yes, but those processes are still going on today with the addition of pollution, agriculture, etc etc. think of it this way, before man wielded fire, some million years ago or so... there were volcanos, crap falling from space, forest fires and thats about it, putting crap in the air.
so ever since man began to controll fire, basically the world has been burnt over and over, for a million years. now theres heaters, fires, nukes, factories, cars, 5 billion or so more farts, billions more cows, tractors, oil rigs, planes, frekin spaceships, etc etc and still volcanoes, forest fires, crap form space... so it is adding up real fast.