Spatial and Temporal Scales of Recent Turbidity Currents in Monterey Submarine Canyon, California

Turbidity currents are responsible for transporting and depositing most of the sand and other coarse clastic sediment to deep-sea fans and deltas, and for creating and maintaining the omnipresent submarine channels on the continental slope. The temporal and spatial scales (duration, speed, and run-out distance) of turbidity currents have always been of keen interest to geologists because of their importance in determining the size and distribution of turbidites - deposits formed by turbidity currents. Here we present in-situ velocity and turbidity data of modern-day turbidity currents measured in Monterey Submarine Canyon during 2002 - 2011. The experiments co-conducted by the U.S. Geological Survey and the Monterey Bay Aquarium Research Institute were among the first studies specifically designed to measure field scale turbidity currents, which have provided by far the most complete picture of any marine turbidity current. Concurrent measurements from downward-looking ADCPs at multiple locations along the canyon provided high-resolution velocity profiles of the turbidity currents. Temperature and turbidity sensors above the ADCPs recorded the time of arrival and the duration of the turbidity currents. These high-resolution, high-frequency data allowed us to quantitatively characterize the bulk properties (maximum speed, thickness, density, etc) and their along-canyon evolution. The measured properties of field turbidity currents are used to examine the validity of empirical relationships obtained from theoretical analysis and laboratory experiments. The correlations between these properties and the lateral size (run-out distance) and the autosuspension criteria are also discussed.