*************************** >From Rick Wunderman at the Smithsonian's Global Volcanism Network *************************** Hello and a huge thank you to all who have sent me messages about the Tonga eruption. We now know that it came from Home Reef starting 8 August 2006, and that produced copious pumice now floating past Fiji. 1. Blogs have indicated that eruptions over the ocean surface were seen on 11 August and the island had emerged by 12 August. We now know that the pumice rafts discussed in recent messages were from Home Reef (not Metis Shoal as initially stated). Home Reef is the next known volcano North of Metis Shoal (not South of Metis Shoal, as I previously stated). 2. Thanks to Scott Hughes and E.B. Joyce for noting the important links showing the new island at Home Reef: www.matangitonga.to/article/tonganews/disasters/new_island061106.shtml http://yacht-maiken.blogspot.com/2006/08/stone-sea-and-volcano.html One of the most impressive pumice raft photos (?pumice to the horizon?) is among those shown. Many of you have kindly mentioned news reports . . . it seems that press coverage of the event has suddenly blossomed, most apparently derived from the links just mentioned. Considerable credit goes to Mary Fonua of Tongan newspaper Matangi (Tonga online). 3. In the last few days we have received some highly informative satellite remote-sensing data bearing on the eruption. To bring you all better up to date and to try to reduce duplicating efforts, I give a brief summary: OMI SO2 data --Simon Carn (U Md BC) used the Ozone Monitoring Instrument (OMI) on NASA?s Aura satellite to provide the following constraints on the timing of the eruption: ?OMI detected SO2 emissions from the vicinity of Home Reef beginning on 8 August . . .. Emissions appear to have peaked sometime on 8-9 August, indicated by the large SO2 cloud detected east of Tonga on 9 August. The total SO2 mass detected by OMI on 9 August was ~25 kilotons. The emission episode was over by 15 August. HYSPLIT forward trajectories indicate that the SO2 released on 8 August may have reached altitudes of 5 km or more. To our knowledge this is the first example of satellite detection of emissions from a submarine volcano. Significant scrubbing of SO2 and other soluble volcanic gases is likely during such events.? ASTER images --Matt Patrick (Mich Tech Univ) asked me whether the 1984 island had completely eroded away. Although we list the summit elevation for Home Reef as -2 meters, we didn't know the answer; this was something left ambiguous in our reports. Matt found an ASTER image from 18 Nov 2005. Despite imperfect visibility that day, no island at Home Reef was apparent then. Accordingly, we hope to inquire with locals and learn the approximate date when the 1984 island eroded. --Matt also sent us an Aster image for 4 Oct 2006 where the new island is clear as are large N- and NE-directed anomalous areas (Stains in the water? Zones of pumice? Atmospheric effects?). The new island is warmer than adjacent Late island. The new island sits at these coordinates: 18.991 S, 174.762 W. (very close to Home Reef?s nominal location, 18.992 S, 174.775 W) . He noted ?. . . it looks like this new island resembles the 1984 island, in being elongate and about 1 km long, more or less, and having an inner pool of water.? Greg Vaughan (a postdoc at JPL working with the ASTER science group on remote sensing of volcanoes) sent us an annotated Aster image zoomed in on the new island on 4 October, which he computed then had an area of 0.245 km2. He made these comments ?The October 4th daytime image shows considerable activity in the water around the new Home Reef island (turbulent ash and pumice? churning up in the water) there is also a thermal plume in the same shape as the pink colored area in the attached VNIR images (ASTER channels 3-2-1 as R-G-B). Also, there are possibly several large floating pumice rafts that must be pretty big to show up in these 15-m pixels (the furthest one is about 5.5 km away from the island). The new island looks similar to, but not exactly like, the island in the photo from 1984 on the Smithsonian website.? --Alain Bernard (http://www.ulb.ac.be/sciences/cvl/homereef/homereef.html ) is working with Aster images of the new island and computed some water temperatures in hot lakes visible on the ASTER thermal bands, maximum temperature measured: 64.7 C. The next issue of Bulletin of the Global Volcanism Network (BGVN 31:09) should be on our website about the middle of next week. Unfortunately, the Home Reef report in that issue will only show a small part of the story, essentially omitting the remote sensing. If you wish to see the above-mentioned imagery right away, please contact the above-mentioned researchers. I'd supply that here but I'm working at home and with a limited interface. ============================================================== To unsubscribe from the volcano list, send the message: signoff volcano to: listserv@xxxxxxx, or write to: volcano-request@xxxxxxxx To contribute to the volcano list, send your message to: volcano@xxxxxxxx Please do not send attachments. ==============================================================
