Cobb hotspot, currently located beneath Axial seamount on the Juan de Fuca ridge, has the temporal
but not the isotopic characteristics usually attributed to a mantle plume. The earlier volcanic products of
the hotspot, from eight volcanoes in the Cobb-Eickelberg seamount (CES) chain, show a westward age
progression away from...
We report new major element, trace element, isotope ratio, and geochronological data on the Galapagos
Archipelago. Magmas erupted from the large western volcanos are generally moderately fractionated tholeiites of
uniform composition; those erupted on other islands are compositionally diverse, ranging from tholeiites to picritic
basanitoids. While these volcanoes do not...
The Rattlesnake Ash-Flow Tuff erupted 7.05±0.01 Ma from the western Harney Basin, southeastern Oregon. The location of the vent area is inferred based on vent-ward increases in size of pumices, in degree of welding, and in degree of post-emplacement crystallization. Today's outcrops cover 9000 km2 and estimated original outcrop coverage...