History Trippin' 

Activity
Make a Volcano

Directions

1. Have children examine images of volcanoes and discuss what they know about volcanoes.

• What is a volcano?
• What are some things that come out of a volcano? (lava, ash, water vapor, carbon dioxide, sulfur)
• Where are some volcanoes on Earth located?
• Are there volcanoes on other planets? (Nearly all the solid planets and moons have some volcanic activity in their history. Some, such as Earth, Venus, and Io are still active.)
• How can you tell volcanoes and craters apart? (Volcanoes have a central crater, raised rims, a circular central opening, and outer edges that are irregularly shaped though roughly circular. However, unlike craters, volcanoes do not have ejecta or an internal central peak. Furthermore, they are raised features while impact craters are low/deep.)
• Does a single volcano form all at once or over a period of time, in stages? (Over time)
• What volcanic features provide hints that it formed in stages? (Stacks of lava layers)

2. Explain that teams will model lava flows from a homemade volcano. Invite them to examine the poster board with the attached cup. Ask: What does the cup represent? (A volcano)

3. Write the following questions on a board or chart paper so everyone can see them. The group will discuss them at the end of the activity, so teams should prepare answers as they work.

• Do all the flows occur on top of each other? (Not always)
• How do earlier flows influence the direction of later flows? (Later flows may flow off to the sides of the earlier ones)
• Does anything else influence the path of lava flow? (Direction of flow out of the volcano)
• Where does the oldest layer occur relative to later flows? (On the bottom)

4. Have teams: (1) Fill each of the four cups with approximately 1/8 cup of vinegar. (2) Add to each cup three drops of food coloring, making each cup of vinegar a different color. (3) Place one tablespoon of baking soda into the "volcano cup."

5. Have each team pour one of its cups of vinegar into the "volcano." The vinegar and baking soda will react and bubble over the edge of the "volcano." When the "eruption" has quieted, have the children use the markers to outline the edge of their "lava flow." Have them mop up the vinegar using the paper towels. (you can put the baking soda directly into your volcano instead of putting it in cups and then pouring it in the volcano, then pour the colored vinegar in, but don't skip the food coloring...you'll need it)

6. Have the children select a Play-Doh color to mark the first lava flow. They should flatten the Play-Doh into a thin sheet (about the thickness of a clip-board) and place it over the area they marked, covering any area where the lava flow extended.

7. Repeat the procedure three more times, using a different color of vinegar and Play-Doh for each lava flow. Remind the children to be gentle when placing layers of Play-Doh on top of each other; they should not smash the layers together.

8. Have the children sketch a map showing the distribution of the exposed part of the flows. Have them use graph paper, a ruler, and a north-south compass and mark each flow with a different color.

Ask them to label which flow came first (oldest), second, third, and fourth (youngest). Make sure they include a scale, key, and direction indicator on their map.

9. Give children straws and have them "core" the lava flows.

• Can they core a location with all four flows? With only one? Two?
• What is the vertical order of flows (e.g., which is on the bottom, top, etc.)?
• What is the relative age of the flow on the bottom? (Oldest)
• Is the vertical order of the flows always the same? (No, the model may have locations where a layer is missing)
• Is the order always the same in terms of timing? (Yes, older layers are always under younger units)

The study of rock layering is called stratigraphy. One of the rules of stratigraphy is called the principle of superposition. It states that older rocks occur under younger rocks. In other words, the rocks on the bottom were laid down first and then covered by more recent deposits. Another rule of stratigraphy is the principle of cross-cutting relationships. It states that any feature (fault, crater, intrusion) must be younger than the rock that it "interrupts."