When two tectonic plates slide past each other, the place where they meet is a transform or lateral fault. This can lead to the formation of huge, high mountain ranges such as the Himalayas. Since neither plate is stronger than the other, they crumple and are pushed up. Neither plate subducts because the crusts have approximately the same density. A convergent boundary forms when two continental plates collide. About 80% of earthquakes occur where plates are pushed together, called convergent boundaries.Īnother form of convergent boundary is a collision where two continental plates meet head-on. Convergent Boundary Where a convergent boundary forms. When two continental plates meet, they create a mountain range. Sometimes the molten rock rises to the surface, through the continent, forming a line of volcanoes. When two oceanic plates meet, they create a trench and island arc. The rocks pulled down under the continent begin to melt. Subduction causes deep ocean trenches to form, such as the one along the west coast of South America. Tectonic plates are large sections of lithosphere, or the Earth's crust. When a continental plate meets an oceanic plate, the thinner, denser, and more flexible oceanic plate sinks beneath the thicker, more rigid continental plate. What is a convergent boundary Boundaries are the types of connections between tectonic plates. The Great Rift Valley in Africa, the Red Sea and the Gulf of Aden all formed as a result of divergent plate motion.Ĭonvergent (Colliding): This occurs when plates move towards each other and collide. The earthquakes that occur along these zones, called spreading centers, are relatively small. Molten rock from the mantle erupts along the opening, forming new crust. The three main types of plate movements include:ĭivergent (Spreading):This is where two plates move away from each other. The movements of the plates help shape the geological features of our planet. Other plates include continents, and some plates include both continents and ocean. Some of the plates have ocean water above them. When the plates finally give and slip due to the increased pressure, energy is released as seismic waves, causing the ground to shake. Most seismic activity occurs at three types of plate boundaries-divergent, convergent, and transform.Īs the plates move past each other, they sometimes get caught and pressure builds up. Volcanic and plutonic rocks of almost all ages are distributed in places reflecting the position and intensity of magmatic activity of that age.Movement in narrow zones along plate boundaries causes most earthquakes.Age of the basement rocks is generally older in the continental side and younger in the ocean side.Numbers of accretionary complexes accumulate in order and part of them are re-arranged by later tectonism.The Japanese islands are characterized as the grown-up continental margin formed by the subduction of the oceanic plate. In addition, subducted oceanic plate brings water into the mantle and contributes to the generation of magma which forms large amounts of plutonic rocks and volcanic activities in and on the continental crust. The deeper part of the accretionary complex is subjected to regional metamorphism. This phenomenon is called "accretion", and ripped sediments and rocks formed by accretion are displayed as "accretionary complex" in geological map. These are ripped into the continental crust together with the trench fill deposits at the subduction. The oceanic crust brings basaltic lava, deep marine sediments, seamounts and so on. The oceanic plate consists of the oceanic crust and a part of the mantle beneath it. This means that the Japanese islands are built under the subduction tectonics. Japan has been situated in the convergent plate boundary during long geohistorical ages. Geological Map of Japan top Subduction and Japan
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