🔥 Magma Types
Basaltic magma (Hawaii) has low silica and is runny — it erupts effusively, creating broad shield volcanoes and flowing lava rivers. Rhyolitic magma (Yellowstone) has high silica, is incredibly viscous, and traps gas — leading to explosive, catastrophic eruptions.
📊 VEI Scale
The Volcanic Explosivity Index measures eruption magnitude on a 0–8 logarithmic scale. Each step is 10× more powerful. VEI 8 "supereruptions" are rare but can lower global temperatures for years by injecting sulfur dioxide into the stratosphere.
💨 Pyroclastic Flows
The most lethal volcanic hazard — dense, fast-moving avalanches of hot gas, ash, and rock fragments travelling at 100–700 km/h at 300–800 °C. No natural shelter can protect against a direct flow. They were responsible for most deaths at Vesuvius and St. Helens.