Texas Tech’s Jeremy Deans was one of 30 scientists aboard the JOIDES Resolution.
It's dark, cold and remote. It's vast, poorly understood and, for the most part, unseen by human eyes. It's probably not what you're thinking.
The ocean floor contains secrets about the Earth that have never been revealed, but a group of scientists, including a Texas Tech University researcher, hopes to change that.
“We know very little about our world's oceans; we know more about our solar system and our galaxy than we do about the ocean floor,” said Jeremy R. Deans, a post doctoral researcher in geology. “The most voluminous part of Earth, called the mantle, has never been accessed in place. You can go see parts of the mantle where they have been thrust onto the continent, but this is not where they form. We have to determine the properties of the mantle based on indirect measurements and experimentation.”
Deans recently spent two months aboard the JOIDES Resolution, a research ship in the middle of the Indian Ocean, where he was one of 30 scientists studying rocks drilled from under the ocean floor as part of Expedition 360.
“This was the first of at least three expeditions that will drill down through the crust and into the mantle,” he said. “Therefore, this expedition provided us with samples from the lower oceanic crust, themselves rare, and it sets the stage for the future recovery and study of the mantle.”
Expedition 360 drilled along the Southwest Indian Ridge, which forms the seafloor underneath the Indian Ocean southeast of Madagascar. Its particular focus was on the lower oceanic crust at Atlantis Bank, what is called an oceanic core complex.
“The ocean floor, the top part of the oceanic crust, is formed at mid-ocean ridges. Oceanic core complexes form along slow-spreading ridges, like the Southwest Indian Ridge and the Mid-Atlantic Ridge, and not along fast-spreading ridges like the East Pacific Rise,” Deans said. “Slow-spreading ridges comprise the majority of mid-ocean ridges on Earth, and we know very little about how the ocean floor is formed there. Oceanic core complexes form by exposing rocks that formed deeper down in the crust. The rocks are exposed due to a fault, which displaces one rock block past another. In this case, it was a normal fault where rocks that were once shallower are displaced deeper, and rocks that were once deeper are displaced shallower. Expedition 360 was the fourth expedition to Atlantis Bank, which provides the first opportunity to compare rocks from different holes along the same complex.”
The decision to drill at Atlantis Bank was not arbitrary; the sea floor there is anomalous compared to the sea floor in other locations on Earth, which offers a distinct glimpse below the surface.
“The average depth of the world's oceans is around four kilometers; at Atlantis Bank it is only 700 meters below sea level,” he said. “This is because of the fault that lifted up the rocks above the seafloor. Additionally, the sea floor there is gabbro, which forms deeper in the crust and is not expected to be at the sea floor. Most of the sea floor on Earth is covered by volcanic rocks called basalt, the material that erupts from volcanoes and makes up Hawaii.”
The expedition was funded through the International Ocean Discovery Program (IODP), which is supported by a consortium of countries including the United States, Japan, Great Britain, France, Germany, Brazil, Canada, India, South Korea, Australia, Italy and more. The program sails all over the world to investigate a variety of scientific problems associated with the ocean floor.
“IODP has open calls to participate in the expeditions,” Deans said. “IODP accepts doctoral students, post docs and faculty to sail. Typically there are certain specialties needed for each expedition. You submit an application indicating your specialty, why you want to sail and what your personal research will focus on. Then a committee decides who to offer to sail.”
IODP contracts with several different ships depending on the expedition goals. The JOIDES Resolution was named jointly for the former Joint Oceanographic Institutions for Deep Earth Sampling, which merged with another organization in 2007 to become the Consortium for Ocean Leadership, and the HMS Resolution, which explored the Pacific Ocean, its islands and the Antarctic region more than 200 years ago under the command of Capt. James Cook.
For Expedition 360, the JOIDES Resolution was home to 30 researchers and about 80 crew members for two months. The researchers were divided into three main groups based on their specialties: igneous geology, metamorphic geology and structural geology. Several smaller teams focused on the physical properties of the rocks, such as thermal conductivity and seismic properties; the rocks' magnetic properties; microbiological life; and the rocks' chemical composition. Each expedition's groups are specifically selected according to the expedition's goals and the rocks that are expected to be recovered. Lastly, two co-chiefs direct the scientific work on the ship.
“There is a distinction between a person's onboard responsibilities and their personal research interests,” Deans said. “Given the limited amount of time and amount of rock that must be described before leaving the ship, each person is tasked with a certain responsibility. For example, I observed and measured all brittle features in the cores. However, my personal research focuses more on non-brittle or ductile features. Since the amount of material available to study is limited, people are encouraged to collaborate with similar or dovetailing research. This leads to people working together all over the world, one of the great successes of the program.”
Deans' research focuses on the change in shape of rocks, called structural geology.
“It is kind of like studying a car crash; I look at the rock that has changed shape (i.e., a crashed car) and try to figure out how and why the rock looks that way (i.e., how the car crashed) and what the rock looked like before it was deformed (i.e., how the car looked before the crash),” he said. “Rocks and minerals form in one shape, then through plate tectonic movements they are pushed and pulled into other shapes. For example, when rocks are pushed, they commonly form folds. When the oceanic crust forms, it is pulled apart as it is cooling, so you must consider how a rock will deform when it is partly melt and partly crystals.”
On the ship, Deans was on a team with four other researchers, each with a different type of observations to make based on different subfields of structural geology.
“My responsibility was to measure all of the brittle features, including fractures and faults. Additionally, I was the leader of the team, so I was in charge of daily reports and weekly reports, along with our final results for the entire expedition,” he said. “The other team members focused on the alignment of minerals, both when the rock was partially molten and when it was solid; veins, which are fractures filled with minerals; and relative timing of events. The majority of our focus is on identifying the minerals that define the change in shape and their orientation in space. Additionally, we look at thin sections of the rocks in the microscope to describe the same features as in the rock.”
Deans also studied the orientation of the mineral alignment when the rocks were mostly molten, called magmatic fabrics, and the orientation of mineral alignment when the rock was completely crystallized, called crystal-plastic fabrics.
The ship is specially designed to accommodate the rigors of drilling very hard rocks and to describe those rocks.
“Deep-sea drilling is very difficult and requires a high level of engineering and special training,” Deans said. “The ship has a 150-foot drilling derrick in the middle of it with a full-time crew specially trained for this type of work. The ship is equipped with tables that are designed to aid in description of these rocks; a variety of analytical equipment, ranging from measuring the magnetic field of the rocks to their chemical composition; and microscopes, making it the perfect place to study the rocks.
“The location of physically studying the rocks is not unique to the ship and some expeditions describe the rocks on land at a core repository, either in College Station; Bremen, Germany; or Kochi, Japan,” he explained. “Because of the geographic location of Expedition 360 rocks, the core will go to Kochi, Japan. Being on the ship in a controlled space and location allows for the main focus of the scientists to be on the core, so the work is done in a shorter timeframe than if onshore.”
Life on board
With only two months of research time available, researchers worked in shifts around the clock to maximize their capabilities. This also served to maximize space for the 110 people living in close quarters.
“Everyone works on shifts close to 12 hours since there is only so much space in the lab. Also, the 12-hour shift allows you time in your room when your bunkmate is on shift,” Deans said. “My team's shift began at 2 a.m., so I typically woke up around 1:30 a.m., went to the mess hall, got breakfast and then went up to the lab to describe the rock recovered the day before.”
Rock was brought up on deck every 4-6 hours, and it had to be described quickly so more could be laid out. When not describing rocks, researchers inputted their data into spreadsheets and wrote reports. Meals were served from 5-7 a.m., 11 a.m.-1 p.m., 5-7 p.m. and 11 p.m.-1 a.m. A scientific meeting each afternoon included group presentations and updates on the drilling progress.
“The experience is amazing since you are wholly focused on describing and reporting on the core recovered every day, and you are on the ship with specialists in different fields leading to very rigorous discussions,” Deans said. “Additionally, the scientific team is from all over the world, so it provides a great cultural experience.”
He credited the ship's 80 crew members – drillers, laboratory technicians, the captain and engine crew, and the service crew in charge of laundry, food and cleaning – with helping to ensure the researchers could do their jobs, but said it wasn't always easy.
“Many people work very hard so the scientists can focus on their daily work,” Deans said. “The main challenges included getting all the work that is required done as a new shift is coming on or more core is coming on deck. The next challenge was getting along well with your team and the rest of the scientific group and staff. Personal space is very limited, so conflicts may arise. Internet access is limited, and keeping up with relations and responsibilities onshore can be difficult. Additionally, bad weather can make it very hard to get things done on the ship. Many people get seasick.”
On the whole, however, he said the team accomplished most of its goals and everyone got along well.
“This expedition gave me a tremendous amount of personal and professional experience,” Deans said. “I made several new friends and lifelong connections with people from all over the world. The expedition was physically and emotionally taxing, so a special bond was made with the people onboard. Professionally and scientifically, the experience is unparalleled with new network connections, rigorous scientific discussions, samples for future work and new lines of study for me and my students.
“The IODP is an amazing organization with many smart and hardworking people, and I hope the program continues unlocking the mysteries of the deep.”