14.3 The Seafloor.
Lesson Objectives
- Describe the obstacles to studying the seafloor and methods for doing so.
- Describe the features of the seafloor.
- List the living and non-living resources that people use from the seafloor.
Introduction
The ocean surface is vast and hides an entire world underneath it. The ocean floor is
sometimes called the final frontier of the modern era. Though people have traveled on the
ocean for millennia, people have explored only a tiny fraction of the ocean floor. We know
very little about the vast expanse of our oceans. Today’s technology has allowed us to
learn more about the seafloor, including both its physical properties and its effects on living
organisms.
Studying the Seafloor
Ancient myth says that Atlantis was a powerful undersea city whose warriors conquered
many parts of Europe. There is little proof that such a city existed, but human fascination
with the world under the oceans certainly has existed for centuries. Not much was known
abouttheaphoticzoneoftheoceanuntilscientistsdevelopedasystemmodeledaftertheway
that bats and dolphins use echolocation to navigate in the dark (Figure14.20). Prompted
by the need to find submarines during World War II, scientists learned to bounce sound
waves through the ocean to detect underwater objects. The sound waves bounce back like
an echo off of whatever object may be in the ocean. The distance of the object can be
calculated based on the time that it takes for the sound waves to return. Finally, scientists
were able to map the ocean floor.
Three main obstacles have kept us from studying the depths of the ocean: absence of light,
very cold temperatures, and high pressure. As you know, light only penetrates the top 200
meters of the ocean; the depths of the ocean can be as much as 11,000 meters deep. Most
places in the ocean are completely dark, which makes it impossible for humans to explore
without bringing a source of light with them. Secondly, the ocean is very cold; colder than
0 oC (32oF) in many places. Such cold temperatures pose significant obstacles to human
exploration of the oceans. Finally, the pressure in the ocean increases tremendously as you
go deeper. Scuba divers can rarely go deeper than 40 meters due to the pressure. The
pressure on a diver at 40 meters would be 4 kilograms/square centimeter (60 lbs/sq in).
Even though we don’t think about it, the air in our atmosphere has weight. It presses down
on us with a force of about 1 kilogram per square centimeter (14.7 lbs/ sq in). In the ocean,