Chapters 5 and 6

1. Chapters 5 and 6 Igneous, Sedimentary, and Metamorphic Rocks..

2. How are Igneous Rocks formed? Question of the Day.

3. Learning Targets • 1). You will be able to explain how igneous rocks are formed. • 2). You will understand how scientists classify igneous rocks; the difference between intrusive and extrusive igneous rocks.

4. Cartoon

5. Chapter 5: Igneous Rocks What is an Igneous rock? • Igneous Rocks:rocks that are formed from the crystallization of magma or lava • Magma = the molten rock found within the Earth’s crust. • Lava = the molten rock that flows out onto Earth’s surface.

6. How can Igneous Rocks look so different from each other? Question of the Day.

7. Learning Targets • 1). You will understand how scientists classify igneous rocks. • 2). You will practice classifying igneous rocks based upon composition as well as crystal size.

8. Cartoon

9. Group Challenge • In your lab groups, I want you to separate these igneous rocks into 2 groups. • Take some time and carefully look at each rock for subtle similarities and differences. • Question For Thought… • 1). What different types of magma may have formed these rocks?

10. Igneous Rocks Types of Igneous Rocks What’s the difference • Extrusive Rocks = fine-grained igneous rocks that cool quickly on Earth’s surface. • Intrusive Rocks = course-grained igneous rocks that cool slowly beneath Earth’s surface. • Granite is the most common intrusive igneous rock

11. Igneous Rocks Composition of Magma • Magma is often a slushy mix of molten rock, gases, and mineral crystals • The elements found in magma are the same major elements found in Earth’s crust. • Silica (SiO2) is the most abundant and has the greatest effect on magma characteristics • There are 3 types of Magma • Basaltic • Rhyolitic • Andesitic

12. How do the liquids we tested in lab resemble the different types of magma? Question of the Day.

13. Three Types of Magma • Basaltic = 45-55% Silica (SiO2) • high in Fe, Mg, Ca, low in K, Na • Low Viscosity = Easier for this type of magma to flow • Gas can more easily escape = Less Violent Eruptions • Andesitic = 55-65% Silica (SiO2) • intermediate. in Fe, Mg, Ca, Na, K • Intermediate Viscosity = Intermediate Rate of magma flow • Rhyoliticmagma = 65-75% Silica (SiO2) • low in Fe, Mg, Ca, high in K, Na • High Viscosity = More Difficult for this type of magma to flow. • Gas has a very hard time escaping = Very Violent Eruptions

14. Types of Magma Basaltic Magma • Made from minerals including olivine, pyroxene, and plagioclase. • Basalt is erupted at temperatures between 1100 to 1250° C. • Basalt is the most common rock type in the Earth's crust (the outer 10 to 50 km). In fact, most of the ocean floor is made of basalt. • Huge outpourings of lava called "flood basalts" are found on many continents. The Columbia River basalts, erupted 15 to 17 million years ago, cover most of southeastern Washington and regions of adjacent Oregon and Idaho. • Basaltic magma is commonly produced by direct melting of the Earth's mantle, the region of the Earth below the outer crust. On continents, the mantle begins at depths of 30 to 50 km.

15. Types of Magma Andesitic Magma • Andesite is a gray to black volcanic rock • Andesites contain the minerals pyroxene and sometimes olivine. • Andesite magma commonly erupts from strato-volcanoes as thick lava flows, some reaching several km in length. • Andesite magma can also generate strong explosive eruptions to form pyroclastic flows and surges and enormous eruption columns. • Andesites erupt at temperatures between 900 and 1100° C. • The word andesite is derived from the Andes Mountains, located along the western edge of South America, where andesite rock is common. • Andesite was the main rock type erupted during the great Krakatau eruption of 1883.

16. Types of Magma Rhyolitic Magma • Low temperature eruptions (750–850ºC) • High gas content • Very explosive • Erupt from Caldera Volcanoes

17. Igneous Rocks Origins of Magma Partial Melting • In lab, most rocks must be heated to temps around 800 – 1200 degrees Celsius before they melt • In nature these temps are found in the upper mantle and lower crust • Not all minerals have the same melting points • Because of this not all parts of the rock melt at the same time • This explains why magma is often a slushy mix of crystals and molten rock • Partial Melting = when some minerals melt at low temps and other minerals remain solid

18. Igneous Rocks Classifying Igneous Rocks Unique Features • Mineral Composition • There are 3 main groups of igneous rocks 1). Felsic • Light-colored • Have high silica contents 2). Mafic • Dark-colored • Lower silica contents and are rich in iron and magnesium 3). Intermediate • Porphyritic Texture= large, well formed crystals surrounded by finer-grained crystals. • Indicates a complex cooling history where a slowly cooling magma suddenly began cooling rapidly

19. Group Challenge • In your lab groups, I want you to separate these igneous rocks into 3 groups based upon color. • Group 1: Light Colored Rocks = Felsic • Group 2: Medium Color = Intermediate • Group 3: Dark Colored Rocks = Mafic

20. What are the 2 ways scientists tell igneous rocks apart? Question of the Day.

21. Learning Targets • 1). You will practice classifying igneous rocks based upon composition as well as crystal size. • You will understand some uses of igneous rocks.

22. Group Challenge • In your lab groups, I want you to visit each station around the room which will give you some practice identifying characteristics of igneous rocks. • You will have approximately 3 minutes at each station to answer the question inside the box. • EVERYONE from your group must write down the answer.

23. 1). Compare and Contrast: Extrusive and Intrusive Igneous Rocks.2). Explain how the color of igneous rocks can help us determine what they are made of. Let’s See What You Remember

24. Learning Targets • 1). You will understand some uses of igneous rocks. • 2). You will understand how sedimentary rocks are formed.

25. Igneous Rocks Origins of Magma Partial Melting • In lab, most rocks must be heated to temps around 800 – 1200 degrees Celsius before they melt • In nature these temps are found in the upper mantle and lower crust • Not all minerals have the same melting points • Because of this not all parts of the rock melt at the same time • This explains why magma is often a slushy mix of crystals and molten rock • Partial Melting = when some minerals melt at low temps and other minerals remain solid

26. Igneous Rocks • Igneous Rocks as Resources • They are useful for building materials because of their strength and resistance to weathering (granite)

31. Memory Clue • To show your understanding of igneous rocks and there characteristics, complete memory clues for vocab 1-8. • Cross out ultra-mafic

32. Cartoon

33. Sedimentary Rocks Formation of Sedimentary Rocks • Sediments= pieces of solid material that have been deposited on Earth’s surface by wind, water, ice, gravity, or chemical precipitation • When these sediments get “cemented” together, they form sedimentary rocks • Occurs from weathering and erosion • Classified into two groups based on how they form. • Clastic • Chemical

34. Clastic Sedimentary Rocks Clastic sedimentary rock= formed as bits of weathered rock become cemented together. • All kinds of rock are subject to weathering • Many different minerals can make up this group of rocks. • Claysand quartz are the most common. Classification of Clastic sedimentary rocks is done according to the size of the sediments that make up the rock. • The table contains the major groups of Clastic sedimentary rocks with their characteristics

35. Chemical Sedimentary Rocks • Chemical sedimentary rocks =form from dissolved minerals that are precipitated or separated from water. • This happens most frequently when water evaporates leaving the minerals behind. • You can see this process taking place in your own home. The white deposits that form around the faucets in your bathroom or kitchen are from minerals left behind as water evaporates. • The table contains the major groups of chemical sedimentary rocks with some of their characteristics:

36. Sedimentary Rocks • Weathering = the process where the Earth’s crust is continually getting worn away by a set of physical and chemical processes. • Chemical Weathering = when minerals in a rock are dissolved or otherwise chemically changed. • Physical Weathering = when the minerals remain chemically unchanged – they just break off • Erosion = The removal and movement of surface materials from one spot to another. • http://ees.as.uky.edu/educational-materials

37. Types of Mechanical Weathering • Frost Wedging • Water expands when it freezes - an ice cube is about 9% larger than the volume of the water before it froze. • The expansion of water when it freezes is one of the most effective processes of mechanical weathering. • *Wedging: A fracture (crack) in a rock provides ice with a lot of leverage. When the temperature drops below freezing, the ice exerts force outward on the rock as it grows. • *Freeze/thaw: Each freezing may wedge the fracture open just a tiny amount, so it takes many cycles of freezing and thawing, with water filling the fracture each time, to break off a piece of rock. • Most effective in cold, wet climates in which there are many opportunities for freeze/thaw cycles with water present. • High altitudes (mountain ranges) are particularly prone to such temperature changes

38. Types of Mechanical Weathering 2. Exfoliation = peeling of layers • describes sheets of rock peeling off a bare rock face • *Rock type: Exfoliation is most common on rock faces of intrusive igneous rocks such as granite. 3. Thermal Expansion and Contraction • Crystals of rock also expand and contract as they heat and cool • Can loosen grains of a rock enough to cause weathering. • Most Common in Desert Regions • Temperature may rise and fall as much as 50 deg Celsius (90 deg Fahrenheit) from day to night • **Fires: Even more pronounced is the fracturing of rocks that occurs during exposure to forest fires. Under these conditions, temperatures may rise briefly by 200 deg C or more, and exposed rock will expand enough to spall many small pieces off the rock face. Similarly, campfires can cause enough thermal expansion for rocks in a campfire ring to crack loudly, startling any nearby marshmallow roasters.

39. Types of Mechanical Weathering 4. Crystal Growth • Salt crystals growing in rock fractures or in the small pores between sedimentary grains can cause rocks to loosen up and break. Usually this happens when salty water gets into the rocks and later evaporation of the water produces crystallization in the pore or fracture space. • by pushing the grains apart. • *Practical Application: For readers who live in cold, snowy climates: be careful how much salt you use to melt ice on your sidewalks, stairways, and driveways. Salt crystal growth is one of the biggest causes of road potholes in the northern United States, and the outdoor stairways leading into many public buildings are in terrible disrepair due to damage from salt crystallization.

40. Mechanical Weathering 5. Tree Roots • Tree root tips are tiny and penetrate easily into fine fractures of rocks. • As the roots grow in diameter, they put stress on the rock that can cause the fractures to expand.. • *Where: In terms of climate, this weathering mechanism can occur anywhere that sufficient precipitation exists to sustain tree growth and rocks are exposed near the surface. Tree root wedging can also occur invisibly, beneath a thin layer of soil.

41. Mechanical Weathering 6. Abrasion • Rocks breaking or wearing down by the direct actions of other rocks. • The rock falling down the cliff as it tumbles down and breaks into pieces. • *Where: Abrasion typically is strongest in the harshest environments: cold and wet (glaciers), high elevations (steep terrains), arid regions (wind), etc

42. Mechanical Weathering Assignment • 1). Pick 1 type of mechanical weathering. • 2). Write 4 sentences explaining what it is and how it happens. • 3). Bring in a real picture that shows your weathering in action.

43. 1). What is a Sediment? Let’s See What You Remember

44. Cartoon

45. Chemical Weathering • Dissolution • Dissolution tears mineral grains apart and carries away the ions (electrically charged atoms or molecules) in solution. • Example: The salt in the ocean all comes from chemical reactions of water with rocks. • Example: Caves in rock are the result of dissolution, usually where the mineral calcite (CaCO3) in limestones has been dissolved by groundwater. • *Acids: Most dissolution in chemical weathering is not performed directly by the water but rather by acids contained in natural waters.

46. Chemical Weathering 2. Oxidation • Oxidation is rust • Many minerals contain elements that can undergo oxidation, although iron (Fe) is by far the most common one. • Many outcrops of iron-rich rock have reddish stains from "rusting" due to chemical weathering by reactions with air.

47. Learning Targets • 1). You will see the process of weathering in action. • 2). You will understand the differences between chemical and physical weathering.

48. 1). Compare and Contrast (physical) mechanical and chemical weathering. Let’s See What You Remember

49. Learning Targets • 1). You will see both processes, chemical and physical (mechanical), of weathering in action. • 2). You will understand what happens after weathering to sediments to form sedimentary rocks: processes of deposition and lithification. • 3). You will see how sedimentary rocks are grouped.

50. Sedimentary Rocks Deposition and Lithification Animation • Deposition = The process of weathered sediments settling out after being moved by erosion. • Lithification= The process that transforms sediments into sedimentary rocks. • Sediments are compacted as they are buried beneath successive layers of sediment and cemented by minerals • Evidence of Past Life • During lithification, parts of organisms are replaced by minerals and turned into rocks. • Bedding= The horizontal layering of sedimentary rocks. • http://gomyclass.com/animations2.html • http://serc.carleton.edu/NAGTWorkshops/geomorph/visualizations/erosion_deposition.html