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New Exploration of the Puerto Rico Trench Aims to Shed Light on Plate Tectonics

Scientists can't stop the seismically active area from triggering another tsunami, but they can learn more about how to prepare.

Off the coast of Puerto Rico, in the deepest part of the Atlantic Ocean, lies a vast undersea trench—parts of which have never explored before. That's why this month a group of 50 scientists from the National Oceanic and Atmospheric Administration and various universities and agencies across the country are conducting three weeks of study and dives.

Their mission is to examine geological anomalies unique to parts of the Puerto Rico Trench, which extends six miles undersea. The area has been of immense interest to geologists for years.


"In 1918, a magnitude 7.5 earthquake rattled Puerto Rico. A tsunami followed the quake, leading to 116 people dying and millions of dollars in damages. It's not if there will be another tsunami in this region, it's when," Dr. Mike Cheadle, the expedition's science co-lead and leading geologist, told Motherboard from NOAA's Okeanos Explorer. "It's why these types of dives are important. We can't prevent it, but we can prepare for it."

Remotely operated vehicle Deep Discoverer is deployed for a dive. Image: ​NOAA Okeanos Explorer Program

The Puerto Rico Trench marks the boundary between the North American and Caribbean tectonic plates, with the North American plate being pushed down beneath Puerto Rico. This tectonic movement created the trench, which, as the NOAA notes online, "is also associated with the most negative gravity anomaly on Earth." Additionally, movement along the tectonic boundary can also produce earthquake-triggered tsunami.

The main goal is primarily exploration, according to Dr. Cheadle. "Once we get these results back to our labs, we can start to work on estimated times a disaster may occur. We won't be doing any kind of preventative work on this trip," he said. Each dive is being streamed online.

Expedition scientists are examining fault features in an attempt to understand how faults move—data which could one day be used by the US Geological Survey for predictive modelling.

This rare dumbo octopus is often called the Blind Octopod due to the lack of a lens and reduced retina in its eyes. Image: ​NOAA Okeanos Explorer Program

On top of the daily dives and studying the information they're rapidly receiving, the team is also communicating daily with people watching the hosted live stream and people who are tweeting in questions or suggestions.


They may only be a few dives in, but lead biologist Dr. Andrea Quattrini is looking forward to what the next dives will bring.

"In an area like this, where nothing has really been explored, every dive is just as exciting as the last," Dr. Quattrini said. "We're seeing something new each and every time. Not knowing what we'll see just makes us want to dive that much faster."

Correction 4/22/15: This story was published with a litany of errors, which we've corrected in the story above and noted below. Those errors represent a fundamental breakdown in the reporting and editing of this story that Motherboard has not previously experienced, and we're reviewing exactly how it happened. In the meantime, we apologize for the errors.

The Puerto Rico Trench has not only been explored just once before, as previously stated. Rather, NOAA is diving in parts of the trench that no one has seen before. This article's headline has also been updated to reflect this. Additionally, an earlier version of this article stated that NOAA had not been granted the funds needed for an expedition of this size until now, which is not the case; NOAA has conducted missions of similar scale multiple times in the last decade.

The 50 scientists involved in this expedition are not all from NOAA, but rather, from NOAA and various universities and agencies across the country. Previously, the diving period was said to last ten weeks. Rather, there will only be three weeks of dives, and the length of the expedition is not unusual, as previously stated.

NOAA is not searching for new species or collecting samples from the region's seamounts, trenches, and troughs on this expedition, as previously stated. Additionally, this article previously stated incorrectly that, in the late 1800s, technology wouldn't allow for live samples to be taken and examined.

An earlier version of this article misstated the relationship between gravity and seismic activity. Rather, gravity does not control earthquake activity. In an earlier version of this article, statements regarding deep-water snapper fish attributed to Dr. Quattrini were inaccurately quoted and have since been removed.