Magma degasses during ascent, erupts as lava flows These flows oozed onto the ground only after the explosive eruption of pumice and ash had stopped. Clearly, by the time the molten rock had reached the surface, much of its dissolved gas had already been released into the atmosphere. Instead of being "trapped" in the magma until the build up of gas pressure became high enough to cause a sudden violent release of gas into the atmosphere (explosion), the dissolved water apparently formed gas bubbles that escaped during its ascent. The lava flows contain less than 0.5% dissolved water compared to 2-3% dissolved water of the earlier explosive magma. This small difference in water content (dissolved volatiles) of molten rock meant the difference between explosive eruptions and the quiet effusion of lava at the surface of the Inyo chain. |
Eichelberger, J.C., Carrigan, C.R., Westrich, H.R., and Price, R.H., 1986, Non-explosive silicic volcanism: Nature, V. 323, no. 6089, pp. 598-602.
Miller, C.D., 1985, Holocene eruptions at the Inyo volcanic chain, California -- implications for possible eruptions in the Long Valley caldera: Geology, v. 13, pp. 14-17.