SCIENTIST THINK THAT EARTH WAS CREATED ABOUT 4.5 BILLION YEARS AGO. IT'S EARLY ATMOSPHERE WERE FORMED (AS BELIEVED SO) FROM THE GASES GIVEN OFF BY VOLCANOS. THE VOLCANOS GAVE OUT CARBON DIOXIDE AND CARBON DIOXIDE AND WATER VAPOR.
VOLCANOS FORMED ON THE LAND MASS AND RELEASED GASES FROM THE EARTH'S INTERIOR THROUGH VIOLEN ERUPTION
AS THE EARTH COOLED DOWN MOST OF THE WATER VAPOR CONDENSED AND FORMED THE OCEAN. THE WATER CAME FROM MELTED COMETS THAT LANDED ON EARTH. THE MOLTEN MATERIALS COOLED AND FORMED LAND MASES
THYE FIRST ORGANISMS IN THE OCEANS BEGAN TO FORM THEY DID NOT USE OXYGEN TO BREATH AS THERE WAS NO OXYGEN. THEY THEN WENT ON TO PHOTOSYNTHENSIZE. BY TAKING CO2 OUT OF THE AIR AND ADDING O2
Algae first evolved around 2.7 billion years ago and during the next billion years or so small green plants began to appear and then animals due to the livable conditions that have led to the atmospher now hving 78% nitrogen and 21% oxygen and 1% other gases