Ofu-Olosega

No significant activity was detected at Ofu-Olosega volcano during the past month. The USGS National Earthquake Information Center reported no earthquakes of magnitude 2.5 or greater in the vicinity of the volcano. 

Background: The islands of Ofu and Olosega in the Manuʻa Islands of eastern American Samoa, with a combined length of 6 kilometers (3.7 miles), are separated by a narrow strait. The islands are formed by two eroded, coalescing basaltic shield volcanoes whose slopes dip to the east and west. The Nuʻutele tuff cone, forming a small crescent-shaped island immediately off the west end of Ofu, is of Holocene age (less than 11,650 years). A submarine eruption occurred in 1866, 3 kilometers (1.9 miles) southeast of Olosega, along the Samoan Ridge between Olosega and Taʻu Island. From: https://volcano.si.edu/volcano.cfm?vn=244010.

More Information: https://www.usgs.gov/volcanoes/ofu-olosega

The Hawaiian Volcano Observatory is one of five volcano observatories within the U.S. Geological Survey and is responsible for monitoring volcanoes and earthquakes in Hawaiʻi and American Samoa.

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Subscribe to these messages: https://volcanoes.usgs.gov/vns2/
Summary of volcanic hazards from eruptions: https://www.usgs.gov/observatories/hvo/hazards
Recent earthquakes in Hawaiʻi (map and list): https://www.usgs.gov/observatories/hvo
Explanation of Volcano Alert Levels and Aviation Color Codes: https://www.usgs.gov/programs/VHP/volcanic-alert-levels-characterize-conditions-us-volcanoes

No significant activity was detected at Taʻū volcano during the past month. The USGS National Earthquake Information Center reported no earthquakes of magnitude 2.5 or greater in the vicinity of the volcano. A Global Positioning System (GPS) instrument on Taʻū Island recorded no significant deformation.

The FAGA broadband seismometer located on eastern Taʻū Island is currently out of service. The TAU broadband seismometer on western Taʻū Island remains operational.

Background: In the Manuʻa Islands of eastern American Samoa, Taʻū Island is the top of a shield volcano, most of which is beneath the ocean. The volcano has a summit caldera, though landslides have removed the southern part of the caldera. Two rift zones are present on Taʻū, one to the northeast and one to the northwest. The northwest rift zone aligns with the Samoan Ridge, a predominantly submarine feature that leads to the islands of Ofu and Olosega. This ridge was formed by volcanic activity associated with the Samoa hotspot, which is currently located at the Vailulu‘u seamount 40 kilometers (25 miles) east of Ta‘ū Island. A submarine eruption occurred in 1866 on the Samoan Ridge between Ta‘ū and Ofu-Olosega. 

More Information: https://www.usgs.gov/volcanoes/ta-u-island

The Hawaiian Volcano Observatory is one of five volcano observatories within the U.S. Geological Survey and is responsible for monitoring volcanoes and earthquakes in Hawaiʻi and American Samoa.

[email protected]

Subscribe to these messages: https://volcanoes.usgs.gov/vns2/
Summary of volcanic hazards from eruptions: https://www.usgs.gov/observatories/hvo/hazards
Recent earthquakes in Hawaiʻi (map and list): https://www.usgs.gov/observatories/hvo
Explanation of Volcano Alert Levels and Aviation Color Codes: https://www.usgs.gov/programs/VHP/volcanic-alert-levels-characterize-conditions-us-volcanoes

No significant activity was detected at Tutuila volcano during the past month. The USGS National Earthquake Information Center reported no earthquakes of magnitude 2.5 or greater in the vicinity of the volcano.

Background: Tutuila Island is an elongated and eroded group of five Pliocene-to-Pleistocene-aged volcanoes constructed along two or three rifts trending south-southwest to north-northeast. The Leone Volcanics, in the southernmost part of the island, represent the youngest eruption deposits. Eruptions occurred during the Holocene (less than 11,650 years ago) along a 5-kilometer (3-mile) north-to-south trending fissure, forming a group of initially submarine tuff cones and subsequent subaerial cinder cones that produced fresh-looking pāhoehoe lava flows. An ash layer overlying a cultural deposit in the southwestern part of the island was radiocarbon dated at 440 ± 200 CE (Addison et al., 2006). From: https://volcano.si.edu/volcano.cfm?vn=244020.

More Information: https://www.usgs.gov/volcanoes/tutuila-island

Additional Resources

• Volcano Alert Levels and Aviation Color Codes in Samoan: https://www.usgs.gov/media/files/volcano-aviation-codes-and-alert-levels-english-and-samoan
• Mauga Mū a Amerika Samoa—Volcanoes of American Samoa https://pubs.usgs.gov/publication/fs20233022
• NOAA National Weather Service Pago Pago https://www.weather.gov/ppg/
• American Samoa Government https://www.americansamoa.gov/

The Hawaiian Volcano Observatory is one of five volcano observatories within the U.S. Geological Survey and is responsible for monitoring volcanoes and earthquakes in Hawaiʻi and American Samoa.

[email protected]

Subscribe to these messages: https://volcanoes.usgs.gov/vns2/
Summary of volcanic hazards from eruptions: https://www.usgs.gov/observatories/hvo/hazards
Recent earthquakes in Hawaiʻi (map and list): https://www.usgs.gov/observatories/hvo
Explanation of Volcano Alert Levels and Aviation Color Codes: https://www.usgs.gov/programs/VHP/volcanic-alert-levels-characterize-conditions-us-volcanoes