******************************************************** Summit activity at Mount Etna Istituto Nazionale di Geofisica e Vulcanologia – Sezione di Catania From: Sonia Calvari (calvari@xxxxxxxxxx) ******************************************************** On 15 August the South-East Crater (SEC) at the summit of Mount Etna started to produce ash emissions from the depression that cuts its eastern flank. The ash cloud was very diluted, rising for just a few tens of meters above the source, and quickly dispersed by the wind. Ash fallout has been observed only on the flanks of the SEC cone forming a deposit red in colour. On 21 August the summit web-camera of the Istituto Nazionale di Geofisica e Vulcanologia – Sezione di Catania (INGV-CT), (http://www.ct.ingv.it/Ufso/Default.asp? Pagina=vulcano.asp&Vulcano=Eev&Refresh=180) started to record at night some incandescent blocks erupted during the most energetic emissions. A field survey carried out on the morning of 22 August showed mainly dilute ash emission associated to collapses within the depression, occurring at a mean frequency of about 2.5 events per hour. During the survey we have used the new high-definition thermal camera FLIR SC640 kindly borrowed from FLIR Systems. This allowed us to observe that a few most energetic events (about 20% of the total) were associated to the ejection of hot, metric, lithic blocks fallen on the eastern flank of the cone, sometimes reaching its base. Photos of the flank of the cone showed a black deposit with white, metric, lithic blocks close to the rim of the depression (Calvari, INGV report of 23 August). In the afternoon of 23 August, the web-camera network of INGV-CT recorded an increase in the frequency of the ash emissions, occurring at about every 5 minutes. An increase of the most energetic events was also recorded by the INGV-CT web-cameras in the night between 23 and 24 August, with incandescent blocks erupted together with ash. The ash was sampled on 21 August and analysed in the laboratories of INGV-CT. The analysis showed that the lithic component is predominant, and this observation confirms that the ash is produced by collapses. Volcanic tremor and seismicity maintained low during the whole period of ash emission, showing that no important supply of fresh magma from below is occurring at the moment. All INGV-CT reports (in Italian) with figures, photos and thermal images can be downloaded from the INGV-CT web page dedicated to updates on the eruptive activity of Mount Etna: http://www.ct.ingv.it/Default.asp?Pagina=./Etna2007/Report.asp. ------------------------------------------------------------------------ Dr. Sonia Calvari Istituto Nazionale di Geofisica e Vulcanologia Sezione di Catania Piazza Roma 2 95123 Catania (Italy) Tel. +39 095 7165800 direct: +39 095 7165862 Fax: +39 095 435801 url: www.ct.ingv.it ------------------------------------------------------------------------ ============================================================== 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. ==============================================================
