These rocks are formed when hot magma or lava is cooled into a solid. Different igneous rocks form whether it is the magma or the lava that cools. This model shows this effect.
Melt some chocolate chips in a double boiler. (Do not get water in the chocolate chips as that will ruin the chocolate.) Pour some of the melted chocolate (the magma) down the cookie sheet “volcano side” to simulate the cooling lava. This lava cools quickly and would form rocks like obsidian and pumice. Let the rest of the chocolate cool in the double boiler. This takes longer and it cools into a different looking chocolate. This simulates the magma cooling below the ground (which usually results in rocks like granite).
Particles of sand, minerals, mud, shells and decaying matter built up in layers over the years. The pressure of the layers over time presses the sediment into rock like sandstone and limestone.
To create your sedimentary rock, layer different things into a sandwich. We had whole wheat bread, Muenster cheese, turkey, cheddar cheese, and whole grain bread. Notice how some layers are thick and some layers are thin? The same thing is seen in the layers of sedimentary rock – there are different thicknesses.
Metamorphic means “to change”. Metamorphic rocks are ones that have been changed by heat and/or pressure.