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Rocks from Layers
Wind and water break rocks into tiny pieces called sediment — sand, mud, pebbles, and clay. Rivers carry sediment and deposit it in layers at the bottom of lakes and oceans. Over millions of years, layer after layer piles up. The weight of the top layers presses down on the bottom layers, squeezing them together. Minerals in the water act like glue, cementing the pieces together. After a long, long time — solid rock! That is SEDIMENTARY rock.