A group of volcanologists from the School of Ocean and Earth Sciences will demonstrate how gases moving through magmas can cause volcanoes to erupt.
Magmas contain gas bubbles, which move through the magma and try to escape to the surface. Some magmas are more viscous, thick and syrupy, and make it hard for bubbles to move, while other magmas are watery and liquid, and bubbles can move easily. If gas bubbles cannot escape the magma, they will cause pressure to build up, and this can trigger a volcanic eruption. The more gas is present in the magma, the more violent and destructive the eruption will be - think of a shaken bottle of sparkling water, erupting as you open it, because all the gases want to escape. However, if the gas bubbles can easily move through the magma and escape from the system, then the eruption is likely to be less violent, as there is no gas left in the magma to blow the system to pieces.
Whether a volcano erupts in a massive explosion or in a gentle lava flow, is down to how easily gas bubbles move through the magma: so it's pretty important to understand that movement!