LESSON 4: ROCKS (EARTH AND LIFE SCIENCE)

This is a teacher-made power point presentation for Lesson 4 in Earth and Life Science.
Learning Competency: Classify rocks into igneous, sedimentary, and metamorphic.

1. ROCKS Discussant: John Mark P. Matamorosa

2. CLASS RULES RULE 1 Listen quietly when others are speaking. RULE 2 Raise your hand for permission to get up or speak. RULE 3 Collaborate with others during group activities. RULE 4 Always treat others with respect. RULE 5 Believe in yourself.

3. LEARNING OBJECTIVES At the end of 60-minute interactive discussion, all of the students are expected to: classify and describe the three basic rock types; explain how and what type of environment each of these rock types are formed; explain how rocks are transformed from one rock type to another through the rock cycle; and identify and describe the different geologic processes that operate within the rock cycle.

4. LET’S PLAY!

5. FACT OR BLUFF? The 3 kinds of rocks are basalt, granite, and quartz.

6. FACT OR BLUFF? Metamorphic rocks are formed through a process of extreme heat and extreme pressure.

7. FACT OR BLUFF? Sedimentary rocks are formed from magma or lava.

8. FACT OR BLUFF? An igneous rock can turn into a metamorphic rock.

9. FACT OR BLUFF? Weathering and erosion are not a part of the rock cycle.

10. ROCKS Rocks are aggregate of minerals. It can be composed of single mineral (e.g. Quartzite, a metamorphic rock composed predominantly of Quartz), or more commonly as an aggregate of two or more minerals. A mineral name can be used as a rock name (e.g. Gypsum Rock which is composed predominantly of the mineral Gypsum (CaSO4)).

11. ROCK CLASSIFICATIONS 1. Igneous rocks - rocks that are formed from the solidification of molten rock material (magma or lava). Molten rock material can solidify below the surface of the earth (plutonic igneous rocks) or at the surface of the Earth (volcanic igneous rocks). Minerals are formed during the crystallization of the magma. Note that the rate of cooling is one of the most important factors that control crystal size and the texture of the rock in general.

12. ROCK CLASSIFICATIONS Question: Differentiate magma and lava. Answer: Magma is a molten rock material beneath the surface of the earth. Lava is molten rock material extruded to the surface of the earth through volcanic or fissure eruptions.

13. ROCK CLASSIFICATIONS Question: Describe plutonic or intrusive rocks and define the process of formation, the texture and give examples. Answer: • from solidified magma underneath the earth • gradual lowering of the temperature gradient at depth towards the surface would cause slow cooling/crystallization • Phaneritic texture • Examples: granite, diorite, gabbro

14. ROCK CLASSIFICATIONS Question: Describe volcanic or extrusive rocks and define the process of formation, the texture and give examples. Answer: • from solidified lava at or near the surface of the earth • fast rate of cooling/crystallization due to huge variance in the temperature between Earth’s surface and underneath • common textures: aphanitic, porphyritic and vesicular • examples: rhyolite, andesite, basalt • pyroclastic rocks: fragmental rocks usually associated with violent or explosive type of eruption. Examples: tuff and pyroclastic flow deposits (ignimbrite)

15. ROCK CLASSIFICATIONS Igneous rocks are also classified according to silica content: felsic, intermediate, mafic and ultramafic. • felsic : also called granitic; >65% silica, generally light-colored • intermediate : also called andesitic; 55-65% silica; generally medium colored (medium gray) • mafic : also called basaltic; 45-55% silica; generally dark colored • ultramafic : <45% silica; generally very dark colored; composed mainly of olivine and pyroxene which are the major constituents of the upper mantle

16. ROCK CLASSIFICATIONS 2. Sedimentary rocks - These are rocks that formed through the accumulation, compaction, and cementation of sediments. They generally form at surface or near surface conditions. • Sedimentary processes at or near the surface of the Earth include: weathering of rocks, sediment transport and deposition, compaction and cementation • Factors in sedimentary processes: weathering and transport agents (water, wind ice) • Common sedimentary features: strata and fossils • Strata: >1cm is called bedding and anything less is called lamination; layering is the result of a change in grain size and composition; each layer represents a distinct period of deposition. • Fossils: remains and traces of plants and animals that are preserved in rocks

17. ROCK CLASSIFICATIONS Non-clastic / Chemical/Biochemical – derived from sediments that precipitated from concentrated solutions (e.g. seawater) or from the accumulation of biologic or organic material (e.g. shells, plant material). They are further classified on the basis of chemical composition.

18. ROCK CLASSIFICATIONS Clastic/terrigenous - form from the accumulation and lithification of sediments derived from the breakdown of pre-existing rocks. They are further classified according to dominant grain size.

19. ROCK CLASSIFICATIONS 3. Metamorphic rocks - rocks that form from the transformation of pre-existing rocks (igneous, sedimentary, or metamorphic rocks) through the process of metamorphism. Metamorphism can involve changes in the physical and chemical properties of rocks in response to heat, pressure, and chemically active fluids. They are commonly formed underneath the earth through metamorphism.

20. ROCK CLASSIFICATIONS Contact metamorphism • Heat as the main factor: occurs when a pre-existing rocks get in contact with a heat source (magma) • Occurs on a relatively small scale: around the vicinity of intruding magma • Creates non-foliated metamorphic rocks (e.g. hornfels)

21. ROCK CLASSIFICATIONS Regional metamorphism • Pressure as main factor: occurs in areas that have undergone deformation during orogenic event resulting in mountain belts • Occurs in a regional/large scale • Creates foliated metamorphic rocks such as schist and gneiss • Non-foliated rocks like marble also form thru regional metamorphism, where pressure is not intense, far from the main geologic event.

22. ROCK CLASSIFICATIONS

23. ROCK CLASSIFICATION PROCESS OF FORMATION PLACE OF FORMATION EXAMPLES 1. Igneous rock formed from the solidification of molten rock material (magma or lava) below the surface of the earth (plutonic igneous rocks) or at the surface of the Earth (volcanic igneous rocks) plutonic- granite, diorite & gabbro volcanic- rhyolite, andesite & basalt 2. Sedimentary rock formed through the accumulation, compaction, and cementation of sediments. surface or near surface conditions Non-clastic / Chemical/Biochemical- Chalk & Limestone Clastic/terrigenous- Conglomerate & Sandstone 3. Metamorphic rock form from the transformation of pre-existing rocks (igneous, sedimentary, or metamorphic rocks) through the process of metamorphism underneath the earth Non-foliated- Hornfels & Marble Foliated- Gneiss & Slate SUMMARY

24. TERMS TO REMEMBER sediments - described as broken up rock erosion - general term for the movement of sediment by wind, water, glaciers weathering - process by which rocks are broken down chemically or physically cementation - process in which sediment are fused or glued together compaction - process in which sediments are pressed together tightly deposition - process in which wind, water, or ice leave materials in a location

25. QUIZ TIME! 1. Which of the following best describes igneous rocks? A. They are rocks that are formed through the process of metamorphism. B. They are rocks that are formed through the cementation of sediments. C. They are rocks that are formed under the action of pressure, volume, and temperature changes. D. They are rocks that are formed from the solidification of molten rock material.

26. QUIZ TIME! 2. Which of the following BEST describes sedimentary rocks? A. They are rocks that are formed from the solidification of molten rock material. B. They are rocks that are formed through the cementation of sediments. C. They are rocks that are formed through the process of metamorphism. D. They are rocks that are formed under the action of pressure, volume, and temperature changes.

27. QUIZ TIME! 3. What is the aggregate of minerals? A. Quartz C. Magma B. Rock D. Gemstone

28. QUIZ TIME! 4. The _________ the cooling time, the _________ the crystal size of a rock. A. longer, larger C. shorter, brighter B. longer, smaller D. longer, brighter

29. QUIZ TIME! 5. What type of igneous rock solidifies below the surface of the Earth? A. extrusive C. plutonic B. volcanic D. clastic

30. QUIZ TIME! 6. What do you call the process of the formation of metamorphic rocks? A. magmatism C. metamorphism B. magnetism D. metamorphosis

31. QUIZ TIME! 7. A never ending process by which rocks are changed from one type to another. A. weathering and erosion B. rock cycle C. heat and pressure D. pressing and cementing

32. QUIZ TIME! 8. When sediments are pressed together tightly, this is called ____________. A. compaction B. cementation C. weathering D. erosion

33. QUIZ TIME! 9. The process in which sediment are fused or glued together. A. compaction B. deposition C. organic rock D. cementation

34. QUIZ TIME! 10. The process by which rocks are broken down chemically or physically is known as: A. weathering B. erosion C. deposition D. transportation

35. KEY TO CORRECTION 1. D 2. B 3. B 4. A 5. C 6. C 7. B 8. A 9. D 10. A

36. ASSIGNMENT A. Direction: In not more than 5 sentences, answer the following questions: 1. How does a vesicular texture in a volcanic rock develop? 2. Explain why the vesicular texture is not associated with peridotites. 3. How do clastic rocks differ from non-clastic rocks in terms of process of formation? 4. Explain how the physical features of sediments change during transport. 5. Differentiate between a foliated and non-foliated rock. 6. What do butterflies and metamorphic rocks have in common? 7. Heat is a major agent in metamorphism and igneous rock formation, but not in sedimentary rocks. Why? 8. Does every rock go through the complete rock cycle, i.e. changing from igneous to sedimentary rock to metamorphic then back to igneous rocks? Explain.

37. ASSIGNMENT B. Direction: Conduct a research on 3 rocks (one for each rock type). Included in the essay are the following: history of formation, common environment of formation, common textures, common use of the rock and the localities in the Philippines where you can find them. The essay should be at least 200 words.

38. ASSIGNMENT 1. How does a vesicular texture in a volcanic rock develop? Answer: As magma rises up to the surface, it is subjected to decreasing pressure, allowing dissolved gases to come out of the solution forming gas bubbles. When the magma reaches the surface (as lava) and cools, the rock solidifies around the gas bubbles. The bubbles are then preserved as holes or vesicles. Also, the texture can also be formed thru the rapid escape of gases.

39. ASSIGNMENT 2. Explain why the vesicular texture is not associated with peridotites. Answer: Peridotites are intrusive rocks formed beneath the earth’s surface and the high pressure conditions prevent gases from forming and escaping.

40. ASSIGNMENT 3. How do clastic rocks differ from non-clastic rocks in terms of process of formation? Answer: Clastic rocks form from rock fragments transported away from their source by wind, water, gravity or ice rather than by chemical processes such as precipitation or evaporation.

41. ASSIGNMENT 4. Explain how the physical features of sediments change during transport. Answer: The farther the sediment is transported, the longer the transport takes, and the smaller, more rounded and smoother the sediment becomes.

42. ASSIGNMENT 5. Differentiate between a foliated and non-foliated rock. Answer: Foliated rocks has a texture in which the mineral grains are arranged in bands or grains, which is absent in a non-foliated rock.

43. ASSIGNMENT 6. What do butterflies and metamorphic rocks have in common? Answer: Butterflies and metamorphic rocks both undergo change from an earlier form (caterpillar for butterfly, parent rock for metamorphic rock) to a new one.

44. ASSIGNMENT 7. Heat is a major agent in metamorphism and igneous rock formation, but not in sedimentary rocks. Why? Answer: Sedimentary processes occur in surface conditions - low temperature and pressure conditions.

45. ASSIGNMENT 8. Does every rock go through the complete rock cycle, i.e. changing from igneous to sedimentary rock to metamorphic then back to igneous rocks? Explain. Answer: No. Rocks can change into any type of rock or even reform as the same kind of rock for several cycles.

46. THANK YOU FOR YOUR ACTIVE PARTICIPATION!