How Were Fossil Fuels Formed?

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This slideshow was produced by George Vibranz and Anne Glausser.

Shale gas is a fossil fuel that formed millions of years ago. Different kinds of fossil fuels -- coals, oils, and natural gases -- formed as dead plants and animals decayed. Scientists refer to such remains as “organic matter.” The element carbon is the foundation for organic matter on Earth. That means that countless carbon-based molecules remain buried far below Earth’s surface. Many of the carbon compounds are combustible -- they can be used to release heat energy to produce electricity; power cars, planes, or trains; or keep your house warm on a cold evening. But once we use them we can’t reuse them. We call them non-renewable natural resources. In this activity you will learn more about how one fossil fuel -- shale gas -- formed thousands of feet beneath certain parts of the United States.

This narrated slide show is part of our Challenges of Non-Renewable Energy series.

Pre-viewing Questions

  • What do you already know about fossil fuels?
  • Which types of fossil energy do you think people rely on the most?
  • How many years do you think Earth’s fossil energy supplies will last: 100? 500? Forever? How could you gather information to answer a question like this?

Focus Questions for Viewing

  • How did shale form over time?
  • What caused natural gas (shale gas) to form?
  • Why are scientists and engineers interested in the Marcellus Shale formation?
  • What are some of the challenges involved in obtaining trapped shale gas?

Post-viewing Questions

  • Scientists say that nearly all of the energy on Earth comes from the sun. How do you think the sun contributed to the development of Earth’s fossil fuels?
  • Why is there interest in finding new sources of energy within the United States?
  • What daily activities of yours connect you to the use of and need for fossil fuels?

Extension Activity

  • Conduct research to find shale gas deposits that have been discovered near your state. Use various sources to determine an estimate of all the shale gas that lies within the current “shale plays.” Compare the formation and location of coal and petroleum to that of shale. Look for similarities and differences among the three fossil fuels and predict why this may be. Develop an explanation for how different types of fossil energy occur in different places.

Links to Learn More

  • Make a Geologic Timeline , Ohio Department of Natural Resources: Geologic time is very difficult to think about in terms of a human lifetime. This activity will help you to understand how long ago the resources we use today were formed.
  • Ohio “Geofacts” – Millions of Years in the Making, Ohio Department of Natural Resources: See how Earth's crust near Ohio formed over a span of hundreds of millions of years.
  • See How Geologists Have Mapped the Earth’s Crust in Ohio, Ohio Department of Natural Resources: In order to find fossil fuels, geologists create maps that show the different layers of deposition within Earth's crust. This map gives you a sense of the composition and depth of the Ohio bedrock.
  • See How the Continents Formed and Moved Over Time , C.R. Scotese, PALEOMAP Project: Earth's surface has changed dramatically in the past 4.5 billion years. These maps show you the changes over time up to the present day.
  • Learn About Devonian Life How much organic plant and animal life existed 400 million years ago? Find out by exploring this history of the Devonian Period.

NGSS Correlations


Performance Expectation: Develop a model to describe the cycling of Earth's materials and the flow of energy that drives this process. MS-ESS2-1

Disciplinary Core Idea: All Earth processes are the result of energy flowing and matter cycling within and among the planet's systems. This energy is derived from the sun and Earth's hot interior. The energy that flows and matter that cycles produce chemical and physical changes in Earth's materials and living organisms. ESS2.A: Earth's Materials and Systems

Crosscuting Concept: Stability and change

Science and Engineering Practices: Constructing explanations and designing solutions