500million years ago earth was a dry planet without no living gases or moisture in its's atmosphere used to contain lot  HCl.  after lot of collisions of comets meteriods with earth an un even surface is formed on it. later  volcanic eruptions an other disasters moisture formed in atmosphere. slowly rains were started but they are acidic rains. later due to water cycle process water and atmosphere are purified and developed. plants and other creatures are formed.this is the story about the evolution of the earth

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ha thanks
phani not hcl it is h2s
acid rains ra
500million years ago eart used to be like a ball of that time there was alayer of ahydrogen sulphide gas which is a very poisonous gas. the climatic condition at that time was very horrible.all the volcanoes eruptd for a lot of time and then it woul rain foir years clearing the molten lava.then organisms started to exist on the that time the homo sapiens didnot know how to cook they would eat what all they got.then slowly the evolution took place .man started to learn how to cook and invent machines