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Chapter 20

Chapter 20. The Holocene. Guiding Questions. Did Earth move directly from the last glacial maximum to the present glacial minimum? Did species that form modern plant communities evolve together? Have climatic changes been gradual during Holocene time?

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Chapter 20

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  1. Chapter 20 The Holocene

  2. Guiding Questions • Did Earth move directly from the last glacial maximum to the present glacial minimum? • Did species that form modern plant communities evolve together? • Have climatic changes been gradual during Holocene time? • When did humans migrate from Eurasia to North America?

  3. Present 11,600 ybp

  4. End of the Ice Age • Glaciers began to retreat around 15,000 years ago • Waters drained to lakes • Sea level rose • Tundra shifted northward • Deciduous trees migrated northward

  5. Younger Dryas • 14,680 years ago • Climates warmed in a decade • 13,000 years ago • Rapid cooling • Younger Dryas • Lasted through 11,600 years ago

  6. Global Warming • Terminal moraine • Southern New Zealand during the Younger Dryas cooling event

  7. End of the Ice Age • Prairie potholes • Depressions formed from remnant mounds of ice

  8. End of the Ice Age • Vegetation changes occurred • Southern floras were very different than today • Trees species shifted at different times • Led to changes within communities

  9. End of the Ice Age • Corals provide gauge for sea level changes • Acropora palmata • Grows with sea level • Radiocarbon, U-Th determined timing • Corrected for tectonic change

  10. Migrations • Humans colonized North America • Clovis people • Approximately 11,000 years ago • Relied on elephants · Woolly mammoth · Mastadon - Tundra - Eastern forests - Small ears, short trunk - Curved molars

  11. Migrations • Clovis hunters • Fluted spear point

  12. Mass Extinction • Large mammal extinction • 12,000–10,000 years ago • All three American elephants • Large beavers • 5 species of horses • North American camel • Giant ground sloths • Giant armadillos • La Brea tar pits • Preserved fauna

  13. Climate change Rapid change Younger Dryas Habitat change Grasslands changes to prairies Overkill hypothesis Human hunting may have led to a mass extinction of large mammals Mass Extinction

  14. Agriculture • Hypsithermal Interval • 9000–6000 years ago • 2°C warmer than today • Agriculture developed • Zagros Mountains • First site • Greek islands • 8000 years ago • Europe • Northern Europe • 6000 years ago

  15. Climate Fluctuations • Tree rings • Non-tropical areas • Annual rings • Bristlecone pine • 4600 years old • Methuselah

  16. Climate Fluctuations • Cooling: cold intervals • 5800–4900 years ago • 3300–2400 years ago • 900–700 years ago • Medieval Warm Period • Viking expansion

  17. Climate Fluctuations • Little Ice Age • Glaciers expanded • Short summers • Ended ~1850

  18. Climate Fluctuations • Droughts also occurred • Dunes • Pine tree rings

  19. Sea Level • Coastlines changed • Glaciers retreated • Lithospheric rebound • Great Britain • Coasts uplifting

  20. Sea Level • Subsidence • Peripheral bulge • Produced by nearby glacier • Southern Great Britain • Northeastern US

  21. Sea Level • Transgression • Lagoonal complexes transgress over coastal plain sediments • New Jersey • Regression • High sediment supply is causing coast to move offshore • Texas

  22. Global Warming • CO2 has increased since the Industrial Revolution

  23. Global Warming • Temperatures have increased • Models predict continued increase in temperature • Increase depends on CO2 concentrations

  24. Global Warming • Warming leads to glacial melting • Mt. Kilimanjaro, 1993 and 2000

  25. Global Warming • Many impacts • Migration • Change in precipitation • Desertification • Changes in plant communities • Sea level change

  26. Global Warming • Sea level may rise 50 cm by 2100 • Antarctic ice cap may expand from increased snowfall • Or ice cap may collapse

  27. Global Warming • Would also flood wetlands • Normally marsh would migrate with coastal change • Blocked by barriers

  28. Global Warming • Flooding in Venice • 1990

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