earth's atmosphere and how its changed. Flashcards
how has the gases in the atmosphere changed from the beginning to now?
decrease in carbon dioxide and other gases - increase in oxygen and nitrogen.
further decrease and increase of the gases.
key factors that affected the earth’s atmosphere at the beginning and what was the effect?
intense volcanic activity which released:
mainly carbon dioxide
water vapour which condensed to form the seas.
small proportions of methane and ammonia.
nitrogen, gradually built up.
what happened in the middle stage of the making of the modern earth’s atmosphere? plants and organisms . rocks and shells. gas reduction or increase?
green plants and algae evolved and:
carbon D reduced; plants took it in and released oxygen.
microorganisms that can’t tolerate oxygen got killed off.
carbon from carbon D locks up in sedimentary rocks formed from the shells and skeletons of marine organisms.
other gases react with oxygen to release nitrogen.
nitrogen produced by bacteria removing nitrates from decaying plant material.
what is the last step in the making of the modern atmosphere in terms of gases?
20% oxygen and 80% nitrogen in atmosphere.
amount of carbon dioxide has decreased significantly.
how long have the proportions of gases in the atmosphere have been more or less the same?
200 million years.
