1. The type of magma it erupts:

* Viscous magma (high silica content) leads to explosive eruptions and steep-sided, cone-shaped volcanoes like stratovolcanoes.

* Fluid magma (low silica content) results in effusive eruptions and wide, gently sloping volcanoes like shield volcanoes.

2. The geological setting:

* Subduction zones produce stratovolcanoes with explosive eruptions due to the interaction of oceanic and continental plates.

* Hotspots and mid-ocean ridges often create shield volcanoes with less explosive eruptions.

These factors work together to determine the volcano's shape, size, and eruptive style.