http://www.ck12.org Chapter 4. Motion and Forces
4.30 Oceanic Pressure
- Explain how and why water pressure changes with depth in the ocean.
- Describe how water pressure affects ocean exploration.
In 2012, the film director James Cameron, who directed the film Titanic, made headlines when he traveled to
Challenger Deep. This is the deepest known point on the ocean floor, almost 11,000 meters below the surface.
Cameron was the first person to travel there alone, and he made the trip in a deep-sea diving vehicle named Deepsea
Challenger. The vehicle pictured above is another deep-sea diving vehicle, named Alvin. Alvin is no longer used for
ocean exploration, but by the time it was retired, it had made thousands of dives. Alvin was even used to explore the
Titanic on the North Atlantic Ocean floor.
Q: Why must divers use special diving machines such as Alvin and Deepsea Challenger to go deep below the surface
of the ocean? Why can’t they just use scuba diving gear?
A: The pressure of the water is too great that far below the surface. It would crush divers long before they could
reach the bottom.
Water Pressure and Depth
Pressureis the amount of force acting on a given area. As you go deeper in the ocean, the pressure exerted by the
water increases steadily. That’s because there is more and more water pressing down on you from above. TheFigure
4.57 shows how pressure changes with depth. For each additional meter below the surface, pressure increases by
10 kPa. At 30 meters below the surface, the pressure is double the pressure at the surface. At a depth greater than
500 meters, the pressure is too great for humans to withstand without special equipment to protect them. At nearly