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Makushin reported activity

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EVENT SPECIFIC INFORMATION

Event Name : Makushin 2006

Start: 2006 ± 1 YearsObserved

Discredited account - no eruption: BibCard
Eruption Type:Not an eruption.
Other""

Description: From Neal and others (2011): "On June 27, a USCG officer made a report to NOAA about a persistent area of discolored seawater in Unalaska Bay, about 3 km (1.9 mi) north of Dutch Harbor and in-line with Wide Bay cone and Table Top volcano, two satellite vents that are part of the larger Makushin volcanic field (McConnell and others, 1998). The officer stated that he had noticed this discoloration for approximately 2 years. NOAA forwarded the report and photographs via email to AVO on July 2.

"AVO considered three possibilities for the discoloration: (1) ship discharge, (2) hydrothermal venting from a submarine volcanic cone, and (3) groundwater discharge or venting through the seafloor. A transient ship discharge was quickly ruled out, due to the phenomenon’s consistent presence and location. Discriminating between a volcanic or groundwater explanation for the discoloration is difficult without further investigation. Unalaska Bay is a normal location for seismic activity, and a quick examination of AVO’s seismic data for the area revealed nothing beyond background. On July 11, the NOAA ship Oscar Dyson conducted a conductivity, temperature, and depth (CDT) study near the site, and on July 24, the NOAA ship Fairweather conducted another CDT study and bathymetric mapping. The Oscar Dyson’s CTD study detected nothing unusual but the study was done too far from the apparent source to rule out a possible hydrothermal plume. The Fairweather’s survey showed seafloor mounds in the vicinity, possibly emitting plumes, but not directly under the anomaly. Conductivity and temperature measurements did not support a volcanic source. Further data collection and analysis in August by NOAA showed numerous sites of probable bubble streams coming out on the seafloor (seen in 2007 imagery). Another NOAA ship reported similar discolored water in a different, but nearby location in July 2008. At this time, we conclude that the multiple locations of discolored water at the surface and at the seafloor point to likely groundwater discharge, possibly through a fault system, rather than a submarine volcanic plume."

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