Sedimentary Rocks

Chapter 3.3nd 3.4 The Earths SurfaceSedimentary and Metamorphic Rocks1I. Sedimentary Rock- This type of rock forms from sediments.

Sediments- are materials that settle out of water and air. They are usually created by weathering and erosion from wind or moving water. 2There are four types of sediments that can be found on earth. These sediments are arranged by their size.

1.Gravel 2.Sand 3.Silt 4.Clay

Largest Smallest

3There are three ways that sedimentary rocks can form.

1. Pressure- sediments can settle out of water or air, which puts weight on top of older layers. As the weight increases, the bottom layers get pressed into hard compact rock.

42. Cementation- This occurs when minerals crystallize around sediments, cementing them together. These types of rocks can form as water evaporates, or over long periods of time as minerals collect between sediments.

5- Some sedimentary rocks form from the remains of plants and animals.

Example: Coal is formed as the remains of prehistoric plants compressed under the weight of the ground.

Limestone forms as coral, shells, plankton and other remains from sea life are cemented or pressed together.

6Metamorphic Rocks- When rocks are put under heat and pressure over time, they undergo metamorphism. Metamorphism means to change into something new.

Examples:

Granite Gneiss Limestone Marble A. Metamorphic rocks can show different characteristics.Foliated rock-Large amounts of heat and pressure cause the minerals in the rock to line up in a process called recrystallization. These minerals form bands, which give the rocks a striped appearance. (example: Gneiss)

2. Nonfoliated Rock- These rocks tend to form when the parent rock is made mostly of one mineral and usually in small areas with lots of heat. ( example: Quartzite)