background image
Geology 101
If you really want to get the dirt on soil, just go out and take a good hard
look at it!
What you need:
· Small garden shovel
· Soft ground
What you do:
1. Take a walk. If you're near a forest, river, or park, look for an area where
the soil is exposed, like the side of a bank or a cliff. Can you see the differ-
ent colors of earth? If you're in the city, look for a construction pit for a
new building. The different layers are easy to see from the safety of the
street.
2. Find a safe spot where you can dig a small hole.
Using a trowel, dig just below the top layer of soil.
What did you find?
3. Digging a little deeper, you should notice the soil
starting to change colors.
4. How deep did you have to go for the soil to change
colors again?
You may be surprised to see that dirt comes in different
colors. Just under the grass and twigs, the topsoil was
probably dark brown or black. It is rich in nutrients
deposited by earthworms and essential to plant life.
The next layer is lighter brown because of leaching:
removal of salts and minerals by water flowing through
it. Next may have been a reddish-brown layer, with tiny
pebbles and gravel or larger rocks and stones. This is
the subsoil. You may even reach bedrock, the underlying
rock layer!
Geologists­scientists who study rocks and soil­can
tell the age of the different layers of soil and rock and
what the climate was like at the time each of them
was formed!
Adapted from:
Geology 101
by Shar Levine & Leslie Johnstone
http://www.education.com/activity/article/geology_first/
99