These bacteria, algae, and other plants produce oxygen by photosynthesis. Cyanobacteria were responsible for the rise in the atmospheric concentration of oxygen beginning 2.3 billion years ago. Living things created much of the third atmosphere, the one that now exists on Earth. Oxygen existed in only trace quantities before life began. They do not react with water or other atmospheric components. The nitrogen and argon accumulated in the atmosphere. Chemical and biological processes transformed CO 2 gas to carbonate rocks. Bodies of liquid water acted as sinks for carbon dioxide. Over a period of thousands of years, the liquid water accumulated as rivers, lakes, and oceans on the Earth's surface.
This produced the second atmosphere.Ĭomet impacts may have increased the amount of water. Volcanic activity in the early, Earth created major changes with release of water vapor, carbon dioxide, and ammonia along with small quantities of SO 2, H 2S, HCl, N 2, NO 2, He, Ar, and other noble gases. More water may have arrived with comets colliding on the surface of the planet. Over time, some of this first atmosphere, particularly the lighter gases, outgassed and was lost. There was no molecular oxygen or other reactive oxides. It consisted of hydrogen and helium, along with methane, ammonia, and water. Molecules in the Atmosphere Molecules in the AtmosphereĮarth's primordial atmosphere was probably similar to the gas cloud that created the sun and planets.