Assertion: hot gas rich magma | /r/CapableOf | approach the surface
Facets:
value: during an eruption
type: TEMPORAL
Source sentences:
text: As gas-rich magma approaches the surface during an eruption, the huge drop in internal pressure caused by the reduction in weight of the overlying rock (which drops to zero at the surface) causes the gases to come out of solution, the volume of gas increasing explosively from nothing to perhaps many times that of the accompanying magma.