The Decade Volcanoes


On 22 December 1989, the United Nations General Assembly designated the oncoming decade – the 1990s – as the International Decade for Natural Disaster Reduction

The gist was to reduce the loss of life and property due to tsunamis, earthquakes, floods, storms, droughts, landslides, and volcanoes. The resolution intended to identify and study some of the locations most prone to natural disaster, then to develop plans to mitigate the negative effects of the disaster.

Tasked with the volcano portion of the plan was the International Association for Volcanology and Chemistry of the Earth’s Interior. The group identified volcanoes worthy of insight because they fit two original criteria: 1) a history of destructive eruptions and B) proximity to massively populated regions. They dubbed 16 fiery mountains as the Decade Volcanoes.

The Decade Volcanoes on the globe

Looking at the list above, you’ll probably recognize some of the Decade Volcanoes. Rainier, Vesuvius, Etna, and Mauna Loa are some of the most recognizable names in vulcanology. Many of the others might only tickle the memory of the volcano aficionado.

The IAVCEI sharpened the list by intensifying the definition of inclusion. To make the final cut, a volcano needed to tick these boxes:

  • exhibit more than one of the following volcanic hazards: tephra fall (material produced by the mountain and shot into the sky), pyroclastic flow (fast-moving current of hot gases and other materials), lava flow (the traditional, red-hot ejections), lahars (mudflow), volcanic edifice instability (will the structure itself deteriorate?), lava dome collapse (often causes explosive consequences)
  • recent activity
  • located near a densely populated area
  • politically and physically accessible for study

Essentially, the Decade Volcanoes have a knack for exhibiting some of the most cataclysmic properties of volcanoes and doing so in a zone full of contemporary humanity. Some volcanoes on the globe might be more calamitous, but these examples pose a massive risk to living beings.

Mount Rainier from the west - photo by Stan Shebs

A little over a year ago, we studied the famous eruption of Mt. St. Helens in 1980 (see Related Articles below). It was the largest eruption in the recorded history of the continental United States. Despite both being a neighbor to Rainier and its extraordinary explosion, the Mt. St. Helens disaster, fortunately, resulted in a relatively small amount of human death. St. Helens could not make the Decades Volcanoes list because its cone of desolation is not close to a major population center. Its cousin Rainier, on the other hand, could wipe out nearly 800,000 people.

If Rainier erupted on the same level as St. Helens, the cumulative effect would dwarf the 1980 disaster. Rainier is about twice the size of St. Helens and contains far more glacial ice. The glaciers could become multiple hazards from the list above. The ice can be tephra; it can cause lahars and contribute to pyroclastic flows. The United States Geological Survey estimates that 150,000 live on old lahar deposits from Rainer.

5,600 years ago, the Osceola Mudflow – a gigantic lahar – covered 210 square miles in muddy sludge. The lahar reached the Puget Sound, nearly 40 miles in a straight line from the summit of Rainier. An event of this magnitude today would be apocalyptic.

Estimated Rainier lahar danger zones - image by USGS

As disastrous as a mega-eruption would be in the greater-Seattle area, Rainier isn’t even close to the top of the population list when it comes to Decade Volcanoes.

Mountains in Italy, Guatemala, Japan, and Colombia would disturb more than a million individuals. Mt. Vesuvius, already famous for human fatalities, sits within range of more than 3 million humans. Mt. Merapi in Indonesia threatens over 5 million people. None of these volcanoes, however, has anything on Taal Volcano in the Philipines. At just 1,020 feet high, Taal might seem to be an insignificant volcano, but appearances are deceiving. This explosive site could reach more than 24 million nearby people, as it is just 30 miles south of Manila!

With population centers this huge, it’s easy to see why the Decade Volcano project was so crucial.

Taal Volcano - photo by Mike Gonzalez

As with most ideas that focus on preventing future disasters, we humans didn’t really want to fund the International Decade for Natural Disaster Reduction, so its overall reach underwhelmed its vision. Yet some important victories emerged from the Decade Volcanoes program.

In 1992, scientists successfully diverted a lava flow from Mt. Etna, saving the town of Zafferana. Studies into the chosen examples produced significant scientific insights into a few of the volcanoes which had previously been poorly understood, including Taal and Galeras in Colombia. Local measures in Washington have greatly improved since the project, as new developments are subject to geological study. The city of Naples now has a comprehensive evacuation plan, should Vesuvius threaten the metropolis.

It hasn’t all been good news when it comes to the Decade Volcanoes, though. Mt. Unzen in Japan produced 43 deaths, despite widespread monitoring. In 1993, a conference in Colombia convened to study Galeras. An impromptu group of vulcanologists decided to visit the summit, whence an unexpected eruption claimed the lives of six scientists and three tourists.

Fortunately, though, to date, none of the Decade Volcanoes has produced “the big one,” giving us more time to prepare for future upheaval.

Mt. Etna eruption, as seen from the International Space Station - image by NASA

For a full list of the 16 Decade Volcanoes and some info on each, see the Further Reading and Exploration section below.

Further Reading and Exploration

The Decade Volcanoes – Wired

The 16 Dangerous Decade Volcanoes – World Atlas

Significant Lahars at Mount Rainier – USGS

Timeline of volcanism on Earth – Wikipedia

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