Back

ATMOSPHERE
Lesson 5 - Page 1

Next 

 POLLUTION OR JUST EVOLUTION

The atmosphere on Earth has evolved during its last 4.5 billion years of existence. The early Earth was probably an accretion of cool particles, possibly composed of compounds of silicon, iron, and magnesium. The particles compacted and eventually produced heat internally. The early atmosphere may have been hydrogen and helium, but it would have been lost quickly into outer space. Therefore, the Earth was devoid of an atmosphere.

The early Earth had no oceans. Life was not even a possibility. The rocks on Earth have only witnessed the last 3.5 billion years, so we can only speculate on the early atmosphere.

The beginning of a permanent atmosphere would have formed by outgassing of volcanoes. This refers to the release of gases trapped in the interior of the early Earth. The oceans may have started to form about 1.5 billion years after the formation of the Earth. The early atmosphere was not preserved. Gases produced were probably similar to those created by modern volcanoes (H2O, CO2, SO2, CO, S2, Cl2, N2, H2) and NH3 (ammonia) and CH4 (methane).


Bombarding particles


Artist view of origin of atmosphere

   Back

[Back to Atmosphere]  [Back to Earth Science]

Next