Plate Tectonic - Volcanoes (K)

  • Exploring that volcanoes produce rocks.
  • Investigating rocks that come from volcanoes.
  • basalt
  • lava
  • magma
  • obsidian
  • pumice

Students sort rocks from volcanoes.


After it erupts ,a volcano leaves evidence of its activity. These clues are the rocks that were created from molten rock, or magma, erupted by the volcano. These rocks are all igneous rocks. If they are associated with the volcano, they are called volcanic rocks. Volcanic rocks are a subset of igneous rocks. If the magma cooled and hardened inside the earth, they are called plutonic rocks.

Rocks from volcanoes can be very different. They can be light in color and weight, or they can be dark and heavy. Students have to learn to become familiar with volcanic rocks by examining them. This is generally true of all rocks. The more a child sees and feels rocks, the more that child can associate a name with its characteristics.

Scientist name volcanic rocks in ways that describe their composition, how they erupted, and how long it took them to cool. Students will learn some of these names and their meanings in later grades.

  1. Volcanoes are "hills or mountains" made of once melted rock that have cooled and hardened. However, all hills and mountains are not volcanoes. Ask students to develop a description of the environment where volcanoes form (i.e., hot and fiery places). If possible, show students pictures of volcanoes to help them develop descriptive terms.
  2. In your module, there are bags containing small pieces of rock and other materials, including basalt (black rock), pumice (gray, light rock), obsidian (shiny black rock), diatomite (white rock), sea cookies (star on a white disc), a sea urchin spine (long, narrow), and pieces of Styrofoam. Divide your class into working groups. Give each group a bag and a hand lens or reflecting light microscope. Instruct the students to separate the items they think are derived from volcanoes. Have them examine their specimens with magnifying lenses. If you wish, you can make you own module with your own rocks and items.
  3. As a class, discuss each item. State whether or not it comes from a volcano. Be sure to discuss how the students arrived at their answers. They may say that volcanic rocks will look like "rocks" - hard, not easy to break and usually dull looking. The volcanic rocks in your module are basalt, pumice, and obsidian. The sea cookie, sea urchin spine, and Styrofoam are not from a volcano, nor are they even rocks.

    Diatomite is the only item that may give students a problem. It is a rock, but it is not volcanic. A hint that you can use to explain this is that diatomite breaks apart very easily, and most volcanic rocks do not. (Remember these are simplifications). Students will learn more complex criteria in the upper grades.

    Students love to observe the sea cookie in more detail. If you wish, have them examine it in detail to reinforce their observational skills. They can describe the 5 part symmetry on the top of the sea cookie. Instruct them to look underneath the sea cookie. They will see two holes. One hole is the mouth and the other is the anus or "poop" hole. Ask students if they know which way the sea cookie moves, mouth first or anus first? The answer is mouth first because the sea cookie doesn’t want to eat their own poop!

  4. Emphasize with the students that rocks from volcanoes were once melted and there are many types of volcanic rocks. Remind them that they are just beginning to learn about rocks. Exposure to samples of volcanic rocks will help students distinguish and learn more in later grades.

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