Predict the Flow

Grade Level: 7-10

AGU logo

Source: NASA and AGI. Adapted with permission for the American Geophysical Union.


Ever play with clay? Using a common modeling compound, you can form a “volcano” and examine its topography to predict which way lava will flow down its slopes. You could also investigate mud flows or debris flows.

Materials

Procedure

  1. Cut a piece of transparency to fit in the bin’s bottom. On it, build a hollow volcano out of modeling compound. Put a hole in the top of the volcano and shape it around your cup. The cup’s opening should be just below the volcano’s crater.
  1. Put a new transparency on the clipboard. Put it on top of your volcano-filled bin. Look down through the clipboard and use a marker to draw the outline of your volcano on the transparency. Include the volcano’s crater on your drawing. Also, mark “North” and “South” on the map and bin.
  1. Use your ruler to mark 1-cm intervals up the side of the bin. Add colored water to a depth of 1 cm in your bin. Look down through the clipboard and draw the new outline of your volcano. Continue adding water in 1-cm increments and drawing the outline until you are less than 1 cm away from the volcano’s peak. This process provides a topographic map of your volcano.
  1. Carefully remove the volcano and pour the water from the bin. Dry the volcano and put it back in the dried-out bin.
  1. Trade the topographic map of your volcano with another group. Based on the new volcano’s topography, where would lava most likely flow first when the volcano erupts? Use your marker to make arrows showing where the lava is likeliest to flow.
  1. Now, get the other group’s volcano and bin. Look at the volcano carefully and see if you want to change your prediction about lava flow. Discuss where it would be safe to be if the volcano erupted. If you have them available, put tiny houses or toothpicks where you think would be safest.
  1. In the small cup just below the volcano’s opening, put about a teaspoon of baking soda, eight drops of detergent, and several drops of food color that contrasts with the color of your volcano. Add a full dropper of vinegar and watch the direction the “lava” flows. How did this meet or contradict your predictions? How can you explain any differences?