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GEOL 208 Lecture 4

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GEOL 208 Lecture 4

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  1. Geology 208: The Earth, Moon and Planets Today a. Climate change: Strahler (Canadian ed.) chap. 5: 122-130 b.Glacial processes & landforms: Strahler (Canadian ed.), chap.20: 593-621 Next class (May the 21st) Quiz # 1 (18:30): please be in your seats by 18:20 “Global Climate Change”

  2. 1. Global Climate Change on Earth • 2. A Planetary Perspective: • Mercury • Venus • Mars • 3. Back to the Future: Earth

  3. Global climate change on Earth • Breakup of Antarctic ice-bridge! • - 2003: Europe, hottest summer on record • 1990s hottest decade on record • - 1999: Earth’s mean surface temperature 5th highest since mid-1800s • Each of the last 9 years (1998-2007) amongst 25 hottest on record • - 2006 (warmest year in century); 2007 & 1998 (second warmest) • - 1998: may have been warmest year of the last 1200 years • 20th century, warmest in millenium • temps. since 1976 have risen 3x faster than in previous 76 years • spring in the northern hemisphere arrives 6 days earlier than in 1959 • longer growing seasons in Europe • leaf unfolding 6 days earlier 6/3/2014 3

  4. Global climate change on Earth California dry 4 6/3/2014 4

  5. Global climate change on Earth Temperature rises and desertification

  6. Global climate change on Earth Temperature rises & ice melt 6

  7. Global climate change on Earth …global thaw… 6/3/2014 6/3/2014 7 7 7

  8. Global climate change on Earth …sea-level rise 6/3/2014 6/3/2014 8 8

  9. http://www.thetechherald.com/media/images/200820/465pxHurricane_Katrina_August_28_2005_NASA_top.jpghttp://www.thetechherald.com/media/images/200820/465pxHurricane_Katrina_August_28_2005_NASA_top.jpg Global climate change on Earth Hurricane Katrina New Orleans under water (post-Katrina) Extreme events, seemingly more frequent/severe than in the past? 6/3/2014 6/3/2014 9

  10. Global climate change on Earth Through geological time the climate of the Earth has oscillated naturally between periods of relative cold & relativewarmth temperatures 6/3/2014 10

  11. “Icehouse” Earth • Pre-Cambrian Eon: 850-630 mya • except for areas around volcanoes, the entire planet was frozen - 11 6/3/2014

  12. “Ice-age” Earth During the last 0.8 - 0.9 million years, 8 major cycles have occurred, each of them 100,000 years in length  20,000 years ago, much of N. America, N. Europe & Asia were under kms of ice  maximum extent - 27% of the land mass on Earth - sea-level = 140 m below present 2014-06-03

  13. Global climate change(mini-cycles) Superimposed on the “grand cycles” are shorter / more frequent “pulses”lasting 500 to 1000 years  Greenland - discovered by Gunnbjorn in 876 or 877 - colonised in 983  - named because of its lush, green appearance Black Death (1347-1351) (not climate change) decimated the colony today, the land is green (not covered by glaciers), only around it margins http://www.eadelaide.com/gregmainhome/greenland/lowres /

  14. Global climate change(mini-cycles) Holland (15th - 18th century) -------------------- portraits of the Dutch skating on their canals and of Hans Christian Anderson, point to recent cool temps. e” http://www.antiquemapsandprints.com/SCANSB/b-1388.jpg

  15. Ice sheets Mass of perennial ice (i.e. the Antarctic) that covers an area ≥ 50,000 km2

  16. Ice caps • 7th largest island in Canada • 31st largest island in the world Mass of perennial ice (Muller ice cap, ~600 m thick, Axel Heiberg Island) that covers an area ≤ 50,000 km2

  17. Glaciers (Axel Heiberg) Smaller mass of perennial ice(Thompson, White Glaciers, Axel Heiberg Island) White Glacier (left) - receding Thompson Glacier (right) - advancing

  18. Ice shelves Ross Ice Shelf,Antarctica Thick floating platform of ice that forms where a glacier or ice cap flows down to a coastline and then onto the ocean surface

  19. Ice shelves Larsen B ice-shelf collapsed/disintengrated in 2002 - climate change an important variable -

  20. Ice calves …the breaking off of a mass of ice from its parent, i.e. ice -sheet, -shelf, -cap, glacier 6/3/2014 20

  21. Icebergs …the mass of ice that has broken away from its parent, i.e. ice -sheet, -shelf, -cap, glacier - ~1/7 (14%) of their mass is exposed (pure ice less dense than water) 6/3/2014 21

  22. Valley Glaciers • flows principally by gravity • constrained by topography • accumulation (upslope) / ablation (downslope) • surrounded by moraines

  23. Valley Glaciers • zone of accumulation (new snow) • material added • zone of ablation • ice lost by melting & evaporation ablation - loss from melting and evaporation

  24. Moraines unconsolidated glacial debris (soil & rock) - plucked off of valley floors or fallen from valley wall -

  25. Medial moraines converging ice-streams

  26. End & lateral moraines

  27. “Hothouse” Earth Anaconda vertebrae on left • South America (60 mya) • Titanoboa cerre jonennsis • 13 m (length), 1135 kg (weight) • avg. temp = 330 C (60 C warmer than today) 6/3/2014 6/3/2014 27 27

  28. Global climate change on Earth 6/3/2014 28

  29. Global climate change on Earth • Temperature change (North America) • steep rise since Industrial Revolution • accompanied by steep rise in CO2 emissions & atmospheric concentration • enhanced “Greenhouse Effect” 6/3/2014 6/3/2014 6/3/2014 6/3/2014 29 29 29

  30. Global climate change on Earth Sun emits short-wave radiation (insolation) • Natural greenhouse effect • Accumulation of heat (non-anthropogenic) due to the presence of CO2, water vapour, methane in the lower atmosphere (troposphere) •  • “absorption” at the Earth’s surface & re-radiation of longwave radiation from the Earth’s surface • natural state (mean) global surface temp = 150C, otherwise cooler by 180C 2014-06-03 30 6/3/2014 30

  31. Global climate change on Earth Enhanced greenhouse effect - increased atmospheric absorption of longwave radiation due to (anthropogenic) presence of CO2, water vapour, methane and CFCs in the lower atmosphere (troposphere) -------------------------- Sources a. combustion of fossil fuels b. permafrost thaw c. pig flatulence, etc. albedo changes play important role in this process(positive feedback) - i.e. ice melt…sea/ocean water - 2014-06-03 31

  32. Global climate change Albedo reflective quality of a surface… …expressed as the % of reflected incoming solar radiation (insolation) -100% is total reflectance-  a.   a function of surface colour b. angle of incidence (lower angles  reflection) c. surface texture (smooth surface reflection) fresh snow more reflective (80 - 95%)…than asphalt (5 - 10%)

  33. Global climate change(celestial mechanics?) http://www.globalchange.umich.edu/globalchange1/ current/lectures/samson/climate_patterns/milankovitch.jpg http://web.uvic.ca/~rdewey/eos110 /images/large/milankovitch.jpg Milankovitch Cycle 1. eccentricity; 2. obliquity; 3. precession of the equinoxes

  34. Global climate change on Earth Much ado about something...? ...on a cosmological scale!

  35. The Solar System 8 planets = 4 gas giants ; 4 terrestrials

  36. The terrestrial planets x x x Three of them (x) could have been (were?) habitable 4 gya

  37. Mercury Myth - Messenger, God of trade, profit & commerce Planet - bleak and barren

  38. Mercury • scarred by craters; brushed by volcanic flows; thin atmosphere • max. daily temperature = (+) 4670 C • min. daily temperature = (-) 1830 C • - Lifeless -

  39. Venus • Myth • Goddess of love & beauty • stirred passions amongst the gods • Planet • - mysterious, veiled by thick clouds

  40. Venus: atmosphere Greenhouse Trap - much less escape to space than on Earth

  41. Venus: atmosphere dense, acidic, hot

  42. Venus A global ocean- 4m deep - is thought to have covered the planet (4gya)

  43. Venus • Today, • no trace of an ocean exists • max. daily temperatures (global) = (+) 4640 C • atmospheric pressure = ~100x that of Earth • 50,000 small volcanoes, 160 ≥ 100 km (in diam.) • thick clouds full of sulphuric acid • Lifeless-

  44. Mars • Roman God of war: “Protector of all Romans” • Warrior in full battle armor, • wears a crested helmet, bears a shield • son of Jupiter and Juno • Ares (Greek equivalent) vain, cruel, delighted in the slaughter of men

  45. Built structures & water? • Giovanni Virginio Schiaperelli (1835-1910) • - network of linear markings seemed to join dark areas… “canali” • “It is as impossible to doubt their existence as that of the Rhine on the surface of the Earth” • notes changes in dark areas • - argued that seas intermittently flooded surrounding landscape 6/3/2014 45

  46. Canals? Percival Lowell (1890s) - sketched canals, identified oases… - many astronomers sceptical • William Campbell (1894) • used spectroscope to study martian atmosphere… …found no water! No water…no life?! 6/3/2014 46

  47. Water marks? Yemen’s desert, coastal mountains, water long past http://wapi.isu.edu/geo_pgt/Mod09_Mars/images/MARSDRAINAGE.GIF Widespread evidence of flow …but where has the water gone? 6/3/2014 6/3/2014 47

  48. Water marks? Canadian Arctic Mars carved (fluvial) channels, linking craters (possible paleo-lakes) 48

  49. Mars Mars,like Venus,is thought to have been covered (at least in the northern hemisphere)by water...early in its history ...but no longer!

  50. Mars: atmosphere dusty, cold & atmospherically sparse 6/3/2014 50

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