CHAPTER 14 ROCKS: MINERAL MIXTURES

1. CHAPTER 14ROCKS: MINERAL MIXTURES • Rocks change through a process called the Rock Cycleand rocks are classified by how they form, by what they are made of, and by their texture.

2. Chapter 14 Objectives • We will learn about the Rock Cycle • We will learn about the three types of rocks • We will learn how each type is formed • We will learn how each type is classified

3. Section 1: The Rock Cycle • What we will learn in this section: • Describe two ways in which rocks are used by people. • Describe the four processes that shape Earth’s features. • Describe how rocks move through the rock cycle. • List two characteristics of rocks that help classify them.

4. The Rock Cycle • Rock- naturally occurring solid mixture of one or more minerals or organic matter. • Rocks are always changing. • Rock Cycle- the series of processes in which a rock forms, changes from one type to another, is destroyed, and forms again by geological processes.

5. The Rock Cycle

6. Value of rock • Rock has always been valuable. • Rocks were the first form of tools. • It has been used to make things in ancient and modern times.

7. Processes That Shape the Earth • Weathering, Erosion, and Deposition • Weathering- breaks rocks down into fragments. • Erosion- the process by which wind, water, ice, or gravity transports soil and sediment from one location to another. • Deposition- the process in which material is laid down.

8. Processes That Shape the Earth • Heat and Pressure • Rocks also form under high heat and pressure. • High pressure can create sedimentary rocks. • Add heat to those rocks and they can melt and turn into Metamorphic rocks.

9. Processes That Shape the Earth • Magma can reach the surface through volcanoes or can cool in the ground and create igneous rocks.

10. Processes That Shape the Earth • How the cycle continues….. • Buried rock can come to the surface by uplift and erosion. • Picture the Earth as a float in a pool, the land is the float and we are “floating” on hot magma.

11. Round and Round It Goes • The rock cycle is always moving very slowly. • New rocks are created, then destroyed, just to be created again. • There is no set path to the Rock Cycle, rocks travel in all directions.

12. Rock Classification • Rocks are divided into three main classes, but now we go further. • Rocks are divided further on how they form. • Scientist study rocks closely to find out how to classify them. • The two main characteristics are composition and texture.

13. Rock Classification • Composition- the chemical makeup of a rock; describes either the minerals or other materials in the rock. • Composition means the percentage of minerals or other materials that make up each rock.

14. Rock Classification • Texture- the quality of a rock that is based on the sizes, shapes, and positions of the rocks grains. • Three types of texture: fine-grained, medium-grained, and coarse-grained. • Texture tells us how and where the rocks were formed.

15. Section 2: Igneous Rocks • What are going to learn: • We will describe the ways that igneous rocks form. • We will explain how the cooling rate of magma affects the texture of igneous rocks. • We will be able to distinguish between igneous rock that cools within the Earth’s crust and igneous rock that cools at Earth’s surface.

16. Igneous Rocks • Igneous is Latin for “FIRE”! • Igneous rocks form when hot magma or lava cools and hardens. • Magma- INSIDE the Earth. • Lava- OUTSIDE the Earth.

17. Origins of Igneous Rock • Begins as magma. • Three ways magma is formed: • When rock is heated. • When pressure is released. • When rock changes composition.

18. Origins of Igneous Rock • When water freezes, it makes ice. When magma “freezes”, it makes igneous rock. • Each mineral has its own melting and freezing point. • Remember, rocks are made from many minerals put together. This means the igneous rock freezes at different temperatures. (Some parts freeze faster than others.)

19. Composition and Texture of Igneous Rocks • Composition • Rocks made from light colored minerals are called felsic rocks. • Rocks made from dark colored minerals are called mafic rocks.

20. Composition and Texture of Igneous Rocks • Texture- Texture of igneous rocks depend on how fast they cool. • Faster cooling causes SMALLER crystals. • Slower cooling causes LARGER crystals.

21. Igneous Rock Formations • Igneous rocks form both inside the Earth and outside the Earth. • Intrusive Igneous Rock- rock formed from the cooling and solidification of magma beneath the Earth’s surface. • Plutons are large intrusive bodies of igneous rock. • Types of plutons include: Batholiths, Stocks, dikes, and sills.

22. Intrusive Igneous Rock

23. Extrusive Igneous Rock • Extrusive Igneous Rock- rock that forms as a result of volcanic activity at or near the Earth’s surface. • Lava cools quickly so it has small or no crystals. • Lava also forms in oceans to create new ocean floor.

24. Extrusive Igneous Rock

25. Section 3: Sedimentary Rock • What we are going to learn: • We will describe where sedimentary rock comes from. • We will describe the three main categories of sedimentary rock. • We will describe the three types of sedimentary structures.

26. Origins of Sedimentary Rock • Weathering cause rocks to break into pieces. • Erosion transports the pieces, called sediment, from one place to another.

27. Origins of Sedimentary Rock • Sediment is deposited in layers, over time these layers are compacted into rock. • The most noticeable feature of sedimentary rock is the strata. • Strata- layers of rock.

28. Composition of Sedimentary Rock • Sedimentary rock is classified by how it forms. • Three main categories of sedimentary rock: • Clastic Sedimentary Rock • Chemical Sedimentary Rock • Organic Sedimentary Rock

29. Clastic Sedimentary Rock • Made of rock fragments (chunks) that are cemented together. • Clastic Sedimentary Rocks have three types of textures: • Fine-grained • Medium-grained • Coarse-grained

30. Chemical Sedimentary Rock • Chemical Sedimentary Rock forms from dissolved minerals in water. • Rain dissolves minerals in rocks and carries them to oceans where they are deposited and harden to form rock.

31. Organic Sedimentary Rock • Organic Sedimentary Rock has fossils in them. • These fossils become cemented together to form fossiliferous limestone.

32. Sedimentary Rock Structures • Stratification- the process in which sedimentary rocks are arranged in layers. • Strata differ from one another depending on the kind, size, and color of their sediment.

33. Sedimentary Rock Structures • Sedimentary rocks can record the motion of wind and waves on lakes, oceans, rivers, and sand dunes. • Ripple marks and mud cracks are formed in the sediment and then hardened into rock. • Even rain drops and foot prints can be preserved in the mud.

34. Metamorphic Rock • What we will learn: • We will describe two ways a rock can undergo metamorphism. • We will explain how the minerals in rocks change as the rocks undergo metamorphism. • We will describe the two categories of metamorphic rock.

35. Metamorphic Rock • Rocks change through metamorphism with heat and pressure. • This comes from the Greek word meta, meaning “change”, and morphos, meaning “shape”. • Metamorphic rocks are rocks that have changed structure, texture, or composition.

36. Origins of Metamorphic Rocks • Temperature and/or pressure surrounding a rock can change and make a metamorphic rock. • Most metamorphism takes place from 132°F and 1,832°F, and at depths deeper than 1.25milesinside the Earth.

37. Contact Metamorphism • When magma flows through the Earth’s crust it melts the rock it touches. • The rocks then re-harden into new, metamorphic rocks.

38. Regional Metamorphism • Pressure in the Earth causes pieces of crust to collide with each other superheating and melting the rock. • This changes large areas underneath contientialcrust.

39. Composition of Metamorphic Rocks • During metamorphism the minerals in a rock change form into more stable minerals. • Some of these minerals form at certain temperatures, these are called index minerals.

40. Composition of Metamorphic Rock • Scientist use these index minerals to tell at what temperature, depth, and pressure the new rocks were formed. • More heat and pressure can cause one metamorphic rock to morph into another kind.

41. Textures of Metamorphic Rock • All metamorphic rock have one of two textures, foliated and non-foliated. • Foliated- the texture of metamorphic rock in which the mineral grains are arranged in planes or bands.

42. Textures of Metamorphic Rock • If you see “bands” on the rock then it was formed with the highest temperature and pressure.

43. Textures of Metamorphic Rock • Non-foliated- the texture of metamorphic rock in which the mineral grains are not arranged in planes or bands. • Non-foliated rock are made from only a few minerals, these minerals melt and re-form in a process called recrystallization.

44. Metamorphic Rock Structures • Metamorphic rock structures are cause by force placed on the rock when it is formed. • Deformation is what the change in shape is called. • The rock becomes folded or bended, this can be really small or really large.

45. THE END!