why has the earths atmosphere composition changed from the ancitent composition?
439965
It first began after man sinned and eventually suffered the punishment of the worldwide flood during Noah's time which changed the earths weather patterns. Today, pollution and deforestation has added to the changes.
72511
the earth was at a stable orbit.  no  tilt or axis to cause differences in the seasons the earths temperature was just about uniform at 72 deg F.  the earth was at that tome also protected by the vapor barrier basically A thin shield of ice in the uper atmosphere that served 2 purposes it blocked out the harmful ultra violet radiation from the sun  and it increased the atmosphereic pressure to 2 atmospheres.\n\nthis caused things to live a lot longer and grow a lot bigger.  plants for one thing.  there is more coal on the earth right now then there are plants to produce it.  meaning if you were to take all the plants on earth right now and turn them into coal the pile of coal that you could make would be less than that currently available in the ground not including what has already been taken out.\n\nplanys grew much taller in this environment and so did reptiles lets take the crocodile.  a croc now a days can live about 100 years.  reptiles throughout thier life never stop growing.  so now you have an animal that in 100 years can grow to be about 15 feet long but instead you give it 900 years to grow.....presto you have a dinosaur.  \nthen a few thousand years ago an ice meteor crashed through the vapor barrier hitting the earth. this caused the barier to colapse and as it fell it began to melt and other various things and the world was covered in a great flood.  the earth finally settled back out into a somewhat normal rotation (you ever seen what happens to a gyroscope when you bump it)\n\nnow the earth has a 27.3? or is it 23.7 deg tilt to its rotation that causes us to have 4 seasons and tropics temperate zones and artic zones.\n\nBTW the earth is between 6000 and 10000 years old SCIENCE CAN PROVE IT.  if you want to know how just ask me.  i'll try to explane it as best as i can or you can wisit this website.  and do some reading\n\nall the SCIENCE is right there.
1165908
Good question. I never understood that, either. Maybe something to do with the government or the some atmosphere changes? I have no idea, really. Sorry.
522813
Definitively a lot of hot air goes up warming the atmosphere.\nAlot comes from certain party and politicians in that party. That definitively aids the  warming phenomena which is due to the changing tilt of the earth.\n\nOn the other hand polution cause the opposite effect . it cause solar diming  wich counteracts the global warming effect.So its a War between those with the hot air and those with particle polutants.\n\nAs far as biological life of animals and plant life it does not go back that far .Because it is the changing tilt of the earth(precession of the poles) that cause either global freezing or cooking.I dont think that evolutionary species like revolutionists could survice these extreme changes.\nThe complete poles precession was calculated by scientist and astronomers to have a cycle of 22,000 years.\n\nAs fAR AS DINOSORS ARE CONCERNED ITS NOT SURVIVAL OF THE FITTEST THAT MAKES THEM SURVIVE. it is the availability of nutritional food that allows them to survive. Besides there was a global flood in the history of the Globe. And that was only a short time ago.(poor Noah).So that anihilated some of the  animals who could not reach higher ground.\nThis bring the question whew did the oil in the ground come into being?\n\nAbout millions of years? there were writing that dated before the flood. and these people also exagerated about Time.The same is the case today . Dont believe those scientists who talk out of the top of their hats.Unless there is positive correct proof.
203325
The earth didn´t quite form from the sun. They were formed out of the same dust and gas cloud though. The planets can be considered as debris left over from the formation of the sun. The sun contains enough heavy materials to build many many earths.\n\nAll the planets had thick atmospheres with lighter elements in the beginning. The planets farther out had a greater mass and collected more. When fusion began in the core of the protosun huge amounts of energy began blasting all planets. Their atmospheres heated. Heat is kinetic energy inbetween atoms and molecules. That new motion made it possible for lighter elements to reach escape velocity. Mercury, being closest to the sun, quickly lost its atmosphere. \nVenus is much heavier but still couldn´t hold on to hydrogen and helium. \nThe same goes for earth where there is no primordial hydrogen left. Earth is heavy enough and far enough from the sun to retain elements heavier than 3 Us so there is He4 in earths atmosphere while He3 is virtually nonexistent. \n\nSo heavier gasses such as water vapor, CO2 and Nitrogen remained in earths atmosphere and its density was much like that of Venus, about 70 times denser as now. As earth cooled down water oceans formed that dissolved a lot of CO2. The CO2 then reacted chemically with hydroxides in the oceans to form carbonates. This process sucked alot of CO2 out of the atmosphere. Later lifeforms began using the same process to create protective shells and speeded up the process. \n\nBut the most devastating thing to the primordial  atmosphere was the event of blue green algea. They took up CO2 and produced oxygen as a waste product. Apart from being poisonous to the organisms that lived in the oceans at the time it is also highly reactive and immediately bonded with iron dissolved in the oceans. The ironoxides then settled on the bottoms of the oceans. It took 2 billion year for the oxygen to run out of iron to react with. Only then did it begin to build up in the atmosphere. \n\nOn earth geological processes return some of the gasses trapped from these chemical and biological processes. If it weren´t for them earth would hardly have an atmosphere today.
1175559
Saw an interesting program on this on the Science channel recently.  Basically scientists think it was because of a mega volcano that erupted that cause the first stage of the extintion.  Then world wide temperature rised 5 degrees and the methane in the bottom of the ocean evaporated and contributed to a super global warming and that raised the Earth's temperature another 5 degrees.  That was the most devastating extintion the planet saw and most of life on Earth and the Ocean died.
562236
Its earth and venus...the reason behind it is due to their some what similar size, mass of planet, rotation and revolution time and gases in some cases. hope so u satisfied with my answer.
186059
Climate would change dramatically due to the shift in solar energy focus from a loss of seasonal influence. The much more interesting point is the loss of magnetism, because the rotation center of the earth cannot parallel that of the magnetoshere and maintain magnetism. \n\nAtmospheric mixing would be different, global winds may change to more closely represent those observed on Jupiter, with banding rather than Rosby waves. Ocean currents begin to shift with wind pattern changes, species change migration routes, continental climates become more severe, and icing more prominent in the polar regions, shifting the balance of water storage and available energy absorption in lower latitudes. \n\nThink of an Antarctica on both poles with summer temps all the time within the lower 30 N and S. The reemergence of glaciers observed. Populations move to the equatorial regions. Economies change, agricultural production would be reduced, and fresh water supplies dwindle.
262988
Neat how the graph excludes prior dates.  20 years ago it was global cooling.\n\nThe temperature varies, greenhouse gasses come from natural occurrences (Krakatoa and Mt. Saint Helens spewed more greenhouse gasses in the air than man has produced in 10,000 years).  The earth recovers.  Liberal activists don't.
532654
Well Venus is much closer to the sun than we are so it is a lot hotter there... stuff that exists as a liquid here (water) would only be able to be a gas there due to the high temps. This also makes the atmosphere there much denser than ours. Not much sunlight would penetrate the thick atmosphere so there isn't any plant life to contribute oxygen to and remove carbon dioxide from the atmosphere the way plants do here.
780338
Oxygen = O\nNitrogen = N\nCarbon Dioxide = CO2\n\nThey take up the space that is allowed them by the gravity and temperature of the planet, but oxygen and nitrogen form the main two constituents of the atmosphere.
619711
The earth (and its chemical reactions) wasn't born until about 8 billion years after the Big Bang ... things had slowed down a bit by then.
406464
Yes.  There is a very small amount of matter that enters the atmosphere from space (meteorites), but essentially it is all just being recycled. Some atoms of oxygen you breathe in may have been breathed by a dinosaur, or one of the pharoahs!
263929
The gas is mostly sulphur dioxide not carbon dioxide. Check out the dust question the earth is being compressed more and more each day as extra terrestrial dust falls on it. Under the crust this pressure and the action of the sun and moons gravitational pull heats the rock until it melts, causing chemical reactions as well as some radioactivity that creates more pressure. As the plates of the earth (pieces of the crust) shift to accomodate these changes, the crust may become thin enough for the internal pressure to burst through it, VOLCANO!
283532
Man_with_a_Plan has no proof that there is no proof. His statement that no theories are sound or have proof is just his opinion and purely speculatory. There is no proof.\n\nI, on the other hand, like the "Murder on the Orient Express Theory". I think that there was huge changes in ocean circulation due to the continents coming together WELL BEFORE Pangaea formed. The geologic evidence suggests that the extinction happened in different places around the world at different times, which suggests that no single event is responsible. I believe that cooling events like plume volcanism in the Siberian traps coupled with warming events like methane hydrate release and greenhouse effect along with the continental positioning at the time may have worked together to cause extreme changes in ocean circulation at various parts of the world at different times, attributing to the extinction event.\n\nVariations in temperature due to greenhouse warming and on/off sulphide cooling would have had the greatest immediate impact on planktic (ocean surface) and shallow water organisms. I also think that ocean circulation was also greatly affected not only by the temperature variations but also the circumstantial orientation of the continents. Heat transport to the north would have been innefficient and consequently northern regions would have been subject to extreme cooling, even at relatively low latitudes. In the southern regions there would have been a huge temperature gradient between top and bottom waters. If this was enough to stop deep water formation and ocean turnover, benthic (bottom dwelling) species would have been destroyed by the lack of oxygen and intermediate to surface water species would have suffered from a lack of nutrients. Because most of the Earth's life at the time was in the water, I am quite sure that it was likely some change in ocean circulation that dealt the fatal blows to life. Obviously good carbon isotope data from the period would be needed to verify this hypothesis. \n\nLife on land would have suffered greatly by climate changes induced by changes in ocean circulation, as well as the extreme variations in temperature. Tropical species would have been devastated by cooling events caused by the plume volcanism.\n\nThere is lots of proof for everything; there just is no definite information that can, as of yet, say for sure exactly how it all happened. That's a tough thing to do, but I really dislike people who refute the claims of others without presenting any evidence themselves.
740908
Not at all.\n\nHelium makes up about 0.0005% of the total mass of the earth's atmosphere.  This has been relatively consistent over the years (since measurements began in 1957).\n\nRecently, the human uses of helium have increased and commercial sources have raised prices rather than increased production.
827581
The Earth's atmosphere has no definite boundary, slowly becoming thinner and fading into outer space. Three-quarters of the atmosphere's mass is contained within the first 11 km of the planet's surface. This lowest layer is called the troposphere. Further up, the atmosphere is usually divided into the stratosphere, mesosphere, and thermosphere. Beyond these, the exosphere thins out into the magnetosphere (where the Earth's magnetic fields interact with the solar wind). An important part of the atmosphere for life on Earth is the ozone layer.\n\nThe atmospheric pressure on the surface of the Earth averages 101.325 kPa, with a scale height of about 6 km. It is 78% nitrogen and 21% oxygen, with trace amounts of other gaseous molecules such as water vapor. The atmosphere protects the Earth's life forms by absorbing ultraviolet solar radiation, moderating temperature, transporting water vapor, and providing useful gases. The atmosphere is one of the principal components in determining weather and climate.\n\nBecause hydrogen gas is light and based on Earth's mean temperature, achieves escape velocity, unfixed hydrogen leaves the Earth. For this reason, the Earth's environment is oxidizing, with consequences for the chemical nature of life which developed on the planet.\n\nYou could get more information from the link below...