GEOLOGY and the Rock Cycle

1. GEOLOGY and the Rock Cycle

2. GEOLOGIC PROCESSES • The earth is made up of a core, mantle, and crust and is constantly changing as a result of processes taking place on and below its surface. • The earth’s interior consists of: • Core: innermost zone with solid inner core and molten outer core that is extremely hot. • Mantle: solid rock, under which is the asthenosphere that is melted pliable rock. • Crust: Outermost zone which underlies the continents. (Lithosphere)

3. Spreading center Collision between two continents Ocean trench Oceanic tectonic plate Oceanic tectonic plate Plate movement Plate movement Tectonic plate Oceanic crust Oceanic crust Subduction zone Continental crust Continental crust Material cools as it reaches the outer mantle Cold dense material falls back through mantle Hot material rising through the mantle Mantle convection cell Mantle Two plates move towards each other. One is subducted back into the mantle on a falling convection current. Hot outer core Inner core Fig. 15-3, p. 337

4. INTERNAL GEOLOGIC PROCESSES • Huge volumes of heated and molten rock moving around the earth’s interior form massive solid plates that move extremely slowly across the earth’s surface due to convection currents. • Tectonic plates: huge rigid plates that are moved with convection cells or currents by floating on magma or molten rock.

5. Folded mountain belt Volcanoes Abyssal plain Abyssal floor Oceanic ridge Abyssal floor Abyssal hills Trench Craton Continental slope Abyssal plain Oceanic crust (lithosphere) Continental shelf Continental rise Mantle (lithosphere) Continental crust (lithosphere) Mantle (lithosphere) Mantle (asthenosphere) Fig. 15-2, p. 336

6. Earth • orbit: 149,600,000 km (1.00 AU) from Sun • diameter: 12,756.3 km • mass: 5.972e24 kg • Earth’s layers (depths in km) • 0- 40 Crust • 40- 2890 Mantle • 2890-5150 Outer core • 5150-6378 Inner core

7. Earth • Earth’s mass (measured in 10^24 kg) • atmosphere = 0.0000051 • oceans = 0.0014 • crust = 0.026 • mantle = 4.043 • outer core = 1.835 • inner core = 0.09675

8. Earth’s Interior • Core is made up mostly of iron/nickel • Temperatures in core reach 7500 K • The crust is primarily quartz. • Taken as a whole, the Earth's chemical composition (by mass) is: • 34.6% Iron 2.4% Nickel • 29.5% Oxygen 1.9% Sulfur • 15.2% Silicon 0.05% Titanium • 12.7% Magnesium

9. The Earth’s Major Tectonic Plates Figure 15-4

10. Major Plates • North American Plate • South American Plate • Antarctic Plate • Eurasian Plate • African Plate • Indian-Australian Plate • Nazca Plate • Pacific Plate

11. Plate Movement • The extremely slow movements of these plates cause them to grind into one another at convergent plate boundaries, move apart at divergent plate boundaries and slide past at transform plate boundaries. Figure 15-4

12. Fig. 15-4, p. 338

13. EURASIAN PLATE NORTH AMERICAN PLATE ANATOLIAN PLATE CARIBBEAN PLATE JUAN DE FUCA PLATE CHINA SUBPLATE ARABIAN PLATE PHILIPPINE PLATE AFRICAN PLATE PACIFIC PLATE SOUTH AMERICAN PLATE NAZCA PLATE INDIA-AUSTRALIAN PLATE SOMALIAN SUBPLATE ANTARCTIC PLATE Divergent plate boundaries Convergent plate boundaries Transform faults Fig. 15-4a, p. 338

14. Trench Volcanic island arc Craton Transform fault Lithosphere Rising magma Lithosphere Subduction zone Lithosphere Asthenosphere Asthenosphere Asthenosphere Divergent plate boundaries Convergent plate boundaries Transform faults Fig. 15-4b, p. 338

15. Convergent Plate Boundary • Two plates pushed together • Oceanic + Continental = Subduction Zone • Oceanic + Oceanic = Trench • Continental + Continental = Mountain Range

16. Divergent Plate Boundary • Plates moves apart from one another • Oceanic plates form oceanic ridges

17. Transform Faults • Plates slide and grind past one another along a fracture in the lithosphere

18. Benefits of volcanoes, earthquakes, and tsunamis • Geological: • Recycle rock and earth’s crust • Form minerals • Ecological: • Speciation (due to isolation) • Maintaining atmosphere thus climate • Enrich soils = more food

19. Geologic Time Scale • ~4.6 billion years ago: Earth believed to have formed, hot ball of rock • 3.9 billion years ago: rainstorms • 3.5 billion years ago: oceans, first living organisms

20. Geologic Eras • Precambrian Era: 4.6 billion years ago- 545 million years ago • 87% of Earth’s history • Prokaryotes dominated • First eukaryotes appeared ~ 1.5 billion years ago • Simple multicellular organisms in seas • Paleozoic Era: 545 million years ago – 248 million years ago • “Explosion of life” • Many types of invertebrates in shallow seas • Early: earliest vertebrates • Middle: amphibians • Later: reptiles

21. Geologic Eras • Mesozoic Era: 248 million years ago – 65 million years ago • Triassic: mammals made first appearance • Jurassic: “age of dinosaurs” • Cretaceous: radiation of mammals and evolution of flowering plants • Plate Tectonics: continental shift • Cenozoic Era: 65 million years ago – now • Mammals flourish • Primates evolve • Extinctions affect diversity • Modern human species evolved ~200,000 years ago

22. EXTERNAL GEOLOGIC PROCESSES Surface processes Based largely on energy from the sun and gravity Tends to wear down Earth’s surface and produce a variety of landforms by the buildup of eroded sediment Erosion Weathering

23. Wearing Down and Building Up the Earth’s Surface Weathering is an external process that wears the earth’s surface down. Figure 15-6

24. EROSION Process by which material is dissolved, loosened or worn away from one part of the earth’s surface and deposited in other places Streams are most important agents of erosion

25. MINERALS, ROCKS, AND THE ROCK CYCLE The earth’s crust consists of solid inorganic elements and compounds called minerals that can sometimes be used as resources. Mineral resource: is a concentration of naturally occurring material in or on the earth’s crust that can be extracted and processed into useful materials at an affordable cost.

26. Nonrenewable mineral resources • Fossil fuels (oil, natural gas, coal) • Metallic minerals (Al, Cu, Fe) • Nonmetallic minerals (sand, gravel, limestone)

27. Minerals and their Uses Metals Nonmetals Sand- glass, concrete, bricks Gravel- roadbeds Limestone- roadbeds, natural buffer Phosphate salts- fertilizers • Al- building, cans • Steel- building • Cu- conductor, electronics • Mn, Co, Cr- used in alloys • Pt- catalytic converters

28. US consumption • 8% of world population but use 75% of metals on earth • Uses: cars, engines, appliances, weapons, satellites

29. ROCK A very slow chemical cycle recycles three types of rock found in the earth’s crust: Sedimentary rock (sandstone, limestone). Formed from sediment of pre-existing rocks that are weathered and eroded Metamorphic rock (slate, marble, quartzite). Formed when pre-existing rock is subjected to high temperatures or pressure Igneous rock (granite, pumice, basalt). Formed from cooled magma at or below earth’s surface

30. Erosion Transportation Weathering Deposition Igneous rock Granite, pumice, basalt Sedimentary rock Sandstone, limestone Heat, pressure Cooling Heat, pressure, stress Magma (molten rock) Melting Metamorphic rock Slate, marble, gneiss, quartzite Fig. 15-8, p. 343