The earth consists of extremely hot mantle under its apple skin thin crust. This super heated mantle remains solid due to the intense planetary pressure. In certain instances which are rare, extremely hot mantle forms in the lower mantle area and liquefies the upper mantle into super heated magma. This magma starts pushing outwards towards the crust, forming a plume 500 to 1000 km wide. This is a hot spot formed under the crust. Because the melted magma has a lower density than the surrounding rocks, it gets pushed upwards by the pressure of the mantle below. If the pressure is great enough, the magma bursts through the crust in an eruption.
Volcanoes are not formed in a particular way; in fact there are four possible reasons why a volcano occurs. The lithosphere is a layer of the earth comprising of the upper mantle and crust is divided into tectonic plates. These plates keep shifting. When these plates diverge from one another, collide with one another or move in opposite vertical directions, volcanoes can erupt. The hot mantle below the crust melts and flows out from these gaps.
Volcanoes are not formed in a particular way; in fact there are four possible reasons why a volcano occurs. The lithosphere is a layer of the earth comprising of the upper mantle and crust is divided into tectonic plates. These plates keep shifting. When these plates diverge from one another, collide with one another or move in opposite vertical directions, volcanoes can erupt. The hot mantle below the crust melts and flows out from these gaps.