Rocks:

1. Rocks: Sedimentary Igneous Metamorphic Keepers of Earth’s History 1

2. What’s in your rock?: Granite Hornblende Orthoclase Quartz aggregates of minerals Biological material Fossil fragments Plant material 3

3. Understanding rocks is the basic foundation of knowledge for earth scientists and materials that make up the earth. • Every rock “speaks” to the observer and gives • clues about where and how it was formed. • Rocks are divided into 3 major groups: • Igneous • formed from solidifying hot molten • rock (magma) • Sedimentary • formed on the surface of the earth from • weathering processes • Metamorphic • pre-existing rocks are subjected to • various pressure and temperature • relationships 4

4. How does an earth scientist distinguish between the three rock types (Ig, Seed, and Met)? • Texture: • the appearance of the rock • size, shape, and arrangement of mineral grains. • Composition(mineral assemblages) • types and relative proportions of minerals • making up a rock • composition, mineral make-up, chemistry--all • indicators of a rock’s composition All rocks are identified based on their texture and composition. 5

5. 6 The Rock Cycle The Sedimentary Cycle

6. The Rock Cycle: • where the earth’s internal forces meet • the earth’s external forces (at the earth’s • surface) 7 Earth’s internal forces Earth’s external forces • the hydrosphere (HC) • atmosphere • erosion (wind, water, ice) • biosphere activities • moving continents (PT) • earthquakes • elevation of mountains • volcanic eruptions Produce a continuous cycle of rising mountains only to be weathered down and uplifted repeatedly. As a result, igneous sedimentary, and metamorphic rocks are created.

7. 8 I Earth Science, especially the rock cycle !!!!!!!!!!!!! Discuss with a friend: • Briefly identify each rock group and • its geologic environment. • 2. Draw the rock cycle, and explain how the • rock cycle works to your neighbor. • 3. Why is the rock cycle a “cycle”??? I will get an A on my exams and quizzes.

8. February 14, 2012 • Agenda: SILENCE YOUR CELL PHONE !!! • Need 8 ½ paper – NAME and DATE ! • QR’s 1,2,3 graded – ready • TH-Quiz-1 on website • Due on Wed, 2-15-12 • Quizzes can be graded before 2-15-12 • EXAM-1, Wednesday 2-21-12 • Exam covers: Intro to ES, Minerals, Rocks Thursday Lab --- EXAM?

9. Geology – Chapter 3 – Igneous Rocks Igneous Rocks 9

10. Magma • the parent material for igneous rocks (if not all rock groups) • typical temperature 1,200oC (2,200oF) • forms about 250 km or 150 miles below the earth’s surface Extrusive - igneous rocks – above the earth’s surface volcanic rocks lava flows Example – Hawaiian Volcanoes Intrusive - igneous rocks – below the earth’s surface plutonic rocks large granite mountains Example – Sierra Nevada Mountain Range 10 Grain size determines if the ig rock is extrusive or intrusive. Magma determines the rock’s composition.

11. When observing “frozen magma” (an igneous rock), how does a geologist know if the rock is an Extrusive or Intrusive igneous rock? checking the crystal size - Does the rock contain visible crystals, or are crystals non-existent? Igneous Rock Textures • Factors that affect crystal size in an igneous rock: • The rate at which magma cools • slow cooling – visible minerals • rapid cooling – non-visible minerals • visible minerals • slow cooling magma • intrusive ig rock • non-visible minerals • rapid cooling magma • extrusive ig rock Cooled above the surface (fine-grained) Cooled below the surface (coarse-grained) 11

12. 14 Composition of Igneous Rocks How much silica (SiO2) is in your igneous rock? • Felsic compositions (feldspar + silica) • light-colored igneous rocks • common minerals: feldspar and quartz • 70% SiO2 • Intermediate compositions: • mixture of felsic and mafic minerals • about 60% silica (SiO2) • Mafic compositions (magnesium + iron) • dark-colored igneous rocks • common minerals: olivine and pyroxene • 50% SiO2 • ultramafic: composed entirely of olivine and pyroxene • and less than 50% silica (SiO2)

13. Igneous rocks are classified based on TEXTURE and COMPOSITION. • How are igneous rocks classified? • Using their TEXTURE and COMPOSITION COMPOSITION Felsic (light color) 70% silica Intermediate color 60% silica Mafic (dark color) 50% silica COARSE phaneritic Granite Diorite Gabbro TEXTURE FINE aphanitic Rhyolite Andesite Basalt Igneous rocks have the same chemistry but different textural characteristics due to the type of geologic environment (cools quickly or slowly).

14. I Earth Science, especially igneous rocks. 4.What is the difference between extrusive and intrusive igneous rocks? 5. How can one tell the difference between an extrusive and intrusive rock texture? 6. The composition of a maficig rock is…. The composition of a felsicig rock is …. 7. A fine-grained, light-colored ig rock is called a …………………. I will get an A on my exams and quizzes. 17

15. I>clicker • An igneous rock that forms below the earth’s • surface is: • a. considered a fine-grained textured rock and • is typical of a granite • b. considered a coarse-grained mafic rock and • typical of a basalt • c. considered a fine-grained felsic rock and • typical of rhyolite • d. considered a coarse-grained felsic rock, typical • of a granite. Use your Ig rock chart – slide # 12

16. Sedimentary Rocks 18

17. How is a sedimentary rock formed??? 19 Why is the earth’s surface 75% sedimentary rocks? erosion sediment Pre-existing Rock water, wind, ice breaks down pre-existing rock Rivers Deposited transported Lakes compacted cemented lithified Sedimentary Rock

18. 21 Erosional processes – later (Chapter 4) • Sediments are separated into 3 broad categories: • Clastic sediments: • inorganic grains or mineral fragments ranging in • size from boulders to clay particles (flour size) • Chemical sediment: • formed by the precipitation of minerals dissolved • in lakes, rivers, or seawater environments • Biogenic (bioclastic) sediment: • sediment composed of animal and plant remains or • material precipitated by biological processes To be a sedimentary rock, it must be lithified.

19. Lithification:processes by which sediment is transformed into sedimentary rock Sediment can be lithified in three common processes: Compaction:Overlying weight of the sediment “squeezes” and compresses pore spaces, which pushes particles together. A. loose, unconsolidated sediment with abundant pore space B. compacted, compressed sediment with reduced pore space A B Cementation:Pore water is expelled from voids, and rising water carries iron, calcium carbonate, and silica which precipitates as geological glue (cement) holding the grains together. • Grains are cemented together by three • types of cements: • iron cement • calcium carbonate cement • silica cement 22

20. Lithification processes Recrystallization:Overlying pressure causes less stable minerals to convert to more stable minerals, producing new substances that cement pre-existing grains. Grain boundaries convert to more stable mineral compositions, “cementing” grains together. Overlying pressure 23

21. Clastic Sediment: lithified gravel sediment ranging from pea-sized to larger conglomerate lithified sand-sized particles (fine to coarse sandpaper) sandstone lithified finer particles – size of table salt siltstone finest sedimentary particles (flour-size) lithified shale 24

22. Chemical Sediments and Sedimentary Rocks Chemical Sediment: sediment formed by the precipitation of minerals dissolved in a lake, river, or seawater All surface water and groundwater contain dissolved ions (chemicals), creating a venue for precipitation of chemical sediment. • Precipitation of chemical rocks takes place in two ways: • Plants and animals alter the chemical balance • of the water body (lake, ocean). • Increasing amounts of calcium carbonate • cause precipitation of limestone. • evaporation of chemically saturated water • bodies 26

23. Evaporation of chemically saturated water creates a chemical sedimentary rock (evaporite). Na+ Na+ Cl- a lake containing sodium (Na+) and chlorine (Cl-)--free ions Cl- Cl- Na+ Na+ Cl- Evaporation Lake water is evaporated, concentrating sodium and chloride ions (saturation). Sodium and chlorine combine to form halite (table salt). NaCl 27

24. 28 The Great Salt Lake, Utah (evaporite halite) As lake becomes saturated, density of water increases. Utah

25. Chemical – sedimentary rocks that have been precipitated or are the result of evaporation Gypsum – evaporite CaSO4 Halite – evaporite NaCl Limestone-- precipitated calcium carbonate 29

26. Biogenic Sediments and Biogenic Rocks: • Biogenic sediment is composed of organic remains of plants and • animals (bioclastic rocks). • shell, bones, teeth, plant fragments, wood, roots 30 • Common Biogenic Rocks: • Limestone • most abundant biogenic sedimentary rock • composed of calcium carbonate CaCO3(calcite, dolostone, • aragonite) • lithified shells, skeletal material • Chert • composed of silica SiO2 • precipitated silica shells (made by sea animals) that protect • microscopic sea animals – Animals die, and silica shells • sink, creating layers of chert beds on the ocean floor. “When the animal dies, it loses the chert off its back.”

27. Common Biogenic Rocks 31 • Peat to Coal • accumulated remains of terrestrial plants • with time and pressure ---- peat • continued pressure and lithification ------ coal lithification Peat Increasing pressure metamorphism Anthracite coal Bituminous coal

28. Biogenic (bio-clastic) rocks – result from animal and plant secretions -- The term “clastic” indicates that these rocks contain fossils or parts of plants, shells, compacted plant material Animal parts Cemented shell fragments Fossil Limestone Microscopic fossils Coquina 32 Chalk

29. What do sedimentary rocks tell the earth scientist? These rock “layers” were deposited one layer at a time and lithified. The banded appearance is known as bedding or groups of layers called strata. The boundary between each stratum is called a bedding surface. Bedding surface bedding strata By observing the sedimentary rock type (clastic, chemical, biogenic) and depositional patterns, an earth scientist can decipher the geologic history – like reading pages in a book. 33

30. Sedimentary Rock Classification Summary Tree Sedimentary Rocks are divided into 3-classification categories: Clastic sediments Chemical sediments Bio-clastic (chemical) sediments formed by precipitation composed of “animal parts” composed of inorganic grains from plants and animals evaporation processes Classification based on Observed fossils, animal parts, Plant/animal secretions classification based on distribution of grain sizes Classification based on lack of grains and chemical composition Fossil-limestone Conglomerate Gypsum (CaSO4) Sandstone Coquina Decreasing grain size Siltstone Halite (NaCl) Chalk Shale Limestone (CaCO3)

31. 36 I sedimentary rock classification. Discuss with a friend: 8. Describe at least 2 characteristics of each sedimentary rock classification (clastic, biogenic, chemical). 9. Give a rock example for each classification. I will get an A on my exams and quizzes.

32. I>clicker • Clastic sedimentary rocks are primarily • composed of: • a. organic material • b. materials that have been chemically percipitated • from oceans and fresh water lakes • c. fossils • d. inorganic fragments and particles of other • rocks.

33. Metamorphic Rocks 37

34. What is “metamorphism?” • meta(change)morphism(form) • transformation of pre-existing • rock to a metamorphic rock • throughpressureand • temperaturerelationships • All changes take place through • solid state transformation. 38

35. Types of Metamorphism • takes place around 150oC(Temperature) • typically at depths of 5 km below the • earth’s surface(Pressure) At this temperature and pressure, new minerals are formed – changed from one mineral to another. 39

36. I metamorphic rocks. Discuss with a friend: 10. How do you define metamorphism? – Be specific. 11. What two major factors are necessary for pre-existing rocks to become metamorphosed? 12. Where does metamorphism typically take place within the earth? I will get an A on my exams and quizzes. 40

37. 2 Common types of metamorphism • contact metamorphism • regional metamorphism 44

38. What is contact metamorphism? • Contact metamorphism: • magma “contacts” solid rock – • heat is transferred into overlying • rocks through conduction – changing • the pre-existing rock it intruded • high heat/low pressure • localized metamorphism • “fast-acting,” like touching a • hot frying pan 45

39. Country rock (surrounding) is baked from conduction. 46

40. What is regional metamorphism? • Regional Metamorphism • Pre-existing rock is subjected to intense • stresses and strains (deformation) usually • from the forces of mountain building. • high heat/high pressure • very widespread geographically • like experiencing a slow sunburn 47

41. Mountain building widespread belts 48

42. I the different ways to create Metamorphism. Discuss with a friend: • 13. Describe the conditions necessary for each • type of metamorphism: • contact metamorphism • regional metamorphism I will get an A on my exams and quizzes. 49

43. I>clicker • What term best describes contact • metamorphism? • a. convection • b. conduction • c. condensation • d. condominium

44. Metamorphic heat sources: Heat sources: contact with hot magma – heat penetrates overlying rocks (conduction) geothermal gradient – heat increases with depth – rocks are hotter when buried 50

45. Geothermal Gradient • Temperature increases • as depth increases. • Large thermal gradient • is at the surface. • Gradient decreases • after 1000 km depth. 0 1000 2000 3000 4000 Steep gradient 51

46. Pressure associated with metamorphism 52 Pressure –increases with depth, various types of pressure rearrange minerals – minerals compact or elongate Confining pressure Differential pressure

47. 53 • How does one know how much metamorphism • has taken place in a rock? • reflected in the rock’s texture Metamorphosed – mineral grains are in a preferred direction -- FOLIATION Not Metamorphosed

48. 54 I to metamorphose. Discuss with a friend: 14. Describe two heat sources associated with metamorphism. 15. Define the differences between confining and differential pressures. 16. Draw a diagram that shows mineral orientation due to confining and differential type pressures. I will get an A on my exams and quizzes.