Frequently Asked Questions

The map and the data

Is this a live volcano map?

No. It is a historical archive of volcanoes and eruptions, refreshed from time to time from the Smithsonian Global Volcanism Program. For current activity, see the GVP Weekly Volcanic Activity Report or your national volcano observatory.

Where does the data come from?

The Global Volcanism Program of the Smithsonian Institution, the standard global catalogue of volcanoes and eruptions. See the about page for how it is processed and cited.

Why does the number of eruptions rise over time?

Mostly because observation improved. Remote and submarine eruptions used to go unrecorded; global satellite monitoring since about 1980 now catches many that would once have been missed. The underlying rate of volcanic activity has not measurably changed.

What do the small markers and the coloured circles mean?

The small hollow markers are the roughly 1,300 volcanoes that have erupted during the Holocene (about the last 12,000 years) — they are always shown. The filled circles are eruptions within the time window you have selected, coloured and sized by Volcanic Explosivity Index: grey for VEI 0–1 or unrecorded, through orange, to bright red for VEI 5 and above.

Why are volcanoes lined up in arcs?

Most sit above subduction zones, where one tectonic plate dives beneath another. Water released from the sinking plate makes the mantle melt along the length of the boundary, so volcanoes form a curved chain — an arc — that parallels it. See Plate Tectonics and Volcanoes.

Volcano science

What does VEI mean?

The Volcanic Explosivity Index, a 0–8 scale for the size of an explosive eruption, based mainly on erupted volume and plume height. It is logarithmic above VEI 2 — each step is about ten times more material. See The Volcanic Explosivity Index.

How many volcanoes are erupting right now?

On a typical day, somewhere between about 40 and 50 volcanoes are in some state of eruption. Over a year, roughly 50 to 70 volcanoes have new eruptive activity (Global Volcanism Program).

What was the largest eruption in recorded history?

The 1815 eruption of Tambora in Indonesia, VEI 7. It ejected around 100 km³ of material and caused the “year without a summer” in 1816. The largest eruptions page has the details.

What is a supervolcano?

Informal term for a volcano capable of a VEI 8 eruption — more than 1,000 km³ of material, at least ten times Tambora. Toba, Yellowstone and Taupō have produced such eruptions in the geological past. None has occurred in recorded human history, and there is no scientific basis for claims that a particular one is “overdue”.

What is the difference between magma and lava?

They are the same molten rock. It is called magma while it is still underground and lava once it has erupted onto the surface.

Are volcanoes and earthquakes connected?

Both concentrate at plate boundaries, so they map onto the same lines. Volcanoes also generate their own small earthquakes as magma moves, which is one of the main warning signs of an eruption. Large tectonic earthquakes only rarely trigger a nearby volcano to erupt.

Can eruptions be predicted?

Often, and much better than earthquakes. Magma has to physically move toward the surface before an eruption, producing earthquakes, ground swelling and gas over days to weeks. Volcano observatories use these signs to raise alert levels and evacuate, as at Pinatubo in 1991. The size and precise timing are still hard to forecast, and remote or unmonitored volcanoes can still erupt with little warning.

Safety

Where can I get volcano alerts and safety information?

Follow your national volcano observatory (for example the USGS Volcano Hazards Program, or your country’s equivalent) for alert levels, and the Volcanic Ash Advisory Centres for aviation. The Global Volcanism Program’s Weekly Volcanic Activity Report summarises activity worldwide. This website is an educational archive and is not a source of emergency information.