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# Indicators: How do Scientists Gather Clues to Climates of the Past?

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Source:
Author: Janice VanCleave

### Problem

How do scientists gather clues to climates of the past?

### Materials

• Modeling clay in three different colors
• 2 index cards
• 1 teaspoon (5 ml) rice
• Straw
• Scissors
• Magnifying lens

### Procedure

1. Soften the clay by squeezing it in your hands. Break off a walnut-sized piece of each color of clay.
2. Flatten one of the clay pieces, and lay it in the center of one index card.
3. Sprinkle the rice over the top surface of the flattened clay piece.
4. Flatten the remaining two pieces of clay and stack them on top of the layer of rice. A three-layer block of clay about an inch deep will be formed.
5. Push the straw through the layers of clay.
6. Pull the straw out of the clay
7. Ask an adult to use the scissors to cut open the straw.
8. Carefully remove the clay plug and lay it on the second index card.
9. Use the magnifying lens to study the clay plug.

### Results

The straw cuts a cylinder-shaped sample from the layered stack of clay. Three layers of clay and possibly some rice can be seen.

### Why?

As the straw cuts through the clay, the clay and rice are pushed up inside the hollow tube. The clay represents different layers of the earth's crust (thin outer layer of the earth), and the rice represents solids, such as fossils (traces of the remains of prehistoric animals and plants). The captured clay is called a core sample, and it reveals what materials are inside the block of clay. Machines that capture core samples are called coring devices. Made of metal, they are used to cut through layers of soil just as the straw cuts through the layers of clay. The metal coring device has a plunger that pushes the soil out so that materials at different depths below the earth's surface can be studied.

Scientists use core samples taken from ocean floors allover the world to discover important clues about the climate in past times. These samples contain tiny ocean creatures known as foraminifera, which are about one-fifth as wide as a human hair. These creatures have been preserved in the ocean floor for millions of years. The shells of these tiny ocean creatures have different shapes and makeups depending on the climate in which they were formed. These core samples from the ocean floor give scientists indications of the earth's major climate changes over the last 100 million years or so.

### Let's Explore

1. Is the clay block exactly the same throughout? Repeat the experiment cutting core samples with the straw from different parts of the clay block. Science Fair Hint: Use diagrams to represent the size, shape, and color of each layer in the core samples.
2. The rice may not be visible on the outside of the core, but slices of the core sample can provide a better view of the core's content. Construct a saw to cut slices from the core sample by tying each end of a 4-inch (10-cm) sewing thread to toothpicks with rounded ends. Pull the toothpicks apart so that the thread is straight and taut between them. Place the thread on top of the core sample near one end. Move the toothpicks back and forth to saw a slice from the end of the clay. Use the magnifying lens to study the surface of the slice of clay. Science Fair Hint: Display photographs of core samples and slices along with diagrams of the magnified surfaces of the samples.

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