Another great question from you Daniel! ok, well we know that ‘lava’ is the erupted form of what geologists call “magma”- a fancy word to describe molten rock that is still underground. Rocks in the mantle and the core of the Earth are still hot from it formed ages ago (about 4.6 billion years ago!). It’s hot enough to partially melt some rocks in the upper mantle, about 50-100 km below the surface. Rocks are made of many different types of minerals that melt at different temperatures which means that when the rock starts to melt, some of the minerals get melted to a much greater degree than others. If this ‘melted rock’ makes it to the surface, through a crack or weak spot in the earths outer crust then it’s called lava. Hope that helps!