地球表面分成大约6大板块,以及一些小的板块。该板块是以许多相互联结成网的海岭,转换断层和海沟为边界。当板块分离时,热熔的地幔物质将流进去,以填补由此产生的缝隙。这种流动而造成的温度上升减低了板块的密度,使他们浮起到较高的位置,从而抬高它们边界的高度,比周围更寒冷的海底高出数千英尺。当板块朝着彼此的方向移动,其中一个板块便会向下倾斜约40度,倾入在另一个板块的前沿下,最终与液态地幔融为一体。随着俯冲板块被加热到地幔的温度,板块中的某些矿物会比其他矿物更早熔化。熔点较低,及轻于周围物质的矿物质往往会往上升,融化并穿破其上方的板块,爆发成为海底的火山喷发。随着火山的成长变化,它们伸出海洋面,逐渐在仰冲板块的前沿形成一系列岛屿。
The surface of the Earth is divided into approximately six large plates, plus a number of small ones. The plates are bounded by an interconnected network of ridges, transform faults, and trenches. As the plates separate, hot molten mantle material flows up to fill the void. The increased heat resulting from this flow reduces the density of the plates, causing them to float higher, thus elevating the boundaries by many thousands of feet above the colder surrounding sea floor. Where the plates move towards each other, one plate is bent downwards at about a 40° angle and plunges under the other plateʹs leading edge, eventually to melt back into the liquid mantle below. As the subducting plate is heated back up to mantle temperatures, certain minerals in the plates melt sooner than others. Minerals that melt at lower temperatures and are lighter than the surrounding material tend to rise, melting their way up through the overriding plate to erupt as volcanoes on the ocean floor. As these volcanoes grow, they rise above the ocean surface to form lines of islands along the leading edge of the overriding plate.
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