Collaborative Research: Rise and Fall of Galapagos Seamounts

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The Galapagos Islands are unique in their construction. The islands sit on a laterally extensive platform consisting of thick layered lava flows and intrusions that rises 3 kilometers above the surrounding seafloor. Sitting on this platform and peeking out of the water are major volcanic islands that form the basis of Darwin's treatise on the Origin of Species. Interestingly enough, the islands only comprise about 5 % of the volume of the Galapagos platform, which is thought to have originated by melting of the mantle and oceanic lithosphere via a thermal plume originating deep in the mantle. With the exception subaerially exposed parts of the volcanic islands, much of the Galapagos platform remains unsampled and unstudied. A recent oceanographic expedition to the Galapagos, funded by the Dalio Foundation and the Ocean Exploration Trust, mapped part of the platform between some of the major islands and discovered 70 previously unknown submerged volcanic edifices that appear to sport wave-cut erosional features on their surface, indicating that, once, parts of them were exposed above sea level. Over 150 rock samples were collected on the expedition, with hopes that their geochemistry would help to unravel the relationships between the plume source of magma and the chemistry of the volcanoes themselves. This research project will analyze these samples and provide more sophisticated processing of the bathymetric and other geophysical data that was collected on the recent cruise to the Galapagos in hopes of better understanding the recent volcanic history and the rise and fall of the platform with relation to sea level. Using cosmogenic isotopes and the He that is released during radioactive decay, it is hoped that the vertical movement of the small submerged volcanic features displaying subaerial erosional features can be dated and related to sea level, thermal upwelling due to plume resurgence, and platform subsidence over time. Hypotheses to be tested include examining whether the 70 small Galapagos seamounts each represent their own tapping into the mantle upwelling with magmatic systems that are distinct from the adjacent volcanic islands and each other. This will be tested by analyzing samples from the seamounts for major and trace elements, radiogenic isotopes of Sr, Nd, U, and Pb, and noble gases. These data will be used to look for geochemical similarities and differences. Coupled with this magma source study will be a refinement of the collected seafloor topography to examine relationships between seamounts and their geomorphic features and to identify additional signs of emergence from the ocean, which may reveal information about sea level changes over time. Broader impacts of the work include providing critical site characterization for the Galapagos Marine Research, a UNESCO World Heritage Site. Because the submerged volcanic edifices are hotspots of marine life and biodiversity, this work also provides important input into the development of Galapagos protected biological site characterization. Additional impacts include support of an early career faculty member whose gender is under-represented in the sciences and who is employed at an institution in Idaho, an EPSCoR state (i.e., a state that does not receive significant federal funding); significant student training; and outreach to transmit the excitement and wonder of marine geology research to the public. Results of the geophysical and submarine topographic studies will be used by the Ecuadorian government to assess potential tsunami hazards from Galapagos volcanic structures.