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What are the three main layers of terrestrial planets?
- Core - highest density material, consisting primary of nickel and iron.
- Mantle - rocky material of moderate density, mostly composed of silicon and oxygen that surrounds the core
- Crust - lowest-density rock, such as granite and basalt (volcanic rock), forms the outer layer.
What is differentiation?
A process in which the materials in planets separated to form distinct layers. This means the planets must have been hot enough at one time for their metal and rock to melt.
What is a lithosphere?
The outer layer of relatively cool and rigid rock composing the crust and part of the mantle. The smaller the planet the larger the lithosphere. A thick lithosphere inhibits volcanic eruptions.
What is geological activity?
The ongoing changes to the surface of a terrestrial planet. Earth is geologically active as volcanoes, earthquakes and erosion constantly reshape its surface.
What is heat of accretion?
The kinetic energy obtained when planetesimals collide. Kinetic energy is converted into heat, adding to the thermal energy.
What is heat from differentiation?
As less-dense materials move outward, mass moves inward losing potential gravitational energy. This energy is converted into thermal energy by the friction generated as materials separate in density.
What is heat from radioactive decay?
When radioactive nuclei decay, subatomic particles fly off at high speeds, colliding with neighboring atoms and heating them. This is the only source of ongoing heat.
What is convection?
The process where hot materials expand and rise, while cooler materials contract and fall. This is caused from heating below. It is a source of cooling.
What is conduction?
The transfer of heat from hot materials to cooler materials though contact. Faster moving molecules transfer heat to slower moving molecules on collision. Source of cooling.
What is radiation?
Planets lose heat as they emit thermal radiation due to their temperature. This radiation (light) carriers energy away, cooling an object. Planets usually emit infrared radiation.
What are the three conditions needed for a magnetic field?
- 1. An interior region of electrically conducting fluid, such as molten metal.
- 2. Convection in that layer of fluid.
- 3. At least a moderately rapid rotation.
What are the three types of volcanoes and why do they form?
- volcanic plains - Formed from runny lava that flows far before it solidifies
- shield volcanoes - Formed from thicker lava that solidifies before it can completely spread out.
- stratovolcanoes - Formed from the thickest lava that cannot flow very far before it solidifies.
What is needed to form an atmosphere?
A body must be large enough to allow significant volcanic outgasing and its gravity strong enough to prevent that gas from being released into space.