Constructing a 1.5-million-year time series of magmatic and hydrothermal activity at the Juan de Fuca ridge

Harvard University, Cambridge MA

Investigators

Abstract

Mid-ocean ridges are the sites of 80% of Earth’s volcanism. This study will collect samples along profiles perpendicular to the Juan de Fuca Ridge offshore Oregon and Washington to study changes in eruption through time. In particular, the time series will allow tests of the hypothesis that ice age cycles may influence cycles of ocean ridge volcanism and associated hydrothermal activity. The idea is that higher sea levels will increase pressure and reduce hydrothermal activity, while lower sea levels will have the opposite effect. Cruises to the Juan de Fuca ridge just off the coasts of Oregon and Washington will permit time series of one million years or more to be obtained for the first time. Understanding volcanic cycles is important because eruptions and hydrothermal activity exert an important control on the chemical composition of the oceans, which influences marine ecosystems and long-term Earth systems. This project will provide support for undergraduate students to participate in the research cruise and contribute to a museum exhibit at the Harvard Museum of Natural History. The project will produce the first continuous, co-registered time series of glass compositions, hydrothermal activity and bathymetry over the past one million years at the Juan de Fuca Ridge. A field program will acquire sediment cores along three transects. Analyses on volcanic glass preserved in the sediment cores will comprise sediment geochemistry for age models and hydrothermal activity, major and trace elements of glasses, radiogenic isotope analyses, volcanological evaluation, modeling of mantle melting, and quantitative statistical and time-series modeling. Broader impacts include training multiple graduate students and post-docs in state of the art techniques, education and participation of undergraduates on the cruises, an international conference on interactions between glacial cycles and solid earth processes, an exhibit at the Harvard Natural History Museum, and international collaborations. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.