Learning Objectives

Each statement represents the primary learning objective for the corresponding major heading within the chapter. After you complete the chapter, you should be able to:

I.1 List and describe the sciences that collectively make up Earth science. Discuss the scales of space and time in Earth science.

I.2 List and describe Earth’s four major spheres. Define system and explain why Earth is considered to be a system.

I.3 Discuss the nature of scientific inquiry, including the construction of hypotheses and the development of theories.

I.1 What Is Earth Science?

List and describe the sciences that collectively make up Earth science. Discuss the scales of space and time in Earth science.

Key Terms:

• • Earth science

  • geology

  • oceanography

  • meteorology

  • astronomy

  • geologic time

• • Earth science includes geology, oceanography, meteorology, and astronomy.

  • There are two broad subdivisions of geology. Physical geology studies Earth materials and the internal and external processes that create and shape Earth’s landscape. Historical geology examines Earth’s history.

  • The other Earth sciences seek to understand the oceans, the atmosphere’s weather and climate, and Earth’s place in the universe. Earth science is also considered an environmental science that examines natural hazards, natural resources, and human impact on the environment.

  • Earth science must deal with processes and phenomena that vary from the subatomic scale of matter to the nearly infinite scale of the universe.

  • The time scales of phenomena studied in Earth science range from tiny fractions of a second to many billions of years.

  • Geologic time, the span of time since the formation of Earth, is about 4.6 billion years, a number that is difficult to comprehend.

I.2 Earth as a System

List and describe Earth’s four major spheres. Define system and explain why Earth is considered to be a system.

Key Terms:

• • Earth system

  • hydrosphere

  • atmosphere

  • biosphere

  • geosphere

  • core

  • mantle

  • crust

  • lithosphere

  • asthenosphere

  • Earth system science

  • system

• • Earth’s physical environment is traditionally divided into three major parts: the solid Earth, called the geosphere; the water portion of our planet, called the hydrosphere; and Earth’s gaseous envelope, called the atmosphere.

  • A fourth Earth sphere is the biosphere, the totality of life on Earth. It is concentrated in a relatively thin zone that extends a few kilometers into the hydrosphere and geosphere and a few kilometers up into the atmosphere.

  • Of all the water on Earth, more than 96 percent is in the oceans, which cover nearly 71 percent of the planet’s surface.

  • Although each of Earth’s four spheres can be studied separately, they are all related in a complex and continuously interacting whole that is called the Earth system.

  • Earth system science uses an interdisciplinary approach to integrate the knowledge of several academic fields in the study of our planet and its global environmental problems.

  • The two sources of energy that power the Earth system are (1) the Sun, which drives the external processes that occur in the atmosphere, hydrosphere, and at Earth’s surface, and (2) heat from Earth’s interior, which powers the internal processes that produce volcanoes, earthquakes, and mountains.

QUESTION: Is glacial ice part of the geosphere, or does it belong to the hydrosphere? Explain your answer. 

I.3 The Nature of Scientific Inquiry

Discuss the nature of scientific inquiry, including the construction of hypotheses and the development of theories.

Key Terms:

• • hypothesis

  • theory

  • scientific method

• • Scientists make careful observations, construct tentative explanations for those observations (hypotheses), and then test those hypotheses with field investigations, laboratory work, and/or computer modeling.

  • In science, a theory is a well-tested and widely accepted explanation that the scientific community agrees best fits certain observable facts.

  • As we discard flawed hypotheses, scientific knowledge moves closer to a correct understanding, but we can never be fully confident that we know all the answers. Scientists must always be open to new information that forces change in our model of the world.

Give It Some Thought

1. The length of recorded history for humankind is about 5000 years. Clearly, most people view this span as being very long. How does it compare to the length of geologic time? Calculate the percentage or fraction of geologic time that is represented by recorded history. To make calculations easier, round the age of Earth to the nearest billion.

2. The average distance between Earth and the Sun is 150 million kilometers (93 million miles). About how long would it take a jet plane traveling from Earth at 1000 kilometers (620 miles) per hour to reach the Sun?

3. This scene is in British Columbia’s Mount Robson Provincial Park. The park is named for the highest peak in the Canadian Rockies. List examples of features associated with each of Earth’s four spheres. Which, if any, of these features was created by internal processes? Describe the role of external processes in this scene.

4. Humans are part of the Earth system. List at least three examples of how you, in particular, influence one or more of Earth’s major spheres.

5. Examine Figure I.9 to answer these questions.

   1. Where is most of Earth’s freshwater stored?

   2. Where is most of Earth’s liquid freshwater found?

6. Refer to the graph in Figure I.10 to answer the following questions.

   1. If you were to climb to the top of Mount Everest, how many breaths of air would you have to take at that altitude to equal one breath at sea level?

   2. If you were flying in a commercial jet at an altitude of 12 kilometers (about 39,000 feet), about what percentage of the atmosphere would be below the plane?

7. The accompanying photo provides an example of interactions among different parts of the Earth system. It is a view of a mudflow that was triggered by extraordinary rains in March 2014. Describe how each of Earth’s four “spheres” was influenced by and/or involved in this natural disaster that buried a 1-square-mile rural neighborhood near Oso, Washington, and caused more than 40 fatalities.

8. As you enter a dark room, you turn on a wall switch, but the ceiling light does not come on. Formulate at least three hypotheses that might explain this observation. Once you have formulated your hypotheses, what should be your next step?