Stryder50
Platinum Member
And it's clear YOU don't know how plate tectonics work.
In a nutshell (or layperson's language which you might understand), the bulk of divergent zones are under the oceans. This is where the asthenosphere brings it's warmth/heat to the surface of the lithosphere adding heat/warmth to the oceans depths. Most underwater volcanoes are also located at or near the divergent zones.
Some illustrations for the general reader public here;
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The asthenosphere (Ancient Greek: ἀσθενός [asthenos] meaning "without strength" and σφαίρα [sphaira] meaning "sphere") is the mechanically weak[1] and ductile region of the upper mantle of Earth. It lies below the lithosphere, between approximately 80 and 200 km (50 and 120 miles) below the surface, and extends as deep as 700 km (430 mi). However, the lower boundary of the asthenosphere is not well defined.
The asthenosphere is almost solid, but a slight amount of melting (less than 0.1% of the rock) contributes to its mechanical weakness. More extensive decompression melting of the asthenosphere takes place where it wells upwards, and this is the most important source of magma on Earth. It is the source of mid-ocean ridge basalt (MORB) and of some magmas that erupted above subduction zones or in regions of continental rifting.
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Asthenosphere - Wikipedia
Divergent Zone
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Divergent boundary - Wikipedia
The tectonic plates of the lithosphere on Earth
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A lithosphere (Ancient Greek: λίθος [líthos] for "rocky", and σφαίρα [sphaíra] for "sphere") is the rigid,[1] outermost shell of a terrestrial-type planet or natural satellite. On Earth, it is composed of the crust and the portion of the upper mantle that behaves elastically on time scales of up to thousands of years or more. The crust and upper mantle are distinguished on the basis of chemistry and mineralogy.
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Lithosphere - Wikipedia
Plate tectonics (from the Late Latin: tectonicus, from the Ancient Greek: τεκτονικός, lit. 'pertaining to building')[1] is the generally accepted scientific theory that considers the Earth's lithosphere to comprise a number of large tectonic plates which have been slowly moving since about 3.4 billion years ago.[2] The model builds on the concept of continental drift, an idea developed during the first decades of the 20th century. Plate tectonics came to be generally accepted by geoscientists after seafloor spreading was validated in the mid to late 1960s.
Earth's lithosphere, which is the rigid outermost shell of a planet (the crust and upper mantle), is broken into seven or eight major plates (depending on how they are defined) and many minor plates. Where the plates meet, their relative motion determines the type of boundary: convergent, divergent, or transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along these plate boundaries (or faults). The relative movement of the plates typically ranges from zero to 10 cm annually.[3]
Tectonic plates are composed of the oceanic lithosphere and the thicker continental lithosphere, each topped by its own kind of crust. Along convergent boundaries, the process of subduction, or one plate moving under another, carries the edge of the lower one down into the mantle; the area of material lost is roughly balanced by the formation of new (oceanic) crust along divergent margins by seafloor spreading. In this way, the total geoid surface area of the lithosphere remains constant. This prediction of plate tectonics is also referred to as the conveyor belt principle. Earlier theories, since disproven, proposed gradual shrinking (contraction) or gradual expansion of the globe.[4]
Tectonic plates are able to move because Earth's lithosphere has greater mechanical strength than the underlying asthenosphere. Lateral density variations in the mantle result in convection; that is, the slow creeping motion of Earth's solid mantle. Plate movement is thought to be driven by a combination of the motion of the seafloor away from spreading ridges due to variations in topography (the ridge is a topographic high) and density changes in the crust (density increases as newly-formed crust cools and moves away from the ridge). At subduction zones the relatively cold, dense oceanic crust is "pulled" or sinks down into the mantle over the downward convecting limb of a mantle cell.[5] The relative importance of each of these factors and their relationship to each other is unclear, and still the subject of much debate.
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