Turbidity currents are waterfalls of sediment that tumble down the planet’s 9,000 submarine canyons, carrying carbon, plastic and pharmaceuticals into the deep ocean. We’re finally learning how often these dramas happen.
January 24, 2023
In November 1929, a major earthquake shook the Grand Banks off the southern coast of Newfoundland, Canada, shaking as far away as New York. As the sea floor shook, a massive amount of sand and dirt began to churn and flow down the canyon, gathering momentum as it went, creating a dramatic underwater avalanche.It involved enough material to make two Mount Everests and sparked tsunami More than 25 people were killed.
It’s the largest known example of an undersea avalanche, but it wasn’t a one-off. Beneath the waves, the world’s largest avalanches regularly occur along Earth’s coasts and oceans, carving out some of the deepest and longest canyons on Earth. Most of the time, they happen without anyone noticing.
For hundreds of years, the only witnesses to these events were fish and deep-sea creatures, who were likely carried out to sea or fed by nutrient-rich sediments carried by ocean currents. More recently, ruptured natural gas pipelines and ruptured communications cables have demonstrated that extremes are taking place. However, over the past few years, things have started to change.
Now, thanks to a series of experiments and a little bit of luck, we’ve caught these Earth-carving events happening. It turns out that the labyrinth of underwater canyons, many of which were long thought to be geologically inactive, are not at all. Armed with new data, researchers are beginning to piece together a better picture of what undersea avalanches look like, how they shape Earth, and their important role in locking up the carbon that warms our world.
The deepest and longest canyon system…