--------------------- #1510 - Earth Evolution
- See Review #1506 for the “ Geological History of the Earth”. It starts with the planet’s formation 4,600 million years ago (MYA) to get to the present day. All learned by studying rocks and minerals.
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- This Review #1510 starts 4,560 MYA and goes to 1,500 MY from now. All learned by studying the atmospheric gases in rocks and ice, and plant and animal fossil records. The two reviews give much the same picture, an amazing history of Earth’s evolution.
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- What will the Earth by like in the distant future?
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- The Sun increases luminosity by10% every 1,000 million years.
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- Plate tectonics will have ground to a halt just 500 million years from now.
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- The Earth will grow warmer as the Sun increases in brightness. As temperatures rise more and more water will evaporate into the atmosphere. Clouds will become so thick they will block the infrared light from escaping the planet. The oceans will evaporate away some 1,500 million years from now.
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- Solar ultraviolet radiation will split the water molecules in the atmosphere allowing the hydrogen to escape. The heavier atmosphere will become corrosive with carbon dioxide and sulfuric acid. To learn what the Earth will be like study the planet Venus. It is 25 million miles closer to the Sun and is 1,000 million years ahead of us.
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- Looking backwards in time, million years ago (MYA):
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- 100 MYA: The first flowering plants occurred.
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- 300 MYA: Thick layers of dead plant material built up in the wetlands creating coal, drawing down the carbon dioxide levels, and leading to the ice age 300 MYA
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- Over 10’s of millions of years plants spread across the land and grew taller.
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- 380 MYA: Forests covered large areas and pumped more oxygen into the air, up to 34% concentration.
- 450 MYA: The atmosphere was nitrogen, oxygen, and argon. But, the concentration levels of oxygen was varying:
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------------------------------------ 450 MYA ---------- 12% concentration level
----------------------------------- 300 MYA ---------- 34%
----------------------------------- 250 MYA ----------- 15%
----------------------------------- 100 MYA ---------- 30%
----------------------------------- Today ---------- 21%
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- The origin of animal life occurred. reptiles , amphibians, dinosaurs and mammals coexisted. Mass extinctions occurred devastating life on the planet several times.
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------------------------------------- 450 MYA extinctions
------------------------------------- 375 MYA extinctions
----------------------------------- 251 MYA extinctions
----------------------------------- 205 MYA extinctions
----------------------------------- 65 MYA extinctions
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- 450 MYA: Plate tectonics slowly pushes more land above sea level.
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- 543 MYA: Rapid diversification of animal life began. The first fishes were 500 MYA. Fossils of animals have been dated back to 585 MYA. Fungi and simple plants spread on to the land.
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- 600MYA: The atmosphere was nitrogen, oxygen water vapor and methane. The Sun is 90% its present luminosity.
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- 600 MYA and 800 MYA and 2,400 MYA the Earth froze over almost completely. Called “ Snowball Earth” occurring soon after the rise in oxygen levels.
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- 2,450 MYA Oxygen first became an important constituent of the atmosphere. The luminosity of the Sun was 85% what we experience today. Positive feedback occurred when oxygen level produced ozone (O3) layers in the upper atmosphere blocking the Sun’s ultraviolet light. This in turn slowed the UV reactions with methane that limited the concentration of oxygen More oxygen produced more ozone slowing oxygen destruction even more.
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- Oxygen tolerant microbes evolved in this oxygen rich atmosphere paving the way for the evolution of plants and animals. Modern algae evolved during this period.
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- 2,700 MYA: The first organisms were single cells that ingested compounds dissolved in seawater. Photosynthesis evolved.
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- 3,800 MYA: The oldest evidence of life is from the ratio of carbon isotopes in sedimentary rock. Metabolism of living cells prefers carbon-12 isotope compared with carbon-13 isotope.
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- 3,900 MYA: Saturn and Jupiter hit a 2 to 1 orbiting resonance that shifted planetary positions throughout the Solar System. This disrupted orbiting comets and asteroids that rained down on the inner planets.
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- 4,200 MYA: The first oceans formed.
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- 4,500 MYA: A giant impact formed the Moon and melted the young planets. Metals sank to the core and a froth of molten rock floated to become the mantle. There was a thick steam atmosphere over the molten rock that lasted for 300 million years. The oldest rocks dated so far were formed 4,000 MYA.
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- Use your binoculars to look at the surface of the Moon. The Great Bombardment is still in evidence there because the Moon has no erosion or tectonic activity.
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- 4,560 MYA: Earth and the other planets formed in the accretion disk orbiting the Sun, the star in the neighborhood. The Sun was only 70% that of today’s luminosity. The atmosphere on Earth was nitrogen, carbon monoxide, and water vapor.
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- 4,600 MYA: See Review# 1509 to learn what our world was like 4,600 MYA. The Orion Nebula in the Star Constellation Orion the Hunter gives you a picture back in time. What you see is what it was like 1,400 years ago. The Orion Nebula is 1,400 lightyears away. At least check out the picture, it is a beautiful scene in color.
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707-536-3272, Friday, November 9, 2012
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