Natural Resources

Once students understand the processes that drive the rock cycle, they discuss how those same processes cause fossil fuels to form. Students use maps to evaluate the science phenomena of the distribution of oil and natural gas reserves in the U.S. and then analyze the physical properties of sedimentary rock samples to determine how oil and natural gas can be stored and contained within Earth.

• The processes that cause sedimentary rock to form are the same that are responsible for the formation of fossil fuels—nonrenewable energy sources that formed millions of years ago from plant and animal matter. Oil and natural gas are two kinds of fossil fuels.
• Because of how fossil fuels are formed, there are patterns in where fossil fuels are found on Earth.

• How are the processes that form oil and natural gas similar to the processes that form sedimentary rock?
• Why are fossil fuels organic?
• Why are oil and gas deposits usually found in areas that used to be ocean or where there is sedimentary rock?
• What properties are needed for sedimentary rock to hold oil and gas?
• Why is it important for oil and gas to be able to move through rock?

Misconception: Geological processes happen in human time frames, and any change will happen within a person’s lifetime. 

Fact: Many of the changes to Earth’s surface occur over thousands or millions of years. Other changes can be very rapid.

Fossil Fuel : a nonrenewable energy source that formed millions of years ago from plant and animal matter

Hydrocarbon : any chemical compound that consists only of the elements carbon (C) and hydrogen (H)

Inorganic : anything that is not living and never was living (e.g., water and rocks)

Organic : anything that is living or was once living (e.g., fallen leaves and animal remains)

Permeability : the ease with which substances move through a material; a property of matter

Porosity : having tiny spaces, called pores, that allow substances—such as oil or water—to pass through; a property of matter

Nonrenewable Resource : a resource that cannot be replenished in a short period of time

A Geological Treasure Hunt

Shar Anderson spends her days using computer models and gathering data about the properties of rocks in particular locations. She sees her job as a treasure hunter, looking for clues on Earth’s surface and underground. Anderson is a petroleum geologist, and her job is to analyze data to determine where the best locations are to drill for oil and gas.

Oil and gas are both fossil fuels—nonrenewable energy sources that formed millions of years ago from plant and animal matter. They are nonrenewable resources because they take millions of years to form and therefore cannot be replenished in a short time.

The search for oil and gas is a part of geology because some of the processes that shape Earth’s surface—including the movement of tectonic plates and the processes that power the rock cycle—are also responsible for the formation of fossil fuels. Petroleum geologists like Shar Anderson use what they know about the movement of the tectonic plates and the properties of different rocks to gather data using a variety of different tools. They then analyze the data for patterns in Earth’s geology that might indicate the presence of fossil fuels.

These scientists analyze the properties of Earth materials for the presence of fossil fuels. This is important because fossil fuels, like many natural resources, are not distributed evenly around the planet. They are formed through specific natural processes, and those processes help to determine where fossil fuels can be found.

Finding fossil fuels begins with an understanding of how interactions between the geosphere and the biosphere caused them to form. Millions of years ago, oceans covered most of Earth. The oceans were home to tiny sea animals and plants called plankton. Like all living things, these plants and animals had chemical potential energy stored in their bodies.

When those organisms died, they sank to the bottom of the ocean. Sand and silt covered their remains. Over millions of years, the same pressure and heat that caused the sand and silt to turn into sedimentary rock also caused chemical reactions that broke the organic matter down into more basic structures.

The breakdown of the organic matter led to the creation of hydrocarbons— chemical compounds made up of hydrogen and carbon. Crude oil is one kind of fossil fuel that is made of heavy and complex hydrocarbons. It is a liquid that is found in underground reservoirs and remains a liquid when it is brought to the surface. Natural gas is another fossil fuel that is made of light and simple hydrocarbons. It is found wherever there is crude oil, but it can be found on its own as well. Coal is a third fossil fuel that was formed when ferns and other tree-like plants died and became buried by layers of sediment.

The Search for Fossil Fuels

So geologists use a variety of instruments to help them in their search. For example, they look for evidence of source rock, reservoir rock, and cap rock. They also look for deposits of salt because salt indicates that there used to be an ocean. Because of how fossil fuels are formed, evidence of an ocean suggests that fossil fuels might be found there. They also analyze surface features, surface rock and soil types. River deltas, deserts, and Arctic areas hold most of the oil and gas in the world today.

Geologists can also use seismic shock waves to find oil and gas reserves. The shock waves travel beneath Earth’s surface. When they come into contact with various rock layers, they are reflected back. The reflections travel at different speeds depending upon the type or density of rock layers through which they must pass.

Geologists use instruments called hydrophones to capture information about the shock waves, and then interpret the data to look for signs of oil and gas traps. Once geologists find a possible oil and gas trap, they can mark the location using GPS coordinates on land or with a buoy on water.

If it sounds as if a rock might contain oil or natural gas, the companies begin to drill to release the oil and gas from the rocks, which are often far below Earth’s surface. Oil sources are often found below the ocean floor, so oil companies have developed technologies that allow them to drill offshore.

How Fossil Fuels Are Used

Fossil fuels play an important role in our society. They are a primary source of energy, and are used to power many vehicles, electronics, and many other modern conveniences.

The reason that fossil fuels are an energy source goes back to the chemical potential energy that the organic matter holds within it. When fossil fuels are burned, that stored energy is released in an exothermic reaction. Exothermic reactions give off energy, making the surrounding temperature warmer. Exothermic chemical reactions that burn fossil fuels are some of the primary sources of energy in the United States today.

Refineries take the crude oil and turn it into gasoline and many other useful petroleum products. Petroleum refers to both crude oil and the products extracted from it at petroleum refineries. Petroleum is used in a wide range of consumer goods, such as detergent, fertilizer, synthetic fibers, vitamins, plastic, CDs and DVDs, candle wax and Band-Aids. Synthetic materials are those materials formed through a chemical process developed by humans, as opposed to those of natural origin.

The length of the chain of atoms in the molecule determines certain properties. As the hydrocarbon molecules get longer, they move from a gas to a liquid. Hydrocarbons with up to four carbon atoms are gasses.

In this lesson, students use maps as models to evaluate the phenomena of the distribution of oil and natural gas reserves in the U.S. Then, they analyze the physical properties of sedimentary rock samples to figure out how oil and natural gas can be stored and contained within Earth.