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USGS HVO Press Release — Annual Surveys of Hawai‘i's Volcanoes Are Underway

April 20, 2009

If you see someone alongside the road next to a white disk-shaped antenna atop a yellow tripod, it could be a U.S. Geological Survey Hawaiian Volcano Observatory (HVO) geophysicist setting up a GPS (Global Positioning System) station to track changes on Hawai‘i's active volcanoes.

Each year, HVO conducts routine campaign-style GPS surveys of about 100 sites to supplement data collected from over 60 continuously recording GPS receivers that are permanently installed on the volcanoes.

GPS, a satellite-based technology, is used to measure ground movements, or surface deformation, on the volcanoes. Deformation is a key indicator of changes within a volcano that indicate where magma is located and whether or not it is likely to erupt, so tracking it is an important monitoring tool.

According to Mike Poland, HVO geophysicist, the sophisticated GPS receivers and data-analysis techniques used by HVO provide exceedingly precise measurements. Horizontal and vertical ground motions on a volcano can be determined to within fractions of an inch.

The biennial GPS survey of Hualālai was completed in early April. Annual GPS surveys of Kīlauea and Mauna Loa, Hawai‘i's two most active volcanoes, are now underway and will continue through May.

To achieve the most accurate measurements, HVO sets up a GPS receiver at the same site on at least two different days and allows it to run for 8 to 24 hours each day. As many as eight GPS units could be collecting data in a particular area on a given day.

Most GPS survey sites measured by HVO can be reached by vehicle or on foot, but some are accessible only by helicopter. Because the fly-to sites are so remote, the impact on residents from the sight and sound of a helicopter will be minimal.

HVO appreciates the cooperation of Hawai‘i Volcanoes National Park, where most of the monitored sites are located, as well as the State of Hawai‘i. Results will be reported in a Volcano Watch article after the full surveys are completed.

Daily updates about ongoing eruptions, recent images and videos of summit and East Rift Zone volcanic activity, maps, and data about recent earthquakes in Hawaii are posted on the HVO website at

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