EQ: How are rocks formed?

1. EQ: How are rocks formed? Standard S6E5.c Classify rocks by their process of formation.

2. What materials are rocks made of? Describe four processes that change rock from one type to another. What are the three main classes of rock? Describe two characteristics of rock that are used to help classify it? EQ: What is the rock cycle?

3. What materials are rocks made of? • Rock is describe as a naturally occurring solid mixture of one or more minerals and organic matter. • Rocks are made of mixtures of minerals and other materials, although some rocks may contain only a single mineral. • When studying a rock sample, geologists observe the rock’s color and texture and determine its mineral composition.

4. What materials are rocks made of? • Texture is described with terms based on grain size, grain shape, and grain pattern. • Most rocks are made up of tiny particles of minerals or other rocks, which are called grains. • A rock’s grains give it its texture. • There are three major groups of rocks: igneous rock, sedimentary rock, and metamorphic rock. • These terms refer to how the rocks in each group were formed.

5. The Rock Cycle • The rock cycle is a series of processes in which a rock forms, changes from one type to another, is destroyed, and forms again by geological processes. • Rocks have been used by humans to make tools and weapons and to construct buildings.

6. Processes That Shape the Earth • Certain geological processes make and destroy rock. • These processes shape the features of the Earth. • Theses processes also influence the type of rock that is found in a certain area of Earth’s surface.

7. Processes That Shape the Earth • Weathering is the process by which water, wind, ice, and heat break down rock. • Erosion is the process by which sediment is removed from its source. • Deposition is the process by which sediment moved by erosion is laid down. • Uplift is the process by which rock within the Earth moves to Earth’s surface.

8. Illustrating the Rock Cycle • Igneous rock is formed when magma or lava is cooled and hardens and solidifies. • Sedimentary rock is formed by the process of weathering, erosion, deposition and compaction and cementation. • Metamorphic rock is formed by heat, pressure or chemical change beneath Earth’s surface.

9. Rock Classification • Scientists classify rocks in detail by using two important criteria – composition and texture. • Composition is the chemical makeup of a rock; describes either the minerals or other materials in the rock. • Texture is the quality of a rock based on the sizes, shapes, and positions of the rocks grains.

10. Classifying Rocks • Classifying Rocks - How Geologists Classify Rocks = When studying a rock sample, geologists observe the rock’s origin, color and texture, and determine its mineral composition • A. Origin = 3 major groups of rocks 1. igneous rock = forms from the cooling of molten rock a. lava = above the surface b. magma = below the surface 2. sedimentary rock = forms in layers from other rocks, plants, and animals that have been compacted and cemented together 3. metamorphic rock = formed when existing rock is changed by heat, pressure, or chemical reactions B. Texture = the size, shape, and pattern of the rock’s grains 1. Grain Size a. fine-grained (small) b. coarse-grained (large) 2. Grain Shape a. smooth and rounded b. jagged 3. Grain Pattern a. lie in flat layers b. wavy, swirling patterns c. looks like rows of multicolored beads d. occur randomly 4. No Visible Grain a. have no apparent grains b. smooth, shiny texture C. Mineral Composition = 1. mafic 2. felsic

11. Classifying Rocks I. Classifying Rocks - How Geologists Classify Rocks = When studying a rock sample, geologists observe the rock’s origin, color and texture, and determine its mineral composition A. Origin = 3 major groups of rocks 1. igneous rock = forms from the cooling of molten rock a. lava = above the surface b. magma = below the surface 2. sedimentary rock = forms in layers from other rocks, plants, and animals that have been compacted and cemented together 3. metamorphic rock = formed when existing rock is changed by heat, pressure, or chemical reactions

12. B. Texture = the size, shape, and pattern of the rock’s grains 1. Grain Size a. fine-grained (small) b. coarse-grained (large) 2. Grain Shape a. smooth and rounded b. jagged 3. Grain Pattern a. lie in flat layers b. wavy, swirling patterns c. looks like rows of multicolored beads d. occur randomly 4. No Visible Grain a. have no apparent grains b. smooth, shiny texture

13. C. Mineral Composition = 1. mafic 2. felsic

14. Quick Check • Which of the following rocks is not normally used as a construction material? • marble • halite • limestone • granite

15. Quick Check 2. The process in which wind, water, ice, and heat break down rock is called • uplift. • intrusion. • recystallization. • weathering.

16. Quick Check 3. What forms when rock partially or completely melts? • limestone • reefs • ripple marks • magma

17. Quick Check 4. Scientists classify rocks • by composition and texture. • by volume. • by mass. • by color and size.

18. Quick Check 5. ________ is a solid mixture of one or more minerals and organic matter. a. Composition b. Rock c. Erosion d. Texture

19. Quick Check 6. The _____________ is a process by which new rock forms from old rock. a. rock cycle b. deposition c. composition d. rock

20. Quick Check 7. The process by which sediment is removed from its source is called _______. a. deposition. b. texture. c. composition. d. erosion.

21. Quick Check 8. The process by which sediment moved by erosion is dropped and comes to rest is called ____________. a. composition. b. rock. c. deposition. d. texture.

22. Quick Check 9. The minerals a rock contains or its chemical makeup determines the _______ of that rock. a. texture b. deposition c. composition d. erosion

23. Quick Check 10. The size, shape, and position of grains that make up a rock determine a rock’s ________. a. composition. b. erosion. c. deposition. d. texture.

24. What characteristics are used to classify igneous rocks? Describe three (3) ways in which igneous rocks differ? What is the difference between extrusive and intrusive rocks? Give an example of each. Why are some igneous rocks dark and others light? How do igneous rocks form?

25. Origins of Igneous Rock • Igneous rocks are classified by their origin of formation, texture of the grains, and composition of the rock. • Igneous rock forms when magma cools and hardens. • Three ways magma can form: • heat/rise in temperature • pressure released • rock changes composition

26. Composition and Texture of Igneous Rock • Igneous rocks differ from one another in what they are made of and how fast they are cooled. • Composition – • Igneous rock that is rich in silicon and light-colored are called felsic rock. • Igneous rock that is poor in silicon and dark-colored are called mafic rock. • Texture – • Fine-grained (small) = cools quickly • Coarse-grained (large) =cools slowly

27. Origin of Formation • Igneous rock formations are located below and above Earth’s surface. • Intrusive igneous rock – Intrusive rock (granite) forms when magma hardens (beneath) Earth’s surface. • coarse-grained (large crystals) • below Earth’s surface • ex. granite • Extrusive igneous rock – Extrusive rock (basalt) forms from lava that has erupted (onto) Earth’s surface. • fine-grained (small crystals) • on the Earth's surface • ex. basalt

28. How do igneous rocks form? • Igneous rocks are classified according to their origin, texture, and mineral composition. • Igneous rocks form either from lava, above the earth’s surface or magma, below the earth’s surface. • They also differ in texture according to the size and shape of their mineral grains. • Igneous rocks differ in mineral composition depending on how much silica and other minerals are present. • Dark igneous rocks form from magma or lava low in silica content (mafic). • Light igneous rocks form from magma high in silica content (felsic). • Light-colored rocks are less dense than the dark-colored rocks.

29. Uses of Igneous Rock • Most igneous rocks are hard, dense, and durable. • Ancient Native Americans used obsidian for making very sharp tools for cutting and scraping. • Granite is used as a building material such as decorative stonework, curbstones, and floors.. • Basalt is crushed to make gravel. • The rough surface of pumice makes a good abrasive for cleaning and polishing. • Perlite is often mixed with soil for strating vegetable seeds.

30. Quick Check 1. Which of the following are ways magma is formed? • by compaction and cooling • by melting and cooling • by changes in composition • by weathering and erosion

31. Quick Check • What kind of texture does igneous rock have when magma cools slowly? • coarse-grained • large-grained • fine-grained • medium-grained

32. Quick Check 3. What kind of texture does igneous rock have when magma cools rapidly? • coarse-grained • medium-grained • large-grained • fine-grained

33. Quick Check 4. What kind of rock is formed when magma intrudes into other rock? • extrusive igneous rock • sedimentary rock • intrusive igneous rock • organic sedimentary rock

34. Quick Check 5. What kind of rock is formed from lava that cools on Earth’s surface? a. organic sedimentary rock b. sedimentary rock c. intrusive igneous rock d. extrusive igneous rock

35. Describe the origin of sedimentary rock. Describe the three main categories of sedimentary rock. Describe three types of sedimentary structures. How is sedimentary rock formed?

36. Sedimentary rocks form from particles deposited by water and wind. After sediment has been deposited, the processes of compaction and cementation change the sediment into sedimentary rock. What is sedimentary rock?

37. Forming of Sedimentary Rock • Erosion – occurs when running water or wind loosen and carries away fragments of rock. • Deposition- the process in which sediment settles out of the water or wind carrying it. • Compaction- the process that presses sediment together. • Cementation- the process in which minerals crystallize and glue particles of sediment together.

38. Geologists classify sedimentary rocks according to the type of sediments that make up the rock. There are three major groups of sedimentary rocks: clastic rocks, organic rocks, and chemical rocks. Types of Sedimentary Rock

39. A clastic rock is a sedimentary rock that forms when rock particles are squeezed together. Examples of clastic rocks: Shale Sandstone Conglomerate Breccia Clastic Rocks

40. Shale forms from tiny particles of clay. Shale feels smooth, and splits easily into flat pieces Clastic Rock: Shale

41. Sandstone forms from the sand on beaches, on the ocean floor, in riverbeds, and in sand dunes. Sandstone is formed when small particles of sand are pressed and cemented together. . Clastic Rock: Sandstone

42. Conglomerate is a rock made up of large particles with rounded edges. Breccia is a rock made up of large fragments with sharp edges. Clastic Rock: Conglomerate and Breccia

43. Organic rock forms from the remains of plants and animals and are deposit in thick layers. The term “organic” refers to substances that were once part of living things. Three important organic rocks: Coal Limestone Chalk Organic Rocks

44. Coal forms from the remains of swamp plants buried in water. Over millions of years, they slowly change into coal. Organic Rock: Coal

45. The hard shell of living things produces limestone. Chalk forms from sediments made of skeletons of microscopic living things found in the ocean. Organic Rock: Limestone

46. Chemical rock forms when minerals that are dissolved in a solution crystallize. Chemical rocks can also form when mineral deposits left when seas or lakes evaporate. Examples: Rock salt gypsum Chemical Rocks

47. Sedimentary Rock Structures • The most important feature of sedimentary rock is stratification. • Stratification is 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. • Ripple marks (1) are made by the motion of wind and water waves on lakes, oceans, rivers, and sand dues. • Mud cracks (2) form when fine-grained sediments at the bottom of a shallow body of water are exposed to air and dry out. • Rain-drop (3) impressions can be preserved in fine-grained sediments, as small pits with raised rims.

48. Uses of Sedimentary Rocks • Sandstone and limestone are used as building materials. • The White House in Washington, D.C. is built of sandstone. • Limestone is also used to make cement.

49. Quick Check 1. Which process forms sediment/ • weathering • cementation • compaction • deposition

50. Quick Check 2. What are strata? • mineral fragments • minerals crystallized out of solution • layers in sedimentary rock • fossils in sedimentary rock