Earth Science Week Classroom Activities

Investigating Different Rock Types

Association of American StateGeologists

Activity Source:

Adapted with permission by the Association of American State Geologists
from AGI’s Investigating Earth Systems, Rocks and Landforms, pp. 1-3.

Background

In this investigation, you will explore the characteristics of various types of rocks. Why are rocks important to citizen scientists? There are a number of reasons:

We live on the topmost layer of the Earth, the crust, which is made of solid rock. We also make structures out of this rock, as well as mine it for useful minerals. When you travel around your community, observe the various buildings and other structures - how many are made from rocks or materials that come from rocks?

Materials

For a group of four:

  • Sedimentary rock samples
  • Samples of igneous and metamorphic rocks (optional)
  • Hand lens
  • Index cards (one per person)

Procedure

  1. Your teacher will give you a rock sample, hand lens, and index card. Observe the rock closely, first just with your eyes and then with the hand lens. Also observe the rock’s shape and texture. Write your name and your observations on the index card.

  2. All the rock samples will be collected and placed in a long line. When everything is ready, look at the line of rocks. Use the information on your index card to find your rock, and take it back to your seat.

  3. In your group, discuss how hard or easy it was to find your rock. What information would make it easier to find? Look over your observations to see whether you included features such as color, size and arrangement of crystals or grains, fractures or breaks in the rock, layering, or relative hardness. Add any new details to your card.

  4. The rocks will be collected and put into a long line again. This time, you will be given someone else’s card and will need to find that person’s rock. When you find the rock, check with the owner to make sure that you have identified it correctly.

  5. Take the new rock and card back to your seat, and use them to answer these questions:

    • How easy was it to find the new rock?
    • What could the owner have done to make finding the rock easier?
    • What can you now say about rocks based on your observations?

  6. The types of rock samples you have been observing are called sedimentary rocks. What kind of evidence do you have to suggest that these rocks all should be placed in one group?

  7. If there is time, your teacher may also give you samples of igneous and metamorphic rocks. Observe these, and compare them to the sedimentary rock samples. How are they the same as or different from each other? What ideas do you have about how each type might have been formed?