Review for Exam 1 (Chapters 1-4, Lutgens and Tarbuck)
Answers to the Review Questions (Chapter 1)
1. The science of geology is traditionally divided into two broad areas - physical and historical.
Physical geology examines Earth's rocks and minerals and seeks to understand the processes
that operate beneath and upon its surface. On the other hand, the aim of historical geology is
to understand Earth's origin and how the planet changed through time. Historical geology
strives to establish the chronology of physical and biological changes of the past 4.6 billion
2. Aristotle's explanations of the natural world were not based on keen observations and experi-
mentation, as modern science is. Instead they were his opinions, based on the limited know-
ledge of his day. Unfortunately, many of his wrong interpretations continued to be believed
for many centuries, thus thwarting the acceptance of better ideas based on observations.
3. Catastrophists believed that Earth was a young planet and that its landscape was shaped by
4. Uniformitarianism, a fundamental concept in modern geology, states that the physical, chemi-
cal, and biological laws that operate today have also operated in the geologic past. The
uniformitarian view is one of a very old Earth, modified by processes that have been at work
for a very long time.
5. The currently accepted age of the Earth is 4.5 to 4.6 billion years, based on meticulous
experimental measurements of lead isotopes on meteoritic and terrestrial samples. The basic
assumptions and results are supported by rubidium-strontium isotopic age determinations on
meteorite samples. The oldest rocks yet dated formed about 4 billion years ago. Because
Earth is a dynamic planet, most rocks we see formed much later during Earth's history and
thus are much younger than the age of the Earth.
6. The principles used to establish the geologic time scale include the law of superposition -
which establishes the sequence of rock layers, and the principle of fossil succession - fossil
organisms succeed on another in a definite and determinable order, and, therefore, any time
period can be recognized by its fossil content. These concepts enable geologists to correlate
similar-age rocks anywhere in the world and to place them in their proper chronological order
and position in the time scale.
7. A scientific hypothesis is a preliminary, untested explanation. On the other hand, a scientific
theory is a well-tested and widely accepted view that scientists agree best explains observable
8. The four, major spheres of our living environment are: 1) the atmosphere - the gaseous
envelope surrounding our planet; 2) the hydrosphere - those environments (oceans, rivers,
lakes, ice, groundwater and water vapor in the atmosphere) involved in the hydrologic cycle;
3) the biosphere - the diverse, surficial and near-surface environments that include all living
organisms and their habitats; and 4) the solid earth - the soils, regolith, and crustal bedrock