Award: OCE-1260408

This project explored linked geological, geophysical, geochemical, and microbiological processes within the uppermost layers of the volcanic ocean crust. The project involved use of five (5) long-term observatory systems that were installed in boreholes drilled into the ocean crust, in 1.5 miles of water, about 60 miles west of Vancouver Island in the northeastern Pacific Ocean. As part of an earlier drilling expedition in this area, chemical tracers were injected into the ocean crust using one borehole, and we returned several years later to collect samples and data that would help to understand how fluids and chemicals move through the ocean crust, and how these processes may influence microbial life. The upper ocean crust has a lot of water moving in and out - when considered on a global basis, this flow is equivalent to the discharge of all of the rivers on Earth into the ocean. But we know little about how this flow occurs and what impacts it has on the nature of Earth's outer layers or the microbes that live below the seafloor. As part of this project, we visited the deep ocean boreholes using a submersible, called Alvin (Fig. 1), which allowed us to recover instruments and download data from the seafloor. With the data in hand, we were able to make calculations and run computer simulations that help to explain how fluid flow and related processes occur below the seafloor. In one study, we determined how the chemical tracer injected into the seafloor during an earlier drilling expedition spread and was transported over several years. In another study, we calculated how water and heat flow within the ocean crust as a result of water flowing in and out through seamounts, extinct volcanoes that were created when the crust was younger. Together, these studies show that fluid velocities are much faster, and the fraction of rock through which water and chemicals are transported is much smaller, than previously thought. These results have important implications for how life developed and has evolved on Earth, how water resources in fractured rock can be more effectively managed, and how excess carbon dioxide might eventually be stored deep inside the Earth. This grant also supported the training of students and other young researchers, and presentations made to several public groups concerning the research and related topics. Last Modified: 09/06/2017 Submitted by: Andrew T Fisher