Question

1. the atmosphere is composed of approximately 78% nitrogen, 21% oxygen and 1% other trace gases.
2. the asthenosphere is a plastic - like layer composed of rock that can flow over long periods of time.
3. the densest layer of earth is the inner core

short answer

1. what are the two main factors that cause earths layers to become dense?
2. how does the atmosphere contribute to supporting life on earth?
3. describe the composition of the lithosphere.
4. what is the role of the asthenosphere in the process of plate tectonics?
5. how does the mesosphere contribute to the movement of tectonic plates?
6. what is the primary composition of the outer core?
7. how does the outer core generate the earths magnetic field?
8. why does the inner core remain solid despite high temperatures?
9. what function does the inner core serve in stabilizing the earth?

Explanation:

1. Gravity and pressure cause Earth's layers to be dense. Gravity pulls materials inward and high - pressure conditions compress them.
2. The atmosphere contributes to life by providing oxygen for respiration, protecting from harmful radiation (ozone layer), regulating temperature through the greenhouse effect, and enabling weather systems that distribute water.
3. The lithosphere is composed of the Earth's crust and the uppermost part of the mantle. It is rigid and divided into tectonic plates.
4. The asthenosphere is a semi - fluid layer beneath the lithosphere. It allows the tectonic plates of the lithosphere to move slowly over it due to its plastic - like behavior.
5. The mesosphere is a rigid layer below the asthenosphere. It resists flow and its movement contributes to the forces that drive tectonic plate motion, such as convection currents in the mantle.
6. The primary composition of the outer core is iron and nickel, along with small amounts of other elements like sulfur and oxygen.
7. The outer core generates the Earth's magnetic field through the movement of its liquid iron - nickel alloy. The convective motion of this conducting fluid, combined with the Earth's rotation, creates electric currents that produce the magnetic field (dynamo effect).
8. The inner core remains solid despite high temperatures because of the extreme pressure at the Earth's center. This pressure overcomes the tendency of the iron - nickel material to melt.
9. The inner core helps stabilize the Earth by contributing to the overall gravitational balance and may also play a role in maintaining the Earth's magnetic field through its influence on the outer - core dynamics.

Answer:

1. Gravity and pressure.
2. Provides oxygen, protects from radiation, regulates temperature, enables weather systems for water distribution.
3. Earth's crust and uppermost mantle, rigid and divided into tectonic plates.
4. Allows tectonic plates to move due to its semi - fluid, plastic - like nature.
5. Its movement contributes to forces driving tectonic plate motion.
6. Iron and nickel with small amounts of other elements.
7. Convective motion of liquid iron - nickel alloy creates electric currents (dynamo effect).
8. Extreme pressure overcomes melting tendency.
9. Contributes to gravitational balance and may influence outer - core dynamics for magnetic field.