Archive for Earth Sciences Forum This site is dedicated to the Earth Sciences. We are here for you to discuss issues regarding any aspect of the Earth sciences, at all levels of knowledge. Questions are welcomed, as are open scientific debates. Enjoy!!!
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scpg02
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Volcanoes key to Earth's oxygen atmosphereIt has been suggested by other sources that the oxygen went up after large impacts.
Volcanoes key to Earth's oxygen atmosphere
Contact: Andrea Elyse Messer
aem1@psu.edu
814-865-9481
Penn State
| Quote: | A switch from predominantly undersea volcanoes to a mix of undersea and terrestrial ones shifted the Earth's atmosphere from devoid of oxygen to one with free oxygen, according to geologists.
"The rise of oxygen allowed for the evolution of complex oxygen-breathing life forms," says Lee R. Kump, professor of geoscience, Penn State.
Before 2.5 billion years ago, the Earth's atmosphere lacked oxygen. However, biomarkers in rocks 200 million years older than that period, show oxygen-producing cyanobacteria released oxygen at the same levels as today. The oxygen produced then, had to be going somewhere. |
http://www.eurekalert.org/pub_releases/2007-08/ps-vkt082707.php
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sneez
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Would the missing ozone layer prohibit forming of oxygen producing life forms due UV radiation reaching the surface.
Would not have been oxygen used up in the atmospheric chemistry predominantly methane and amonia reactions ?
Is there some latest theory of how the early atmosphere formed. In the book I had for atmospheric chemistry its explicitly stated that no completely coherent theory exists yet.
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Baywax
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There's a lot of "what ifs" and "think it might have been"s associated with understanding the formation of planetary atmospheres.
| Quote: | The creation of a planetary atmosphere from the planet’s interior is called outgassing. What is outgassing? Well, gases from the solar nebula get trapped in the interior of a planet. These gases were mostly hydrogen and helium. These gases were light, and the heat from the planet basically "blew off" these gases. As the rock material baked and cooled, new gases were released from the rocks, forming an atmosphere. Scientists think that planets formed relatively rapidly, and the heat generated from the forming planet could not escape into space. This heat melted the planets as they formed, and in their molten state (liquid rock) gases were allowed to escape. The gases that did not get "blown off" into space were heavier, and that’s why the inner planets have atmospheres with ‘heavier" gases – gravity could hold onto those gas particles. The lighter ones escaped.
Scientists are pretty sure that atmospheres are not formed entirely by outgassing. Some of the gas components of an atmosphere are thought to have been "added" later on by comet impacts and late accretion of matter in the formation of planets. |
http://sunshine.chpc.utah.edu/labs/atmosphere/formation.html
| Quote: | | You may be wondering WHY Earth has so little carbon dioxide in the atmosphere (!) when Venus and Mars have so much. Well, it’s like this: Outgassing from a forming planet such as Earth would release mostly carbon dioxide and water vapor. Carbon dioxide is very soluble in water, and the earth’s surface temperature is just right for it to be covered with water. Much of the carbon dioxide released in outgassing dissolves in oceans and combines with minerals in seawater to form deposits of silicon dioxide, limestone, etc. So the carbon dioxide has been removed from Earth’s atmosphere and buried in the Earth’s crust (rocks). |
same source.
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