Earths Early Atmosphere VS Today

EARTH'S EARLY ATMOSPHERE(approx 4.6 billion years ago): - large amount of carbon dioxide - little or no oxygen - small amounts of other gases (ammonia and methane..) Volcanic activity also released water vapour, which condensed(as earth cooled) forming the oceans. Nitrogen was probably released too & gradually built up in the atmosphere as its unreactive. EARTH'S ATMOSPHERE TODAY: - Nitrogen: 80% roughly - oxygen: 20% roughly - Other gases (CO2, water vapour, noble gases...): the rest