# Volcano Watch — The three U.S. Volcano Observatories

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The U.S. Geological Survey's Volcano Hazards Program funds the operations of three volcano observatories in the United States. They are the Hawaiian, Cascades, and Alaska Volcano Observatories, and, as their names imply, each is responsible for monitoring volcanoes in a specific geographic area.

The U.S. Geological Survey's Volcano Hazards Program funds the operations of three volcano observatories in the United States. They are the Hawaiian, Cascades, and Alaska Volcano Observatories, and, as their names imply, each is responsible for monitoring volcanoes in a specific geographic area.

The Alaska Volcano Observatory (AVO) was recently in the news when Pavlof Volcano, located near the tip of the Alaska Peninsula, began to erupt on Monday, September 16. Although the continuing eruption poses no immediate threat to people living in the area, AVO personnel in Anchorage were manning the Observatory around the clock to monitor the activity.

This constant surveillance is required because volcanoes of the Pacific "Ring of Fire" are capable of ejecting ash to great heights. Many airline routes are over the Alaskan/Aleutian volcanoes, and the ash plumes can reach altitudes at which the planes fly and can damage or disable the jet engines.

When a large explosive event is detected by AVO, the Federal Aviation Administration (F‘A‘ā) is immediately notified, and planes are diverted around the volcano. The drifting ash cloud is tracked with radar by both ground and satellite platforms, and the F‘A‘ā is kept informed.

Both AVO and CVO maintain home pages on the worldwide web, and more information about those observatories can be obtained by browsing their web sites at their respective addresses: AVO at http://www.avo.alaska.edu/ and CVO at http://vulcan.wr.usgs.gov/. HVO does not have a home page because of our slow and limited network connection, but we do provide information and data for several web sites which are linked to AVO's and CVO's home pages.

The Volcano Hazards Program is in the process of designing a web site where general and specific volcanic information can be obtained. HVO intends to place our home page at this site when it is developed.

### Volcano Activity Update

The eruption from flank vents on the western side of Puu Oo continues unabated, with lava flowing through the six-mile long tube system and entering the ocean at Laeapuki. During the early morning hours of Thursday, September 19, a large block of the Lae`apuki bench slid into the ocean. No one witnessed the collapse, but sufficient energy was transferred to the ground for the HVO seismic network to detect the event, which lasted for eight minutes.

One earthquake was reported felt during the past week. Residents of Leilani Estates were awaken at 10:44 p.m. on Tuesday night, September 17, by a shallow temblor located five miles east-southeast of Pahoa. A magnitude of 2.3 was registered for the earthquake. The shallow depth of focus and proximity to a populated area accounted for such a small earthquake being felt.