Chapter 22

1. Chapter 22 Earth’s Interior

2. 22.1 Earth’s Structure • Scientists can’t see into Earth • We can listen (earthquakes as sound waves) • Or, 12 km holes (about 8 miles) can be drilled for use in analysis

3. The Science of Geology • Geology- the study of planet Earth, including its composition and structure • Geologist study geology • Constructive forces vs. destructive forces • Constructive forces shape the surface by building mountains, etc. • Destructive forces wear away mountains, etc. • Uniformitarianism- geologic processes that happen today happened in the past. This was defined by James Hutton in the late 1700’s, a physician and farmer who studied rocks he could only explain if they were older than other people thought, and that they came from other rocks. This means that mountains and canyons happen over a long time.

4. A Cross Section of Earth • Earth has three layers of different density • Crust • Mantle • Core

5. Crust • Rocky outer layer • Thinnest • Made of silicates (Si and O, maybe Al, Fe, Ca) • Two types of crust • Continental • Less dense • Made of granite • ~40 km thick • Oceanic • Dense • Made of basalt • 7 km thick

6. Mantle • Thick layer of hot, solid rock • 2850 km • P and T increase closer to the core • Silicates, Fe, Mg • Three layers • Lithosphere- cool, rigid rock, uppermost layer, 100 km thick • Asthenoshpere- softer, weaker rock, taffy-like motion • Mesosphere- stronger rock nearest core

7. Core • Fe, Ni • 3.6 million times normal pressure • 5500 degrees Celsius • Outer core- high T, liquid metal, magnetic and electric current source • Inner core- high P, solid

8. 22.2 Minerals • Emeralds green from Cr • Rock- solid combination of minerals or mineral materials • Mineral- naturally occurring, inorganic solid with crystal structure and characteristic chemical composition • Inorganic- not made from living things (coal is organic since it’s from plants) • Concrete is not a mineral- man-made • Minerals are the building blocks of rocks • 4,000 minerals, but only a few are common, like quartz, feldspar, mica, hornblende (granite) • Crystal- repeating pattern of atoms

9. Properties of Minerals • Crystal structure • Color • Streak • Luster • Density • Hardness • Fracture • Cleavage

10. Crystal Structure • Geometric shape • Some large, some small crystals, but all same shape for a certain mineral • Prisms, cubes, sheets, needles, threads • Halite (table salt) is cubic • Garnet (Jan.) is 12 sided (octahedral)

11. Color • Pyrite (fool’s gold) is golden yellow • Sulfur is yellow • Quartz can take in different chemicals and be different colors

12. Streak • Color of mineral’s powder • Scrape on porcelain, or streak plate • Not always same as color of mineral • Hematite (black) has a red streak

13. Luster • Way mineral reflects light • Shiny • Galena and pyrite metallic luster • Sulfur resinous-to-greasy luster • Rough is called earthy • Silky, pearly, vitreous (glassy)

14. Density • D = m/v • High atomic mass means high density • P. 667 table • We’ll do calculations in lab experiments

15. Hardness • Resistance to scratching • Hard scratches soft • Mohs hardness scale 1-10 • Talc to diamond • Fingernail is 2.5

16. Fracture and Cleavage • Fracture is a break, some are even, some not • Cleavage is an even break • Graphite (pencils) • Glass (uneven)

17. 22.3 Rocks and the Rock Cycle • 3 types of rocks • Igneous- formed from magma (molten rock and gases) which turns into lava. The rock occurs when it cools. Intrusive rocks are coarse and large. Extrusive are smooth, small. They are usually dark in color. • Sedimentary- made from weathered or broken rocks, found in oceans, lakes, streams, deserts • Clastic- broken pieces held by cement • Chemical- chemical reactions, like evaporation or acid rain • Organic- ex. coral • Metamorphic- changes form, P or T. Particles lined up maybe bands (foliated rock) • Rock cycle

18. 22.4 Plate Tectonics • Theory that lithosphere moves slowly on asthenosphere. • Continental drift (Earth as puzzle) • Alfred Wegener and Pangaea • Mid-ocean ridge- underwater mountains • Sea-floor spreading- process by which new oceanic crust is created at mid-ocean ridges as older crust moves away • Subduction- plates sink into mantle • Trench- depression • Evidence of movement of mantle (magnetic stripes)

19. Plate Boundaries • Divergent- plates move away, magma flows • Convergent- plates come together, mountain • Transform- plates slide past (earthquake)

20. 22.5 Earthquakes • Earthquake- movement of lithosphere that occurs when rocks in lithosphere suddenly shift, releasing stored energy in vibrations called seismic waves • Caused by stress in plate movement • Fault- break in a mass of rock along which movement occurs ex. San Andreas • Fold- a bend in layers of rock • Focus- center of earthquake beneath Earth • Epicenter- center of earthquake on Earth’s surface • P waves- longitudinal waves like sound waves (accordion), first detected • S waves- transverse waves, can’t travel through liquid • Surface waves- when seismic waves reach Earth’s surface, slower than P and S, but larger ground movement • Measured by seismograph using Richter Scale (most well known), Moment Magnitude Scale (best), or Modified Mercalli Scale (observations)

21. 22.6 Volcanoes • Volcano- mountain that forms when magma reaches the surface • Most inactive • Like a soda bottle • Magma goes from magma chamber, to pipe, to vent, or opening • Top is called a crater, unless collapsed, which is a caldera • Quiet if very hot, low in silica; high silica is loud • Most on plate boundaries (Ring of Fire) • Hot spot- region where hot rock extends from deep within the mantle to the surface

22. Types of Volcanoes • Shield- quiet, wide, flat • Cinder Cone- ash and cinder, steeple • Composite- explosive (traditional), lava and ash