The Atacama Trench in the Pacific Ocean is also home to funky but fascinating creatures including a deep-sea snailfish that can “melt rapidly when brought to the surface”
You might have never heard of the Peru–Chile trench but what goes on in this underwater trough more than 90 miles off the western coast of South America can impact coastlines and communities many miles away.
Also called the Atacama Trench, it’s more than 3,500 miles long, 40 miles wide and up to around 8,000 meters (five miles) deep.
The trench formed around 23 million years ago when the Nazca tectonic plate collided with the South American plate and started being pushed underneath into the Earth’s mantle.
This created a huge chasm which is still shifting today as the plates continue to move towards each other. Each year, an area of the Nazca plate smaller than a butter knife (between 6 and 10 cm) nudges further under the South American plate.
This movement is how the Andes mountains were created and it can also cause earthquakes and landslides.
Scientists have found evidence of a ‘mega-submarine slide’ along the Peru–Chile trench caused by the sloped seafloor collapsing and debris pouring down into the trench. Experts think this happened in several stages over a long period of time.
If submarine landslides are big enough, their impacts don’t necessarily stay far below the ocean’s surface. The rushing sediment displaces water, which can create huge waves and sometimes cause tsunamis.
“Submarine landslides can generate enormous turbidity currents that carry 500 km3 or more of sediment down to the oceans' abyssal plains,” explain the authors of a 1993 paper in the journal Nature. That’s enough to fill the Dead Sea four times over and still have a little to spare.
“The slides can cause tsunamis and may release large amounts of methane to the air,” they write in the study.
Although a remote underwater wilderness prone to landslides and earthquakes might not sound like the best place to make a home, animals do live here.
Schmidt Ocean Institute scientists think the trench “could host ecosystems brimming with living fossils.” Shelled animals called brachiopods (which look a little like clams) and woodlouse-like chitons have been caught accidentally by fishers, they write on their website, adding that these creatures “previously were only known as fossils in [the Atacama Desert].”
Studying this region of the deep sea is challenging but scientists who have made the intense effort to get there have been rewarded with amazing discoveries.
In 2023, deep sea researchers found a tiny crustacean that looks like a dinky version of the Xenomorph from the Alien movies. Measuring nearly 4cm long, Dulcibella camanchaca was found 7,902 metres deep.
“Dulcibella camanchaca is a fast-swimming predator that we named after ‘darkness’ in the languages of the peoples from the Andes region to signify the deep, dark ocean from where it predates,” says Johanna Weston, a hadal ecologist at the Woods Hole Oceanographic Institution (WHOI), in a press release.
Scientists have also seen several different types of snailfish down here. When they put a baited camera on the seabed thousands of metres deep, lots of these tadpole-like fishes came in for a bite.
No other fish can survive in waters this deep so the snailfish don’t have much competition. The video they captured shows that “they seem to be quite active and look very well-fed,” says deep-sea fish expert Thomas Linley in a 2018 press release.
“Their gelatinous structure means they are perfectly adapted to living at extreme pressure,” adds Linley, who was a researcher at Newcastle University at the time of the discovery. “Without the extreme pressure and cold to support their bodies they are extremely fragile and melt rapidly when brought to the surface.”
