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Igneous rocks are formed deep inside the earth where it is very hot. It is so hot that rocks melt! All kinds of rocks and minerals melt and get mixed together. Melted underground rock is called magma. Magma is under a lot of pressure from all the land above it. Any weak spot in the earth's surface can allow that magma to come spilling out. Magma that is above the ground is called lava. Over time, hardened lava piles up outside the weak spot. That is how volcanoes are formed. Hardened lava is called igneous rock. Igneous rocks get various colors from the different rocks and minerals which melted into the original magma. A volcano may erupt several times, creating bands or streaks in the igneous rocks. Igneous rocks get their textures based on how long it took them to cool down. Lava that cools fast makes a smooth igneous rock. However, the gas bubbling out of slow-cooling lava makes a rough, bumpy igneous rock.
Sources: Anderson, Alan, et. al. Geology
Crafts for Kids: 50 Nifty Projects to Explore the Marvels of
Planet Earth. New York: Sterling Publishing Co., Inc., 1996. Science and Technology for Children. Rocks and Minerals. Burlington, NC: Carolina Biological Supply Company, 1997. |