Fernandina Volcano: Why the Galapagos hotspot isn’t so hot

James Allan, Ph.D.
National Science Foundation—Ocean Drilling Program

Wednesday, June 7, 2000
3:00 p.m.—Pacific Forum

Fernandina Volcano, the most active of Galapagos volcanoes and the one most directly overlying the Galapagos hotspot, has erupted homogenous, plagioclase-phyric tholeiitic lavas over its accessible history. Within its shallow magma chamber, underlying a well-defined, 850m-deep, 5 by 6.5 km caldera, efficient mixing of already-evolved
(Mg# < 0.63) parental melts occurs. Fernandina lavas are in sharp contrast to more primitive, olivine-dominated Hawaiian lavas. The lack of primitive melts in the shallow Fernandina magmatic system implies that substantial fractionation and heat loss occurred during lithospheric melt transport to the edifice magma chamber, despite traversing through warm, young, and thin lithosphere adjacent to the Cocos-Nazca ridge. The diffuse nature of Galapagos volcanism suggests that the Galapagos plume is relatively diffuse, weak, and significantly less thermally intense than the vigorous Hawaiian plume, and may be waning.

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