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Unformatted text preview: 20: Global Change al Change: 1 Global Change: Definitions • Earth system: global interactions of the geosphere (solid & magma Earth), hydrosphere (water planet), atmosphere (gaseous envelope), biosphere (living world), exosphere (outer space), and anthroposphere (humans and their structures) • Global change: modifications in the Earth system • Gradual change: modifications that take place over millions or billions of years • Catastrophic change: modifications that take place instantaneously (geologically speaking) • Unidirectional change: modifications that never repeat • Cyclic change: modifications that repeat al Change: 2 Origin of solar system Nebula: cloud of gas or dust in space. Nebula theory of planet formation: gravity and collisions within a nebula cause the formation of a central sun and orbiting planets. Occurred ~____ billion years ago billion al Change: 3 Plate, p. 26-27 Artist’s drawing Hadean: Hell on Earth 4600-3800 mya • L ava ocean--produced by heat from _________________________ Vertical slice Fig. 13.4 Artist’s drawing • Differentiation: dense material sinks, light Differentiation dense material rises; forms ultramafic mantle and iron-rich core (but no crust yet) iron-rich Fig. 23.3 al Change: 4 Archean formation of atmosphere & oceans 3800-1600 mya Q1. Which gas was not a significant component of Earth's early atmosphere? A. NH 3 B. SO2 C. CH 4 D. O2 E. H 2O • Role of volcanic outgassing: excess water ______________________ ______________________ Side view Lightning Modern volcanic outgassing, Krafla volcano, I celand al Change: 5 Archean: formation of crust Side views Fig. 13.5 Q2. Based on the above diagram, the formation of continental crust is primarily related to ___. A. magnetic field reversals B. processes at conservative plate boundaries C. seafloor spreading D. subduction and collision al Change: 6 Archean: formation of crust Side views Fig. 13.5 • M afic oceanic crust forms by partial melting of ultramafic mantle • L ess-dense intermediate to felsic rocks form unsubductable volcanic/magmatic arcs (proto-continents) above subduction zones arcs • M antle plumes form unsubductable oceanic plateaus and large hot-spot islands islands • Collisions between proto-continents produce larger proto-continents; regional al Change: 7 Archean: formation of crust • Continental crust cannot be subducted; continents __________ through time <0.5 Older core (craton) surrounded Older by younger rocks; ages are in ages billions of years billions >2.5 1.9 1.8 >2.5 <0.5 1.8 1.6-1.7 Fig. 13.10 Map view al Change: 8 1.1 <0.5 Fig. 13.6 Archean: first life Bacteria fossils in 3.2 billion-yearold chert from South America Fig. 13.7 al Change: 9 Proterozoic: atmosphere Fig. 13.12 Fig. 13.13 • Role of life: _________________ Role • Banded iron formations (BI Fs) – Fe dissolved in the ocean reacted with O2, forming worldwide FeO deposits. r eacted al Change: 10 10 Paleozoic: tectonics • Supercontinental cycle: smaller continents coalesce to form a supercontinent, which then rifts and breaks apart, only to recombine as oceanic crust created during seafloor spreading is subducted Side views Fig. 23.5 al Change: 11 11 Paleozoic: tectonics Proterozoic supercontinent 500-250 mya Appalachian orogeny: r ecord of assembly of Pangea in eastern North America due to subduction and collision ________________________ _ ________________________ ________________________ Pangea Fig. 11.39 Side views al Change: 12 12 Paleozoic: tectonics 500-250 mya • Subduction and collision produce ___________________ Subduction ___________________ Map views al Change: 13 13 Fig. 13.22 Paleozoic: age of invertebrates Fossil trilobites Fig. 13.19 al Change: 14 14 Artist’s drawing M esozoic: Progressive breakup of Pangea 8 6 2 1 1 3 3 5 3 3 4 7 Map views Fig. 13.25 Oldest: Jurassic (~200 mya) ______________________ al Change: 15 15 Fig. 13.28 Youngest: T ertiary (~60 mya) ___________________ M esozoic: superplumes Fig. 13.17 Vertical slice M esozoic superplumes yield high sea level, hot-house world--> hot-house _____________ al Change: 16 16 M ass Extinctions 0 Ma 100 M a 200 M a Biggest 300 M a Q3. The Cretaceous-Tertiary (K-T) event took place ___ millions of years ago. A. 540 B. 245 C. 65 D. 25 400 M a 500 M a Fig. 23.14 al Change: 17 17 K/T Boundary Cenozoic: age of mammals Start of Cenozoic: Tertiary (T) T ertiary End of M esozoic: Cretaceous (K) Cretaceous Fig. 13.26 M esozoic: age of reptiles Dinosaurs became extinct at 65 mya Fig. 23.4 Artists’ drawings al Change: 18 18 K/T Boundary Age of mammals no dinosaurs; other reptiles present no 65 mya 65 Age of reptiles mammals present • M ammals filled niches _______________________ Fig. 23.4 al Change: 19 19 K/T boundary layer Tektites: glass spheres formed from r apid cooling of molten material QuickTimeª and a TIFF (Uncompressed) decompressor are needed to see this picture. Photo of thin slice of quartz viewed under microscope 5 mm Shocked quartz: forms as a result of r apid increase and decrease in pressure, such as from a nuclear explosion al Change: 20 20 K/T boundary layer Gubbio, Italy H. M ichel, F. Asaro, W. & L. Alvarez, 1980 I ridium anomaly: higher than normal concentration of I r--not common in crust or mantle but common in Earth’s core, ________________________ QuickTimeª and a TIFF (Uncompressed) decompressor are needed to see this picture. QuickTimeª and a TIFF (Uncompressed) decompressor are needed to see this picture. Fern spike: marked increase in abundance of fern pollen; ferns are first plants to grow after disaster Charcoal / soot Tsunami deposits al Change: 21 21 I mpact hypothesis: evidence cited here and previous evidence slide indicates K/T extinction was caused by slide _____________ I mpact Site Alan Hildebrand, Glen Penfield, and others— 1991: re-discovered it (using oil-exploration techniques) and linked it to K/T event Fig. D.13 Carl Swisher et al: Chicxulub crater, Yucatan Peninsula, M exico Crater diameter: Crater ~180 km ~180 Asteroid diameter: Asteroid ~10 km ~10 Energy released: Energy equivalent to 1014 10 tons TNT . tons al Change: 22 22 Side view 65 M a--absolute 65 dating of melt rocks dating I mpact Processes Side views 1 2 3 4 1. M oment of impact causes massive, momentary increase in pressure 2. After passage of shock wave, very abrupt decrease in pressure causes material to be 2. blown out of crater blown 3. Removal of ejected material causes parts of crater floor to uplift & later subside 4. Final state al Change: 23 23 Killing mechanisms • “Nuclear winter”: material ejected into atmosphere blocked out sun, ______________________ sun, ______________________ Artist’s drawings Also: 1 3 • direct blast and fire ball set off global forest fires • acid rain • megaearthquakes & mega-tsunamis al Change: 24 24 Fig. 13.30 4 2 Fig. 23.14 Contributing factor? M assive eruption of basalts associated with mantle plume, Deccan Traps, I ndia Krafla fissure eruption, 1977, Northern I celand al Change: 25 25 Cenozoic: closing of Tethys • H imalayas: ____________ • Alps: _______________ Tethys Fig. 13.31 al Change: 26 26 Map views Cenozoic: ice ages Chemical weathering reaction: CaSiO3 + CO2 —> CaCO3 + SiO2 Q4. A. True / B. False: As rates of chemical weathering increase, the amount of CO2 in the atmosphere increases. • Uplift of Himalaya and intensification of weathering: ______________ __________ Added to air Block diagram al Change: 27 27 Fig. 23.7 Taken from air Global climate change • Biogeochemical cycle: describes movements & interactions of chemicals essential to life through atmosphere, biosphere, hydrosphere & lithosphere Fig. 23.7 Block diagram Carbon cycle Added to air al Change: 28 28 Taken from air Global climate change Q5. Which of the following processes removes CO2 from the atmosphere? A. burning of fossil fuels B. exhalation by animals C. photosynthesis D. volcanism Block diagram Carbon cycle al Change: 29 29 Added to air Taken from air Global climate change • Greenhouse effect: trapping of long-wave infrared radiation by certain gases (CO2, CH 4, O3, N2O) in atmosphere causes atmospheric warming Side view al Change: 30 30 Global climate change • Changes in CO2 levels in the atmosphere: increased since I ndustrial Revolution, primarily from fossil-fuel burning Q6. The rate of increase in CO2 concentration since 1960 has been ___. A. decreasing B. increasing C. constant Fig. 23.20 Percent increase since 1800: (370-275)/275* 100% = 34.5% (370-275)/275* 34.5% al Change: 31 31 Percent increase since 1960: (370-315)/315* 100% = 17.5% (370-315)/315* 17.5% Global climate change Graph B: CO2 concentration for last 375 million years Graph A: Same as Fig. 23.20, but scale expanded to include zero. al Change: 32 32 Graph C: x-axis from Graph A; y-axis from Graph B Global climate change Q7. The increase in the average global temperature in the 20th century is _____. A. ~0.5°C B. ~0.75°C C. ~1.0°C D. ~5.0°C • From 1000 to 1900, global temperatures decreased by 0.15°C (but estimates are based on indirect data and have large error bars). al Change: 33 33 Fig. 23.22 Global climate change • General circulation models: 3-D models of Earth’s climate system based on weatherforecasting models predict future temperature change Q8. General circulation models with increased CO2 in the atmosphere predict the most warming ___. A. at low latitudes (near equator) B. at middle latitudes C. at high latitudes (near poles) Map view • BUT: Average model prediction for 20th Century using measured increase in CO2: ______ measured ______ al Change: 34 34 (°C) Global climate change • General circulation models: 3-D models of Earth’s climate system based on weatherforecasting models predict future temperature change 2x pre-industrial 2x CO2: CO _________ global warming al Change: 35 35 Global climate change • Possible consequences of global warming Possible 1. Changes in precipitation & vegetation patterns 1. vegetation 2. ________ storminess 2. ________ Map views al Change: 36 36 Fig. 23.23 Global climate change 3. ________ length of growing 3. ________ season. season • Consequences of global warming warming +11.5% -20% 4. _________ Arctic snow cover & 4. _________ Arctic sea-ice extent sea-ice -30% al Change: 37 37 Ruddiman (2001) Global climate change Ruddiman (2001) • Consequences of global warming global 4. _________ Arctic snow 4. _________ cover & sea-ice extent sea-ice -6% View of Arctic Ocean and North Pole Fig. 23.21 al Change: 38 38 Global climate change • Possible effects of global warming Possible 5. M elting of glaciers & ice sheets --> _____ sea level 5. _____ sea Fig. 23.21 1941 Fig. 23.24 al Change: 39 39 M uir glacier: 12 km retreat 2004 Global climate change • Other considerations Other 1. Oceans may absorb additional CO2. 2. I ncreased evaporation --> ________ cloudiness --> decreases? temperature 2. ________ cloudiness Ruddiman (2001) al Change: 40 40 Review Questions 20-1. Earth became differentiated into concentric layers during the _______ eon. A. Archean B. Hadean C. Proterozoic D. Paleozoic 20-2. A. True / B. False: The heat responsible for the Hadean lava ocean and differentiation of the Earth was derived from collisions during and after the formation of the Earth and decay of radioactive isotopes. 20-3. Oxygen in Earth’s atmosphere is derived from ______. A. volcanic outgassing B. photosynthesis C. animal respiration D. ocean water breaking down into hydrogen and oxygen during evaporation 20-4. Pangaea is a supercontinent that assembled during the _______. A. Archean B. Hadean C. M esozoic D. Paleozoic 20-5. Which is the oldest mountain range? A. Alps B. Appalachians C. Himalaya 20-6. A. True / B. False: North America and Africa were the last continents to separate during the breakup of Pangea. 20-7. The Chicxulub crater is located in which continent? A. North America B. Asia C. South America al Change: 41 41 D. Africa Review Questions 20-8. An iridium-rich layer of clay, glass spherules, and shocked quartz grains indicate that the K-T mass extinction was at least in part caused by ____. A. a long trend of global warming B. a long trend of global cooling C. worldwide explosive volcanism D. the impact of an asteroid or comet 20-9. Which is not evidence supporting an asteroid impact at the K-T boundary. A. fern-spike in Tertiary rocks immediately above the K-T boundary B. lava flows of the Deccan traps dated at 65 million years ago. C. melt rocks from within the Chicxulub crater dated at 65 million years ago. D. very abrupt extinction of numerous life forms in the very last part of the Cretaceous period. 20-10. Which of the following statements is most correct? A. Cretaceous/Tertiary extinction was most likely caused by a rise in sea level. B. I ridium is relatively abundant in the Earth's crust. C. M ammals evolved after the dinosaurs became extinct at the Cretaceous/Tertiary boundary. D. Permian/Triassic extinction was the largest known mass extinction event in the last 500 million years. 20-11. A. True / B. False: CO2 levels in the atmosphere are higher now than at any time in the past. al Change: 42 42 Review Questions 20-12. Which of the following processes removes CO2 from the atmosphere? A. burning of fossil fuels B. exhalation by animals C. photosynthesis D. volcanism 20-13. A. True / B. False: Humans are the only biological agents responsible for adding CO2 to the atmosphere. 20-14. Which of the following processes releases carbon dioxide to the atmosphere? A. burning of fossil fuels B. photosynthesis C. weathering of rocks 20-15. Which of the following is not a possible effect of global warming? A. changes in vegetation patterns B. decreased storminess C. melting of glaciers & ice sheets D. rising sea level 20-16. Which of the following is not an example of unidirectional change? A. area of continental crust B. assembly and breakup of supercontinents C. evolution of life forms D. oxygen content of atmosphere 20-17. Which of the following is not an example of cyclic change? A. assembly and breakup of supercontinents B. growth and retreat of ice sheets C. biologic evolution D. rise and fall of sea level al Change: 43 43 ...
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