20_globalchange_09_post - 20: Global Change Global Change:...

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Unformatted text preview: 20: Global Change Global Change: Definitions • Earth system: global interactions of the lithosphere, hydrosphere, atmosphere, and biosphere • 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 Global Change: 1 Global 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. Hadean: Hell on Earth • Lava ocean--produced by heat from… Plate, p. 26-27 Fig. 13.4 • Differentiation: dense material sinks, light Differentiation: material rises; forms concentric shells Fig. 23.3 Global Change: 3 Global Change: 4 4600-3800 mya Archean formation of atmosphere & oceans 3800-1600 mya Archean: formation of crust • Subduction --> island arcs; collisions --> early continents • Role of volcanic outgassing… outgassing… • Composition of early atmosphere: methane (CH4), H2O, ammonia (NH3), H2S, CO2 Fig. 13.5 Global Change: 5 Global Change: 6 Archean: formation of crust Archean: first life • Continental crust cannot be subducted; continents grow in size through time <0.5 Older core (craton) surrounded by (craton) younger rocks; ages are in billions of years >2.5 1.9 Bacteria in 3.2 billion-year-old chert from South America 1.8 >2.5 <0.5 1.8 1.6-1.7 Fig. 13.10 1.1 <0.5 Fig. 13.6 Fig. 13.7 Global Change: 7 Global Change: 8 Proterozoic: atmosphere 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 Fig. 13.12 Fig. 13.13 • Role of life… life… Fig. 23.5 • Banded iron formations (BIFs) – Fe dissolved in the (BIFs) ocean reacted with O2, forming worldwide FeO deposits. Global Change: 9 Paleozoic: tectonics Global Change: 10 Proterozoic supercontinent Paleozoic: tectonics • Subduction and collision produce… produce… Fig. 13.22 500-250 mya Appalachian orogeny: record of assembly of Pangea in eastern North America due to subduction and collision Pangea Fig. 11.39 Global Change: 11 Global Change: 12 500-250 mya Paleozoic: age of invertebrates 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. Which gas was not a significant component of Earth's early atmosphere? A. NH4 B. H2S C. CH4 D. O2 E. H2O Fig. 13.19 20-4. 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 20-5. The formation of continental crust is primarily related to ___. A. differentiation B. seafloor spreading C. subduction and collision 20-6. Pangaea is a supercontinent that assembled during the ____________. A. Archean B. Hadean C. Mesozoic D. Paleozoic 20-7. Which is the oldest mountain range? A. Alps B. Appalachians Global Change: 13 Global Change: 14 Mesozoic: Progressive breakup of Pangea C. Himalaya Mesozoic: superplumes Fig. 13.17 Fig. 13.25 Oldest: Jurassic (~200 mya) Global Change: 15 Fig. 13.28 Mesozoic superplumes yield high sea level, hothouse world--> Youngest: Tertiary (~60 mya) Global Change: 16 K/T Boundary Mass Extinctions 0 Ma Cenozoic: age of mammals Cenozoic: Cretaceous / Tertiary (K/T) 65 mya 100 Ma Start of Cenozoic: Tertiary (T) End of Mesozoic: Cretaceous (K) Fig. 13.26 200 Ma Mesozoic: age of reptiles Dinosaurs became extinct at 65 mya 300 Ma 400 Ma Fig. 23.14 500 Ma Global Change: 17 Fig. 23.4 Global Change: 18 K/T Boundary K/T boundary layer Age of mammals Tektites: glass spheres formed from rapid cooling of molten material no dinosaurs; other reptiles present 65 mya Age of reptiles mammals present • Mammals filled niches formerly filled by dinosaurs Shocked quartz: forms as a result of rapid increase and decrease in pressure, such as from a nuclear explosion Fig. 23.4 Global Change: 19 Global Change: 20 Impact Site K/T boundary layer Gubbio, Italy Alan Hildebrand, Glen Penfield, and others—1991: rediscovered it (using oil-exploration techniques) and linked it to K/T event Fig. D.13 H. Michel, F. Asaro, W. & L. Alvarez, 1980 Iridium anomaly: higher than normal concentration of Ir--not common in crust or mantle but common in Earth’s core… Fern spike: marked increase in abundance of fern pollen; ferns are first plants to grow after disaster Charcoal / soot Tsunami deposits Global Change: 21 Impact hypothesis: evidence cited here and hypothesis: previous slide indicates K/T extinction was caused by… by… Impact Processes 1 2 Carl Swisher et al: Chicxulub crater, Yucatan Peninsula, Mexico Crater diameter: ~180 km Asteroid diameter: ~10 km Energy released: equivalent to 1014 tons TNT. TNT. Global Change: 22 Killing mechanisms • “Nuclear winter”: material ejected into atmosphere blocked out sun… sun… Also: 3 4 1 2. After passage of shock wave, very abrupt decrease in pressure causes material to be blown out of crater 3 • direct blast and fire ball set off global forest fires • acid rain 1. Moment of impact causes massive, momentary increase in pressure 65 Ma--absolute dating of melt rocks • megaearthquakes & megatsunamis Fig. 13.30 4 2 3. Removal of ejected material causes parts of crater floor to uplift & later subside 4. Final state Global Change: 23 Global Change: 24 Fig. 23.14 Cenozoic: closing of Tethys Contributing factor? Massive eruption of basalts associated with mantle plume, Deccan Traps, India • Himalayas: • Alps: Krafla fissure eruption, 1977, Northern Iceland Fig. 13.31 Global Change: 25 Global Change: 26 Review Questions Cenozoic: ice ages 20-8. Which pairs of continents or land masses separated first during the progressive breakup of Pangea? A. Africa / North America B. Europe / Greenland C. Greenland / North America D. South America / Africa • Uplift of Himalaya and intensification of weathering: 20-9. Which pairs of continents or land masses separated last during the progressive breakup of Pangea? A. Africa / North America B. Europe / Greenland C. Greenland / North America D. South America / Africa 20-10. The Cretaceous-Tertiary (K-T) event took place ___ millions of years ago? A. 540 B. 245 C. 65 D. 25 Weathering reaction: CaSiO3 + CO2 —> CaCO3 + SiO2 Fig. 23.7 Global Change: 27 20-11. The Chicxulub crater is located in which continent? A. North America B. Asia C. South America D. Africa 20-12. 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 Global Change: 28 Review Questions 20-13. Which of the following is not evidence in support of 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. Global climate change • Biogeochemical cycle: describes movements & interactions of chemicals essential to life through atmosphere, biosphere, hydrosphere & lithosphere Fig. 23.7 20-14. Which of the following statements is most correct? A. Cretaceous/Tertiary extinction was most likely caused by a rise in sea level. B. Iridium is relatively abundant in the Earth's crust. C. Mammals 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. 20-15. A. True / B. False: CO2 levels in the atmosphere are higher now than at any time in the past. 20-16. A. True / B. False: As rates of chemical weathering increase, the amount of CO2 in the atmopshere increases. Global Change: 29 Global climate change • Greenhouse effect: trapping of longwave infrared radiation by certain gases (CO2, CH4, O3, N2O) in atmosphere causes atmospheric warming Carbon cycle Added to air Taken from air Global Change: 30 Global climate change • Changes in CO2 levels in the atmosphere: increased since Industrial Revolution, primarily from fossil-fuel burning Q1. 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% Global Change: 31 Global Change: 32 Percent increase since 1960: (370-315)/315*100% = 17.5% Global climate change Global climate change Q2. 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 Fig. 23.22 • From 1000 to 1900, global temperatures decreased by 0.15°C (but estimates are based on indirect data and have large error bars). Global Change: 33 Global Change: 34 Global climate change Global climate change • General circulation models: 3-D models of Earth’s climate system based on weather-forecasting models predict future temperature change • General circulation models: 3-D models of Earth’s climate system based on weatherforecasting models predict future temperature change 2x pre-industrial CO2: (°C) • Most warming is at… at… • BUT: Average model prediction for 20th Century using measured increase in CO2: Global Change: 35 Global Change: 36 Global climate change Global climate change • Possible consequences of global warming 3. Increased length of growing season. 1. Changes in precipitation & vegetation patterns 2. Increased storminess • Consequences of global warming Ruddiman (2001) +11.5% -20% 4. Decreased Arctic snow cover & sea-ice extent -30% Fig. 23.23 Global Change: 37 Global Change: 38 Global climate change • Consequences of global warming 4. Decreased Arctic snow cover & seaice extent Global climate change Ruddiman (2001) • Possible effects of global warming 5. Melting of glaciers & ice sheets --> Fig. 23.21 1941 Fig. 23.24 -6% Fig. 23.21 Global Change: 39 Global Change: 40 Muir glacier: 12 km retreat 2004 Global climate change Review Questions • Other considerations 20-17. Which of the following processes removes CO2 from the atmosphere? A. burning of fossil fuels B. exhalation by animals C. photosynthesis D. volcanism 1. Oceans may absorb additional CO2. 2. Increased evaporation --> increased cloudiness --> reduces increase in temp. Ruddiman (2001) 20-18. A. True / B. False: Humans are the only biological agents responsible for adding CO2 to the atmosphere. 20-19. Which of the following processes releases carbon dioxide to the atmosphere? A. burning of fossil fuels B. photosynthesis C. weathering of rocks 20-21. General circulation models with increased CO2 in the atmosphere predict the most warming: A. at low latitudes B. at middle latitudes C. at high latitudes 20-22. 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 20-23. 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 Global Change: 41 Global Change: 42 ...
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