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Short-Term Environmental Changes

  • Easiest to understand because we can see them

  • Major impacts within seconds, hours, or days

Earthquakes

4.3 Understanding Rates and Scales of Environmental Change

  • Cause changes in the geosphere within seconds or minutes

  • People feel about 400 earthquakes per year, only about 100 cause damage

Volcanic Eruptions

  • Can last for hours, days, or weeks

  • Their effects take hundreds of years to be fully realized

  • Volcanic ash produces fertile soil

Landslides

  • Catastrophic failure of the ground’s stability that occurs in seconds to minutes
  • Can dam a stream and cause a lake to form
  • Signal the beginning of environmental changes that takes years to complete

Oil Spills

Long-Term Environmental Changes

  • Can happen in minutes, hours, or days
  • Oil becomes widely dispersed, evaporates, or accumulates on the ocean floor
  • Negatively affects animal populations

Floods

  • Occur within minutes or days

  • Floods disperse sediment that produce farmlands

  • Many processes take place at slow rates and require longer periods to accomplish significant changes
  • Earth is about 4.5 billion years old
  • Understanding Earth’s dynamic and evolving past is important to understand our present-day Earth

Evolution of the Atmosphere

  • Volcanism released gases (carbon dioxide and water vapor) that became Earth’s early atmosphere
  • Cyanobacteria started releasing oxygen 3.5 billion years ago, but it took another billion years for the oxygen levels to increase in the atmosphere
  • About 600 million years ago, the oxygen levels reached about what it is today

Origins of Oceans

Scales of Environmental Change

  • Earth was not covered by oceans in its earliest stages of development
  • Volcanic activity released water from the geosphere into the atmosphere where it could be precipitated on Earth’s surface
  • First ocean formed about 3.5 BYA

  • Environmental changes can affect a pond, river, ocean, or a continent

  • Changes are interrelated

  • Ex. volcanic eruptions, mercury in the environment, and eroding farmland

Evolution of Life

  • Biosphere started with very simple, single celled organisms
  • Multi -celled organisms happened about 3 BYA
  • About 600 MYA life started to become very diverse

Assembling Continents

  • Large continents formed between 2.3 and 3 BYA
  • Plate tectonics cause continents to collide, split apart, and collide again
  • Some collisions aggregate all the continents in to supercontinents

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