How Are Sedimentary Rocks Formed?

As an amateur rock climber or rock climbing wannabe, you may be wondering, “How are sedimentary rocks formed?”. Sedimentary rock cliffs can be challenging for climbers. But what exactly are sedimentary rocks? The following overview should answer some of your questions.

Definition Of Sedimentary Rocks

You learned about rocks in school, in a geology or physical science class. But that was a long time ago and, honestly, you haven’t given the subject a second thought. Now your newfound interest in rock climbing has you interested in science again. Here are is review to refresh your memory.

Sedimentary rock is one of three classifications of rock: igneous, sedimentary, and metamorphic. Rocks are naturally occurring aggregates of minerals and mineral-like substances. The earth’s outer shell, or lithosphere, is made up of rocks. They are generally classified by their mineral and chemical composition, particle texture, and formation process.

Formation Of Sedimentary Rocks

Sedimentary rocks are formed by fragments of organic matter, chemicals, and loose particles called sediments. Rock formation occurs as the sediments are deposited, compacted, and cemented in a process called diagenesis.

In order for sedimentary rocks to form, natural materials in the earth are first broken down by weathering and erosion. The sediments are then transported by wind, water, glacial ice, or gravity to a place where they are deposited. Beach and river sand are examples of sedimentary deposits through water transport. Sediments can also settle from standing or slow-moving water, such as lakes and oceans. Sand dunes and loess are examples of wind transport and deposit. And glacial moraine and till are examples of ice-transported sediments.

Examples Of Sedimentary Rocks

Sedimentary rocks are classified by grain size: boulder, cobble, pebble, sand, silt, and clay. They form on the earth’s surface, or very near it. More than two-thirds of all sedimentary rocks are mud rocks. Examples include mudstone, siltstone, and shale. Sandstone makes up another 20 percent. The remaining sedimentary rocks are carbonate rocks, such as limestone and dolostone.

Although sedimentary rocks cover the earth’s surface, they are merely a veneer that covers a crust mostly consisting of igneous and metamorphic rocks.

Benefits Of Sedimentary Rocks

Sedimentary rocks are deposited in layers called strata, and they form a structure called bedding. Sedimentary rocks are excellent sources of natural resources such as drinking water, coal, and fossil fuels.

Their study is helpful to civil engineering, for the construction of roads, tunnels, buildings and other structures. And as rocks formed at the earth’s surface, sedimentary rocks are the best record of the earth’s environmental, climatic, and biologic history.



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