′05″W / 14.175°S 169.618°W / -14.175; -169.618
Topo map USGS
Type Shield volcanoes
Last eruption September to November 1866

Ofu and Olosega are parts of a volcanic doublet in the Manu‘a Group of the Samoan Islands—part of American Samoa. The twin islands, formed from shield volcanoes, have a combined length of 6 km. They are geographic volcanic remnants separated by the narrow 137m wide Asaga strait, a natural bridge of shallow coral reef. Before 1970, one had to wade between the two islands at low tide; now a single-lane road bridge over the strait connects villages on Ofu island with those on Olosega.

The highest peak on Ofu is Mount Tumutumu (491m, also referred to as Tumu) and the highest elevation on Olosega is Mount Piumafua (629m). The most recent volcanic eruption took place in 1866, 3 km south east of Olosega.[1]

Archaeology field work carried out in the 1980s yielded pre-historic evidence including ceramics, adzes, shell and bone which have been significant in furthering understanding of the ancient history of the Samoa Islands and Polynesia. This included samples of red-slipped plainware ceramics that appeared to be in the tradition of Lapita culture. The work, carried out by a team that included Pacific archaeology specialist Patrick Vinton Kirch, focused on a site called To'aga (site AS-13-1), a 2 km coastal stretch on the south coast of Ofu. The results showed continuous human habitation of about 3,000 years.[2]


South shore of Ofu seen from Olosega across the narrow strait that separates them. The sharp peak, an eroding dike complex, is named Sunu‘itao.

Ofu is the western part of the volcanic outcrop of Ofu-Olosega Island. The main village of Ofu is located on the western shore, protected behind an offshore islet (eroded tuff cone) known as Nu'utele. Ofu has a small airport (IATA: OFUICAO: NSAS) and a boat harbor that serve the population on Ofu and Olosega. Before regular airline service was discontinued in 2009, the flight from Pago Pago took about half an hour.

Olosega village 1896

Most of the southern shore and associated coral reef are part of the National Park of American Samoa. In 2005 the U.S. National Park Service was negotiating with village councils on Olosega to expand the park around that island.

The island forms the Ofu County subdivision of the Manua District. It has a land area of 7.215 km² (2.786 sq mi), and had an official population of 289 persons as of the 2000 census.

Situated on the south coast of the island is To'aga lagoon which has a high diversity of corals and fishes. The marine site has been part of long term research and study on coral reefs and global climate change.

The island is also home to the Samoa Flying-fox (Pteropus samoensis), a species of bat threatened by habitat loss.


Aerial view - Olosega village on the right, Ofu on the left. Both islands are connected via a single-lane bridge, crossing the Asaga strait.

Olosega Island is a remnant of the Sili shield volcano, the caldera of which may lie submerged off the north shore.

The volcanic eruption of 1866 was actually 3 km east of Olosega, on a submarine ridge that extends east southeast to nearby Ta‘ū.

The island forms the Olosega County subdivision of the Manua District. It has a land area of 5.163 km² (1.993 sq mi), and had an official population of 216 persons as of the 2000 census.

There are two villages on Olosega: Olosega and Sili. Sili, situated on the northwestern-facing shore, now consists of but one standing inhabited residence after much of the village was destroyed by cyclones (and subsequently abandoned).

Almost all the population of Olosega now reside in Olosega village along the southwestern-facing shore.

Olosega village also has Olosega Elementary School with instruction through grade 9 for children on both islands.


See also[edit]


  1. ^ "Global Volcanism Program, Ofu-Olosega". Smithsonian National Museum of Natural History. Retrieved 13 July 2010. 
  2. ^ Jason Tyler, Patric V. Kirch, Terry L. Hunt, Lisa Nagaoka (November 1989). "Final Report on Archaeological Investigations at Site AS-13-1, To'aga, Ofu Island, American Samoa". Department of Parks and Recreation, Government of American Samoa. Retrieved 13 July 2010. 

External links[edit]

Original courtesy of Wikipedia: http://en.wikipedia.org/wiki/Ofu-Olosega — Please support Wikipedia.
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27 news items

Fri, 16 Jan 2015 10:59:13 -0800

A new island is now growing at the eruption site between Hunga Ha'apai and Hunga Tonga Islands. As of yesterday, it had an east-west elongated 1.5-2 km long and approx. 1 km wide shape with a half-open cone around the crater reaching almost 100 m in ...
Wed, 07 Jan 2015 05:41:11 -0800

Activity continues, but seems not to have breached the surface (for now). Recent satellite imagery with clear views show a discolored water plume and a steam plume but no ash, suggesting that that the activity is still well below the surface. Hunga Ha ...
Tue, 16 Dec 2014 02:41:15 -0800

The active lava lobe that has been advancing along the northern flow margin of the lava flow that had entered Pahoa in Nov, but then stopped, continues to advance towards the town and is now only approx. 1700 m away from the commercial center of the ...
Sat, 20 Dec 2014 07:55:07 -0800

Kīlauea's East Rift Zone lava flow continues to advance downslope toward the Pahoa Marketplace. This photo is of a small breakout from the edge of the inflated flow several hundred meters (yards) back from the active front. (HVO). Advancement of the ...
Mon, 10 Nov 2014 22:11:15 -0800

County of Hawaii media image of burning house on November 10, 2014 on the outskirts of Pahoa village. Latest update map from USGS-HVO showing lava near transfer station on November 10. 2-week old map of lava flow first crossing the residence area ...
Fri, 24 Oct 2014 06:30:00 -0700

The lava flow continues to advance towards Pahoa and might cut the first road very soon. During an overflight on 22 Oct, the most advanced front of the 27 June flow, a narrow lobe, was only approx. 480 m away from the Apa'a road. The rate of advance of ...
Mon, 27 Oct 2014 02:59:50 -0700

After crossing Apaʻa Street and the cemetery, lava flows continue to advance towards the inhabited main part of Pahoa. From this morning's update by HVO who monitor the situation closely: "The relatively narrow finger of lava that crossed Apaʻa Street ...
Sun, 26 Oct 2014 02:45:00 -0700

The June 27th lava flow crossed Apaʻa Street / Cemetery Road at 3:50 AM, HST, Saturday morning, October 25, 2014. In this photo, which was taken at about 9 AM Saturday, the flow is moving from right to left, with burning asphalt visible along it's NW ...

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