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Our Changing World . 2.5. Our Changing World. Earth’s daily rotation is easily visible in the light Weather changes are obvious with lightning and snow/rain Water cycle can be seen in action (evaporation, condensation, cloud formation, etc.)

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our changing world1
Our Changing World
  • Earth’s daily rotation is easily visible in the light
  • Weather changes are obvious with lightning and snow/rain
  • Water cycle can be seen in action (evaporation, condensation, cloud formation, etc.)
  • Some of the biggest changes are happening so slowly that humans may never see them
changes in the earth
Changes in the Earth
  • Moving plates have kept the Earth’s surface in a constant state of change
  • Over 200 million years ago, Earth had a single landmass called Pangaea
  • Plate movement caused the landmass to break apart
  • Plate movement continues to change the position of continents and ocean borders
  • People cannot see this movement, but we can measure it
  • Rocky Mountains: stopped rising after shock waves stopped pushing the rock formations up
  • Half their height due to erosion
global climate
Global Climate
  • For most of Earth’s history, temps have been 5◦C-8◦C warmer than they are today
  • About 925 million years ago, periods of severe cold began known as ice ages
  • Ice ages produce enormous ice sheets known as glaciers across most of the planet
climate change
Climate Change
  • 18,000 years ago, nearly 1/3 of Earth’s land was covered with ice
  • The ice sheets altered the landscape by carving out hills and valleys, eventually melting to form lakes
  • Greatly affects species in the area and how they can thrive
measuring change
Measuring Change
  • Earth has existed much longer than people have been writing about it
  • Rocks provide the best record of Earth’s history
  • Most rocks form in layers as bits of gravel, sand, and mud pressed together
  • These are known as sedimentary rocks
  • These preserve a rough record of the past
  • Sometimes sedimentary materials trap living and dead animals and plants
  • These preserved traces or remains are called fossils
  • Fossils can show that animals from northern areas lived in southern areas during a past ice age
  • Rocks can provide fossil evidence of Earth’s past climate
proxy data
Proxy Data
  • Fossilized evidence that helps scientists understand past climate conditions
    • Cross section of rings in a tree trunk show growth
    • The width of rings show warm, wet, dry or cold
    • Growth rate of coral reefs reflect climate conditions
    • Trapped air (bubbles) in glaciers are analyzed by scientists to learn what the atmosphere was like
looking ahead
Looking Ahead
  • Studying Earth’s physical history teaches people many things
    • shows when and how Earth’s land, air, and water have changed
    • Shows the impact these changes have had on Earth’s life forms

Humans are now a major force shaping life on Earth

  • Pangaea
  • Ice Age
  • Glacier
  • Sedimentary Rock
  • Fossil
  • Proxy Data