Dr. Christina Simmons' research has had many ups and downs. Simmons, who used to research mountain peaks, is the director of the DEEPSEA CHALLENGE project, in which James Cameron, National Geographic's explorer-in-residence, completed a record-breaking solo dive to the bottom of the Mariana Trench. I was the science coordinator.
Simmons' transition from the top to the bottom began in 1994. After completing her geological and tectonics research in the Rocky Mountains of Montana and the Sierra Nevada of California, she went on a ship to explore the underwater topography of the ocean floor south of New Zealand.
“Once I got on the boat, I was sold,” she says. “I had already finished.”
After her research cruise, she switched her focus from terrestrial (terrestrial) geology to bathymetry and hydrographic surveying, that is, measuring and mapping the ocean floor.
While much of Earth's terrestrial landscape has been mapped, much of the ocean floor remains unknown. Through bathymetric and hydrographic surveys, Simmons was able to better understand the geology and plate tectonics of the ocean floor.
During a trip to New Zealand, she studied the area where the Pacific and Australian plates meet.
“This is similar to what would happen if you took the San Andreas Fault and put it in the ocean,” she says. “It's a strike-slip fault, but there's a very high ridge. It's called Macquarie Ridge.”
echo sounder
Simmons said the team used a sounder to map the area. An echo sounder is a device that measures depth by measuring the time it takes for high-frequency sound waves to reach the ocean floor and the echoes to return to the instrument.
Fishing vessels use single-beam echo sounders, which use a single high-frequency sound pulse to measure water depth. Single-beam echo sounders also alert fishing vessels to the approximate depth of fish schools.
Multibeam echo sounders used by marine geologists provide scientists with even more information. Multibeam echo sounders cover the ocean floor with a series of pulses shaped like a triangular pyramid.
“Multi-beam (echo sounder) means you send multiple beams in the direction of the entire cone and listen for all the beams to come back,” Simmons says.
Echo sounders can be towed behind the research vessel or mounted at the front of the vessel near the bow. Simmons said most echo sounders are now attached to the ship's hull.
mow the lawn
During their first six weeks off the coast of New Zealand, Simmons and his team mapped a section of the ocean floor the size of the U.S. state of Georgia.
“We call it mowing,” Simmons says of the process of mapping the ocean floor. “It's back and forth, back and forth. You have to know the width of the area you're going and then make sure you change direction. As I recall, our footprints were about 15 kilometers (9 miles) apart. If you do it right, you'll end up with a really nice map with no blank spaces.”
By mapping the ocean floor, scientists were able to determine the exact location of plate boundaries.
“We followed the ridge,” Simmons says. “Even then, we didn't know whether the plate boundaries were on the ridge, on the east side, or on the west side. Where does this one plate begin and this other plate end? We found out that it was the very crest because there was a nice big fault at the top of the ridge itself.It was actually V-shaped and there was a small valley at the top of the ridge.
One of the challenges in mapping the ocean floor is changing sea level conditions.
“One of the challenges is ocean conditions because we’re dealing with Mother Nature, water, and ships on water,” Simmons said. “How rough is it? Are there a lot of waves or a storm? You can't get good data if the ship is rocking.”
Simmons said the deep ocean floor is easier to map than shallower areas. “One of the big challenges is that the water is actually shallower, because the sound just disappears and comes back, so it doesn't have time to travel that far from the ship, so it can't reach a wide area.” she says. . “If you think about it, the deeper the sound, the longer it takes to travel and the wider the range it has to come back.”
deep sea challenge
Since visiting New Zealand, Simmons has worked on projects investigating plate subduction in the Peru-Chile Trench off the west coast of South America, the Tonga-Kermadec Trench between New Zealand's North Island and Tonga, and the Aleutian Trench south of Alaska. Aleutian Islands.
One of her recent projects was serving as the science coordinator for the Deep Sea Challenge. This project is about National Geographic's resident explorer James Cameron's record-breaking solo dive in 2012 into Challenger Deep in the Mariana Trench, the deepest known point in the ocean.
“There was certainly a lot of data collected and things that my scientists and I were working on, processing, and analyzing,” she says.
She helps make all the scientific discoveries of geological and other expeditions available to the public.
“We have so much data and so much time spent collecting it that it's better to bring it to classrooms and educators, or put it in a place where everyone can see it, use it, and learn from it.” ” she says.
Although her main interests are ocean geology and plate tectonics, the Deep Sea Challenge led Simmons to wonder how the topography of the Pacific Basin's ocean trenches affects the life there. I did.
“If there is an animal that can survive under 10 kilometers of pressure, can it cross the wall between ditches and return to the next ditch?” she asks herself. “If we couldn't do that, almost every trench would have its own evolved biology.”
Ultimately, Simmons hopes to create a tectonic map of the ocean floor or a structural map of the ocean floor. Information gleaned from Simmons' research could help scientists better understand why and how earthquakes and tsunamis occur.
But there are so many unexplored places on the ocean floor that geologists like Simmons will have to work for long periods of time to perfect the ocean's picture.
“There’s a lot left to do,” she says with a laugh.