Volcano Hazard Zone Calculator

Hazard radius from eruption type and VEI.

VEI (0-8)

Eruption type (0-3)

Summit elevation (m)

Your distance (km)

Tab to move between fields

Pyroclastic flow radius (km)

7.94

Lahar hazard distance (km)19.06

Ashfall radius (km)223.87

Eruption column (km)11.19

Ejecta volume (m³)10,000,000

Risk at your distance (0-100)54.5

How to Use This Calculator

Select the Volcanic Explosivity Index (VEI 0–8): 0 is gentle Hawaiian lava flows, 3 is sub-Plinian, 8 is supervolcano scale.
Choose the Eruption type: 0=Effusive, 1=Explosive/Plinian, 2=Phreatic steam-driven, 3=Pyroclastic flow-dominant.
Enter Summit elevation (m) — snow-capped, high-elevation volcanoes produce more dangerous lahars when snow melts.
Enter Your distance (km) from the volcanic vent to get a site-specific Risk score (0–100).
Compare your distance to the Pyroclastic flow radius (km), Lahar distance (km), and Ashfall radius (km) to understand which hazards reach your location.

What each input means

VEI (0-8): Volcanic Explosivity Index. 0=gentle effusive, 3=severe, 5=paroxysmal, 8=supervolcano.
Eruption type (0-3): 0=Effusive (lava), 1=Explosive (Plinian), 2=Phreatic (steam), 3=Pyroclastic (flow-dominant).
Summit elevation (m): Volcano summit height. Higher summits with snow increase lahar risk.
Your distance (km): Distance from the volcanic vent to assess risk at your location.

Pyroclastic flow radius (km): Maximum extent of deadly pyroclastic flows and surges.
Lahar hazard distance (km): Maximum travel distance for volcanic mudflows along valleys.
Ashfall radius (km): Estimated radius for significant ashfall (>1 cm deposit).
Eruption column (km): Estimated eruption column height above the vent.
Ejecta volume (m³): Total volume of erupted material based on VEI.
Risk at your distance (0-100): Relative hazard level at your specified distance from the vent.

Identify Input Parameters
4 parameters
VEI (0-8) = 3, Eruption type (0-3) = 1, Summit elevation (m) = 3000, Your distance (km) = 10 = 4 input(s) provided
Calculate Pyroclastic flow radius
Pyroclastic flow radius = min(100, typeMultiplier * pow(10, 0.4 * vei - 0.3))
7.94 = 7.94
Calculate Lahar hazard distance
Lahar hazard distance = min(200, pyroclasticFlowRadius * 1.5 * snowFactor)
19.06 = 19.06
Calculate Ashfall radius
Ashfall radius = min(1000, columnHeightKm * 20)
223.87 = 223.87