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Control on the emplacement of the andesite lava dome of the Soufriere Hills volcano, Montserrat by degassing‐induced crystallization
Author(s) -
Sparks,
; Murphy,
Lejeune,
Jenni Barclay,
Paul Young
Publication year - 2000
Publication title -
terra nova
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.353
H-Index - 89
eISSN - 1365-3121
pISSN - 0954-4879
DOI - 10.1046/j.1365-3121.2000.00267.x
Subject(s) - lava dome , geology , lava , porphyritic , andesite , volcano , magma , petrology , dome (geology) , geochemistry , magma chamber , volcanic rock , geomorphology , paleontology , quartz
Lava solidification is controlled by two mechanisms: external cooling and gas exsolution, the latter inducing crystallization due to increasing liquidus temperature. The andesite lava dome of the Soufriere Hills Volcano, Montserrat, is an extrusion dominated by crystallization caused by gas exsolution where cooling is unimportant in controlling emplacement. In the magma chamber the magma has an estimated viscosity of 7 × 10 6 Pa s. During ascent, gas exsolution caused the magma to extrude in a highly crystalline state, with only 5–15% residual melt, viscosities in the range 10 13 –10 14 Pa s and mechanical strength > 1 MPa. Deformation can be heterogeneous with extrusion along shear zones. Rheological stiffening in the upper conduit also causes large overpressures, shallow seismicity, and cyclic patterns of dome extrusion. Gas‐rich porphyritic andesites tend to be the least mobile kind of lava, because transition from magma into hot crystalline material was reached during ascent.