Why do some volcanoes explode?
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Here are some examples of each kind of volcano. What do you notice about the shape?


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Here are a couple of rocks collected from each type of volcano. What do you notice?


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Below are ideas for extending this topic beyond the activity & exploration you just completed.
  • End of Mystery Assessment and Answer Key
  • Video: Molten Paradise — The first 10 minutes of this video from USGS shows spectacular footage of volcanoes in Hawaii with commentary from the scientists who study them.
  • Reading: A reading about lava in English and Spanish, free with registration on Newsela Elementary.
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Image & Video Credits

Mystery Science respects the intellectual property rights of the owners of visual assets. We make every effort to use images and videos under appropriate licenses from the owner or by reaching out to the owner to get explicit permission. If you are the owner of a visual and believe we are using it without permission, please contact us—we will reply promptly and make things right.

Lesson Image
Java vulcan semeru by M. Rietze , used under CC BY-SA
world map by Celestia , used under CC BY
spring transition by Spencer Thomas , used under CC BY
eruption plume by Mike Doukas
Mt. St. Helens by Harry Glicken
Mt. St. Helens today by SD4ever
timber by USGS
Reid Blackburn's car by Danial Dzurisin
volcano eruption from space station by NASA Goddard , used under CC BY
Vesuvius by Joseph Wright
Tavurvur volcano by Taro Taylor , used under CC BY
Hawaii lava hike by NewMastersound , used under CC BY
What is lava? by HUGEFloods.com , used under CC BY
Kilauea volcano by PublicResourceOrg , used under CC BY
Etna's crater by Boris Behncke , used under CC BY
Costarica by Samoano , used under CC BY-SA
Fuji by 名古屋太郎 , used under CC BY-SA
Mauna Kea by Nula666 , used under CC BY-SA
Mt. Mayon by Tomas Tam , used under CC BY
Pas bellecombe by Nananère , used under CC BY-SA
sheild volcanos by Smithsonian Institution , used under CC BY
lava flow by KillerPX1 , used under CC BY
Syracuse University lava project by Sam Morrison , used under CC BY
thick lava by Andi Rosadi / VolcanoDiscovery Indonesia , used under CC BY
Mount Semeru by permadhi , used under CC BY
Mt. St. Helens plume by Lyn Topinka
sheep by Daniel Flathagen , used under CC BY-SA
cup by DiegoAbud , used under CC BY-SA
pencil by Charm
spoon by SOLO Estonia , used under CC BY-SA
Print Prep
Activity Prep

In this Mystery, students will investigate how differences in lava types explain differences in the shape and eruption patterns among volcanoes. In the activity, Bubble Trouble, students compare two different types of "lava" -- thin and thick. They use this information to figure out why volcanoes have different shapes and how the type of lava explains why some volcanoes explode.

Preview activity

Number of students:
Lava Experiments worksheet 1 per student
Lava Mat worksheet 1 per pair
Table Covering (eg. Trash Bags)
2 bags per pair
Clear Plastic Cups (10 oz)
Dixie cups will also work.
2 cups per pair
2 cups per class
Measuring Cup
1 cup per class
Paper Plates
1 plate per pair
Plastic Spoons
1 spoon per pair
Plastic Straws (Not Bendable)
1 straw per student
Ziploc Bags (Gallon)
Used to mix the flour and water. Can also use a large mixing bowl.
1 bag per class
Prep Instructions

You will need access to water for this activity.

We recommend students work in pairs. Homeschool students can work on their own.

Prepare the “Lava”

To prepare the “lava,” you will need water, flour, a 1-gallon Ziploc bag (or large mixing bowl), measuring cups, scissors, and (optional) red food coloring.

For thin lava, use plain water. You can optionally add a drop or two of red food coloring to make it look more like lava. A few cups of water will be enough for about 30 students (15 pairs).

To make thick lava, mix up the flour with water and (optional) red food coloring. Watch this video to see how we mix up a batch in a plastic Ziploc bag without making a mess. You can also mix your lava in a mixing bowl. This should make enough thick lava for about 30 students (15 pairs).

Fill Cups with “Lava”

Fill half of the cups about halfway with the “thin lava.” Fill the other half of the cups about halfway with the “thick lava.”

Download this Mystery to your device so you can play it offline: