Materials:

• One prepared leader - with practice using rock cutter and preferably paleobiology experience
• Rock cutter
• Number of pieces of fossiliferous limestone from Wang's Corner outcrop (one per student would be ideal)
• Rock Hammers depending on size and maturity of group
• Hand lenses
• Moist paper towels
• *Fossil guide for leader review

*Provided in hard copy in Mudd 71, or at link above.

Concepts Used:

• Formation of fossils
• Time Scale
• Ancient Animals
• What are of Sedimentary rocks?

Skills Emphasized:

• Biology
• Geology

Background:

We can tell what types of animals and plants lived long, long ago because we can find fossils of these organisms. When most things die they decompose but if a plant or animal is covered up quickly (like a flood, storm, or eruption), and the conditions are just right, then the plant or animal is fossilized. That means that a long lasting form of it is preserved. You can have imprint fossils- such as fossilized paw prints. Or you can have fossil casts - such as a hard material filling a snail shell and then when the shell disappears the filling is left in the shell shape. You can also have the minerals in the shell change so that the shell becomes really hard and is preserved. Usually only hard parts of an animal are preserved. Talk about what types of things you would expect to find (teeth, bones, shells) and what you would not expect to find (skin, muscle, ext.).

Sometimes rocks are made almost entirely of fossils!

Description of activity

• Estimated prep time (before student arrival): 1hr
• Estimated activity time: 25-35 min depending on complexity and number of students.

Teacher Preparation:

Collect pieces of limestone from Wang's Corner Outcrop - Ask any Geology Professor for directions. Review fossil guide.

1) Pass out chunks of limestone and ask the class to describe what they see.

2) Hand out hand lenses and ask them to look closer - Write down their descriptions on the board.

3) Tell the class where you got the rocks. Tell them that around 500 million years ago Northfield and most of Southern Minnesota was covered by a huge ocean and that lots and lots of strange creatures that no longer exist lived in this ocean. Explain that these animals died and were covered up at the bottom of the ocean and over time were turned into rock.

4) Point out a sample with the "cheerio shaped fossil" (crinoid column). Show them pictures of what the crinoids used to look like. Explain that they ate by catching food in their feathery tentacles as it floated by.

5) Point out a fossil with a brachiopod shell. Explain that brachiopods are a lot like clams today but they are not the same WHY

6) Point out any piece of a trilobite fossil - show whole trilobite fossils from the collection.

7) Point out any gastropod or cephalopod fossils - talk about how they moved.

8) Take a few samples (or one large sample) and cut it in half with the rock cutter.

9) Let them wet fresh face of the samples with a moist paper towel. Have them look at it with a hand lens.

10) Show cool examples of fossils from the fossil collection.

Review and Questions:

Talk about what they could see in the rock with and with out the hand lens. Talk about what they could see when they cut it open. Talk about how Minnesota (and the rest of the world) has not always looked like it does today and how the rocks can tell us about what it used to be like in the past. Talk about how fossils help us know more about the ancient surroundings.

What fossils did you see in the rocks?

How did the fossils get there?

What do the fossils tell you about the past?

Additional Resources:

This is a great website about collecting fossils in Minnesota:

http://www.tc.umn.edu/~brams007/mnpaleo/collecting.html

Alternatives for older/younger ages:

• For older students include acid bottles and let them drop acid on the limestone and explain why it fizzes. You can also talk about the three types of rocks (igneous, metamorphic, and sedimentary and what some examples are of each)
• For younger students talk about fossils but focus on how you can see so much more about a rock when you cut it and look closely.

Idea for the activity:

came from Introduction to Geology.