There are some volcanoes, designated as Decade Volcanoes, which scientists are watching very closely. Decade Volcanoes are those that need extra monitoring because of their proximity to significant populations and propensity for large, explosive eruptions.
Nine Decade Volcanoes feature in our list: Mount Etna, Mount Nyiragongo, Mount Vesuvius, Mount Rainier, Sakurajima, Galeras, Mauna Loa, Mount Unzen and Mount Merapi. These and other volcanoes on our planet could erupt at any moment, wiping nearby settlements – and their inhabitants – from the face of the Earth.
10. Kagoshima – Sakurajima
Nicknamed the ‘Naples of the Eastern world,’ Kagoshima is a densely populated city of 680,000 people that lies in the shadow of a great volcano. Directly across the bay, just a few kilometers away, is the looming presence of Sakurajima – a volcano that has been venting small explosions almost nonstop since 1955. Yet a single larger eruption may occur at any time. Living in the knowledge that a volcano with the capacity to destroy your city is just a few kilometers away must be nerve-wracking, especially when the sirens blow for evacuation drills.
The Japanese government has built shelters to enable the people of Kagoshima to take refuge from falling volcanic debris and ash – should Sakurajima erupt as it did in 1914. The 1914 eruption was the most violent witnessed by Japan during the 20th century. The lava flows – which lasted for months – were so great they connected what was then a volcanic island to the mainland, forming a peninsula. There is never a feeling of total safety in Kagoshima; one only has to look across the water to see that symbol of ever-present danger, Sakurajima.
9. Catania – Mount Etna
Rising to a height of 3,329 meters (10,922 ft), Mount Etna towers over the plains and city of Catania in Sicily, Italy, and remains in a state of almost constant activity. One of its largest eruptions occurred in 1669 when lava flows reached the city walls of Catania, breaching them in one section and destroying structures.
Today not only Catania but also other towns and villages on the slopes of the volcano remain at risk – at least ten such settlements were obliterated in 1669 – and local inhabitants never know when the next eruption may arrive. The most significant recent blast occurred on May 12, 2011, when the authorities had to close Catania airport after a thick layer of ash blanketed its runway. While this was a minor incident compared to the 1669 eruption, it may be a sign of things to come. Mount Etna may yet vent her latent fury on Catania’s population of almost 300,000.
8. Hilo – Mauna Loa
Mauna Loa is an absolute behemoth, the largest volcano on the planet in terms of sheer volume. Even though it has lain quiet, like a sleeping giant, since 1984, danger is still present for those who live in its vicinity. The city of Hilo, home to more than 43,000 people, is actually built on top of old lava flows from the 19th century – so clearly the rivers of molten rock have the capacity to reach it again. Indeed, after an eruption in 1935 planes dropped bombs in the path of lava –which travelled 24 kilometers (15 mi) in just three hours – to divert it away from Hilo. The 1984 eruption also produced fast-moving lava flows that threatened Hilo, stopping just 4 km (2.5 mi) from the city limits.
Mauna Loa’s rapid lava flows have engulfed whole villages during past eruptions, and while many who live on the Island of Hawaii may give the volcano’s destructive potential little thought in light of its recent quiescence, Frank Trusdell of the Hawaiian Volcano Observatory warns: “Mauna Loa will erupt again, and there’s a good chance that it will be during your lifetime.”
7. Goma – Mount Nyiragongo
Inside Virunga National Park, 20 kilometers (12.4 mi) from the city of Goma (in the Democratic Republic of the Congo) stands Mount Nyiragongo, a deadly volcano that has erupted dozens of times since 1882. An eruption in 1977 caused the volcano’s lava lake to drain rapidly, sending torrents of highly fluid molten rock hurtling down the slopes of the volcano at speeds of up to 100 km per hour (60 mph), devastating villages and killing least 70 people (though other reports suggest a much higher death toll numbering several thousand).
Then, in 2002, a stream of lava up to 1 kilometer (0.6 mi) wide and two meters (6.5 ft) deep sped down the mountain and right through the center of Goma. Some 400,000 people were evacuated. Luckily there had been enough warning for most people to get out safely. However, about 47 died from inhaling carbon dioxide, and nothing could save the buildings that stood in the lava’s path: 4,500 structures (about 15% of the city) were destroyed, rendering some 120,000 people dispossessed. Amazingly, the people returned and rebuilt, trusting to fate that they would be kept safe. Nyiragongo is monitored closely, particularly as another lava lake has formed in its bosom.
6. Pasto – Galeras
Galeras is an extremely active volcano – the most active in Colombia – located near the city of Pasto. Just 9 kilometers (5.6 mi) away from Galeras, Pasto has been blanketed with ash several times during eruptions over recent years. The 450,000 people who live in the city need to be constantly on guard, and in 2005 were forced to wear face masks and goggles after one volcanic explosion.
The 8,000 or so people who live in the most dangerous area nearest Galeras are practically always ready to evacuate – and have regularly been forced to do so in recent times – which must make for some sleepless nights. In 1993, an eruption killed six volcanologists and three tourists who were at the summit of the volcano, but rock falls and pyroclastic flows pose a potential threat to others much further from the volcano’s crater – not least the residents of Pasto.
5. St. Pierre – Mount Pelée
Famed as the ‘Paris of the Caribbean,’ St. Pierre – the former capital of the French colonial island of Martinique – was utterly annihilated by the massive, and infamous, eruption of Mount Pelée that occurred in 1902. Pyroclastic flows with temperatures exceeding 1,075 °C (1,967 °F) raced down the mountainside obliterating everything in their path. It is considered the 20th century’s worst volcanic disaster.
St. Pierre is just 6.4 kilometers (4 mi) from the summit of Mount Pelée, and the lives of only two or three of its 30,000 inhabitants were spared as the city was engulfed in a matter of minutes. An eyewitness at the time said: “[T]he mountain was blown to pieces, there was no warning.” Though it has never been restored to anything like its former glory, some smaller settlements have been built over parts of the old city, and today’s much smaller population of less than 5,000 keep a wary eye on the volcano that proved Saint-Pierre’s bane.
4. Seattle – Mount Rainier
Mount Rainier in the state of Washington holds a number of fears for authorities. While it is quiet at the moment, around 5,000 years ago a massive lump of the volcano broke away, sending a volcanic mudflow (or lahar) as far as the areas now occupied by Tacoma and south Seattle.
If an event like the Osceola Mudflow of five millennia ago were to happen again, the lahar would obliterate a number of towns in the vicinity of Mount Rainier – not to mention parts of downtown Seattle itself, which lies some 87 kilometers (54 mi) distant. Speaking of the volcano’s destructive potential, USGS scientist K. Scott has confirmed: “A home built in any of the probabilistically defined inundation areas… is more likely to be damaged or destroyed by a lahar than by fire.” For the millions of residents in Seattle and nearby settlements, such an event could be catastrophic.
3. Shimabara – Mount Unzen
Volcanoes don’t just kill because of the effects of lahars, pyroclastic surges or lava flows. In 1792, one flank of Mount Unzen in Japan collapsed, creating a landslide. This in turn triggered a megatsunami that killed 15,000 people in what has gone down in history as Japan’s worst ever volcano-related disaster.
In more recent times – 1991 to be precise – 43 people were killed by a pyroclastic flow following a large eruption. Warning systems and evacuation plans have been established because such disasters could easily happen again. The city center of Shimabara lies just 6 km (3.7 mi) from one of Unzen’s peaks. Its 48,000 inhabitants must live in at least some trepidation.
2. Naples – Mount Vesuvius
Nine kilometers (5.6 mi) east of the Italian city of Naples looms Mount Vesuvius, the famous volcano that destroyed the Roman cities of Pompeii and Herculaneum in 79 AD. It’s a scary thought when you remember that there have been at least three appreciably larger eruptions than this in the volcano’s history. What’s more, Vesuvius is still active, with magma bubbling in its belly, and when it explodes again the volcanic material it spews forth could reach Naples, home to almost one million people.
During the eruption of Vesuvius that occurred 3,800 years ago (known as the Avellino eruption) pyroclastic surges traveled over great distances – reaching as up to as 15 kilometers (9.3 mi) from the volcano’s vent – and there were deposits up to 3 meters (9.8 ft) deep in the area where Naples now lies. There is nothing to stop such an enormous eruption from happening again. Thankfully experts are better able to make predictions about potential eruptions nowadays, and emergency evacuation procedures are in place that would save lives.
1. Yogyakarta – Mount Merapi
Mount Merapi (meaning ‘Mountain of Fire’) stands 28 kilometers (17 mi) from the Indonesian city of Yogyakarta – home to over a million-and-a-half people. More worryingly, thousands of people live on the slopes of the volcano. Historically, there have been numerous large eruptions; a particularly tragic one in 1930 wiped out 13 villages and killed 1,400 people after pyroclastic flows were unleashed.
Nowadays, Merapi remains an extremely active volcano, with smoke billowing from its vent almost year-round. In 2006, despite warnings and evacuation orders, many villagers returned following an eruption for fear that their animals would be stolen. Then the Yogyakarta earthquake struck on May 27, killing 5,000 and leaving 200,000 displaced.
Destroyed house in Cangkringan Village after the 2010 Eruptions of Mount Merapi
Last year – 2010 – was another tragic year for those living on Merapi’s slopes. In October, authorities raised the alert to its highest level and ordered evacuations, but by December volcanic eruptions had killed 353 people – with a number of victims dying from severe burns – and hundreds of thousands were left homeless. One rescuer reported: “I found three bodies – a child, mother and father, still on their bed. They must have been sleeping when the hot ash struck their house.” There is ongoing monitoring of Merapi, and locals make offerings to appease the mountain’s spirits, but this remains a deadly volcano that will claim the lives of many thousands more if there is another major eruption.
Bonus 1: Manizales – Nevado del Ruiz
Another deadly volcano located in Colombia, Nevado del Ruiz killed an astonishing 23,000 people as recently as 1985. The Armero Tragedy occurred when a small volcanic eruption triggered massive lahars – fast-moving flows of mud and volcanic debris – that buried and utterly destroyed the town of Armero. It was the deadliest lahar in recorded history and the fourth deadliest volcanic eruption since 1500 AD.
Today Armero itself is a ghost town, but it is now recognised that it’s not just one town that’s at risk from future lahars, but many settlements: up to half a million villagers and townspeople occupy the danger area near Nevado del Ruiz. As you can see in this picture taken from the city of Manizales, the lahars would not have to travel far to reach human habitation. Lahars are almost unstoppable; small mercy then that predictions about when they might occur can better be made these days, and evacuations could – and have been – carried out.
Bonus 2: Plymouth – Soufrière Hills
The volcano known as Soufrière Hills dominates the Caribbean island of Montserrat. It is a constant reminder of the destruction it has brought since 1995, during which period its eruptions have made half the island uninhabitable. Plymouth remains the capital city to this day, but in name only: it has been overwhelmed and destroyed by volcanic explosions and pyroclastic surges that have incinerated its buildings and buried the town in several meters of rubble. Thick layers of ash have blackened the skies and rained down from overhead, while one of the 1997 eruptions left 19 dead.
Plymouth, just 6 kilometers (3.7 mi) from Soufrière Hills, is now is part of an exclusion zone that encompasses the south half of the island. Over two thirds of Montserrat’s population has been evacuated overseas and Plymouth itself completely abandoned. Slowly the island is rebuilding its tourism – another casualty of the volcano – but no one can feel completely safe. The threat of another eruption remains.