Human earth shapers/ETHS101/Earth Systems Exchange/System Exchange

=System Exchange - The first earth shaping =

Early Earth's atmosphere and oceans would have been toxic to us. There was no free O2. Archaea are a branch of life that can tolerate extreme conditions. They were probably widespread at this time. They are still with us today, but tend to hide away as oxygen is toxic to many of them. Because they can live in hydrothermal vents, geysers and hot springs where the fluids are as acidic as battery acid and temperatures are between 60 and 100 degrees Celsius, they are called extremophiles. They are what astrobiologists look for on Mars.

The rise of free oxygen in the Earth's oceans and atmosphere was caused by another micro-organism. It was cyanobacteria which consume CO2 and expel oxygen and eventually changed Earth's environment into a habitable planet for all the life that evolved after. As the oceans became saturated in oxygen, oxygen could escape into the atmosphere. It is estimated that around 2.4 billion years ago there was an event called 'The Great Oxygenation Event', that marks the rise of atmospheric oxygen. Here is an example of the biosphere changing the environment and probably precipitating the first mass extinction of micro-organisms

Feedback in systems
The exchange of material, and in particular, the exchange of carbon, between the biosphere, hydrosphere and atmosphere, is critical for maintaining a habitable earth. This page explores some of the important exchanges between earth's carbon reservoirs, and introduces the concept of feedbacks in the earth system