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
- 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