Unit 3 Lesson 2 The Rock Cycle

1. Unit 3 Lesson 2 The Rock Cycle

2. Unit 3Lesson 2 The Rock Cycle Let’s Rock! What is rock? • Rock is a naturally occurring solid mixture of one or more minerals and may also include organic matter. • Most rock is made of minerals, but some rock is made of non-mineral material that is not organic, such as glass. • Rocks are always changing through time.

4. Unit 3Lesson 2 The Rock Cycle What processes change rock? • Natural processes make and destroy rock. They change each type of rock into other types of rock and shape Earth’s features. • Different natural processes influence the type of rock that is found in each area of Earth’s surface.

5. Unit 3Lesson 2 The Rock Cycle What processes change rock? • Water, wind, ice, and changes in temperature can change rock in a number of ways. • Weatheringis the process by which rock is broken down by water, wind, ice, and changes in temperature. • Weathering breaks down rock into fragments called sediment.

6. Unit 3Lesson 2 The Rock Cycle What processes change rock? • Erosionis the process by which sediment is moved from one place to another. • Water, wind, ice, and gravity can erode sediments, which are eventually deposited in bodies of water and other low-lying areas. • Sediment comes to rest by a process called deposition.

7. Unit 3Lesson 2 The Rock Cycle What processes change rock? • Rock that is buried can be squeezed by the weight of rock or layers of sediment above it forming sedimentary rock.

8. Unit 3Lesson 2 The Rock Cycle What processes change rock? • At high enough temperature and pressure, buried rock can change into metamorphic rock.

9. Unit 3Lesson 2 The Rock Cycle What processes change rock? • In some cases, the rock under the Earth’s surface gets hot enough to melt, forming magma, or molten rock. • If the magma reaches Earth’s surface, it is called lava. • The magma and lava eventually cool to form new rock. Lava Magma

10. Unit 3Lesson 2 The Rock Cycle Classified Information! What are the classes of rocks? • Igneous rockforms when molten rock cools and hardens. It forms on or beneath Earth’s surface. • Sedimentary rockforms when sediment from older rocks or minerals that form from solutions get pressed and cemented together. • Metamorphic rockforms when pressure, temperature, or chemical processes change existing rock.

11. Unit 3Lesson 2 The Rock Cycle What are the classes of rocks? • Sedimentary rock is composed of minerals formed from solutions or sediments from older rock. The sediment is deposited, then other sediment is deposited on top until the high pressure of the layers above squeeze and cement the layers together • Sedimentary rocks are named according to the size and type of fragments they contain.

12. Unit 3Lesson 2 The Rock Cycle What are the classes of rocks? • Igneous rock forms from molten rock that cools. • As molten rock cools, crystals form. The longer the cooling takes, the more time the crystals have to grow and the larger the crystals will be. • Molten rock will cool slower under the surface because the temperature changes more evenly. At the surface, it cools much quicker because of the drastic temperature change.

13. Unit 3Lesson 2 The Rock Cycle What are the classes of rocks? • Igneous rocks that form when magma cools beneath Earth’s surface are called intrusive igneous rock. • Igneous rocks that form when lava cools on Earth’s surface are called extrusive igneous rock.

14. Pegmatite Intrusive Igneous Rock Rhyolite Extrusive Igneous Rock Tiny Crystals Large Crystals

15. Unit 3Lesson 2 The Rock Cycle What are the classes of rocks? • Metamorphic rock forms when high temperature and pressure change the texture and mineral content of rock. • Metamorphic rocks are changed by temperature, pressure, temperature and pressure combined, or fluids or other chemicals.

16. Unit 3Lesson 2 The Rock Cycle What is the rock cycle? • Over millions of years, any of the three rock types can be changed into another of the three types. • The series of processes by which rock changes from one type to another is called the rock cycle. • A rock’s identity can be changed by factors such as temperature, pressure, weathering, and erosion.

17. Unit 3Lesson 2 The Rock Cycle What is the rock cycle? • Igneous rock that is exposed can break down into sediment. Beneath Earth’s surface, it can change into metamorphic rock. • With temperature and pressure changes, sedimentary rock can become metamorphic rock, or it may melt and become igneous rock. • Under certain temperature and pressure conditions, metamorphic rock can melt into magma and then form igneous rock or form a different metamorphic rock.

18. Unit 3Lesson 2 The Rock Cycle What is the rock cycle? • Describe what happens in each part of the rock cycle. 1. Weathering, Erosion, Deposition & Cementation Igneous Rock Sedimentary Rock Cooling 4. 3. Melting 2. Temperature & Pressure Magma Metamorphic Rock

19. What type of rock? “Scoria” “Shale” “Gneiss” This rock forms As moltenrock emerges from the Earth. The pressure upon it is reduced and the dissolved gas starts to escape in the form of bubbles. If the molten rock solidifies before the gas has escaped the bubbles become small rounded or elongated cavities in the rock. Shale is fine-grained rock that forms from the compaction and cementation of silt and clay-size mineral particles that we commonly call "mud". This composition places shale in a category known as "mudstones". This rock has been modified by heat and pressure while buried deep below Earth's surface. Exposure to these extreme conditions has altered the texture and chemical composition of the rock. It is known as “foliated” because of its distinct banded and/or layered appearance. Extrusive Igneous Rock Sedimentary Rock Metamorphic Rock

20. What type of rock? “Granite” “Limestone” “Marble” Limestone is composed primarily of calcium carbonate (CaCO3). Most form in shallow, calm, warm marine waters. That type of environment is where organisms form calcium carbonate shells and skeletons. When these animals die their shell and skeletal debris accumulate as a sediment that compacts into stone. Marble forms when limestone is subjected to high heat and pressure. It is composed primarily of the mineral calcite (CaCO3). Under these conditions, the calcite in the limestone recrystallizes to form a rock that is a mass of interlocking calcite crystals. It is known as “non-foliated” because it does NOT have a layered or banded appearance. Granite is a light-colored rock with grains large enough to be visible with the unaided eye.  It forms from the slow crystallization of magma below Earth’s surface. Sedimentary Rock Metamorphic Rock Intrusive Igneous Rock

21. Unit 3Lesson 2 The Rock Cycle How do tectonic plate motions affect the rock cycle? • Tectonic plate motions can move rock around, leading to changes in the rock. These plate motions can move rock up or down. • Upliftis the rising of regions of the crust to higher elevations, increasing the rate of weathering and erosion. • Subsidenceis the sinking of regions of the crust to lower elevations, producing basins where sediment is deposited.

24. Unit 3Lesson 2 The Rock Cycle How do tectonic plate motions affect the rock cycle? • A rift zoneis a set of deep cracks that form between two tectonic plates that are pulling apart. • Blocks of crust in the center of the rift zone subside, and molten rock below Earth’s surface rises up. Rift Zone

26. Unit 3Lesson 2 The Rock Cycle How do tectonic plate motions affect the rock cycle? • The rocks in the middle of a rift zone subside, leaving scarps (steep slope) that can be weathered and eroded. • Sometimes the decrease in pressure at a rift zone causes magma to form and solidify. Scarps

27. Scarp