Besides dust, lava, and rocks volcanoes also spew out gigantic amounts of CO2 into the atmosphere. In the early history of the earth volcanic activity was much stronger than today. Three to four thousand million years ago the atmosphere of the Earth contained an estimated 30 percent carbon dioxide (today it’s about 0.038 %), but almost no oxygen. This CO2 today is in the biosphere, in limestones and in fossil fuels.

Chapter 2