* Magma composition: The composition of the magma determines the viscosity of the magma, which in turn affects the type of eruption. Magma that is rich in silica is more viscous and tends to produce explosive eruptions, while magma that is low in silica is less viscous and tends to produce effusive eruptions.
* Gas content: The amount of gas in the magma also affects the type of eruption. Magma that contains a lot of gas is more likely to produce explosive eruptions, while magma that contains less gas is more likely to produce effusive eruptions.
* Volcano shape: The shape of the volcano also affects the type of eruption. Volcanoes that are steep-sided and have a narrow vent are more likely to produce explosive eruptions, while volcanoes that are gently sloping and have a wide vent are more likely to produce effusive eruptions.
In addition to these factors, the type of eruption can also be influenced by the interaction between the magma and the surrounding environment. For example, if magma erupts into water, it can produce a violent eruption that generates ash clouds and pyroclastic flows.
As a result of all of these factors, volcanoes can sometimes have more than one type of eruption. For example, a volcano may start out with an effusive eruption, but then transition to an explosive eruption as the composition of the magma changes or the amount of gas in the magma increases.