Rock Cycle - Rocks (KA)

  • Discovering the two different types of igneous rocks.
  • Making a display of plutonic and volcanic rocks.
  • igneous
  • magma
  • plutonic
  • rock
  • volcanic
  • volcano

Students create a picture that shows that rocks are created from volcanoes.

a gas flare of lava, black is cooled obsidian


There are two types of igneous rocks, based on rates of cooling. Volcanic rocks cool quickly, and form on the Earth’s surface around volcanoes. These are sometimes referred to as "lava rocks." Lava refers to the molten rock, or magma, which cools to make volcanic rock. 

The second type of igneous rock is plutonic rock, which forms from the slow cooling of magma within the crust of the earth.


  1. In your kit you have samples of the volcanic rock rhyolite and the plutonic rock granite. Show the rocks to the children and have them describe them. Both rocks are light in color, but one of the rocks has large gray, white, and black minerals. This is granite. The other rock has very small minerals that cannot be seen with the naked eye; this is rhyolite. Under a microscope the children may be able to see very small minerals, but not as large as those in the granite.  Use the magnifier to look at the specimens closely.

    The reason that one rock has large minerals (granite) is that it cooled much slower (by thousands of years) than the other (rhyolite). Volcanic rocks tend to be fine grained (minerals are small) and plutonic rocks tend to be coarse grained (large minerals). This is a generalization, but is basically correct.

  2. Have students color the worksheet. Tell students that there are many igneous rocks being formed in currently erupting volcanoes.
  3. Glue some of the  large grained sand in the plutonic area of the volcano they colored. The small grained sand should be glued in the volcanic area.   Use the magnifier to look at the grains of sand.

    If you do not have sand, just use confetti or similar art material, with two different sizes. The larger size should be glued in the plutonic area, the smaller should be glued in the volcanic area. This exercise emphasizes that plutonic rocks have large minerals and volcanic rocks have smaller crystals. 

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