Journal of Volcanology and Geothermal Research, 21(1984) 1--23 Elsevier Science Publishers B.V., Amsterdam -- Printed in The Netherlands THE VALLE DEL BOVE, MOUNT ETNA- ITS ORIGIN AND RELATION TO THE STRATIGRAPHY AND STRUCTURE OF THE VOLCANO J.E. GUEST ~ , D.K. CHESTER: and A.M. DUNCAN 3 ' University of London Observatory, Mill Hill Park, London NW7 2QS ([7.K.) Department of Geography, University of Liverpool, Liverpool L69 3BX (U. K.) 3Department of Science (Geology), Luton College of Higher Education, Luton LUI 3JU (U.K.) (Received March 8, 1983; revised and accepted December 7, 1983) ABSTRACT Guest, J.E., Chester, D.K. and Duncan, A.M., 1984. The Valle del Bove, Mount Etna: its origin and relation to the stratigraphy and structure of the volcano. J. Volcanol. Geotherm. Res., 21:1--23 The Valle del Bove is a major horseshoe-shaped depression some 5 km in diameter and over 1000 m deep, carved into the eastern flank of Mount Etna volcano, The origin of the Valle del Bove has been a subject of debate for over a century but recent models relate it to the collapse of the ancient Trifoglietto II Centre of Etna, either by caldera collapse or phreatomagmatic explosive activity. Careful morphological analysis shows the Valle del Bove to have formed after the post-Trifoglietto II, Ellittico and Leone Centres and therefore to be considerably younger than the Trifoglietto II Centre. It has also been argued that the pyroclastic deposits that occur on the flanks of the volcano in close spatial relationship with the Valle del Bove were produced by the same event. These pyroclastics are divided on the basis of age and composition into two groups: the upper and lower tephra deposits. The stratigraphy, petrology and radiocarbon date of the lower tephra deposits indicate a Trifoglietto II age at least 20 000 years before the formatio~l of the Valle del Bove. The upper tephra deposits have a strong phreatomag- matic character and are closest in age to the Valle del Bove. There is no evidence, how- ever, to link them with its formation. Morphological study shows the Valle del Bore to consist of a series of coalescing scallops indicative of formation by landsliding. The mate- rial removed by slope failure and subsequent fluvial transport followed a valley to the coast where it forms a fan-shaped accumulation, the "Chiancone", consisting of vol- caniclastics of fluvial and mudflow origin. It is argued that the Valle del Bove did not result from simple caldera collapse but formed from a series of collapses caused by gravitational slope failure. The Chiancone is considered to be the product of this collapse. INTRODUCTION The Valle del Bove is a "large craterfform valley" (Lyell, 1858) on the eastern flank of Mount Etna. In plan view the main area of the hollow is sub-circular with a diameter of about 5.5 kin, but to the east it opens to- wards the sea, giving it a key-hole shape; the length is about 6.5 km from the 0377-0273/84/$03.00 C~ 1984 Elsevier Science Publishers B.V.