What are Sedimentary Rocks

Sedimentary rocks are shaped from deposits of pre-existing rocks or portions of once-living organism that accumulate on the Earth's surface. If sediment is buried deeply, it will become compacted and cemented, forming sedimentary rock. These rocks frequently have specific layering or bedding and create many of the picturesque views of the desolate tract southwest. Sedimentary rocks are categorized into three groups: Clastic, Biologic, and Chemical.

Key Terms

Clastic Sedimentary Rock

Clastic sedimentary rocks are made up of portions (clasts) of pre-existing rocks loosened via weathering. These rocks have particles ranging in measurement from microscopic clay to massive boulders; their names are decided by using the clast or grain size. The smallest grains are referred to as clay, then silt, then sand. Grains large than two millimeters are referred to as pebbles. Some of the biggest examples of clastic sedimentary rock can be observed at: 

Biologic Sedimentary Rock

Biologic sedimentary rocks shape when dwelling organisms die, pile up, and are then compressed and cemented together. Types of biologic sedimentary rock consist of coal (accumulated plant fabric that is carbon-rich), or limestone and coquina (rocks made of marine organisms). Excellent examples of biologic sedimentary rock in country wide parks can be discovered at:

Chemical Sedimentary Rock 

Chemical sedimentary rocks shape with the aid of chemical precipitation that starts when water touring thru rock dissolves some of the minerals. These minerals are carried away from their supply and ultimately redeposited, or precipitated, when the water evaporates away. To view examples of chemical sedimentary rocks in the National Parks visit:

Castile Evaporite

Castile Evaporite (chemical sedimentary rock) of southeastern New Mexico and West Texas are interbedded layers of gypsum and calcite

Photo courtesy of Heather Walborn