Newly recognized turbidity current structure can explain prolonged flushing of submarine canyons
نویسندگان
چکیده
Seabed-hugging flows called turbidity currents are the volumetrically most important process transporting sediment across our planet and form its largest sediment accumulations. We seek to understand the internal structure and behavior of turbidity currents by reanalyzing the most detailed direct measurements yet of velocities and densities within oceanic turbidity currents, obtained from weeklong flows in the Congo Canyon. We provide a new model for turbidity current structure that can explain why these are far more prolonged than all previously monitored oceanic turbidity currents, which lasted for only hours or minutes at other locations. The observed Congo Canyon flows consist of a short-lived zone of fast and dense fluid at their front, which outruns the slower moving body of the flow. We propose that the sustained duration of these turbidity currents results from flow stretching and that this stretching is characteristic of mud-rich turbidity current systems. The lack of stretching in previously monitored flows is attributed to coarser sediment that settles out from the body more rapidly. These prolonged seafloor flows rival the discharge of the Congo River and carry ~2% of the terrestrial organic carbon buried globally in the oceans each year through a single submarine canyon. Thus, this new structure explains sustained flushing of globally important amounts of sediment, organic carbon, nutrients, and fresh water into the deep ocean.
منابع مشابه
Turbidity Current Hydrodynamics and Seabed Morphology
Our main goal is to assess the hydrodynamics of turbidity currents and mudflows and their ability to produce morphological features such as ripples, dunes, antidunes and gullies along their paths. Of particular interest is to elucidate the role played by turbidity currents on the inception of submarine channels and canyons. To this end, understanding the mechanics of sediment erosion, including...
متن کاملThe Effect of Event Sequences on the Characteristic of Turbidity Current Deposits
Similar submarine canyon systems exist on scales ranging from less than a kilometer to nearly 1000 km. The shallowest end is a submarine canyon and canyon head(s). Further down the canyon is buried by the upper part of a submarine fan with meandering and cross-cutting channels. The fan eventually merges with a nearly flat-lying depositional basin. We have used the deposits associated with these...
متن کاملSediment Waves and Gullies Generated by Turbidity Currents
Our objective is to improve our understanding of the genesis of large-scale bed forms similar to those observed in various submarine settings, and thought to be created by both confined and laterallyspreading turbidity currents and related dense underflows in continental slopes and rises. Two types of bed forms are the main focus of this work. First, slope gullies, which are parallel, evenly-sp...
متن کاملTurbidity Currents and Seabed Morphology
Our main goal is to assess the hydrodynamics of turbidity currents and mudflows and their ability to produce morphological features such as ripples, dunes, antidunes and gullies along their paths. Of particular interest is to elucidate the role played by turbidity currents on the inception of submarine channels and canyons. To this end, understanding the mechanics of sediment erosion, including...
متن کاملUndersea landslides: extent and significance in the Pacific Ocean, an update
Submarine landslides are known to occur disproportionately in a limited number of environments including fjords, deltas, canyons, volcanic islands and the open continental slope. An evaluation of the progress that has been made in understanding Pacific Ocean submarine landslides over the last 15 years shows that mapping technologies have improved greatly, allowing a better interpretation of lan...
متن کامل