Change of Earth's Environment Over Time

Short history of humans -> is now representative of before in Earth’s history?

• Homo Sapiens ~ 200,000 years ago
• Everything in book ~ past 10,000 years.
• Did we fuck up bad or are these natural disasters today natural?

Alfred Wagner: continental drift and Pangaea

• evolved into plate tectonics and crustal spreading
• periodic for billions of years
• split up ~ 180M years ago

Ocean and Atmosphere §

Formation of Ocean §

• 70% of Earth is water
• Water rose to surface after formation?
• Maybe from outer space
  • icy comets?
  • Elsa magic?

Formation of Atmosphere §

• don’t know how atmosphere was formed either
• CO${}_2$ absorbed by ocean + plants
• ~800M years ago atmosphere -> habitable

Fire and Ice §

Volcanoes §

• volcanic eruption -> ash -> mass depletion (loss of diversity through failure to produce new species) -> mass extinction (mass destruction of most species)
• recent mass volcanism was ~180-160M years ago
  • continental separation
• Pacific Ring of Fire: ocean-girdling zone of crustal instability, volcanism, earthquakes
  • trace of Pangaea separation
• 73,500 years ago: Mount Toba eruption -> destroyed much genetic diversity in humans

Ice Age §

• Ice Age -> greatest extinction
• usually accompanied by periods of heat
• Pleistocene Era deep freeze
  • long glaciation
    • permanent ice deep into landmasses in North
    • no habitat
    • 100,000 years
    • Wisconsin Glaciation most recent
      • smart humans survived
      • tools in hunting/fishing/gathering communities + language
  • short, warm interglaciation
    • ~120,000 years ago -> humans
    • Holocene after Wisconsin
    • Global warming ~18000 years ago
      • Mud floods across Mississipi Valley -> delta

Little Ice Age §

• 14th century
• cold
• decreased rainfall
• winds
• shortened growing seasons
• stormy seas
• advancing glaciers in Greenland and Iceland
• famines in Europe
• ended in 1850
• just minor glaciation

Impact on Humans §

• humanity almost fucked
• famines in Europe
• Mongols thrived -> dynasty in China and empire
  • brought Black Death to weakened Europe

China §

• huge fleet under Ming empire
  • 315 ships
  • 27000 people
  • hella trade, almost everywhere
• eventually fucked by Little Ice Age
  • no rain -> famine
  • ships had to stop

Tambora §

• destroyed islands
• debris over entire Indonesia
• global famine