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Continental crust is a tertiary crust, formed at subduction zones through recycling of subducted secondary (oceanic) crust. [18] The average age of Earth's current continental crust has been estimated to be about 2.0 billion years. [21] Most crustal rocks formed before 2.5 billion years ago are located in cratons.
Geothermal gradient is the rate of change in temperature with respect to increasing depth in Earth 's interior. As a general rule, the crust temperature rises with depth due to the heat flow from the much hotter mantle; away from tectonic plate boundaries, temperature rises in about 25–30 °C/km (72–87 °F/mi) of depth near the surface in ...
The red line shows direct surface temperature measurements since 1880. [ 2] Global surface temperature (GST) refers to the average temperature of Earth 's surface. It is determined nowadays by measuring the temperatures over the ocean and land, and then calculating a weighted average. The temperature over the ocean is called the sea surface ...
Outside of the seasonal variations, the geothermal gradient of temperatures through the crust is 25–30 °C (77–86 °F) per km of depth in most of the world. The conductive heat flux averages 0.1 MW/km 2. These values are much higher near tectonic plate boundaries where the crust is thinner.
Crust (geology) The internal structure of Earth. In geology, the crust is the outermost solid shell of a planet, dwarf planet, or natural satellite. It is usually distinguished from the underlying mantle by its chemical makeup; however, in the case of icy satellites, it may be distinguished based on its phase (solid crust vs. liquid mantle).
The remaining 29.2% of Earth's crust is land, most of which is located in the form of continental landmasses within Earth's land hemisphere. Most of Earth's land is somewhat humid and covered by vegetation, while large sheets of ice at Earth's polar deserts retain more water than Earth's groundwater , lakes, rivers and atmospheric water combined.
Asthenosphere. The asthenosphere (from Ancient Greek ἀσθενός (asthenós) 'without strength') is the mechanically weak [ 1] and ductile region of the upper mantle of Earth. It lies below the lithosphere, at a depth between ~80 and 200 km (50 and 120 mi) below the surface, and extends as deep as 700 km (430 mi). However, the lower ...
Earth's inner core is the innermost geologic layer of the planet Earth. It is primarily a solid ball with a radius of about 1,220 km (760 mi), which is about 19% of Earth's radius [0.7% of volume] or 70% of the Moon 's radius. [ 32][ 33] The inner core was discovered in 1936 by Inge Lehmann and is generally composed primarily of iron and some ...