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EARTH MATERIALS REVIEW
ROCK CYCLE: the ways that rocks change from one form to another; This can take
millions of years!
IGNEOUS ROCK: rock formed from melted rock that comes from deep within the earth;
When this melted rock (or magma) comes near the surface of the earth it cools to form
igneous rock. (Ex: Cooled lava and granite)
SEDIMENTS: very small pieces that break off or wear off rock
SEDIMENTARY ROCK: rock formed when sediments are pressed or cemented
together; Fossils are often found in sedimentary rock. (Ex: Sandstone and Shale)
METAMORPHIC ROCK: rock formed when igneous or sedimentary rock is changed by
heat or pressure; This heat or pressure occurs when the igneous or sedimentary rock is
buried under a mountain, or deep in the Earth’s crust. (Ex: Slate)
MINERAL: a natural, nonliving solid with a definite chemical structure; Minerals are the
small pieces that make up rocks. They can be identified by shape, size, color and how
hard they are.
MAGMA: liquid rock found beneath the earth’s surface
HUMUS: decaying plant and animal materials
SOIL: a mixture of eroded materials, rock fragments, and decomposed plant material
HORIZON: each layer of soil
A HORIZON: uppermost layer of soil; this is the “topsoil” and is the most
valuable for farming
B HORIZON: not as well-developed as the A Horizon: contains minerals that
have been washed down from the A Horizon by water
C HORIZON: very little organic material; appears as a jumble of rocks