Earth Science Week Classroom Activities

Natural Gas Formation

American Association of PetroleumGeologists

Activity Source:

Adapted by AAPG from the American Geosciences Institute. Adapted with permission.

Natural gas, which is mostly methane, is an energy resource used for generating electricity and heating, powering transportation, and manufacturing products. Right now, one-quarter of the world’s energy comes from natural gas.

Natural gas formation, one of the processes occurring on our ever-changing Earth, takes a very long time. Natural gas is formed from marine organisms that die, sink to the bottom of the ocean, and get covered with sediments. Most of the dead organisms decay before becoming covered with sediments. Some of them, however, are buried along with the rest of the sediment. As more and more sediment is deposited over time, the temperature slowly increases. If the pattern of the temperature increase is just right, some of the dead organisms are changed into natural gas and oil.

In this investigation, you will make a simple model of how gases can form from decaying material. You will also explore the effects of temperature on gas formation.


  • Two bags of fresh bean sprouts (you will need to buy one 10 days after the first)
  • Two bags of fresh lettuce (you will need to buy one 10 days after the first)
  • 1 cup measure
  • Three gallon-size zip-closing plastic bags
  • Black Sharpie™
  • Refrigerator
  • Sunny window
  • Metric tape measure
  • Notebook and pen


  1. Tear the lettuce into small pieces. Measure out a cup of lettuce and a cup of bean sprouts into one plastic bag. Press out all the air in the bag, seal it securely and use the Sharpie™ to label it with the date and the word “Refrigerator.” Measure the circumference of the bag with your tape measure. Record this number and any observations you have about the bag in a notebook. Put this bag into the hydrator, or “crisper,” in your refrigerator.
  2. Prepare the second plastic bag in the same way, but label this one “Sunny Window.” Record the circumference of the bag and any observations in your notebook. Put the bag in a sunny window or other warm place.
  3. Every day for 10 days, check on both of your bags. Measure and record their circumferences and any other observations you may have. At the end of the 10 days, compare both bags and write down what you measure and observe. Compare the state of the lettuce and bean sprouts with fresh samples of these vegetables. What happened to them over the 10-day period?
  4. Discuss: How can you account for changes in the bags over 10 days? How can this investigation help you to understand how natural gas forms? What is the role of heat in forming natural gas?