why isn't the ozone layer the sixth layer in the atmosphere?

Answer 1

Ozone is in all layers of the atmosphere. Ozone in the stratosphere helps protect earth and more importantly life on earth from the suns UV death rays. The ozone layer or cloud is very thin but moves around like water vapor and water vapor clouds, but unlike water clouds, you can not see them.
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Answer 2

cos of so much carbon monoxide in the atmosphere.