Gravity pulls the denser water to the bottom driving

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Gravity pulls the denser water to the bottom, driving the less dense oil to the top, in a process called differentiation. Moon's small core by assuming it formed from debris blasted out of Earth's rocky outer layers;
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the debris would have contained relatively little high density metal and therefore would have accreted into an object with a very small metal core. A planet's outer layer consists of relatively cool and rigid rock, called the lithosphere. A thick lithosphere is much stronger and inhibits the passage of any molten rock from below, making volcanic eruptions and the formation of mountain ranges less likely. P waves result from compression and stretching the direction of travel. S waves vibrate up and down or side to side perpendicular to the direction of travel. Three sources of interior heat of terrestrial worlds: * Heat of accretion: accretion deposits energy brought in from afar by colliding planetesimals, upon impact, much of the kinetic energy is converted to heat, adding to the thermal energy of the planet. * Heat from differentiation: the sinking of dense material and rising of less dense material means that mass moves inward, losing gravitational potential energy. This energy is converted to thermal energy by the friction generated as materials separate by density. * Heat from radioactive decay: The rock/metal that built the terrestrial worlds contained radioactive isotopes of elements such as uranium, potassium, and thorium. When radioactive nuclei decay, subatomic particles fly off at high speeds, colliding with neighboring atoms and heating them. This transfers some of the mass energy (E = mc^2) of the radioactive nuclei to the thermal energy of the planetary interior. Size is the primary factor in determining geological activity. Three Basic heating processes for planetary interiors: Convection: the process by which hot material expands and rises while cooler material contracts and falls. Conduction: The transfer of heat from hot material to cooler material through contact; occurs through microscopic collisions of individual atoms/molecules. Radiation: Planets lost heat, objects emit thermal radiation characteristic of their temps; the radiation (light) carries energy away and therefore cools an object. Planets radiate primarily infrared. Three basic requirements for a global magnetic field: 1. An interior region of electrically conducting fluid, such as molten metal 2. Convection in that layer of fluid 3. At least moderately rapid rotation
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