The rock cycle

Rock Cycle

1. THE ROCK CYCLE

2. LESSON OBJECTIVES Name at least five (5) rock forming processes. Define accurately the rock forming processes. Label accurately the rock cycle. Explain with the aid of diagram the rock cycle and the rock forming process. Create a model of a sedimentary rock and then change the rock to igneous using knowledge gained about rock formation.

3. What is the Rock Cycle? The rock cycle is the process by which rocks of one kind change into rocks of another kind. TYPES OF ROCKS: There are three main kinds of rocks: igneous rock, metamorphic rock, and sedimentary rock. Each of these rocks can change into the other kinds by physical processes. Cooling Weathering and erosion, Compacting and cementing, heat and pressure (metamorphosis), Melting

4. The Rock Cycle Process 1. The rock cycle begins with molten rock. Molten rock is called magma when it is below ground, and lava when it is above ground. When magma cools and hardens, it forms igneous rock. This process is called cooling or solidification or crystallization . 2. Weathering and erosion , break the original rock into smaller pieces. The smaller material is called sediment and is carried away ( transported ) by rivers, wind, and glaciers and deposited elsewhere. These sediments can then be buried and hardened (called compaction and cementation ) forming sedimentary rock. This process is called lithification .

5. 3. Sedimentary rock can be deeply buried and be exposed to heat and pressure , which over time, cause it to change its structure into metamorphic rock. This process is called Metamorphism , which means change. 4. Eventually, these metamorphic rocks may be heated to the point where they again melt into magma and the process or cycle starts again.

6. TYPES OF ROCKS Rocks are not unchangeable! R ocks undergo changes of form in a rock cycle . A metamorphic rock can become an igneous rock, or a sedimentary rock can become a metamorphic one. Rocks change very slowly under normal conditions. So what are the three types of rocks, and how do they change into each other?

7. Three types of rock: Igneous rocks are formed when hot magma (melted rock) is rapidly cooled. Granite, obsidian, and pumice are all common examples of igneous rocks. Sedimentary rocks are formed by layers of sediment (dirt, rock particles, etc.) being mixed and compressed together for extended periods of time. Common examples of these rocks are limestone, sandstone, and shale. Sedimentary rocks often have lots of fossils in them because plants and animals get buried in the layers of sediment and turned into stone. Metamorphic rocks are a combination of rock types, compressed together by high pressure and high heat. They usually have a more hard, grainy texture than the other two types. Schist, slate, and gneiss are metamorphic rocks.

8. THE ROCK CYCLE These rocks change over hundreds of years in the five steps of the rock cycle: (1) Weathering & Erosion: Igneous , sedimentary, and metamorphic rocks on the surface of the earth are constantly being broken down by wind and water. Large rocks are worn down to small particles . When the particles are broken off a rock and stay in the same area, it is called weathering . When the particles are carried somewhere else , it is called erosion . (2) Transportation & Deposition: Eroded rock particles are carried away by wind or by rain , streams , rivers, and oceans. As rivers get deeper or flow into the ocean , their current slows down, and the rock particles ( mixed with soil ) sink and become a layer of sediment.

9. (3) Compaction & Cementation ( Lithification ) : As the layers of sediment stack up (above water or below), the weight and pressure compacts the bottom layers. Dissolved minerals fill in the small gaps between particles and then solidify , acting as cement. After years of compaction and cementation, the sediment turns into sedimentary rock . (4) Metamorphism: Over very long periods of time, sedimentary or igneous rocks end up buried deep underground, usually because of the movement of tectonic plates . While underground, these rocks are exposed to high heat and pressure , which changes them into metamorphic rock. This tends to happen where tectonic plates come together: the pressure of the plates squish the rock that is heated from hot magma below . ( Tectonic plates are large sections of the earth’s crust that move separately from each other. Their movement often results in earthquakes .)

10. (5) Rock Melting: Metamorphic rocks underground melt to become magma. When a volcano erupts, magma flows out of it. (When magma is on the earth’s surface, it is called lava.) As the lava cools it hardens and becomes igneous rock. As soon as new igneous rock is formed, the processes of weathering and erosion begin, starting the whole cycle over again!

11. CLASSWORK Write the definition for the following rock forming processes: Cooling (solidification/crystallization) Weathering Compaction Metamorphism Melting