RUI: The Evolution of the Galapagos Hotspot

Colgate University, Hamilton NY

Investigators

Abstract

Many of the world's volcanic island chains, such as Hawaii or the Galápagos, are the surface manifestation of mantle plumes, one of the most important but least well understood tectonic phenomena on Earth. The dominant theory is that mantle plumes originate in the deep mantle, transporting material from the core-mantle boundary to the surface, a distance of nearly 3000 km. As such, variations in the chemical composition of lavas erupted at ocean island volcanoes may provide the only way to sample material from such great depths and, in the process, to determine the composition and structure of these otherwise inaccessible parts of the planet. The primary goal of this project is to carry out a field and geochemical study of the 3 oldest Galápagos Islands to investigate persistent questions related to ocean islands: 1) what is the nature of the material supplying the Galápagos plume, which in turn will provide information about the composition of the deep Earth; 2) how does the plume's composition vary with time; and 3) how do Galápagos volcanoes evolve as they are carried away from the plume's center? The latter question, which addresses the life cycle of ocean island volcanoes, is particularly relevant to ongoing conservation and preservation efforts at oceanic archipelagos worldwide. These questions will be addressed in two stages. First, field studies will be carried out on the 3 oldest, most poorly characterized islands, Santa Cruz, San Cristobal, and Española, which together record almost 3 million years of the plume's history. Radiogenic isotopes, major and trace element, and Ar-Ar analyses will be applied to understand the chemical evolution. The second phase is a focused effort to define the compositions of Galápagos mantle reservoirs by applying high-resolution lead isotopic analyses to a selection of lavas from across the archipelago. Taken together, these efforts will permit evaluation of competing hypotheses for the complex geochemical variation observed in the Galápagos and insight into the origins and nature of mantle plumes. One of the most important goals of this project is the engagement of undergraduates as integral members of the research team. They will also participate in a seminar on mantle dynamics, which will be used to develop a digital repository of presentations by experts in the field that will be archived and made available online. Ecuadorian students will participate in fieldwork and spend a summer at Colgate, where they will also be trained in analytical geochemistry techniques. Finally, students will participate in an established outreach program at Colgate, working with K-12 students from across upstate NY performing hands-on science activities and developing a state-of-the-art presentation on volcanic evolution at the Colgate Visualization Lab.