ENV 151 Study Guide - Quiz Guide: Outgassing, Radiant Energy, Hadean

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13 Dec 2018
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Chapter 12
1. Explain why Earth is just the right size.
If Earth were larger, its increased gravity would have retained a more hostile
atmosphere of gases such as ammonia, methane, hydrogen, and helium.
2. Why is Earth’s molten, metallic core important to humans living today?
The molten core creates Earth’s magnetic field, which shields life forms from lethal
cosmic rays.
3. Why is Earth’s location in the solar system ideal for the development of higher life
forms?
If Earth were closer to the Sun it would be too hot to sustain life, whereas if it were
further from the Sun it would be too cold. Its proximity to this modest-sized star with its
consistent radiant energy has allowed the evolution of higher life forms.
4. What two elements made up most of the very early universe?
Hydrogen and helium.
5. What is the name of the cataclysmic event in which an exploding star produces all the
elements heavier than iron?
Supernova.
6. Briefly describe the formation of the planets from the solar nebula.
After the supernova explosion, there was a cloud of gas and dust. The nebular cloud
begins to contract and become a flattened, rotating cloud. Over time, planetesimals form
by way of accretion and these planetesimals eventually become planets.
7. Describe the conditions on Earth during the Hadean.
Earth was hot and molten. Conditions were hot enough to melt iron and nickel, which
eventually settled into Earth’s core.
8. What is meant by outgassing, and what modern phenomenon serves that role today?
Outgassing is the release of gases from the Earth and was responsible for creation of the
early atmosphere. Volcanoes serve that role today.
9. Identify the most abundant gases that were added to Earth’s early atmosphere through
the process of outgassing.
Methane, ammonia, carbon dioxide, and water vapor.
10. Why is the evolution of a type of bacteria that used photosynthesis to produce food
important to most modern organisms?
These bacteria respired oxygen into the atmosphere.
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