How is lava formed in the volcano?
Lava (or that magma stuff again) forms in the earth’s mantle or the lower part of the crust. A big chunk of the mantle or crust probably does not actually sit there and melt. Instead, melting probably occurs around the boundaries of the mineral grains that make up the rocks, and then it accumulates to form bigger globs of melt. When it gets big enough it may then rise to the surface. Think of it like a bowl of ice cubes. Water accumulates because all the ice cubes melt a little bit, rather than one ice cube melting completely while the others are unaffected. At first there is just a little bit of water, but as more ice melts, more water forms.
