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People Behind the Science

Rachel Louise Carson (1907–1964)

achel Louise Carson was a U.S. biolo- World War II, she wrote fisheries informa-
Rgist, conservationist, and campaigner. tion bulletins for the U.S. government and
Her writings on conservation and the dan- reorganized the publications department
gers and hazards that many modern prac- of what became known after the war as the
tices imposed on the environment inspired U.S. Fish and Wildlife Service. In 1949, she
the creation of the modern environmental was appointed chief biologist and editor
movement. of the service. She also became occupied
Carson was born in Springdale, Penn- with fieldwork and regularly wrote free-
sylvania, on May 27, 1907, and educated at lance articles on the natural world. During
the Pennsylvania College for Women, study- this period, she was working on The Sea
ing English to achieve her ambition for a Around Us. Upon its publication in 1951,
literary career. A stimulating biology teacher this book became an immediate best-seller,
diverted her toward the study of science, and was translated into several languages, and
she went to Johns Hopkins University, grad- won several literary awards. Given a mea-
uating in zoology in 1929. She received her sure of financial independence by this suc-
master’s degree in zoology in 1932 and was cess, Carson resigned from her job in 1952 of a Presidential advisory committee on
then appointed to the department of zool- to become a professional writer. Her second the use of pesticides. By this time, Carson
ogy at the University of Maryland, spending book, The Edge of the Sea (1955), an eco- was seriously incapacitated by ill health,
her summers teaching and researching at logical exploration of the seashore, further and she died in Silver Spring, Maryland, on
the Woods Hole Marine Biological Labora- established her reputation as a writer on April 14, 1964.
tory in Massachusetts. Family commitments biological subjects. Her most famous book, On a larger canvas, The Silent Spring
to her widowed mother and orphaned The Silent Spring (1962), was a powerful alerted and inspired a new worldwide move-
nieces forced her to abandon her academic indictment of the effects of the chemical ment of environmental concern. While writ-
career, and she worked for the U.S. Bureau poisons, especially DDT, with which hu- ing about broad scientific issues of pollution
of Fisheries, writing in her spare time ar- mans were destroying Earth, sea, and sky. and ecological exploitation, Carson also
ticles on marine life and fish and produc- Despite denunciations from the influential raised important issues about the reckless
ing her first book on the sea just before the agrochemical lobby, one immediate effect squandering of natural resources by an
Japanese attack on Pearl Harbor. During of Carson’s book was the appointment industrial world.

Source: © Research Machines plc 2006. All Rights Reserved. Helicon Publishing is a division of Research Machines.

general features of the adjacent land that is above water, such as
24.3 THE OCEAN FLOOR
hills, valleys, and mountains, but these features were smoothed
Some of the features of the ocean floor were discussed in off by the eroding action of waves when the sea level was lower.
chapter 18 because they were important in developing the the- Today, a thin layer of sediments from the adjacent land covers
ory of plate tectonics. Many features of the present ocean basins these smoothed-off features.
were created from the movement of large crustal plates, accord- Beyond the gently sloping continental shelf is a steeper fea-
ing to plate tectonics theory, and in fact, some ocean basins are ture called the continental slope. The continental slope is the
thought to have originated with the movement of these plates. transition between the continent and the deep ocean basin. The
There is also evidence that some features of the ocean floor water depth at the top of the continental slope is about 120 m
were modified during the ice ages of the past. During an ice age, (about 390 ft), then plunges to a depth of about 3,000 m (about
much water becomes locked up in glacial ice, which lowers the 10,000 ft) or more. The continental slope is generally 20 to 40 km
sea level. The sea level dropped as much as 90 m (about 300 ft) (about 12 to 25 mi) wide, so the inclination is similar to that
during the most recent major ice age, exposing the margins of encountered driving down a steep mountain road on an inter-
the continents to erosion. Today, these continental margins are state highway. At various places around the world, the conti-
flooded with seawater, forming a zone of relatively shallow water nental slopes are cut by long, deep, and steep-sided submarine
called the continental shelf (Figure 24.23). The continental shelf canyons. Some of these canyons extend from the top of the
is considered to be a part of the continent and not the ocean, slope and down the slope to the ocean basin. Such a submarine
even though it is covered with an average depth of about 130 m canyon can be similar in size and depth to the Grand Canyon on
(about 425 ft) of seawater. The shelf slopes gently away from the the Colorado River of Arizona. Submarine canyons are believed
shore for an average of 75 km (about 47 mi), but it is much wider to have been eroded by turbidity currents, which were discussed
on the edge of some parts of continents than on other parts. in the section on ocean currents.
The continental shelf is a part of the continent that happens Beyond the continental slope is the bottom of the ocean
to be flooded by seawater at present. It still retains some of the floor, the ocean basin. Ocean basins are the deepest part of the

616 CHAPTER 24 Earth’s Waters 24-20