Skip to content
ENExplore Calculators

Volcano Eruption Volume Calculator

Work out volcano eruption volume instantly with clear inputs, formula shown and shareable results.

About Volcano Eruption Volume Calculator

Eruption volume is deposit area times average thickness, but tephra is porous, so the figure is converted to dense rock equivalent by scaling with the density ratio against magma at about 2500 kg/m3. 120 square kilometres at 0.35 m gives 0.042 cubic kilometres bulk, about 0.017 DRE - a VEI 4 event.

Formulas

Bulk volume

volume = deposit area x average thickness

Dense rock equivalent

DRE = bulk volume x deposit density / magma density

Worked example

With the default values below, Volcano Eruption Volume Calculator returns Bulk Deposit Volume of 0.0420. Change any input above and every figure here is recalculated in your browser.

Inputs used

Area covered by depositsminimum 0 km2
120 km2
Average deposit thicknessminimum 0 m
0.35 m
Deposit bulk densityminimum 0 kg/m3
1,000 kg/m3

Results

Bulk Deposit Volume
0.0420 km3
Dense Rock Equivalent
0.0168 km3
Approximate Volcanic Explosivity Index
3
Erupted Mass
4.2000 × 10⁷ t

Step by step

  1. 1Values used
  2. 2Bulk volume
  3. 3Dense rock equivalent
  4. 4Bulk Deposit Volume= 0.0420 km3
  5. 5Dense Rock Equivalent= 0.0168 km3
  6. 6Approximate Volcanic Explosivity Index= 3
  7. 7Erupted Mass= 42,000,000.0000 t

Assumptions and limits

  • The result is derived only from the 3 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

Why convert to dense rock equivalent?

Because tephra deposits are up to 60% void space. Comparing eruptions needs the equivalent volume of solid magma.

How is VEI defined?

By erupted bulk volume on a logarithmic scale: VEI 4 is 0.1-1 km3, VEI 5 is 1-10 km3, and each step is a tenfold increase.

Related Calculators

Volcano Eruption Volume Calculator | Calcrivo