Explore! Mars: Inside and Out

Make a Volcano


Volcanos - Go with the Flow is a 30–45 minute activity in which teams of Geologic Scene Investigators, ages 8–13 create volcanos like those they have just examined on Earth and Mars. Using baking soda, vinegar, and Play-Doh, they model volcanic eruptions and older children can map the lava flows (optional). The children explore how volcanos grow, how later lava flows overlap earlier ones, and how earlier flows influence the paths of subsequent flows. They determine a volcano's history of eruptions based on the layering of different flows, and reflect on what the presence of volcanos means about a planet's interior.

This activity has been modified from Lava Layering, an activity in Exploring the Moon: a Teacher's Guide with activities for Earth and Space Sciences, NASA Education Product EG-1997–10–116-HQ by J. Taylor and L. Martel.

What's the Point?

  • Volcanos may erupt multiple times, creating several volcanic layers. Earlier/older layers influence where more recent/younger lava flows go.
  • The oldest volcanic layers are found under successive flows, with the geologically most recent/youngest volcanic layer being on top.
  • The presence of volcanos on the surface of a planet or moon is evidence that the interior of that planet was once — or still is — hot enough to produce molten rock — lava!
  • Models — such as the children are using here — can be tools for understanding the natural world
  • Geologists use features on Earth to help them understand how similar features may have formed on other planets, like Mars.


For each child:

For each team of 3 to 5 children:

  • A ~2 foot square sheet of poster board or cardboard, or a tray on which to build the volcano. Box lids also work well.
  • 3 balls of Play-Doh (each about the size of a lemon) in different colors
  • Small paper cups (4 ounce or smaller)
  • Scotch tape
  • 1 clear straw, cut in three 2" sections
  • Several paper towels
  • 1/4 cup vinegar
  • 2 tablespoons of baking soda
  • A pencil
  • Gridded paper for mapping by older children
  • Colored pencils or markers
  • Copies of volcano images from the Setting the Scene activity

For the facilitator:


  • Prepare an area large enough to accommodate the volcanos for the number of teams participating.
  • For each group of 3 to 5 children, prepare the materials for building a volcano:
    • If you are going to have the older children map the flows, create a grid of lines, spaced 1 to 2 inches apart on the poster board, tray, or box lid. Similarly grid the paper the children will use. The scale of the paper and poster board will be different, but the number of grid cells should match.
    • Cut the top half off one paper cup and tape the cup bottom to the middle of the poster board or tray. Pour the baking soda into the cup.
    • Pour 1/4 cup of vinegar into the second cup.
    • Cut straws in 2" sections.
    • Place 3 balls of Play-Doh, a pencil, the straw pieces, and vinegar near the poster board.
    • Make copies of volcano images.


1. Share with the children that they are going to create three volcanic eruptions and examine how the lava flows! Each team of investigators will model three eruptions and observe how volcanos are created from flowing lava, what factors influence lava flows, and where the oldest and youngest layers of volcanic flows are positioned.

2. Have each team pour about 1/3 of the vinegar into their cup – the volcano caldera.

  • Can they describe what happened? The liquid began to bubble and flow over the edge of the cup.
  • What is it called when magma — molten rock — bubbles over the edge of a volcano? An eruption.
  • What does the liquid flowing out of the cup represent? Lava — molten rock flowing across the surface of a planet.

In this activity, the lava came from a cup. Where does lava really come from? Lava is molten — or liquid — rock that comes from inside the Earth. When it is inside the Earth, it is called "magma." When it flows at the surface, it is called "lava."

3. After the eruption, have the children trace around the general outline of the flow, and then blot (don't wipe!) up as much of the liquid as possible. Have them take one ball of Play-Doh, flatten it into a thin sheet, and place it on the area where the lava flowed, following the lava flow boundary marked.

You may wish to have children ages 10 to 13 map the different layers. If so, have them create a map of the flow on their paper that matches where their flow covered the grid on the poster board. Invite them to color the flow and create a key for the map. They will repeat this step for each flow.

4. Have the children repeat the lava flow procedure two more times, using different colors of Play-Doh to mark each flow. It is important to place the Play-Doh exactly where the lava flowed - even if it is on top of another flow!

5. When they have completed their three flows, invite them to examine their volcano.

  • What is the shape of the volcano? A low hill or cone.
    Facilitator Note: the children's volcanos probably do not look like the steep sided Mount St. Helens that is constructed from lava flows that are thick and explosive. The Play-Doh volcanos actually look more like the low-sloped shapes of the Hawaiian volcanos and the volcanos on Mars. These have low slopes because they are constructed from layer after layer of thin, runny lava.
  • Can they see all three flows? Did any flows completely cover up other flows?
  • Can they see exactly where each flow went? No, some of the later/younger flows probably covered the older/earlier flows.
  • Did the second and third volcano flows go exactly on top of the first flow? Probably not.
  • There are several things that might have caused them to flow differently. Can they name a few? Earlier flows helped to divert or direct later flows. Some flows had more lava.

6. Invite the teams to exchange volcanos.

  • Can the new team determine which flow came first? Second? Third?
  • Can they determine exactly where the first flow went? The second? The third?

7. Invite the teams to use the straw sections to collect core samples. Geologists collect cores to determine what is below the surface, how thick layers are, and how far layers may extend. Each team may choose 3 locations on their volcano from which to collect a core sample.

  • What questions might they want to address? Perhaps they want to know how many layers there are, which layers are where, and how far a layer may be from the volcano caldera.
  • How might they use their few core samples to determine answers to these questions?

8. Once the teams have collected the core samples, ask them to share what they found.

  • How many layers are there?
  • Does each core sample contain the same number of layers? Why or why not? Each lava flow went into a different area, sometimes over the older flows, and sometimes into new places. Chances are that at least one of the cores was taken in an area that did not contain all three layers.
  • Which is the oldest layer? The youngest? How can they tell? Ask the children to think about a laundry pile that might be in their rooms right now! Which part of the laundry pile was put down first — or is the oldest? The oldest dirty clothes are on the bottom; the youngest dirty clothes are the ones they put on the pile yesterday. J The ages of the volcano layers are similar. The oldest unit is the one on the bottom. It was the lava layer that flowed first. The top unit is the youngest. It is on top of the older units and it represents the lava flow that flowed last. Geologists apply the Law of Superposition to determine which layers are relatively old and which are young: unless something else — like folding or faulting — has happened, the oldest (first) layers are on the bottom and the youngest are on the top.
  • Can they determine how far each layer spread from the volcano caldera? They can make a few statements, based on finding certain units at core sites, but they will need many core samples to create an accurate map.

If you have time, invite the teams to collect more core samples to see if they can map the layers.

If the children mapped the layers, have the team that created the volcano share their map with the team that is coring the volcano. Were the coring team's conclusions correct about which unit is the oldest? About where the different units are?


Have the children reflect on what they observed and the images from Mars and Earth. Invite them to record what they learned in their GSI Journals.

  • Did they observe volcanos on Earth? Mars? Yes — both!
  • Is there evidence of volcanos erupting on Earth? Yes, there are pictures of active volcanic eruptions!
  • Is there evidence of volcanos erupting on Mars? Not of actual eruptions, but there are volcanos on Mars. Scientists are not sure how old they are, or if they are still active. These are questions scientists still are researching.
  • If a planet has active volcanos, what does that tell you about the planet? That it is still hot enough inside to melt rock and make magma that erupts from the surface.
  • Even if Mars' volcanos are not active today, what can we say about the inside of Mars? That at one time it was hot enough to make magma that erupted at the surface.

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