![]() Sedimentary rocks are formed particle by particle and bed by bed, and the layersare piled one on top of the other. Layering, or bedding, is the most obvious feature ofsedimentary rocks. Slightchanges in particle size or composition result in the formation of layers, alsocalled beds, in the rock. The largest, orheaviest, settle first, and the smallest, or lightest, settle last. ![]() He found that solid particles settlefrom a fluid according to their relative weight or size. With the passage of time and the accumulation of more particles, andoften with chemical changes, the sediments at the bottom of the pile become rock.Gravel becomes a rock called conglomerate, sand becomes sandstone, mud becomesmudstone or shale, and the animal skeletons and plant pieces can become fossils.Īn idealized view of a modern landscape and some of the plants and animals that could be preserved as fossils.Īs early as the mid-1600's, the Danish scientist Nicholas Steno studied therelative positions of sedimentary rocks. Thesesedimentary particles may bury living and dead animals and plants on the lake orsea bottom. Thegravel, sand, and mud settle to the bottom in rivers, lakes, and oceans. ![]() ![]() Most of the rocks exposed at the surface of Earth are sedimentary-formed fromparticles of older rocks that have been broken apart by water or wind. The layers of the rocks are the pages in our history book. Fossils, Rocks, and Time: Rocks and Layers ROCKS AND LAYERS We study Earth's history by studying the record of past events that is preserved in the rocks. ![]()
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