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Ofu-Olosega

Photo of this volcano
  • Country
  • Primary Volcano Type
  • Last Known Eruption
  •  
  • 14.175°S
  • 169.618°W

  • 639 m
    2096 ft

  • 244010
  • Latitude
  • Longitude

  • Summit
    Elevation

  • Volcano
    Number
Most Recent Weekly Report: 24 August-30 August 2022 Citation IconCite this Report

Data from seismometers recently installed on Tutuila, Ta’u, and Ofu-Olosega islands of American Samoa to monitor an ongoing seismic swarm indicated that the events were related to Ta’u Island and not Ofu-Olosega. HVO lowered the Volcano Alert Level to Normal and the Aviation Color Code to Green on 26 August. The report warned residents of Ofu-Olosega that they could still be significantly affected by events that may take place on or around Ta’u Island.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)

Weekly Reports - Index


2022: August


24 August-30 August 2022 Citation IconCite this Report

Data from seismometers recently installed on Tutuila, Ta’u, and Ofu-Olosega islands of American Samoa to monitor an ongoing seismic swarm indicated that the events were related to Ta’u Island and not Ofu-Olosega. HVO lowered the Volcano Alert Level to Normal and the Aviation Color Code to Green on 26 August. The report warned residents of Ofu-Olosega that they could still be significantly affected by events that may take place on or around Ta’u Island.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)


17 August-23 August 2022 Citation IconCite this Report

HVO reported that an earthquake swarm in the Manu’a Islands of American Samoa continued to be recorded and felt by residents of Ta’u Island and Ofu-Olosega. About 20 earthquakes per hour were recorded by four microseismometers distributed on Tutuila, Ta’u, and Ofu-Olosega Islands. The largest events were estimated to be between magnitudes 2 and 3; most events are too small to be felt. Analysis of the seismic data indicated that the earthquakes were occurring beneath or around the Manu’a Islands, likely closer to Ta’u rather than Ofu-Olosega, though the exact locations, depths, and magnitudes were unknown. The number, size, and frequency of earthquakes recorded by instruments and being felt by people and on both islands indicated that seismicity was above background levels; HVO changed the Volcano Alert Level to Advisory and the Aviation Color Code to Yellow for both volcanoes. Earthquakes continued to be recorded at around the same rate during 20-22 August. Two additional seismometers were installed on Ta’u during 22-23 August.

Source: US Geological Survey Hawaiian Volcano Observatory (HVO)


The Global Volcanism Program has no Bulletin Reports available for Ofu-Olosega.

This compilation of synonyms and subsidiary features may not be comprehensive. Features are organized into four major categories: Cones, Craters, Domes, and Thermal Features. Synonyms of features appear indented below the primary name. In some cases additional feature type, elevation, or location details are provided.

Eruptive History

There is data available for 1 Holocene eruptive periods.

Start Date Stop Date Eruption Certainty VEI Evidence Activity Area or Unit
1866 Sep 12 1866 Nov 15 ± 5 days Confirmed 2 Observations: Reported Submarine vent 3 km SE of Olosega
Deformation History

There is no Deformation History data available for Ofu-Olosega.

Emission History

There is no Emissions History data available for Ofu-Olosega.

Photo Gallery

Clouds drape the tops of the two islands of Ofu (left) and Olosega (right) in eastern Samoa in this International Space Station image (N is to the top left). The islands, 6 km in combined length, are separated by a narrow strait. They are formed by two eroded, coalescing basaltic shield volcanoes truncated by mostly-submarine calderas. A submarine eruption took place in 1866 about 3 km SE of Olosega, along the ridge connecting Olosega with Ta'u Island.

NASA International Space Station image ISS002-E-6878, 2001 (http://eol.jsc.nasa.gov/).
A narrow strait (just left of center) separates the two triangular islands of Ofu (left) and Olosega (right) in eastern Samoa. The islands are formed by two eroded, coalescing shield volcanoes. The narrow, steep-sided ridge forming the W side of Ofu Island is cut by volcanic dikes and an intrusive plug forms the sharp spire on Ofu Island to the left. A submarine eruption took place in 1866 at the far end of the two islands, 3 km SE of Olosega, along the ridge connecting Olosega with Ta'u Island.

Photo by Peter Craig, 1995 (U.S. National Park Service).
Ofu (left) and Olosega (right) in eastern Samoa are parts of the same volcano separated by the Asaga Strait, with the island group reaching nearly 9 km across (including the smaller island to the west), shown in this 29 October 2018 Sentinel-2 satellite image (N is at the top). The islands have likely been shaped by flank failures with resulting debris avalanches below sea level.

Satellite image courtesy of Copernicus Sentinel Data, 2018.
GVP Map Holdings

The Global Volcanism Program has no maps available for Ofu-Olosega.

Smithsonian Sample Collections Database

There are no samples for Ofu-Olosega in the Smithsonian's NMNH Department of Mineral Sciences Rock and Ore collection.

External Sites