Introduction — Volcanic Explosivity Index (VEI)
The Volcanic Explosivity Index (VEI), developed in 1982 by C. G. Newhall and S. Self (USGS), is a semi‑quantitative ordinal scale designed to compare the size and explosiveness of volcanic eruptions and to assist in hazard assessment. Assignment of a VEI integrates measured tephra volume, observed eruption cloud (column) height, and field-based qualitative descriptions of eruption style (ranging from low‑intensity to “mega‑colossal”), yielding a single explosivity class for each event. The index is open‑ended but historically reaches as high as magnitude 8; a value of 0 denotes non‑explosive activity. Quantitatively, VEI = 0 corresponds to eruptions producing less than 1.0×10^4 m3 (≈3.5×10^5 ft3) of tephra, whereas VEI = 8 characterizes supervolcanic eruptions that can eject on the order of 1.0×10^12 m3 (≈240 mi3) of material and produce eruption columns exceeding ~20 km (≈66,000 ft), with attendant stratospheric injection and widespread climatic and dispersal consequences. The VEI is largely logarithmic—each integer step approximates a tenfold increase in erupted volume—although the pattern departs from strict decade scaling at the lowest classes (VEI‑0, ‑1, and ‑2).
Classification
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The Volcanic Explosivity Index (VEI) is an ordinal scale from 0 to 8 that characterizes eruptions primarily by bulk ejecta volume, plume height and eruption duration. Above VEI‑1 the scale is effectively logarithmic: each integer step from VEI‑2 upward corresponds to roughly a tenfold increase in erupted volume. There is, however, a discontinuous jump between VEI‑1 and VEI‑2, where the minimum ejecta volume rises from 10^4 m3 to 10^6 m3; thereafter threshold volumes increase by about an order of magnitude with each index.
Low-intensity eruptions (VEI 0–1) are dominated by effusive or gentle Strombolian activity. VEI‑0 (<10^4 m3) describes sustained, Hawaiian-style lava production with plumes generally below 100 m and negligible stratospheric injection (e.g., Kīlauea, recent Fagradalsfjall and Mauna Loa episodes). VEI‑1 (>10^4 m3) denotes small, frequent events producing 100 m–1 km plumes and only minor tropospheric perturbation (representative examples include some Dieng complex and small submarine eruptions).
Moderate explosive eruptions (VEI 2–3) mark the transition to true explosive behavior. VEI‑2 (>10^6 m3) encompasses Strombolian–Vulcanian activity with 1–5 km plumes and recurrence on the order of weeks; stratospheric delivery is not expected. VEI‑3 (>10^7 m3) covers more severe Strombolian/Vulcanian to sub‑Plinian styles with 3–15 km plumes, periodicities of months, and the potential for some stratospheric injection (examples range from Stromboli and Mount Etna to Nevado del Ruiz).
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Large explosive eruptions (VEI 4–5) produce sustained Plinian or Peléan eruptions with substantial atmospheric effects. VEI‑4 (>0.1 km3) typically generates plumes >10 km, recurs on the order of years, and commonly injects material into the stratosphere (e.g., Pelée 1902, Eyjafjallajökull 2010). VEI‑5 (>1 km3) denotes more powerful Plinian events with decadal recurrence intervals, significant stratospheric injection and widespread impacts (e.g., Vesuvius 79, St. Helens 1980, Hunga Tonga–Hunga Haʻapai 2022).
Very large to super‑colossal eruptions (VEI 6–7) are infrequent but globally consequential. VEI‑6 (>10 km3) (Plinian/Ultra‑Plinian) produces plumes often exceeding 20 km and recurs on centennial timescales, while VEI‑7 (>100 km3) (Ultra‑Plinian) represents extreme eruptions with interarrival times of centuries to millennia and extensive tropospheric and stratospheric injection (historical and geologic examples include Pinatubo 1991, Krakatoa 1883, Tambora 1815 and several older caldera‑forming events).
VEI‑8 (>1,000 km3) defines the rarest “mega‑colossal” supereruptions, with plumes extending well into the stratosphere, global aerosol loading and recurrence on very long (tens of thousands of years) timescales. Geological records identify several VEI‑8 events (e.g., La Garita, Yellowstone, Toba), with the Oruanui eruption of Lake Taupō (~>27 kyr) the most recent recognized VEI‑8; none are known from the Holocene.
Long‑term and catalog statistics reflect both eruption frequency and preservation biases. Roughly 40 VEI‑8 events have been identified in the last ~132 million years (30 of those in the past ~36 Ma), though under‑recognition implies the true number could be higher (some estimates exceed 60). At least ten VEI‑7 eruptions occurred during the Holocene. The Smithsonian Global Volcanism Program had assigned VEI values to 7,742 Holocene eruptions (about 75% of known Holocene activity) by 2010; of these, roughly half are VEI‑2 or lower and about 90% are VEI‑3 or lower, indicating that small to moderate eruptions dominate the observed record.
Limitations
The Volcanic Explosivity Index (VEI) simplifies eruption characterization by aggregating different eruptive products—ash, lava, lava bombs and ignimbrite—into a single scale without distinguishing their physical nature. It likewise omits material properties such as density and vesicularity, so highly porous or extensively vesiculated tephra or lava are treated equivalently to dense, non‑vesicular deposits. To correct for this, volcanologists sometimes compute the dense‑rock equivalent (DRE), which converts erupted deposits into the volume or mass of non‑vesicular rock and thus provides a better estimate of the actual amount of magma erupted.
The VEI also does not capture eruption power (mass/energy release rate), a limitation that complicates VEI assignment for prehistoric or unobserved events where intensity cannot be directly measured. Furthermore, while the VEI is useful for ranking explosive magnitude, it is a poor proxy for atmospheric and climatic effects: sulfur dioxide emissions are more directly tied to atmospheric chemistry and climate forcing. Consequently, a comprehensive geological and climatic assessment of an eruption requires multiple metrics—VEI for explosive magnitude, DRE for true magma quantity, and quantified sulfur dioxide release for atmospheric and climatic consequences.
Lists of notable eruptions — summary
An interactive global eruption imagemap plots notable volcanic events as clickable bubbles whose apparent volume is scaled linearly to the measured tephra volume, and whose colour encodes age according to the map legend. Tectonic context is overlaid: convergent margins are shown, divergent boundaries are distinguished, and intraplate hotspots are marked, allowing each eruption to be read in both spatial and geodynamic frameworks. This visual encoding permits rapid cross‑comparison of erupted volume, age and tectonic setting without changing geographic position.
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Complementary chronological and thematic catalogues provide multiple temporal windows and analytical foci. A timeline emphasizing the last 2,000 years documents the frequency and distribution of very large late‑Holocene eruptions—many near VEI‑6—while a dedicated catalogue covers eruptions from 1500–2000 to characterise early modern and modern clustering and yields. A separate record for the 21st century (from 2001) tracks recent activity within contemporary observational networks. The human consequences of volcanism are addressed by a mortality‑ranked list that places fatalities alongside tephra and VEI metrics.
Longer‑term compilations situate individual events in geological perspective: a Holocene list catalogs VEI‑5 to VEI‑7 eruptions that produced significant regional to hemispheric tephra deposits; an extended record spanning over 450 million years compiles eruptions assessed at VEI‑5 to VEI‑8; and a targeted subset identifies the largest known events (mostly VEI‑7 to VEI‑8), which occur predominantly within approximately the last 500 million years. Together, the imagemap and these lists enable integrated spatial–temporal analysis—linking where (coordinates and tectonic setting), when (age/century/epoch), and how large (tephra volume/VEI) major eruptions were—to support comparative studies of volcanic hazard, frequency, and Earth‑system impacts.