James Stewart

The VEI scale is open-ended in principle, but all known events are graded between 0 and 8. Events scoring 0 are represented by eruptions of low viscosity, or runny, lava at volcanoes such as Kilauea or Manalahu on Hawaii. Although these eruptions can involve large volumes of material and are dangerous in their own right, they are what geologists term effusive in nature.

The VEI scale is open-ended in principle, but all known events are graded between 0 and 8. Events scoring 0 are represented by eruptions of low viscosity, or runny, lava at volcanoes such as Kilauea or Manalahu on Hawaii. Although these eruptions can involve large volumes of material and are dangerous in their own right, they are what geologists term effusive in nature.

This means that the lava flows rather than explodes from the volcano's vent. Go up the scale to a VEI of 2 and you reach the sort of eruption represented by the ongoing activity at Mount Etna in Sicily. Keep going, and at a VEI of 3, you get to something like the eruption of Sufriere Hills, which covered much of the Caribbean island of Montserrat with ash in 1996 and 1997.

This means that the lava flows rather than explodes from the volcano's vent. Go up the scale to a VEI of 2 and you reach the sort of eruption represented by the ongoing activity at Mount Etna in Sicily. Keep going, and at a VEI of 3, you get to something like the eruption of Sufriere Hills, which covered much of the Caribbean island of Montserrat with ash in 1996 and 1997.

This means that the lava flows rather than explodes from the volcano's vent. Go up the scale to a VEI of 2 and you reach the sort of eruption represented by the ongoing activity at Mount Etna in Sicily. Keep going, and at a VEI of 3, you get to something like the eruption of Sufriere Hills, which covered much of the Caribbean island of Montserrat with ash in 1996 and 1997.

At a VEI of 4, you reach the 2010 eruption of the Icelandic volcano whose ash clouds spread over Europe and the Atlantic Ocean, disrupting air travel for several weeks. Because many of an eruption's attributes can't be determined with certainty, there's sometimes disagreement about what score should be assigned to a given eruption.

At a VEI of 4, you reach the 2010 eruption of the Icelandic volcano whose ash clouds spread over Europe and the Atlantic Ocean, disrupting air travel for several weeks. Because many of an eruption's attributes can't be determined with certainty, there's sometimes disagreement about what score should be assigned to a given eruption.

At a VEI of 4, you reach the 2010 eruption of the Icelandic volcano whose ash clouds spread over Europe and the Atlantic Ocean, disrupting air travel for several weeks. Because many of an eruption's attributes can't be determined with certainty, there's sometimes disagreement about what score should be assigned to a given eruption.

The 2022 Tonga event, with an erupted rock volume of about 1.9 cubic kilometres and a plume that reached a height of 58 kilometres, earns a five on the VEI scale by most estimates, although some volcanologists push it up to a six. This is roughly on a par with the famous 1980 eruption of Mount St. Helens in Washington State in the US.

The 2022 Tonga event, with an erupted rock volume of about 1.9 cubic kilometres and a plume that reached a height of 58 kilometres, earns a five on the VEI scale by most estimates, although some volcanologists push it up to a six. This is roughly on a par with the famous 1980 eruption of Mount St. Helens in Washington State in the US.

The 2022 Tonga event, with an erupted rock volume of about 1.9 cubic kilometres and a plume that reached a height of 58 kilometres, earns a five on the VEI scale by most estimates, although some volcanologists push it up to a six. This is roughly on a par with the famous 1980 eruption of Mount St. Helens in Washington State in the US.

And in case you're wondering what 1.9 cubic metres looks like, it's roughly the volume of a large open-pit mine, such as the Myrrh Diamond Mine in Russia, or the Bingham Canyon Copper Mine in the US.

And in case you're wondering what 1.9 cubic metres looks like, it's roughly the volume of a large open-pit mine, such as the Myrrh Diamond Mine in Russia, or the Bingham Canyon Copper Mine in the US.

And in case you're wondering what 1.9 cubic metres looks like, it's roughly the volume of a large open-pit mine, such as the Myrrh Diamond Mine in Russia, or the Bingham Canyon Copper Mine in the US.

Even more violent eruptions than Tonga, those firmly within category 6, include the 1991 eruption of Mount Pinatubo in the Philippines, which caused a small but measurable cooling of the globe due to the aerosols it injected into the stratosphere.

Even more violent eruptions than Tonga, those firmly within category 6, include the 1991 eruption of Mount Pinatubo in the Philippines, which caused a small but measurable cooling of the globe due to the aerosols it injected into the stratosphere.

Even more violent eruptions than Tonga, those firmly within category 6, include the 1991 eruption of Mount Pinatubo in the Philippines, which caused a small but measurable cooling of the globe due to the aerosols it injected into the stratosphere.

And the 1883 eruption of Krakatawa in Indonesia, whose ash might have been responsible for the lurid red sky depicted by Edvard Munch in his painting The Scream. A VEI of 7 is reserved for the greatest eruptions in recorded history. These come with the accompanying descriptor super colossal compared to the merely cataclysmic eruptions like Tonga in the VEI 5 bracket.

And the 1883 eruption of Krakatawa in Indonesia, whose ash might have been responsible for the lurid red sky depicted by Edvard Munch in his painting The Scream. A VEI of 7 is reserved for the greatest eruptions in recorded history. These come with the accompanying descriptor super colossal compared to the merely cataclysmic eruptions like Tonga in the VEI 5 bracket.

And the 1883 eruption of Krakatawa in Indonesia, whose ash might have been responsible for the lurid red sky depicted by Edvard Munch in his painting The Scream. A VEI of 7 is reserved for the greatest eruptions in recorded history. These come with the accompanying descriptor super colossal compared to the merely cataclysmic eruptions like Tonga in the VEI 5 bracket.