Underwater avalanches of sediment are the primary architects of the deep ocean floor

Nature · Published 3 October 2026 Swipe more like this →

In short: Turbidity currents are rapid, gravity-driven flows of sediment-laden water that act like underwater avalanches. By scouring the seafloor and transporting massive amounts of material from continental shelves to abyssal plains, these transient, high-density currents carve out the deep-sea canyons that define the topography of our planet's hidden underwater landscapes.

A turbidity current is a suspension current where gravity acts upon a dense, turbid mixture of fluid and sediment. Because this mixture is denser than the surrounding ambient water, it flows downhill, often accelerating as it gathers more particles. This process creates a feedback loop: as the current gains speed, it increases turbulence, which allows it to erode and entrain more sediment, further increasing its density and velocity. This 'snowballing effect' allows these currents to scour the seafloor, acting as a primary agent in the formation and maintenance of submarine canyons.

While traditionally defined as flows where sediment is suspended by fluid turbulence, recent research suggests the mechanism may be more complex. Observations from the Monterey Bay Aquarium Research Institute indicate that a layer of water-saturated sediment moving rapidly over the seafloor may be the primary actor, with the visible sediment-laden water plume acting as a secondary tail-end to the main pulse of moving seafloor material. These events can be triggered by earthquakes, slope slumping, or sediment-heavy river outflows, particularly during periods of low sea level when rivers empty directly into canyon heads.

The impact of these currents is profound. They act as essential conduits, transporting sand-sized sediments from continental margins to the deep sea. When these currents reach the flatter abyssal plains, they lose energy and deposit their load, forming structures known as turbidites. This process is not limited to the ocean; it also occurs in alpine reservoirs, where turbidity currents follow the thalweg to the deepest areas near dams, potentially impacting intake structures. Understanding these flows is vital, as they are responsible for shaping the physical architecture of the ocean floor, from the steep walls of submarine canyons to the vast, sediment-rich plains beyond.

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