Photographs coming soon…
Members of the UCSC Hydrogeology group have collaborated with colleagues on numerous studies of seafloor, ridge-flank hydrothermal circulation, often in areas located far from the magmatic and tectonic influence of seafloor creation. Ridge-flank systems are common globally, but only a few have been studied with sufficient detail to resolve rates and patterns of fluid flow, quantify the redistribution and extraction of lithospheric heat, and sample hydrothermal fluids and microbial ecosystems in the largest aquifer on the planet. In past decades, the UCSC Hydrogeology group have completed observational and numerical studies of four iconic systems on the eastern flank of the Juan de Fuca Ridge, southern flank of the Costa Rica Rift, eastern Cocos Plate, and western flank of the Mid-Atlantic Ridge. Our studies were the first to identify and simulate, first in one dimension and two dimensions, and later in three dimensions, the development and sustainability of a “hydrothermal siphon,” linking sites of seafloor recharge to distant discharge, often separated by tens of kilometers. Through this research, we have helped to identify locations where water enters and exits the seafloor, mapped patterns of flow in the surrounding seafloor, and located seeps and springs that allowed collection of the first pristine samples from these globally-important systems.
We have often used heat as a tracer, and have helped to develop new instrumentation and processing and display tools for seafloor geothermal surveys. Instruments we have applied include multi-penetration heat flow probes, outrigger probes for core barrels, and probes deployed with a submarine or remotely-operated vehicle. We recently published a paper that presents graphically interactive processing tools and a workflow that can improve processing of marine geothermal data. We often collaborate with colleagues having expertise in seismic reflection data collection and interpretation, sediment coring and analysis, fluid geochemistry and seafloor/subseafloor microbiology, as subseafloor hydrogeologic systems have important implications for global flows of solutes, reactions in the upper lithosphere, and the development and sustainability of microbial communities. Historically, much of this work was completed in association with ocean drilling expeditions, installations, and surveys, which was essential for understanding the “plumbing” of subseafloor pathways and the nature of mixing, reactions, and transport. We were also part of the Center for Dark Energy Biosphere Investigations (C-DEBI), an NSF-funded Science and Technology Center run out of the University of Southern California.
The UCSC Hydrogeology group has joined with colleagues at numerous other institutions as part a NASA funded project on Exploring Ocean Worlds, linking planetary scientists and astrobiologists with Earth/ocean scientists who have expertise in hydrothermal systems. As part of this work, we ran simulations of Earth-type hydrothermal circulation under ocean-world gravity conditions, to assess the interplay between reduced buoyancy (which should tend to reduce the flow between two ends of a hydrothermal siphon) and reduced secondary convection and higher reaction temperatures (a consequence of reduced buoyancy), which should result in more efficient heat transport. Simulations suggest higher reaction temperatures and greater power output under ocean-world gravity, which may help to sustain advective heat extraction on small ocean worlds, even when geothermal heating is limited. We recently extended this work with a Monte Carlo framework that links analytical calculations to explore thousands of parameter options for these kinds of flow systems. Addition numerical simulations are underway, including the use of heterogeneous property distributions and discrete-fracture network modeling, in collaboration with colleagues from Los Alamos National Laboratory.