One of the most frequent questions I get when talking to people about the field sites I study is - "Where is that located?". I figured this may be a question to some of you had as well. So while I am stuck in quarantine, I figure I would use this time to discuss:
Where is the Southern East Pacific Rise located? To get started, I need to back up a few steps to help explain the processes that make the East Pacific Rise. The East Pacific Rise is what is knows as a Mid-Oceanic Ridge spreading center. Mid-Oceanic Ridge spreading centers are found globally where two tectonically active plates spread apart from each other. In the Pacific Ocean, "the ring of fire" - a ~40,000 km (~25,000 miles) tectonically active region around the rim of the Pacific - is know to be an area of increase volcanism and earthquakes. As a part of the "ring of fire", the East Pacific Rise extends from the Gulf of California to Antarctica, and is made of multiple plates that are sliding or spreading apart from each other at variouse rates. The Southern East Pacific Rise just referrers to any part of the East Pacific Rise that is located from the equator to Antarctica. On this expedition, we will be specifically exploring and sampling sites between 15-18 S along the Southern East Pacific Rise. What makes these a good site for hunting for hydrothermal vents? Along the East Pacific Rise, the rate at which the plates spread apart from each other varies. The Southern East Pacific Rise is what is known as the an ultra fast spreading ridge. This means the plate spread apart at a rate of 141-162 mm/yr (5.6-6.4 in/yr). To put this in perspective, the rate of parts of the Northern East Pacific Rise (e.g. a fast spreading ridge) is ~110 mm/yr (4.3 in/yr) and the Mid Atlantic Ridge in the Atlantic Ocean (e.g. a slow spreading ridge) moves at 20-50 mm/yr (0.79-1.97 in/yr). These different rates impact the volcanisms and shape of the ridge along the ocean floor. Due to the fast rate of spreading along the Southern East Pacific Rise, the ridge is constantly being flattened and reformed creating a relatively shallow ridge formation comparted to other Mid-Oceanic Ridges. But more importantly, Mid-Oceanic Ridges (and specifically the Southern East Pacific Rise) make excellent sites for hunting for underwater volcanoes (i.e. hydrothermal vents). Hydrothermal vents are formed when seawater is circulated through hot, chemically reactive, porous crust, creating hydrothermal fluids. The hydrothermal fluids are less dense (reaching temperatures between 350-400 C or 662-752 F) then deep ocean water (2 C or 35.6 F), creating underwater hot-springs that produce chemically-rich plumes. The vent chimneys are created through the precipitation process of sulfide or other minerals building up, focusing the stream of hydrothermal fluids into the deep ocean. In addition to these high temperature vents, there are low temperature vents that are classified by being less particle-rich and having fluids between 50-100 C (122-212 F). Recent work along the Southern Pacific Rise, has shown that the parts of the ridge we will be visiting are dominated by diffuse low-temperature hydrothermal vents. This makes an exciting place to study and investigate hydrothermal processes and the role of low-temperature diffuse flow in these systems. Why do we care? There are many reasons to care about hydrothermal systems. For one, they are exciting places to explore, but also hot beds for biological diversity in the deep sea, mineral production, and questions about origin of life. In some cases, certain species are only found along specific ridge systems-an area of active study. In 2013 a ~4300 km (~2700 miles) hydrothermal plume was found emanating from the Southern East Pacific Rise. To this day, it is still the largest known hydrothermal plume. What was more surprising was how far certain trace elements (iron, manganese, aluminum, etc) plumes extended as well. Iron is depleted in much of the ocean, and initially thought to precipitate and settle out of hydrothermal plumes. However, over the last decade, we have discover multiple mechanisms for iron to be stabilized and transported away from the vent and into the ocean interior. One of these mechanisms is with metal binding-organic ligands. Metal-binding organic ligands stabilize, and aid in the utilization of iron for marine microorganisms. Our motivation is to investigate and characterized iron-binding organic ligands in hydrothermal plumes along the Southern East Pacific Rise. We are specifically targeting low-temperature systems, but also hope to be able to compare it to a few local high-temperature sites as well. Understanding how iron is stabilized and protected from oxidation, as well as utilized by microorganism within/around the hydrothermal plume is critical for constraining the global and local geochemical impact of hydrothermal ridge systems, like the Southern East Pacific Rise. References
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AuthorColleen L. Hoffman is a scientist by day and adventurer by night. She is currently a postdoctoral scholar at the University of Washington. Categories
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