Unknown
In:
J. Geophys. Res., Dordrecht, Netherlands, Dr. W. Junk, vol. 106, no. B6, pp.
11101-11114, pp. L08304, (ISSN: 1340-4202)
Publication Date:
2001
Description:
We use laboratory experiments and numerical models to examine the effects of
volcano loading on the propagation of buoyant dikes in a two-dimensional elastic
half-space. In laboratory experiments we simulate the propagation of buoyant dikes in an
isotropic regional stress field by injecting air into tanks of solidified gelatin. A
weight resting on the surface of the gelatin represents a volcanic load. A numerical
model is used to simulate these experiments. Both experiments and numerical simulations
show that as a dike ascends, it begins to curve toward the load in response to the local
stress field imposed by the load. The lateral distance over which dikes curve to the
load increases with the ratio of average pressure at the base of the load to the dike
driving pressure. For realistic volcano and dike dimensions this pressure ratio is going
to be large, suggesting that dikes can converge to a volcano over lateral distances
several times the load width. Numerical calculations involving an anisotropic regional
stress field, however, predict that the lateral extent of dike attraction shrinks as the
regional horizontal compressive stress decreases relative to the vertical compressive
stress. Dike focusing will be substantial if the regional differential stresses are less
than the average pressure at the base of the load. If this is the case, then our models
predict a positive feedback between the size of volcanoes and the area of dike
attraction. This feedback may promote the development of large discrete volcanoes and
also predicts a positive correlation between the spacing and sizes of adjacent
volcanoes. To test this prediction, we examine nearest-neighbor pairs of the 21 largest
volcanoes in the Cascade Range. The 14 pairs examined show a large range in volcano
spacing (6 - 115 km) and a statistically significant correlation between spacing and
average volcano height. This result is consistent with our model results and suggests
that the local compressive stress induced by these volcanoes may be an important factor
in controlling magma transport in the lithosphere.
Keywords:
Elasticity
;
Gravimetry, Gravitation
;
Modelling
;
magma
;
ascent
;
JGR
;
1829
;
Hydrology:
;
Groundwater
;
hydrology
;
8414
;
Volcanology:
;
Eruption
;
mechanisms
;
8429
;
Lava
;
rheology
;
and
;
morphology
;
8499
;
General
;
or
;
miscellaneous
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