What are Turbidity Currents?
Turbidity currents are swift, gravity-driven currents of dense, sediment-laden water that flow along the bottom of oceans, lakes, and reservoirs. They resemble underwater avalanches, carrying sand, silt, and clay down slopes, often originating from submarine landslides, earthquakes, or river floods that destabilize sediments on continental shelves.
Key Principles and Characteristics
These currents are characterized by their high density, caused by the suspended sediment, which allows them to flow downslope under the influence of gravity, even on gentle gradients. They can travel hundreds to thousands of kilometers at speeds up to 100 km/h, carving out submarine canyons and depositing distinctive layered sediments known as turbidites. The current's energy keeps the sediment suspended, preventing it from settling prematurely.
A Practical Example: Submarine Canyon Formation
A classic example is the formation of submarine canyons. Turbidity currents originating on the continental shelf or slope repeatedly flow through these channels, eroding their walls and deepening their beds over time. The 1929 Grand Banks earthquake off Newfoundland, for instance, triggered a massive turbidity current that severed multiple transatlantic telegraph cables, providing direct evidence of their existence and immense power, as the breaks occurred sequentially down the slope.
Importance and Applications
Turbidity currents are crucial for understanding deep-sea sedimentation, ocean basin evolution, and the global carbon cycle. They transport organic matter and nutrients from shallower waters to the deep sea, influencing marine ecosystems. From an economic perspective, understanding turbidite deposits is vital for petroleum exploration, as these ancient sediments often form significant oil and gas reservoirs, and for assessing risks to submarine cables and pipelines.