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Observations suggest that gas in protoplanetary disks orbiting young stars have lifetimes of a few to several million years. [1] If planets with masses of around an Earth mass or greater form while the gas is still present, the planets can exchange angular momentum with the surrounding gas in the protoplanetary disk so that their orbits change gradually.
A planetary core acts as a heat source for the outer layers of a planet. In the Earth, the heat flux over the core mantle boundary is 12 terawatts. [30] This value is calculated from a variety of factors: secular cooling, differentiation of light elements, Coriolis forces, radioactive decay, and latent heat of crystallization. [30]
Munk & Wunsch (1998) estimated that Earth experiences 3.7 TW (0.0073 W/m 2) of tidal heating, of which 95% (3.5 TW or 0.0069 W/m 2) is associated with ocean tides and 5% (0.2 TW or 0.0004 W/m 2) is associated with Earth tides, with 3.2 TW being due to tidal interactions with the Moon and 0.5 TW being due to tidal interactions with the Sun. [3] Egbert & Ray (2001) confirmed that overall ...
In heat-pipe tectonics, volcanism is the major heat transport mechanism in which melts of rock are transferred to the surface by localised vents. [1] [3] [9] Advection, referring to the transfer of mass and heat, occurs when a moving fluid carries substances or heat to or away from a source and through a surrounding solid along channels. [10]
Schematic of the Earth's inner core and outer core motion and the magnetic field it generates. The Earth's inner core is thought to be slowly growing as the liquid outer core at the boundary with the inner core cools and solidifies due to the gradual cooling of the Earth's interior (about 100 degrees Celsius per billion years). [49]
Primordial heat is the heat lost by the Earth as it continues to cool from its original formation, and this is in contrast to its still actively-produced radiogenic heat. The Earth core's heat flow—heat leaving the core and flowing into the overlying mantle—is thought to be due to primordial heat, and is estimated at 5–15 TW. [23]
Earth's outer core is a fluid layer about 2,260 km (1,400 mi) in height (i.e. distance from the highest point to the lowest point at the edge of the inner core) [36% of the Earth's radius, 15.6% of the volume] and composed of mostly iron and nickel that lies above Earth's solid inner core and below its mantle. [31]
In 1862, Lord Kelvin calculated the age of the Earth at between 20 million and 400 million years by assuming that Earth had formed as a completely molten object, and determined the amount of time it would take for the near-surface to cool to its present temperature. Since uniformitarianism required a much older Earth, there was a contradiction.