When foam cups are lowered in a mesh bag deep into the ocean, will they dissolve? Just get wet? Or maybe a shark will eat them? These were the initial predictions made by 7- and 8-year-old students at St. George’s Preparatory school this month as they completed a new, two-part lesson offered by the BIOS Curriculum Enrichment Program on “Force: The Science of Ocean Pressure.”
The answer, they later learned, is that under the weight of tons of water pressure, the air pockets in the cups compress, and the cups shrink.
“We talked about the effect that pressure has on scuba divers, and why submersibles and other deep-diving machines and robots are built with special materials that won’t crumble under the weight of the water while exploring the ocean,” said BIOS science education officer Claire Fox, who partnered on the lesson with St. George’s Preparatory teacher Kelly Rodday.
Students also learned about adaptations that some deep-diving animals have that support their survival under extreme pressures. Fish have swim bladders that they regulate with air as they move up and down through the water column. The deepest-dwelling fish have reduced muscle and tissue density, higher fat content, and minimal bone structures so their bodies are better able to withstand pressure. Whales, on the other hand, can safely collapse their lungs, relying on stored oxygen in their blood to dive to greater depths.
To demonstrate ocean pressure, researchers and educators exploring the ocean frequently take Styrofoam objects, often cups that have been decorated with permanent marker, and attach them to diving submersibles or sampling equipment. After Rodday’s students decorated their cups and offered predictions during their initial lesson with Fox in February, she relied on BIOS research technician Claire Medley, who works aboard BIOS-operated research vessel Atlantic Explorer, to attach them to a device used for water sampling in the Sargasso Sea.
Through a video from the ship, Medley showed the cups in a blue mesh bag attached to the sampling device and heading into the water. At depths of hundreds of feet, water pressure begins to mount, pressing the air bubbles out of the cups. At greater depths, they were squeezed even more dramatically, crushing the cups uniformly to a third of their former size. Several hours later, they returned to the surface with the sampling device from a maximum depth of 14,700 feet (4,500 meters). Rodday’s students’ cups had been reduced to tiny dense objects, each just over an inch in height.
Students in their second lesson this month with BIOS had a chance to revisit their predictions and see if they still agreed, make new predictions, and finally explore their now-shrunken cups and talk about what happened during the trip far below the surface.
“We can talk about forces and water pressure all day, but to actually see the cups shrink down was really meaningful to them,” said Rodday, who teaches 15 students in her P3 class. “They were blown away.”
Watch the St. George’s Prep cups under pressure Force: The Science of Ocean Pressure.