Скачать или смотреть The History of the Atmosphere - Part 1

How did the atmosphere evolve to the atmosphere we know today? Learn about the history of the atmosphere in this 3 part series. Subscribe for weekly videos: https://goo.gl/COrUU6

Mr. Weather’s World is a weekly video series bringing you interesting and reliable information about the Earth Sciences, Space Weather, and Climate Change. Tune in each week for exciting new content with host and meteorologist Curt Silverwood (Millersville University Alum).

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Step outside and breathe in the fresh air. You might already know that the air you breathe contains oxygen — which is vital to your survival — but our atmosphere wasn’t always suitable for life as we know it.

Over 4.5 billion years ago our Earth formed.

The initial atmosphere that the planet had was mostly composed of Hydrogen and Helium. These two gases are the most commonly found gases in the entire universe. The atmosphere started to change as volcanic activity at the surface as well as impacts of asteroids and comets led to other, heavier gases to form.

Earth’s gravity held onto these heavier gases and lighter gases like Hydrogen and Helium escaped into space. The first atmosphere consisted of about 55% Water vapor, 15% Carbon Dioxide, 15% Nitrogen, 15% ammonia, and trace amounts of methane. Wait! No oxygen?

Around 4 billion years ago, it is believed that the Earth endured many meteorite impacts which could have made the surface temporarily molten.

This caused water and early oceans to evaporate. After this period of heavy bombardment, the surface cooled and water vapor condensed back into its liquid form. Since then, the planet’s surface has remained below the boiling point of water.

Most of the gases in our atmosphere bond with minerals or dissolve in sea water but Nitrogen is an inert gas so it doesn’t do that — Nitrogen became the most abundant gas. Our second atmosphere was mostly Nitrogen, 20% carbon dioxide, with lesser amounts of volcanic gases and variable amounts of water vapor.

How did Oxygen develop? Well, it appeared in our current and third atmosphere.

Oxygen isn’t released by volcanic activity, it’s released by photosynthetic organisms. About 3.8 to 3.5 billion years ago, the first organisms appeared. Tiny blue-green single-celled, photosynthetic organisms, called cyanobacteria, that thrived in the oceans. Through photosynthesis carbon dioxide was converted into oxygen.

For a very long time oxygen would be absorbed by rocks or dissolved in water and there were only trace amounts of it in the atmosphere. Then, around 2.7 billion years ago, eukaryotic cells appeared. These cells have nuclei, and the organisms were more efficient in carrying out photosynthesis.

The increasing abundance of oxygen set the stage for multi-cellular life. Oxygen concentration in the atmosphere stayed relatively low around 5% until about 600 million years ago. Now our atmosphere contains about 78% Nitrogen, 21% Oxygen, and less than 1% contains Carbon Dioxide and other trace gases. Water in our atmosphere, or water vapor, can be seen as clouds or sometimes fog near the ground.

Overall, our atmosphere is like a safety blanket over our planet, providing a great deal of protection from harmful radiation from the sun and it keeps temperatures comfortable. Not too hot and not too cold! Without our atmosphere, Earth would be as empty as the moon.

Stay tuned for part two, as I discuss the lower layers of our atmosphere!
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Thanks for watching!