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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 c. 80 and 200 km (50 and 120 mi) below the surface, and extends as deep as 700 km (430 mi).
The lithosphere–asthenosphere boundary lies between Earth's cooler, rigid lithosphere and the warmer, ductile asthenosphere. The actual depth of the boundary is still a topic of debate and study, although it is known to vary according to the environment. [1]
The poles of astronomical bodies are determined based on their axis of rotation in relation to the celestial poles of the celestial sphere. Astronomical bodies include stars, planets, dwarf planets and small Solar System bodies such as comets and minor planets (e.g., asteroids), as well as natural satellites and minor-planet moons.
The age of onset of the South Asian monsoon is not widely agreed upon. [38] The South Asian monsoon may have begun in the Early [26] [49] [4] or Late Miocene. [31] This uncertainty makes investigation into the interactions of climate with other Earth systems (especially the direction of causality) in the Himalaya through time difficult.
Turns out, the direction of a portion of the magnetic field deep beneath this area has already flipped! And scientists say that’s one reason why the field has been steadily weakening since 1840.
The north orbital pole of a revolving body is defined by the right-hand rule. If the fingers of the right hand are curved along the direction of orbital motion, with the thumb extended and oriented to be parallel to the orbital axis, then the direction the thumb points is defined to be the orbital north.
The seismic velocities very near the surface (≲ 220±30 km) are markedly lower than at greater depths, demarking the LVZ. In geology , the low-velocity zone (LVZ) occurs close to the boundary between the lithosphere and the asthenosphere in the upper mantle .
Plate tectonics (from Latin tectonicus, from Ancient Greek τεκτονικός (tektonikós) 'pertaining to building') [1] is the scientific theory that the Earth's lithosphere comprises a number of large tectonic plates, which have been slowly moving since 3–4 billion years ago.