🌋Volcano Eruption Physics Simulator - Plume Height, VEI, Magma Viscosity, Volcanic Bombs

How to use Volcano Eruption Physics

1. 1Under Eruption column, drag the mass eruption rate and duration or pick a historical eruption; read the column height, volume and VEI, and set SO₂ to see the cooling
2. 2Under Viscosity & bubbles, change SiO₂, temperature, water and ascent speed; watch bubbles grow in the conduit, the fragmentation depth and the predicted eruption style
3. 3Under Volcanic bombs, set the launch speed, angle and size and compare ranges with and without drag, plus the hazard radius
4. 4Under Lava flow, set the thickness, slope and viscosity to get the flow speed from Jeffreys' equation

FAQ

Why do some volcanoes explode while others just pour out lava?

It comes down to whether gas can escape as magma rises. Deep magma holds a few weight percent of dissolved water; as pressure drops, water exsolves (solubility ∝ √P) into bubbles that expand quickly. Basalt is runny (about 10²–10³ Pa·s), so bubbles merge and escape, giving lava fountains and flows. Silica-rich rhyolite and dacite can be a million times more viscous, trapping the bubbles until gas fills about 75 % of the volume and the magma shatters into ash, driving a Plinian column. Faster ascent and more water make an explosion more likely.

How is the Volcanic Explosivity Index defined?

VEI is based mainly on erupted volume: VEI 0 is under 10⁴ m³, VEI 1 from 10⁴ m³, VEI 2 from 10⁶ m³ and VEI 3 from 10⁷ m³, and each step after that is ten times larger: VEI 4 about 0.1 km³, VEI 5 1 km³, VEI 6 10 km³, VEI 7 100 km³ and VEI 8 over 1,000 km³. Column height is a secondary guide. Mount St. Helens in 1980 was about VEI 5, Pinatubo in 1991 VEI 6 and Tambora in 1815 VEI 7, the largest eruption in recorded history.

How does column height depend on eruption rate?

An eruption column rises on the buoyancy of heated air, and plume theory (Morton, Taylor and Turner) predicts a height proportional to the fourth root of the heat flux. Mastin et al. (2009) fitted observations as H ≈ 2.0·V^0.241 km, where V is the dense-rock volume erupted per second. A tenfold increase in eruption rate raises the column only about 1.7 times, and lofting ash above 30 km into the stratosphere takes hundreds of millions of kilograms per second.

Why can eruptions cool the whole planet?

Large explosive eruptions inject sulfur dioxide into the stratosphere, where it turns into sulfate aerosol within weeks. The droplets reflect part of the sunlight back to space and linger for a year or two. Pinatubo's roughly 17 Mt of SO₂ cooled the global mean by about 0.5 °C, and Tambora made 1816 the 'year without a summer'. If the column stays in the troposphere, rain washes the sulfate out within days and the cooling is small. The tool's estimate is a rough one-box energy balance.

How far can volcanic bombs fly?

It depends on launch speed, angle and size. Vent speeds are typically one to a few hundred metres per second. In a vacuum the range is v²/g, about 4 km at 200 m/s, but air drag shortens it a lot. Drag grows with cross-section while weight grows with volume, so big blocks feel relatively little drag and fly close to a parabola, while small fragments slow quickly. Exclusion zones around volcanoes are usually set at the maximum ballistic range plus a safety margin.