Chapter 1 Summary

The topics covered in this chapter can be summarized as follows:

1.1 What is Geology?

Geology is the study of Earth. It is an integrated science that involves the application of many of the other sciences. Geologists must take into account the fact that the geological features we see today may have formed thousands, millions, or even billions of years ago, and over very long time spans.

1.2 Why Study Earth?

Geologists study Earth out of curiosity and for other, more practical reasons, including understanding the evolution of life on Earth; searching for resources; understanding risks from geological events such as earthquakes, volcanoes, and slope failures; and documenting past environmental and climate changes so that we can understand how human activities are affecting Earth.

1.3 What Do Geologists Do?

Geologists work in the resource industry, and in efforts to protect the environment. Geologists work to minimize the risks from geological hazards (e.g., earthquakes), and to help the public understand those risks. Geologists investigate Earth materials in the field, in and in the lab.

1.4 We Study Earth Using the Scientific Method

Scientific inquiry requires a careful process of making a hypothesis and then testing it. If a hypothesis doesn’t pass the test, it’s time for a new one. A theory is a hypothesis that has been tested repeatedly and never failed a test. A law is a description of a natural process.

1.5 Three Big Ideas: Geological Time, Uniformitarianism, and Plate Tectonics

Geological time: Earth is approximately 4,570,000,000 years old; that is, 4.57 billion years or 4.57 Ga or 4,570 Ma. It’s such a huge amount of time that even extremely slow geological processes can have an enormous impact.

Uniformitarianism: Processes that occur today also occurred in the geologic past.  We can use our observations of the present to understand the processes that shaped the Earth throughout its history.

Plate tectonics: Earth’s surface is broken into plates that move and interact with each other.  The interactions between these plates are key for understanding the mechanisms behind geologic processes.

Review Questions

1. How does the element of time make geology different from the other sciences, such as chemistry and physics?
2. List three ways in which geologists can contribute to society.
3. The following dates are written with the abbreviations Ga, Ma, and ka. Express the dates in years. (For example, 2.3 Ma = 2,300,000 years)
   1. 2.75 ka
   2. 0.93 Ga
   3. 4.2 Ma
   4. 0.2 ka.
4. Dinosaurs first appear in the geological record in rocks from about 215 Ma and then most became extinct at 65 Ma. What percentage of geological time does this represent?
5. If sediments typically accumulate at a rate of 1 mm/year, what thickness of sediment could accumulate over a period of 30 million years?
6. Does uniformitarianism mean that conditions on Earth are uniform, and never change?
7. Summarize the main idea behind plate tectonics.