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The Principle Events in the Evolution of the Earth’s Atmosphere

The literal translation of the word atmosphere is “sphere of vapors”. The Earth’s atmosphere is a protective sphere of vapors, or air that surrounds the Earth and provides it with a layer of insulation from the harmful rays of the sun. It is a vital part of the Earth, and has changed dramatically since the beginning of time. The earth’s atmosphere has gradually changed since the Earth’s birth approximately 4. 6 million years ago. In the beginning, the Earth’s composition was very different that how it exists today.

A long time ago the Earth’s atmosphere was very similar to today’s Venus and Mar’s atmosphere. It had about 95% carbon dioxide, 2-3% nitrogen, and very little, less than 1% oxygen. Today the Earth contains 79% nitrogen, 21% oxygen, and 3% water vapor. It is evident that there were many events that happened over billions of years that have contributed to this change in the Earth’s atmosphere. The Earth had developed so drastically because of the tremendous dust and gas cloud within the Milky Way galaxy. The Earth grew larger as huge meteorites hit it, and the surface was covered with dust.

Volcanoes began to form and emitted lava, ash, and most importantly gases. Carbon dioxide, water vapor, and nitrogen were released into the atmosphere from the volcanoes. This process is called outgassing, and took place within the first million years or so of the Earth’s formation. Then, about 4 billion years ago, the planet cooled, and the outgassed water vapors condensed into clouds. It rained and produced the oceans, and even enough to cover 95% of the Earth. In addition, because it rained, there was less carbon dioxide in the atmosphere.

The carbon dioxide was lost over billion of years, as the ocean formed there was a chemical reaction in which carbon dioxide and water formed carbonic acid. It is shown in the equation CO2 + H2O = H2CO3. The carbonic acid dissolved oceanic rock into sand, silt, and mud. It is evident because of this geochemical process occurred there is more carbon in the rocks and minerals and there is less in the Earths atmosphere. The Earths first ever oxygen emerged about two millions years ago because of ultraviolet radiation.

The water in the Earths atmosphere was split into oxygen and hydrogen because of the ultraviolet radiation from the sun. The equation for this process is UV-* 2H20 -* 2H2 + O2. The first ever oxygen is from the ultraviolet radiation that occurred in the Earths atmosphere. It is interesting to note that 600 million years ago only about 1% of the Earths atmosphere was oxygen. Significant quantities of oxygen did not begin until plants arrived on the scene. The percentage of oxygen increased when plant life evolved and photosynthesis began to happen on the Earth.

The first ever plants were blue-green algae, which lived the Earths oceans. Plants used sunlight, water, and carbon dioxide to make their food in a process called photosynthesis. The process of photosynthesis can be easily seen in the equation 6CO2 + 6H2O = C6H12O6 + O2. The plants breathe in carbon dioxide and then release oxygen during photosynthesis, within 500 million years oxygen was the second largest part of the atmosphere after nitrogen. As oxygen became a greater part of the atmosphere the ozone shield emerged.

The shield was formed when solar ultraviolet radiation forces the reaction for oxygen to form ozone, also known as 03. The ozone protects the Earth and its inhabitants from the harmful radiation from the sun. In conclusion, the Earths atmosphere has changed dramatically since the Earths origin about 4. 6 billion years ago. There are many factors that contributed to this change over time. By getting a better understanding of our Earths atmosphere we can use in many useful ways. We can use this knowledge of the atmosphere for a worthy cause in many areas of science and greatly benefit from it.

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