Sunday, July 05, 2015
The Story of the Earth
This is a small extract of the evolution of the Earth as learned from Robert Hazen's book :
1. Formation of the Earth - Sun formed and then the rest of the debris formed the planets. Even today 99%+ mass of the solar system is concentrated in the Sun. The first four planets are the rocky planets and the rest are made of Gas.
2. The swirling debris first coalesced into planetesimals and the planets started forming with massive impacts.
3. The interesting thing to note is that matter in the stars makes the first 6 elements. After that, the process is much more laborious and proceeds till it hits Iron. Anything further requires extreme events like a Supernova to form.
4. How the moon- 'Thebia' came about. Competing theories but the most likely is that the moon was a planetesimal which crashed into earth. The resulting impact was immense and (the best possible hypothesis) the 2-celestial planetesimal debris coalesced to form the moon. The moon was much closer to the earth but is moving away at a slow space.
5. A very hot basaltic earth was the first phase of the earth. There was no granite then.
6. The oceans formed after this phase. One memorable statistic : All of the oceans only form 0.2 % of the mass of the earth. The steps above happened in the first 150-200 million years of the earth's birth.
7. First there was only Basalt but then due to melting of basalt came crystallization and granite. Granite is much more hardier than basalt (and lighter). This was the origin of continents. Happened between 200-500 millon years.
8. The origins of "Life" are to be found here. An automatic 'chain-reaction' which was autocatalytic in nature lead to the advent of 'replicating' microbes. 500 million to 1 billion years.
8. There was the great Oxidation effect and the percentage of oxygen in the atmosphere increased. This was because of the single celled microbes that started producing oxygen. From 1 billon to 2.7 billion years.
9. A Billion Years passed with nothing 'dramatic' happening. From 2.7 billlion to 3.7 billion years. Only the supercontinent of Columbia formed which broke up.
10. From 3.7 billion to 4 Billion The Cold and Hot cycle. Suggest that there were at least 3 glaciations in this period. This was also the period of the second great Oxidation effect. At the very end of these three glaciations, small marine animals (i.e Tribolites etc.) were already present.
11. From 4-4.5 billion years :
Act 1 : The supercontinent cycle was well underway with the break-up of the second supercontinent 'Rodinia'. Superocean was Mirovia.
Act 2 : Around 300 million years ago the supercontinent of Panagea formed. (Laurentia and Gondwana) collapsed to become one supercontinent. The superocean was Panthalassa.
Act 3 : The breakup of Panagea broke up the landmasses into 2 parts - Laurasia and Gondwanaland. The sea in the middle of them was the Thethys sea.
12. Around 65 millon years ago a 6 mile asteroid stuck the Yucatan Peninsula wiping out the Dianosaurs.
12. There have been several mass-extinctions in the animal and plant history of the earth. The other most devastating was the Permian extinction.
1. Formation of the Earth - Sun formed and then the rest of the debris formed the planets. Even today 99%+ mass of the solar system is concentrated in the Sun. The first four planets are the rocky planets and the rest are made of Gas.
2. The swirling debris first coalesced into planetesimals and the planets started forming with massive impacts.
3. The interesting thing to note is that matter in the stars makes the first 6 elements. After that, the process is much more laborious and proceeds till it hits Iron. Anything further requires extreme events like a Supernova to form.
4. How the moon- 'Thebia' came about. Competing theories but the most likely is that the moon was a planetesimal which crashed into earth. The resulting impact was immense and (the best possible hypothesis) the 2-celestial planetesimal debris coalesced to form the moon. The moon was much closer to the earth but is moving away at a slow space.
5. A very hot basaltic earth was the first phase of the earth. There was no granite then.
6. The oceans formed after this phase. One memorable statistic : All of the oceans only form 0.2 % of the mass of the earth. The steps above happened in the first 150-200 million years of the earth's birth.
7. First there was only Basalt but then due to melting of basalt came crystallization and granite. Granite is much more hardier than basalt (and lighter). This was the origin of continents. Happened between 200-500 millon years.
8. The origins of "Life" are to be found here. An automatic 'chain-reaction' which was autocatalytic in nature lead to the advent of 'replicating' microbes. 500 million to 1 billion years.
8. There was the great Oxidation effect and the percentage of oxygen in the atmosphere increased. This was because of the single celled microbes that started producing oxygen. From 1 billon to 2.7 billion years.
9. A Billion Years passed with nothing 'dramatic' happening. From 2.7 billlion to 3.7 billion years. Only the supercontinent of Columbia formed which broke up.
10. From 3.7 billion to 4 Billion The Cold and Hot cycle. Suggest that there were at least 3 glaciations in this period. This was also the period of the second great Oxidation effect. At the very end of these three glaciations, small marine animals (i.e Tribolites etc.) were already present.
11. From 4-4.5 billion years :
Act 1 : The supercontinent cycle was well underway with the break-up of the second supercontinent 'Rodinia'. Superocean was Mirovia.
Act 2 : Around 300 million years ago the supercontinent of Panagea formed. (Laurentia and Gondwana) collapsed to become one supercontinent. The superocean was Panthalassa.
Act 3 : The breakup of Panagea broke up the landmasses into 2 parts - Laurasia and Gondwanaland. The sea in the middle of them was the Thethys sea.
12. Around 65 millon years ago a 6 mile asteroid stuck the Yucatan Peninsula wiping out the Dianosaurs.
12. There have been several mass-extinctions in the animal and plant history of the earth. The other most devastating was the Permian extinction.
