Sedimentary Rock

What are sediments? How do we get sediments? How do these sediments become rocks?

Weathering and Erosion

Mechanical Weathering Physical disintegration ~ breaking into smaller pieces. Plants, animals, water freezing cause mechanical weathering

Mechanical weathering

Chemical Weathering Rain water, acid, plant decay Oxidation and carbonic acid cause chemical weathering

Climate and weathering Warm climates favor chemical weathering. The warmer the climate the faster the chemical weathering occurs.

Which type of weathering is this?

Erosion Moving of materials from point A to point B Waves, streams, gravity, wind, glaciers cause erosion

Made from sediments Sediments are formed from the breaking up of a parent rock. The size and shape of the sediment tells how and where that rock was created.

Sedimentary Rock Formation Step 1: Derive a sediment via weathering or erosion from a parent rock. Step 2: Lithify the sediment You have a sedimentary rock!

Two Stages of Lithification Compaction grains are compressed together due to an overlying weight Cementation minerals invade pore spaces between sediments and solidify

Three types of sedimentary rocks 1. Clastic ~ from sediments (sandstone) 2. Organic ~ from organisms (fossil limestone) 3. Chemical ~ from minerals left by evaporation (halite)

Detrital Sedimentary Rocks Clastic sediments = loose fragments of pre-existing rocks or minerals formed weathering Classified by grain size, shape, sorting, and composition

Chemical Sedimentary Rocks Minerals precipitate out of solution May appear crystalline Classified by composition Rock Salt Biochemical Limestone

Depositional Environment Depositional Environment: A locality in which sediment is deposited by a depositional agent, including wind, water, ice, and gravity Observations of these environments in the rock record can used to identify ancient conditions

Review Questions What are the three types of sedimentary rocks? What is the difference between compacting and cementing?