What is a dense mix of dry hot rock fragments and hot gas erupting from volcanic vent at high speed is

Magma is called for the dense mix of dry hot rock fragments and hot gas erupting from volcanic vent at high speed. Gas bubble, making up the lave are energetic in nature, because they keep on expanding in all directions, they will go all out to the only open are of a volcano, the vent, in an upward direction. 

answergeosphere;