Volcano Eruption & Magma Dynamics Lab
Control magma temperature, silica and gas content and watch the eruption style flip between a gentle lava flow and an explosive blast.
How to use: set the magma's temperature, silica and gas content and the chamber's overpressure and vent width, then press "Trigger eruption" to see the resulting eruption style. Watch how viscosity and the Explosivity Index respond in "Show my work", then try the Challenge tab.
Challenge: produce a highly explosive eruption
Real eruptions get more explosive when magma is viscous (high silica, cooler) and gas-rich: the gas cannot escape smoothly through thick magma, so pressure builds until it shatters the magma into ash. Set the sliders so the Explosivity Index reaches 7.0 or higher, then press Check.
Challenge 2: produce a gentle effusive eruption
Basaltic lava flows happen when magma is runny (low silica, hot) and gas can escape easily through a wide vent. Set the sliders so the Explosivity Index drops to 2.0 or lower, then press Check.
About the Volcano Eruption & Magma Dynamics Lab
Free volcano eruption & magma dynamics lab. Control magma temperature, silica and gas content and watch the eruption style flip between a gentle lava flow and an explosive blast. Drag, change the sliders and see the result live. No sign-up, works on phone and computer. Built for geology, the volcano eruption & magma dynamics lab runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Control magma temperature, silica and gas content and watch the eruption style flip between a gentle lava flow and an explosive blast. Use it to explore geology ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Volcano Eruption & Magma Dynamics Lab
- Use the controls to change Magma temperature, Silica content (SiO₂), Dissolved gas content, Chamber overpressure, Vent diameter. The simulation reacts instantly.
- Press "Trigger eruption", "Reset chamber", "Reset to defaults", "📄 Lab Report" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Push silica above 65% and gas above 3% and see the eruption turn explosive.
- Set silica low and temperature high for a lazy effusive flow.
- Try the challenge: reach an Explosivity Index of 7 or higher.
- Watch how narrowing the vent changes the same magma from mild to violent.
Key ideas you can learn
- Viscosity rises steeply with silica content and falls as magma gets hotter.
- Thick, viscous magma traps gas bubbles until pressure shatters it into ash: that is an explosive eruption.
- Runny, low-silica (basaltic) magma lets gas escape smoothly, producing effusive lava flows.
- A narrow vent restricts gas escape and raises explosivity; a wide vent lowers it.
Where this is used in the real world
Volcanologists use exactly these viscosity-silica-gas relationships to forecast whether a volcano like Kilauea (effusive) or Mount St. Helens (explosive) will erupt gently or catastrophically.
Who is this simulation for?
Students, teachers and curious learners of all ages.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
Why is rhyolite more explosive than basalt?
Rhyolite has more silica, which makes long silicate chains that raise viscosity, trapping gas until it bursts out violently.
What is the Volcanic Explosivity Index modeling here?
A simplified index combining viscosity and gas content, matching the real pattern that gassy, viscous magma erupts more explosively.
Is the Volcano Eruption & Magma Dynamics Lab free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Volcano Eruption & Magma Dynamics Lab work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.