Final answer:
Magma high in silica leads to explosive eruptions due to its high viscosity and resistance to flow, which traps gases and builds pressure until a violent release occurs.
Step-by-step explanation:
Magma high in silica tends to produce explosive eruptions. This type of magma has a high viscosity, meaning it is resistant to flow. Because of this increased resistance, gases that are dissolved within the magma cannot escape easily as the magma ascends towards the surface. Instead, these gases build up pressure until they are released catastrophically, leading to potentially violent and explosive volcanic eruptions. The high silica content makes the magma thick and sticky, compounding the tendency towards explosive behavior.
Volcanic glass, like obsidian, is also related to high-silica magma. These glasses form when the high-silica magma cools so rapidly that atoms do not have time to arrange into a crystal structure, producing glass with a random arrangement of atoms.
Understanding the composition of magma is essential for predicting an eruption's style and potential hazards. Magma type is closely associated with volcano type and eruptive style, with high-silica magma often indicating a more dangerous and explosive volcanic risk.