Physics
Scientific paper
Dec 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992pepi...74..127i&link_type=abstract
Physics of the Earth and Planetary Interiors, Volume 74, Issue 3-4, p. 127-138.
Physics
3
Scientific paper
The width change of a planar path filled with magma is analyzed, assuming that the process is controlled by laminar flow of an incompressible viscous magma between movable parallel walls of country rock. The analysis shows that the width of a planar path changes at a rate is proportional to the effective opening pressure, which is defined as the pressure of the penetrating magma plus the tensile stress component stretching the fluid interface. When the opening pressure is a positive constant, the fissure widens at an accelerating rate and finally diverges at a critical time constant, which depends on the initial size of the fissure and the viscosity of magma as well as on the opening pressure. In contrast, the fissure gradually narrows under a negative opening pressure. This result is applicable to a variety of magmatic processes. First, the orientation of a volcanic fissure or a dike is such that the tensile stress component is maximized, because a fissure with this orientation becomes wider than those at other orientations, as it has the minimum value of critical time constant. Second, local irregularities in the geometrical and mechanical conditions of the magma sheet lead to significant variations in fissure width in the widening process. This nonuniform increase in width is further exaggerated by mechanical and thermal erosion of the wall rock, which makes the irregular surfaces irrecoverable. In this manner, a planar magma path tends to be split into isolated cylindrical conduits when the magma pressure is reduced and the fissure closes as a whole. Some actual fissure eruptions, such as those at Kilauea and Izu-Oshima, show evolutionary processes consistent with this prediction. Another application of the analysis is to explain how the style of a volcanic eruption is determined by the tectonics. Specifically, extensional tectonics, which gives a positive opening pressure for any magma pressure, allows magma to ascend dispersively along various paths, and produces a group of small monogenetic volcanoes. In contrast, contractional tectonics, in which new fissures can be made only for a very high magma pressure, concentrates magma into a restricted number of vents and leads to the growth of large polygenetic volcanoes.
No associations
LandOfFree
Width change of a planar magma path: implication for the evolution and style of volcanic eruptions does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Width change of a planar magma path: implication for the evolution and style of volcanic eruptions, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Width change of a planar magma path: implication for the evolution and style of volcanic eruptions will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1140715