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What It Demonstrates

Real eruptions sit along a continuum set mostly by two magma properties: how viscous the melt is (governed by silica content and temperature) and how much dissolved gas — mostly H₂O and CO₂ — it carries. Low-viscosity magma lets gas bubbles rise and escape almost as fast as they form, so pressure never builds: the result is effusive, fountaining behaviour. High-viscosity magma throttles that escape, so gas stays trapped until it overcomes the magma's strength — the more gas trapped, the more violent the release.

How to Use

Drag the Viscosity and Volatile content sliders, or click a real-world preset, and watch the classification box, VEI, and plume height update instantly along with the 3D eruption. Drag on the canvas to orbit the camera and scroll to zoom. Use Trigger now to force an event for Strombolian/Vulcanian styles, which erupt in discrete pulses rather than continuously.

About this simulation

Written by MySimulator Team · Reviewed by MySimulator Editorial Review

Last updated: 20 July 2026

Eruption style is classified here from two independent axes — magma viscosity (log₁₀ Pa·s) and dissolved volatile content (wt%) — combined into a continuous explosivity index that also drives an approximate VEI and plume height, while a four-way rule assigns the Hawaiian / Strombolian / Vulcanian / Plinian label.

🔬 What it shows

Viscosity governs how easily gas bubbles rise, merge, and escape through the conduit; volatile content sets how much gas there is. Low viscosity keeps the system "open" (gas leaks out, eruptions stay gentle); high viscosity plus high gas builds trapped overpressure until the magma fragments explosively.

🎮 How to use

Drag the Viscosity and Volatile content sliders, or click a real-world preset (Kīlauea, Stromboli, Sakurajima, Pinatubo). Watch the classification box, VEI, and plume height update live, orbit the camera by dragging on the canvas, and use Trigger now to force a pulse for the burst-style eruptions.

💡 Did you know?

The 1991 Pinatubo Plinian column reached roughly 35 km — into the stratosphere — and cooled global average temperatures by about 0.5 °C for over a year, while Kīlauea's Hawaiian fountains rarely exceed a few hundred metres, despite both being basaltic-to-silicic points on the very same viscosity–gas continuum.

Frequently asked questions

What determines whether an eruption is explosive or effusive?

Mainly two things: magma viscosity and dissolved gas (volatile) content. Low-viscosity magma lets gas bubbles rise and escape passively, so pressure never builds and the eruption is effusive. High-viscosity magma traps that same gas until it overcomes the magma's strength, fragmenting it explosively.

Why is Hawaiian the gentlest eruption style?

Hawaiian eruptions come from very fluid basaltic magma (viscosity as low as 10-100 Pa·s). Gas bubbles rise through it almost as fast as they nucleate, so the system stays "open" and degasses continuously as lava fountains and flows rather than building the overpressure needed for a violent blast.

What makes Strombolian eruptions rhythmic and repetitive?

In a Strombolian system, large gas bubbles ("slugs") form and rise up a relatively fluid conduit at a fairly steady rate. Each slug bursts individually at the surface, producing the short, evenly spaced explosions that gave Stromboli its nickname, the "Lighthouse of the Mediterranean."

Why do Vulcanian eruptions happen in sudden violent bursts?

Vulcanian eruptions involve stickier magma that can solidify into a plug sealing the vent between events. Gas pressure accumulates beneath the plug until it fails catastrophically, releasing a short, sharp blast of ash and blocks — then the cycle restarts as a new plug forms.

What makes Plinian eruptions the most dangerous style?

Plinian eruptions need magma that is both highly viscous (often rhyolitic or dacitic) and gas-rich. The trapped gas fragments the magma almost completely on ascent, driving a sustained, buoyant column that can pierce the stratosphere, collapse into deadly pyroclastic flows, and inject ash and sulphur aerosols that affect global climate.

What is the Volcanic Explosivity Index (VEI) shown here?

VEI is a logarithmic 0-8 scale used by volcanologists, based mainly on erupted volume and plume height. This simulation derives an approximate VEI from its own explosivity index (a function of viscosity and gas content), so it is illustrative rather than a calibrated measurement of a specific real eruption.

Is the classification a hard boundary or a continuum?

It's a continuum. The four named styles are useful labels for regions of viscosity-gas space, but real eruptions can sit near a boundary, drift between styles as magma composition changes mid-eruption, or blend characteristics — the explosivity index behind the scenes is fully continuous.

Is this simulation physically accurate?

It is an educational model, not a research-grade conduit-flow solver. It captures the right qualitative relationship — viscosity throttles gas escape, gas content sets how much pressure can build, and both together set explosivity — but real eruptions also depend on conduit geometry, magma supply rate, and crystal content that are simplified away here.