Controls on extrusion at mid-ocean ridges

A magma lens can erupt to form extrusives only if it is under greater pressure than the static pressure in a column of magma reaching from the lens to the surface. The excess pressure results partly from overburden pressure caused by the presence of high- and low-density rocks (dikes and extrusives,...

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Bibliographic Details
Published in:Geology (Boulder) 1997-10, Vol.25 (10), p.935-938
Main Authors: Buck, W. Roger, Carbotte, Suzanne M, Mutter, Carolyn Z
Format: Article
Language:English
Subjects:
basalts
controls
crust
density
depth
eruptions
extension
extrusive rocks
flexure
Geophysics
igneous and metamorphic rocks
igneous rocks
lithosphere
magma chambers
magmas
Marine
mechanical properties
mid-ocean ridges
oceanic crust
Oceans
Petrology
plate tectonics
pressure
sea-floor spreading
solid Earth (tectonophysics)
spreading centers
stress
thickness
viscosity
volcanic rocks
Volcanoes
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Summary:A magma lens can erupt to form extrusives only if it is under greater pressure than the static pressure in a column of magma reaching from the lens to the surface. The excess pressure results partly from overburden pressure caused by the presence of high- and low-density rocks (dikes and extrusives, respectively) above the lens. The thicker the pile of low-density extrusives, the lower the average overburden density. Thus, extrusion above a lens should be self-regulating, in that thickening the extrusive layer reduces the driving pressure for subsequent eruptions. Flexural stresses may affect extrusion by altering the pressure on a magma chamber. For ridges lacking an axial valley, we predict that deeper magma lenses should correlate with thicker extrusive layers, consistent with recent observations.
ISSN:0091-7613
1943-2682
DOI:10.1130/0091-7613(1997)025<0935:COEAMO>2.3.CO;2