Abstract
THE interaction between gravity and thermal effects largely determines the structural and magmatic evolution of volcanic constructs at scales spanning several orders of magnitude, from small cones to the oceanic crust1–3. Although gravitational spreading is a direct consequence of this interaction and a fundamental process in volcano growth, it is rarely recognized as such. Here we describe a striking example of this process, at Etna volcano, in Italy. The volcano and its clay-rich substratum are slowly spreading towards the east and south, driven by gravity. Spreading produces extensional structures in the summit region and contpressional structures at the base of the volcano. Eastward movement of the volcanic edifice over a stationary magma supply may be the cause of an apparent westward migration of volcanic activity. As gravitational spreading seems to control the location and magnitude of shallow seismicity and flank eruptions, an appreciation of its effects could become an essential element of future volcanic hazard evaluation. Our model proposed here for Etna may also be relevant to a reinterpretation of the geological history of a number of other volcanoes.
Published Version
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