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## Sedimentary Rocks The word sedimentary is derived from the Latin word *sedimentum*, which means matter which has settled down at the bottom of a liquid. Sedimentary rocks are formed by the deposition and consolidation of small fragments of rocks called sediments. These sediments are created by...

## Sedimentary Rocks The word sedimentary is derived from the Latin word *sedimentum*, which means matter which has settled down at the bottom of a liquid. Sedimentary rocks are formed by the deposition and consolidation of small fragments of rocks called sediments. These sediments are created by the breaking down of pre-existing bigger rocks and are transported and deposited by the actions of wind, river, and ice. Over time, the sediments accumulate in layers with the oldest layer being at the bottom and the youngest layer at the top. The sediments are then compressed and hardened to form sedimentary rocks. These rocks are known as secondary rocks because they are formed by the solidification of sediments from original igneous, sedimentary, or metamorphic parent rocks. There are three types of sedimentary rocks based on their formation: - **Mechanically formed rocks** contain fragments of other rocks that have broken up, such as sandstone and clay. - **Chemically formed rocks** are created from the deposition of chemicals, like salts, through evaporation, with rock salt being an example. - **Organically formed rocks** contain remains of dead plants and animals, such as limestone and coal. ## Replicated Sedimentary Rock **Objective:** How sedimentary rock forms **Materials needed:** - An empty water bottle - Gravel - Topsoil - Dead plant material **Procedure:** 1. Start by pouring a layer of sand and topsoil. 2. Insert the dead plant material and gravel. 3. Fill the bottle about 3/4 full with water. 4. Shake the bottle until all the components settle into different layers. 5. Over time, observe and record how the ingredients settle into different layers. 6. Focus on the dead plant material and make a hypothesis about what happens over a long period of time. 7. After completing the experiment, compare the materials to sedimentary rocks. ## Metamorphic Rocks The word metamorphic is derived from the Greek word *metamorphose*, which means to transform. These rocks were once igneous or sedimentary rocks that have been changed by heat and chemical processes. The factors responsible for this process include pressure, temperature, and the chemical composition of the surrounding rocks. Since metamorphic rocks are made up of minerals, they may change in both composition and texture due to these factors.