Controls on extrusion at mid-ocean ridges

• 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
• ISSN: 0091-7613; 1943-2682
• DOI: 10.1130/0091-7613(1997)025<0935:COEAMO>2.3.CO;2

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.