Explore - Mars: Inside and Out! - Setting the Scene

The Icing on the Plate - Why are the Volcanos on Mars so Tall?


The Icing on the Plate is a 20 to 30 minute activity in which older children, ages 10 to 13, create models with cake icing to compare the volcanos formed on planets with stationary surfaces and planets with moving plates. Children gain an understanding of why volcanos on Mars are so large compared to those on Earth, and what the patterns of Earth's volcanos tell us.

What's the Point?

  • Earth is composed of several rigid plates (lithospheric plates) that are in constant motion.
  • Mars' outer surface is not divided into plates. Its surface is stationary.
  • Plate movement on Earth (plate tectonics), results in plates gradually passing over deeper chambers of magma. Volcanos build up, fed by the magma chamber, then the plate moves and another volcano is started at the new location. This process results in relatively small volcanos in chains on Earth.
  • Mars' stationary surface results in volcanos being located over chambers of magma for a long time. The volcanos grows as long as the chambers provide new lava. This process results in relatively large volcanos, more randomly located, on Mars.
  • Models — such as the children are using here — can be tools for understanding the natural world.
  • Geologists use comparisons between features on Earth and other planets, like Mars, to help them identify differences in how the features may have formed or changed.


For each child:

For each team of 3 to 4 children:

  • 1 cake decorator bag with large tip (may be purchased at stores that sell hobby or craft items)
  • 1 slightly sharpened pencil
  • 2 large, heavy cardboard plates or meat trays (for example, a 12S meat tray)
  • 1 16 oz. container of cake icing (not the kind in a squirt can); instant mashed potatoes, made to the same consistency as icing, can be substituted.
  • A spatula or large spoon
  • Several wet wipes
  • Glue stick
  • Scissors
  • Images of Olympus Mons and the Hawaiian Islands, taken from space

For the Facilitator:


  • For each team fill the decorator bag with a full container of cake icing and attach a tip with a large opening.


1. Introduce the activity by revisiting what the children know about Mars and Earth volcanos.

  • From your paper models of Olympus Mons and Mauna Kea, which planet has the tallest volcano in the solar system, Earth or Mars? Mars has the tallest volcano — Olympus Mons.
  • Was it a little larger, or a lot larger? It was a "lot" larger!
  • What do you think could cause the volcanos on Mars to be so big compared to those on Earth? Answers will vary.

2. Explain to the children they will create another model to demonstrate why Olympus Mons is the tallest volcano in the solar system. They are going to create and compare models of volcanos that form on planets that have plates on their surfaces that move, and on planets that have stationary surfaces, with no plates.

3. Distribute the plates, glue stick, scissors, slightly sharpened pencil, and schematic to each team. Invite each team to examine the pictures.

  • What do the pictures show? These are pictures of the Hawaiian Islands and Olympus Mons taken by spacecraft. These images are at the same scale. In other words, the Hawaiian islands are small compared to Olympus Mons; part of the Hawaiian Island chain would fit across Olympus Mons!
  • What do you notice about the pattern of the islands?
  • Are they in a chain? Yes, the volcanos on Earth form a chain.
  • As the children will be making volcanos, what might the big bag of icing represent? Magma — molten rock beneath the surface of the Earth.

4. Have the children glue Olympus Mons to one plate and the Hawaiian Islands to the other plate. They may need to "round out" the edges with the scissors to get them to fit. The images should be pressed and smoothed flat onto the plates. With the slightly sharpened pencil, have the children carefully poke large, open, holes into the plates where each volcano occurs (you may wish to assist younger children with making the holes). These holes represent the calderas, the opening in the volcano where lava pours out.

5. Provide each group with a bag of icing and invite the children to create models of Mars and Earth volcanos! The icing in the bag is going to be placed under the plates and squirted out at each volcano.

  • What do the plates represent? The surface of Mars, with Olympus Mons, and the surface of Earth with the Hawaiian Islands.
  • What does the icing in the bag represent? Magma in the bag, and flowing lava when it reaches the surface.

Challenge each team to figure out how to make the volcanos erupt at each volcano in the Hawaiian chain without moving the bag of magma! This is very important. How will they get the volcanos to erupt first at Kauai (the oldest volcano in the image), then Oahu, then Molokai, Maui, and finally Mauna Kea on the Big Island (the youngest, or most recently created, volcano) without moving the magma "chamber?" Allow a few minutes to share ideas before proceeding. Help guide them to the conclusion that, if the magma chamber itself cannot move, the plate above it has to!

For older children, you may want to share the actual ages of the islands. Scientists have dated many rocks from each island. There is a pattern to the ages – the islands get younger from the north west (Kauai) to the south east (Big Island).

The volcanic rocks that make up the island Kauai erupted from a volcano 5 million years ago. Rocks forming Oahu are about 3.7 to 2.6 million years old. Molokai is made of rocks about 1.9 to 1.7 million years old. Rocks on Maui are between 1.3 and 0.75 million years old, and, finally, the rocks that make up the Big Island are erupting from its volcanos, including Mauna Loa and Mauna Kea, today! This island began forming about a half a million years ago.

6. Invite the children to experiment. Have one team member hold the plate. Have another team member be the timer — they will allow 3 seconds for each "eruption." Have a third team member hold the "magma chamber" (the bag with icing). Caution: Keep the icing bag twisted closed so the magma is forced out of the top of the chamber and not onto the floor!

From under the plate, have the team member with the "magma chamber" push the tip up through the hole in the Kauai volcano — the oldest in the Hawaiian Island Chain. The tip itself can be used to enlarge the hole (the tip should extend slightly higher than the plate's surface). When the timer says "go," they should squeeze the icing out of the bag, through the hole, and onto the plate until the timer says "stop" 3 seconds later. The team member should then move the plate, not the magma chamber, so that the next island in the chain is over the magma chamber. Repeat the eruption process for each island.

7. Review with the group what they learned about the formation of the Hawaiian volcanos.

  • How did you form the chain of Hawaiian volcanos without moving the magma chamber? By moving the plate!
  • What do you think the plate represents? Earth's outer layer.
    Share that Earth's outer layer is broken into several large plates that move relative to each other – sometimes into each other and sometimes alongside each other, and sometimes away from each other. We tend to get volcanos at many of these plate boundaries, as the children may have observed in the previous activity, Puzzling Patterns. We also get volcanos when a plate moves over a stationary magma chamber — a magma chamber, or "hot spot," that is deep in Earth's interior and does not move around. That is what we think is happening with Hawaii and that is what the model represents — the Pacific Plate moving over a hot spot.
  • Do you think the plates on Earth move in much the same way as your volcano plate model? Yes, just not as quickly. The plates on Earth move at a speed of a little over a half centimeter to 8.5 centimeters each year (about 1/4 to 3 1/2 inches each year).
  • What do you think the volcano would look like if neither the magma chamber (icing) nor the plate moved? Would it be larger or smaller? Answers will vary.

8. Next invite the children to create a model of Olympus Mons, but this time they will not move the magma chamber or the plate! In this case, have the teams hold the plate and the "magma chamber" steady and repeat the squeezing of magma onto the Martian surface until they have used all their "magma."


Compare the volcanos on Earth and Mars! Invite the children to record their ideas in their GSI Journals..

  • In what ways are the volcanos on Earth and Mars alike? Answers will vary but should include that they are made of the same "stuff," they are about the same shape, and they were both created when magma from underground erupted through the surface.
  • In what way(s) are the volcanos different on the two planets? Answers will vary but should include that Olympus Mons is "a lot" bigger!
  • How might the model explain why Olympus Mons is much larger than Earth's tallest volcano, Mauna Kea? Mars' surface does not move, so the lava just keeps building and building and building a huge volcano. On Earth, the surface is divided into plates and, in places like Hawaii, a plate moves over a magma chamber, shifting with time and not allowing one single volcano to grow really big.