Seafloor spreading occurs at divergent plate boundaries. As tectonic plates slowly move away from each other, heat from the mantle's convection currents makes the crust more plastic and less dense. The less-dense material rises, often forming a mountain or elevated area of the seafloor. Eventually, the crust cracks.
It should be noted that a volcanic arc results from ridgeconvergent while tectonic movements and is associated with mid ocean ridge.
<h3>What is a volcanic arc ?</h3>
A volcanic arc can be regarded as a chain of volcanoes, which some miles long and it is usually formed above a subduction zone.
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