‘Mechanical erosion by flowing lava’

Gli argomenti trattati sono di interesse per coloro che lavorano in vulcanologia, geologia strutturale, tettonofisica, geomorfologia, modellisica dei processi fisici e scienze dei materiali.

Abstract:

      Hot lava is a viscous fluid that, driven by gravity, moves along the Earth’s surface. Intuitively, one attributes constructional properties to lava, it accumulates in volcanic landforms, compound lava fields and, in the end, entire mountains. On the other hand, there are also examples of the erosive power of lava: on Earth and especially on other planets in the Solar System, there exist channels incised by flowing lava. The origins of these erosive features have long been debated among volcanologists and planetologists. The dominant paradigm is thermal erosion, although it leaves many questions open.

      The 2001 eruption on Mount Etna has left a lava channel whose features cannot be explained in the frame of thermal erosion. Field observations led to the development of a model for mechanical erosion that explains the main, and opens alternative ways to describe erosion by flowing lava. The essential erosion mechanism was abrasive wear.

Consequently, the erosional processes resembling the wear phenomena in glacial erosion are possible in a volcanic environment. The occurrence of a lava flow able to abrade a hard surface made of solidified lava is surely an extraordinary event and can be related to a rapid, syn-eruptive increase of magma viscosity, which was caused by an efficient volatile loss and the consequent nucleation of Fe-oxides and other anhydrous crystalline phases. The significant increase of magma viscosity directly in the upper part of the conduit, besides leading to the emission of a high viscosity lava flow brought the eruption to its end.

      Invoking ideas of abrasion and wear makes it possible to account for high erosion rates in relatively short times and at comparatively low lava outputs. These results can stimulate intensified research about the role of mechanical erosion mechanisms in the investigation and interpretation of lava channels observed on many celestial bodies of our Solar System.

References:

- Ferlito and Siewert, 2006-Lava channel formation during the 2001 eruption on Mount Etna: Evidence for mechanical erosion. PHYS. REV. LETT. 96, 28501

- Siewert and Ferlito, 2008-Mechanical erosion by flowing lava, CONTEMPORARY PHYSICS, 49,43-54