1. Basaltic magma: This is the most common type of magma, characterized by its low silica content (45-55%). It is typically found in oceanic environments and is associated with hot spots and mid-ocean ridges. Basaltic magma produces fluid, fast-moving lava flows and is responsible for the formation of shield volcanoes and oceanic plateaus.

2. Andesitic magma: This magma has an intermediate silica content (55-65%). It is commonly found in subduction zones where oceanic plates collide with continental plates. Andesitic magma produces more viscous lava flows, leading to the formation of composite volcanoes (stratovolcanoes) with steep slopes and explosive eruptions.

3. Rhyolitic magma: This type of magma has the highest silica content (65-75%). It is often found in continental settings and is associated with continental rifts and volcanic arcs. Rhyolitic magma is highly viscous, creating thick, slow-moving lava flows and highly explosive eruptions. Rhyolitic eruptions can produce massive caldera formations.

The factor that determines these classifications is the silica content of the magma.

* Silica (SiO2) acts as a framework for magma, and its abundance directly influences the viscosity of the magma.

* Higher silica content results in more viscous magma, making it thicker and more resistant to flow.

* Lower silica content leads to less viscous magma, which is more fluid and flows easily.

This difference in viscosity significantly impacts the eruptive style of volcanoes, with high silica magmas producing more explosive eruptions and low silica magmas producing more effusive flows.