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People Behind the Science

Eduard Suess (1831–1914)

duard Suess was an Austrian ge- work devoted to analyzing the physical
Eologist who helped pave the way for agencies contributing to Earth’s geographi-
modern theories of the continents. Born cal evolution. Suess offered an encyclope-
in London, though of Bohemian ances- dic view of crustal movement, the struc-
try, Suess was educated in Vienna and at ture and grouping of mountain chains,
the University of Prague. He moved to sunken continents, and the history of the
Vienna in 1856 and became professor of oceans. He also made significant contribu-
geology there in 1861. In addition to his tions to rewriting the structural geology
geological interests, he occupied himself of each continent. In many respects, Suess
with public affairs, serving as a member cleared the path for the new views associ-
of the Reichstag for 25 years. His geologi- ated with the theory of continental drift in
cal researches took several directions. As the twentieth century. In view of geological
a paleontologist, he investigated grapto- similarities among parts of the southern
lites, brachiopods, ammonites, and the continents, Suess suggested that there had
fossil mammals of the Danube Basin. He once been a great supercontinent, made up
wrote an original text on economic geol- of the present southern continents; this he
ogy. He undertook important research North Africa and southern Europe caught named Gondwanaland, after a region of
on the structure of the Alps, the tectonic his attention. India. Wegener’s work was later to estab-
geology of Italy, and seismology. The pos- The outcome of these interests was lish the soundness and penetration of such
sibility of a former land bridge between The Face of Earth (1885–1909), a massive speculations.

Source: From the Hutchinson Dictionary of Scientific Biography. © Research Machines plc 2003. All Rights Reserved. Helicon Publishing is a division of Research Machines.

The mass extinction at the end of the Permian period is thought to be due to either a major change in climate at the end
unusual in several ways. It resulted in the extinction of about of the last ice age or hunting by humans as they expanded their
90 percent of organisms and took place over a very short time— range from Africa to Europe, Asia, and the Americas. Many
less than a million years. Because of this, it is often referred to people are convinced that we are currently experiencing a mass
as the “Great Dying.” Both marine and terrestrial organisms extinction because of our ability to alter the face of Earth and
were affected. Because this extinction event occurred over a destroy the habitats needed by plants and animals.
short time and affected all species, it is assumed that a major,
worldwide event was responsible. However, at this time, there CONCEPTS Applied
is no clearly identifiable cause. Suggestions include a meteorite
impact, massive volcanic activity, or a combination of factors. Fossil Animals
The extinction at the end of the Triassic period was relatively
You have no doubt seen many illustrations of various kinds
mild compared to others. About 50 percent of species appear to
of extinct animals, for example, the different kinds of
have gone extinct. There is no clear cause for this extinction.
dinosaurs. Have you ever wondered how anyone can know
The mass extinction at the end of the Cretaceous period
what these animals looked like? Certainly the general size
resulted in the extinction of about 60 percent of species. Based and shape can be determined by assembling fossils of
on evidence of a thin clay layer marking the boundary between individual skeletal parts, but most of the shape of an animal
the Cretaceous and Tertiary periods, one theory proposes that a is determined by the size and distribution of its muscles.
12
15
huge (16 km, or 9.9 mi, diameter and 10 kg, or 1.1 × 10 tons, An understanding of physics provides part of the answer.
mass) meteorite struck Earth. The impact would have thrown a The skeleton of an animal is basically arranged like a large
tremendous amount of dust into the atmosphere, obscuring the number of levers. For example, a leg and foot consists of
Sun and significantly changing the climate and thus the condi- several bones linked end to end. The size of a bone gives
tions of life on Earth. The resulting colder climate may have led a clue to the amount of mass that particular bone had to
support. Various bumps on the bones are places where
to the extinction of many plant and animal species, including
muscles and tendons attached. By knowing where the
the dinosaurs. This theory is based on the clay layer, which the-
muscles are attached and analyzing the kinds of levers they
oretically formed as the dust settled, and its location in the rock
represent, we can calculate the size of the muscle. Thus,
record at the time of the extinctions. The layer is enriched with the general shape of the animal can be estimated. However,
a rare metal, iridium, which is not found on Earth in abundance this doesn’t provide any information about the color or
but occurs in certain meteorites in greater abundance. surface texture of the animal. That information must come
As we approach current times, the extinction of the many from other sources.
species of large mammals during the Quaternary period is

534 CHAPTER 21 Geologic Time 21-14