Etna Volcano - Italy, June 1995
Geology of the area - Sicily is a region where eruptions, mainly from the volcanoes of Etna Volcano and Stromboli, have often threatened populated areas. The most recent events are linked to the craters at Etna's summit. The lower part (up to an altitude of about 2900 mt) of this continental volcano, with its base of about 60x40 km, is a shield, while the upper part is a strato volcano. Since Etna's magma chamber is located deep inside the lithosphere, the chemical composition of the rocks in this area is very similar to that of the earth's mantle; the difference is due to the enrichment in sodium and potassium that occurs when the basaltic lavas pass into the upper part of the earth's crust. This is the reason why the most diffuse volcanic rocks in this site are made of andesite.   Monitoring activity - The last 20 years have been characterised by persistent volcanic activity on this site: forty-six eruptions have occurred over this period, most of them concentrated in the period from 1991 to 1993. This means that accurate and frequent surveys must be made by using both instrumental and field survey techniques. A permanent instrumental network has been installed and continuous field surveys ensure an efficient real-time surveillance in the urbanised areas closest to the active vents.  Italy, Sicily, June 1995 - A collection of Landsat 5 TM images of the Etna Volcano.
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