 |
 |
 |
 |
 |
 |
|
|
|
 • Basic Overview
Early Earth
Welcome to Earth...four billion years ago.
In Earth’s first four billion years—the time known as the Precambrian—life first evolved, flourished, and changed the planet forever.
The early Earth was a very different place.
The atmosphere contained mostly carbon dioxide, nitrogen, and water vapor. Most oxygen molecules were bound to other molecules, not free in the atmosphere. You could not have breathed.
High levels of carbon dioxide trapped the sun’s heat, creating surface temperatures of up to 120 degrees Fahrenheit. Meteorites bombarded the planet.
The first land and seas formed.
Volcanoes poured lava and released gases from deep inside the Earth. As the lava cooled, it hardened to form the first continents. Volcanic steam condensed into heavy rains, which accumulated into shallow oceans.
On this hostile Earth, how did life get its start?
Continue to Theories of Life’s Origin. >>
|
|
|
|
|
|
