Question: Where does all the magma come from and is it an infinite source?

Elena Maters answered on 5 Feb 2021:

Magma is melted material that comes from the Earth’s mantle – this is the layer between the core and the crust. The material in the mantle is melted by changes in temperature and pressure, for example as tectonic plates carrying continents and ocean floors move against/over/under one another, and we get volcanic eruptions where this material rises up and breaks through the Earth’s crust. Yes magma is continuously being produced in the mantle and so volcanic activity on Earth has kept going for billions of years!