What causes volcanoes to erupt?

Although there are several factors triggering a volcanic eruption, three predominate the buoyancy of the magma, the pressure from the exsolved gases in the magma and the injection of a new batch of magma into an already filled magma chamber. ... This lighter magma then rises toward the surface by virtue of its buoyancy.

Explanation:

The rock inside the planet we live on can melt to form molten rock called magma. This magma is lighter than the rocks around it and so it rises upwards. Where the magma eventually reaches the surface we get an eruption and volcanoes form.

when the pressure from the magma rises to the surface

c

explanation:

the relative standard reduction potential of the half-cell in which reduction occurs; more positive than the other half-cell. reduction is a chemical process in which electrons are added to an atom or an ion; it always occurs accompanied by oxidation of the reducing agent.