Does the Temperature Underground Vary as Much as the Surface Temperature Does?
Talk It Over
The soil below the earth's surface is home to many living things. Some insects live underground for all or part of their life cycles. Some larger animals, such as moles and earthworms, live underground all the time. Others, such as the prairie dog, spend part of their time on the surface and part in a burrow they dig below ground. What might be some of the advantages of living below ground? Are animals cooler or warmer below ground?
- Permission to dig small holes in a few spots in the ground
- Small shovel or trowel
- Craft sticks and marker
- Digital instant-read thermometer*
- Select your sites with care. Ideally, you want to investigate some places that are sunny and warm and others that are shaded and cool.
- Plan ahead for this project. The longer you collect data (over weeks, even months), the better your project will be.
- At each site you want to study, dig a small hole or "burrow" in the ground. Don't dig it straight down, like this:
Dig it at an angle, like this:
- Write a name for your site on a craft stick and push the stick into the ground near the burrow you have dug. With luck, it will stay in place and mark your study site for as long as you continue to collect data.
- Hold the thermometer in the air near your burrow. Read and record the air temperature.
- Place the thermometer on the ground near your burrow. Read and record the surface temperature.
- Put the thermometer into the burrow. Leave it for a few seconds, then pull it out quickly and read it immediately (before the surface air temperature has time to change it). Record.
- Repeat steps 3–7 for each site you study. Return daily, for as long as you can, to collect as much data as you can.
Don't trespass on anyone's land. Don't dig holes where people might step into them. Don't put a thermometer into a burrow an animal has dug. The animal might still be inside!
Use the "Go" procedure to study a warm, sunny spot and a cool, shaded spot.
Make some telephone calls to see whether you can borrow a pyranometer from a commercial or college laboratory. With a pyranometer, you can measure albedo, which is the amount of light reflected from a surface. Albedo can affect both surface and air temperatures. Does it affect underground temperatures? Design and conduct a study that will let you relate albedo to your air, surface, and underground temperature data.
Show Your Results
For each site you study, make a data table like this:
For each site, make a line graph with temperature on the vertical axis and time on the horizontal axis. Use different color lines for air, surface, and underground temperatures. The shapes of the lines should tell you something about how temperatures vary and where they vary most.
For "Go Far," make similar data tables and graphs to relate albedo to air, surface, and underground temperatures.
Tips and Tricks
- If you have some sites you can study both day and night, you might try to answer the following question: Do underground temperatures vary as much over the 24-hour cycle as surface temperatures do? If you can extend your project over several months, try to assess seasonal variations as well.
- Make sure you keep with you a fresh battery for your instant read, digital thermometer. You don't want to run low when you are in the field taking temperatures.
Warning is hereby given that not all Project Ideas are appropriate for all individuals or in all circumstances. Implementation of any Science Project Idea should be undertaken only in appropriate settings and with appropriate parental or other supervision. Reading and following the safety precautions of all materials used in a project is the sole responsibility of each individual. For further information, consult your state’s handbook of Science Safety.