Other volcanoes which exhibit “classic” strombolian behaviour are Yasur Volcano (Vanuatu) 17, which erupts magmas containing 35–40 vol% crystals 10 Erebus Volcano (Antarctica) 18, where magmas contain 30 vol% anorthoclase feldspar 19 and other crystal-rich basaltic-andesitic arc centres, such as Pacaya 20, Fuego 21, Pavlov 22, and Karymsky 23. Magmas erupted from Stromboli Volcano are highly crystalline, containing up to 40 vol% phenocrysts 11, 12, 13 and it is likely that the exsolved gas phase interacts with the crystal cargo of the magma 14, 15, 16, thereby modifying the dynamics of the eruptions. At Stromboli Volcano, Italy, the type example of such activity, the gas slugs are often rich in CO 2 over more soluble volcanic gases 5, 6, indicating an origin of a few kilometres depth or more 7, where extensive crystal-rich magma reservoirs are inferred to exist 8, 9, 10. The periodicity of typical strombolian eruptions has been attributed to the rise and bursting of large, conduit-filling, over-pressurized gas slugs 1, 2, 3, 4. Highly crystalline shallow portions of basaltic conduits may act as a flow valve, transforming a steady gas flux into a series of discrete gas slugs which cause explosions.Ī link between strombolian activity and crystal-rich magmas With higher gas fluxes, continuous channelised gas flow occurs. The continued supply of gas leads to the formation of a new intrusion, and the cycle repeats. As the pressure in the intrusion falls, the gas pocket collapses. Once the pressure in the intrusion overcomes the effective tensile strength of the particle pack, a localised channel opens, allowing gas to propagate upwards. A steady flux of gas is supplied to the base of a particle-rich liquid layer, generating a localised gas intrusion, which initially grows through plastic deformation. Through analogue experiments, we explore a new mechanism to form gas slugs and strombolian explosions. The magmas associated with strombolian activity, however, are typically not only volatile-rich but also highly crystalline, with mush regions in the shallow plumbing system, where an exsolved volatile phase may also be abundant. Strombolian volcanic explosions are commonly attributed to the rise and burst of conduit-filling gas slugs.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |