At https://phys.org/print463137812.html … volcanoes are not fed by molten magma is the claim but by reservoirs of volcanic mush – areas of mostly solid crystals with magma in the space between the crystals. Earth scientists understanding of the mechanics of volcanoes are based on a presumption – magma being stored in liquid filled magma chambers. These large underground areas of liquid magma have never been seen – in spite of all those clever pictures and graphs you might seen in a book on volcanoes. Surprise – it is all a theory.
A study by researchers from Imperial College London and Bristol University is published this week in Nature (December 2018) and suggests the theory of magma chambers requires a serious rethink. We don't know why eruptions occur. In addition, we need to understand the formation of metal ore deposits associated with volcanic systems.