Submarine canyons are thought to be major conduits for sediment movement from the continents into the deep-sea. This image shows the morphology of Monterey Bay and the adjacent Salinas Valley with arrows which schematically represent some of the major sediment transport routes for the materials which may enter the canyon.
Most scientists agree that the majority of the sediment that passes through submarine canyons probably moves only in relatively brief sediment transport events. Some of these events are entirely marine, but some are land-linked. Examples of marine events include submarine slope failures (e.g. slumps or slides), that move material from the canyon walls to the canyon floor and may generated turbidity flow that continue down the canyon. Earthquakes or major storms may trigger such events.
Satellite images of suspended sediments in a 1998 flood
Land-linked events may occur when high rainfalls cause rivers to flood. The water carried by most river systems usually form buoyant plumes of fresh water that over the seawater where the river discharges into the ocean. However, rapid flows during flooding rivers can pick up and carry enough suspended sediment so that the river water becomes denser than seawater. Thus, when the suspended sediment loaded waters from these rivers enter the ocean, they can form hyperpycnal plumes that continue to flow along the bottom.
While sensors in the axis of Monterey Canyon will provide unique data on the dynamics of hyperpycnal events, other supporting data need to be collected simultaneously to maximize our understanding of these events. We are prepared to deploy event response cruises following big storms or earthquakes. The objective of the event response cruises will be: (1) to capture the suspended materials in the water column to calibrate the signals at the sea floor instruments sites, (2) to determine the vertical properties of the flows which will allow the volume of transported material to be constrained, and (3) to determine how far down canyon the transport event extended. All the critical data will be obtained using the R/V Point Lobos and its hydrocast gear.