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The internal structure of Earth are the layers of the Earth, excluding its atmosphere and hydrosphere. The structure consists of an outer silicate solid crust , a highly viscous asthenosphere , and solid mantle , a liquid outer core whose flow generates the Earth's magnetic field , and a solid inner core .
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 20% of Earth's radius or 70% of the Moon's radius. [1] [2] There are no samples of the core accessible for direct measurement, as there are for Earth's mantle. [3]
The Greek philosopher Empedocles (c. 450 BC) was the first to propose the four classical elements as a set: fire, earth, air, and water. [9] He called them the four "roots" (ῥιζώματα, rhizōmata). Empedocles also proved (at least to his own satisfaction) that air was a separate substance by observing that a bucket inverted in water did ...
Gravity at different internal layers of Earth (1 = continental crust, 2 = oceanic crust, 3 = upper mantle, 4 = lower mantle, 5+6 = core, A = crust-mantle boundary) Earth's radial density distribution according to the Preliminary Reference Earth Model (PREM). [13] Earth's gravity according to the Preliminary Reference Earth Model (PREM). [13]
Isaac Newton applied his theory of mechanics to the tides and the precession of the equinox; and instruments were developed to measure the Earth's shape, density and gravity field, as well as the components of the water cycle. In the 20th century, geophysical methods were developed for remote exploration of the solid Earth and the ocean, and ...
Researchers are still discovering more about the Earth's center.A team at Australian National University (ANU) has found evidence of a new layer to the planet sitting within the inner core. This ...
He described how fire gave rise to the other elements as the: "upward-downward path", (ὁδὸς ἄνω κάτω), [3] a "hidden harmony" [4] or series of transformations he called the "turnings of fire", (πυρὸς τροπαὶ), [5] first into sea, and half that sea into earth, and half that earth into rarefied air.
But the elements can also check, control and conflict: Wood's roots penetrate Earth, so tension arises. Earth shapes Water, so domination crops up. Water extinguishes Fire, so one overshadows the ...