Images

Photograph of the Colorado River in the Grand Canyon, Arizona, USA. Photo taken on September 8, 2023.

This reference map depicts the volcanoes in the Manuʻa Islands, American Samoa, the site of seismic unrest between July and September 2022. Marked on the map are the locations of Hawaiian Volcano Observatory GPS and seismometers in the islands.

Map of the American Samoa volcano-monitoring network (top). Data from Wake Island hydrograph (located about 4,500 km, or 2,900 miles, northwest of Taʻū Island) shows the general trend in the number of events during the 2022 earthquake swarm (bottom left). Locations for larger earthquakes (M2.5 and greater) are available starting August 20, 2022 (bottom right).

A USGS scientist installs a seismic station on Tutuila island in American Samoa. This station joins several other stations recently installed in the Manu‘a Islands to monitor activity in American Samoa. USGS photo by A. Ellis.

On the northwest coast of Ta‘ū Island (near Faleāsao village), half of a tuff cone, which is likely thousands of years old, is visible. Ocean waves have eroded away the other half of the tuff cone, which formed when hot magma interacted with either shallow groundwater or sea water. USGS image by J. Chang.

The tuff cone on the northwest coast of Ta‘ū Island (near Faleāsao village) is mostly composed of fine-grained ash with larger lithic clasts (fragments of older rock material). Some of these lithic clasts are larger than 1 meter or 3 feet in diameter and are scattered throughout the tuff cone. USGS image by J. Chang.

USGS staff are on Ta‘ū Island in American Samoa to begin installing Global Positioning System (GPS) receiver monitoring sites. GPS equipment is able to detect very slight movements of the ground and will help the USGS to better understand what is happening beneath the ground and provide more accurate hazard assessments. USGS image by J. Chang.

Photograph of a Global Positioning System (GPS) station on Ta‘ū Island in American Samoa. Solar panels and batteries in a weather-proof enclosure power the station, which consists of a GPS unit placed on a tripod that is leveled and centered over a benchmark.

This reference map depicts the topography and bathymetry of the volcanoes in the Manu‘a Islands, American Samoa, where seismic unrest has been ongoing for several weeks. The highest elevation in the area is Lata Mountain on Ta‘ū Island, standing 3,179 feet (969 meters) above sea level.

This reference map depicts the topography and bathymetry of the volcanoes in the Manu‘a Islands, American Samoa. The highest elevation in the area is Lata Mountain on Ta‘ū Island, standing 3,179 feet (969 meters) above sea level.

Wake Island is about 2,800 miles (4,500 km) northwest of Ta'ū volcano in American Samoa. Both are located in the Pacific Ocean. 

A USGS Hawaiian Volcano Observatory geologist collects a rock sample using a rock hammer on Ta‘ū Island, American Samoa. HVO staff are in American Samoa responding to earthquake activity. While there to install monitoring instrumentation, they are also collecting rock samples to better understand past volcanic activity in American Samoa. USGS image by J. Chang.

A USGS Hawaiian Volcano Observatory geologist collects a sample of a pāhoehoe lava flow above a thick ‘a‘ā lava flow on Ta‘ū Island, American Samoa. At that location, samples of a sequence of alternating pāhoehoe and ‘a‘ā lava flows were sampled to help reconstruct the eruptive history of Ta‘ū volcano.

The base of a tuff cone near the coast of Ta‘ū Island in American Samoa. Tuff cones are created from phreatomagmatic processes through the interaction of lava with shallow seawater. This part of the tuff cone contains mostly sand size material that hosts larger blocks and bombs that are up to several feet (one meter) in diameter.

A cliff on Ta‘ū island in American Samoa, exposing part of a tuff cone that was created from phreatomagmatic processes through the interaction of lava with shallow seawater. This part of the tuff cone contains mostly sand-sized material that hosts larger blocks and bombs that are up to several feet (one meter) in diameter.

A view of the summit region of Ta‘ū island, in the Manu‘a island group of American Samoa. Ta‘ū island is the exposed top of a volcano that formed as a result of volcanic activity at the Samoa hotspot. Most of the volcano is under the ocean surface.

A broadband seismometer being installed on Ta‘ū island near Fiti‘uta on August 23, 2022, by the USGS Hawaiian Volcano Observatory, NOAA National Weather Service, and with help from the American Samoan government and local residents of Ta‘ū island.

A broadband seismometer was installed on Ta‘ū island on August 22, 2022, by the USGS Hawaiian Volcano Observatory and NOAA National Weather Service team. This is one of two broadband seismometers that have been placed on Ta‘ū island to help detect earthquakes that started to be felt in the region starting in late July. USGS photo by D. Downs.

An afternoon view of the tuff cone near Faleāsao village located in northwest Ta‘ū island, with the islands of Ofu and Olosega visible in the distance. This tuff cone, which is thousands of years old, formed when hot magma interacted with either shallow groundwater or sea water. There are several tuff cones located within the northwest corner of Ta‘ū island.

A Raspberry Shake microseismometer was installed on Ta‘ū island, American Samoa, on August 19, 2022, by the USGS Hawaiian Volcano Observatory and NOAA National Weather Service team. This is one of several microseismometers that have been placed within the Manu‘a islands to help detect earthquakes in the region that started to be felt in late July. USGS photo by D.

Earthquakes in oceanic environments can generate pressure waves that travel long distances within the ocean itself. Much like seismographs record ground shaking, this energy is recorded by submerged hydrophones measuring pressure changes in water.