Sedimentary Rock

What is sedimentary rock?

Sedimentary rock is formed from sediments deposited by water on the bottom of rivers, lakes, and oceans. The sediments are pieces of earth that have eroded, or worn away and washed downstream into rivers, lakes, and oceans and then settled out. As subsequent layers of sediment are overlaid over previous layers, the pressure from the weight causes the sediments to form rock.

Layers of sedimentary rock are formed by slow deposition from winds and normal rains and also from rapid deposition from catastrophic processes such as large rains, tsunamis, earthquakes, floods, etc.

Fossils are found in many sedimentary rock layers. It is believed that the fossils are primarily deposited during catastrophic depositions since rapid burial is needed to fossilize a living organism.

Some different types of sedimentary rock layers are called sandstone, limestone, shale, gypsum, and conglomerate rock.

Other types of non-sedimentary rock include igneous and metamorphic rock.

Some types of igneous rock include granite, basalt, obsidian, and pumice.

Some types on metamorphic rock include quartz, amethyst, marble, slate, gneiss, graphite, and coal.

Our understanding of how sedimentary rocks were formed and how fossils in those rocks became fossilized is critical to understanding what the rocks really tell us about our true origins.

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