Relationship between volcanoes and plate tectonics
Since the establishment of plate tectonics theory, many scholars have established a global volcanic model on the basis of plate theory, they believe that most volcanoes are distributed on the plate boundaries and a few in the plates, the former constitutes four major volcanic belts, namely, the Circum-Pacific Volcanic Belt, the Mid-Ocean Ridge Volcanic Belt, the East African Rift Volcanic Belt and the Alpine-Himalayan Volcanic Belt.
According to plate theory, the crust is more active at the junction of the two plates, where volcanoes and earthquakes are mostly distributed. Two plates move relatively to each other along the boundary, according to the direction of movement, plate boundaries can be divided into three categories: The first is the divergent boundary, also known as the growth boundary, which is the boundary between two plates that are separated from each other; the second is the convergent boundary, also known as the extinction boundary, which is the boundary between two convergent and extinct plates; the third type is the transition boundary, where strike-slip motion of plates on both sides parallel to the boundary, lithosphere does not proliferate or die out, and the occurrence of volcanoes is closely related to plate movement and plate boundaries.
There are roughly three pathways for volcanic eruption：The first is that magma upwells along subduction zones of convergent plates to form volcanic belts; the second occurs in the context of the extensional plate (with divergent boundaries), where magma upwells along extensional zones to form submarine volcanic rocks; the third is that magma erupts along plumes of mantle within plates to the surface to form volcanoes.
Distribution of Volcanoes on Earth
Volcanic activity often occurs in unusual geological settings, most of which occur at the large plate boundaries that make up the lithosphere. About 80% of the active volcanoes and their related volcanic activities occur at the intersection of two plates, and one of them subducts below the other, the plate subducting, on the one hand, increase local pressure due to compression, on the other hand, melt into magma themselves; at this point, the upper plates under pressure if there are cracks or weak spots, the highly pressurized magma will erupt from these places and form volcanoes. Another difference is that on the axis of the Mid-Ocean Ridge, magma flows out of the mantle and separates from each side of the ridge to form a new ocean floor. Such volcanic activity actually occurs underwater. Recently, some scholars have put forward the theory of bipolar compression, which reveals the mystery of the earth's development, he believes that under the action of bipolar compression, the earth's equatorial axis expands to form longitudinal tension and latitudinal compression, global volcanoes are mainly distributed in the longitudinal and latitudinal tectonic belts.
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