31 The Changing Face of the Earth

1. 31 The Changing Face of the Earth Before After Flooding of Mississippi & Illinois Rivers 1993 PS 100 -- Chapter 31

2. At which type of plate boundary would you expect to find large, deep focus earthquakes, but no volcanoes? • Continent-continent collision boundary • Continental rift boundary • Transform boundary • Ocean-ocean collision boundary PS 100 -- Chapter 31

3. What is a Natural System? • Group of natural, interdependent parts or components • Interactions between parts forms the system • Forces drive the system • All systems tend toward a state of maximum disorder (entropy) called equilibrium • Earth’s two major systems are: • Hydrologic System • Tectonic System PS 100 -- Chapter 31

4. System of moving water Rivers Oceans, Lakes Glaciers Groundwater Water Vapor in Atmosphere Effects of Hydrologic System Erosion Transportation of Sediment Deposition of Sediment Creation of Numerous Landforms Hydrologic System PS 100 -- Chapter 31

5. Hydrologic System PS 100 -- Chapter 31

6. Where is Water Found in the Hydrologic System? 97% PS 100 -- Chapter 31

7. What Forces Drive this System? • Solar Radiation • Average ~342 W/m2 = ~342 joules/sec m2 • Causes evaporation • Gravity • Pulls water down slopes • Causing erosion, transportation of sediment PS 100 -- Chapter 31

8. Subsystems of Hydrologic System • River Systems • Glacial Systems • Groundwater Systems • Ocean/Shoreline Systems • Desert Systems PS 100 -- Chapter 31

9. Rivers • Primary mechanism for erosion • Move sediment from mountains to oceans • Also carry dissolved ions (salts) • Can be easily disturbed by human activity • Dams • Pollution • Irrigation PS 100 -- Chapter 31

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12. Glaciers • Rivers of Ice • Very effective agents of erosion • Carve different topography than rivers • Many glaciers are currently shrinking due to global warming PS 100 -- Chapter 31

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14. 2004 1875 Pasterze Glacier, Austria PS 100 -- Chapter 31

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16. Groundwater • Rocks can hold a lot of water! • Porosity • Permeability • Groundwater is a major source of drinking and irrigation water • Groundwater is often affected by human activity • Overpumping • Pollution • Irrigation PS 100 -- Chapter 31

17. Water Table PS 100 -- Chapter 31

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21. Oceans & Shorelines • Beautiful, but changeable • Shorelines are places of active… • Erosion • Transportation • Deposition • Human activity can have a significant effect on shorelines PS 100 -- Chapter 31

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23. PS 100 -- Chapter 31 NASA

24. PS 100 -- Chapter 31 Smiley Pool, Dallas Morning News

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26. 17 July 2001 17 Sep 2004: After Ivan 31 Aug 2005: After Katrina PS 100 -- Chapter 31 Dauphin Barrier Island: Alabama National Geographic

27. Barrier islands and wetlands No barrier islands or wetlands: Effects of artificial subsidence & sea level rise PS 100 -- Chapter 31 National Geographic

28. Deserts • Dominated by wind • Carries light-weight particles (sand & dust) • Leaves the rest behind • Human effects • Desertification • Overgrazing • Poor Farming Practices • Destruction of Soil • Irrigation adds salts PS 100 -- Chapter 31

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31. Climate Change • All of these systems are affected by the changing climate • Earth’s climate changes naturally over time • At times in the past the Earth has been much cooler and at other times much warmer • Human activity can speed up the rate at which these changes occur • Pollution • CO2 and CH4 can help hold heat around the Earth • Particulates (dust and smoke) can reflect sunlight and lead to cooling of the Earth PS 100 -- Chapter 31

32. What is Earth’s Past History?How do we know? PS 100 -- Chapter 31

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34. What Causes Climate Change? • Amount of Solar Radiation Reaching the Earth • Milankovich Cycles • Distance of Earth from Sun (100,000 yr cycle) • Tilt of Earth on its axis (41,000 yr cycle) • Precession of Earth on its axis (23,000 yr cycle) • Amount of Solar Radiation Trapped in the Lower Atmosphere • Greenhouse Effect • Carbon Dioxide • Methane • Water Vapor PS 100 -- Chapter 31

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38. What is the evidence that Earth is warming up? PS 100 -- Chapter 31

39. ICE CORE DATA PS 100 -- Chapter 31

40. Recent Sea Level Changes PS 100 -- Chapter 31

41. Possible Human Effects on Climate • Declining CO2 trend reversed 8000 years ago • Correlates with clearing of European forests & beginning of rice cultivation • Declining CH4 trend reversed 5000 years ago • Correlates with flooding of lowlands and beginning of rice cultivation PS 100 -- Chapter 31

42. Should we do anything? PS 100 -- Chapter 31

43. Geologic record indicates that past sea level changes when polar glaciers melt have been hundreds of meters. The cost would be catastrophic. PS 100 -- Chapter 31

44. Risk, Cost, & Benefit • Cost of reducing greenhouse emissions will certainly be billions of dollars • Certainty of global warming is not 100% • Current predictions depend on imperfect models • Environmental and economic consequences could be truly catastrophic • Some say global warming could cause the end of technological civilization • As voters & consumers, these are your issues PS 100 -- Chapter 31

45. Climate change is caused mainly by changes in the balance between the amount of solar radiation received and the amount of heat radiated back into space by the Earth. • True • False PS 100 -- Chapter 31