Before Iceland's Eyjafjallajokull volcano decided to let off some steam, few people would have guessed that a small volcanic eruption would be capable of grounding almost every flight across Europe for almost a week. We consider ourselves living in a sophisticated, modern and resilient society, so it came as a bit of a shock to see how helpless we can quickly become. Yet, volcanoes are not the only trump cards that nature holds: There is a whole array of potential disasters that could have unpredictable and alarming consequences. Here are some of the main contenders.
Solar weather
Every few days, variations in the Sun's magnetic field produce vast storms, known as coronal mass ejections (CMEs). "They thrust out billions of tonnes of particles at speeds up to 8 million kilometres per hour," says Pal Brekke, of the Norwegian Space Centre in Oslo. And every so often, the Sun's weather blows our way. In March 1989, a large CME slammed into the northern hemisphere, dumping 1,500 gigawatts of electricity (25 times the amount in the National Grid) into the atmosphere. The Canadian power grid was fried and six million people were left without power for nine hours. Historical records suggest, however, that such solar storms can be up to ten times more intense. "Very long durations of electric power outages might be plausible on a continental to planetary scale," says John Kappenman of the Metatech Corporation, the US government's principal investigator on the impact of severe solar storms.
Kappenman estimates that it could take months or years to restore power to the US or northern Europe after a hit from a big solar storm. Critical parts of infrastructure — such as drinking water, perishable food and medicine, sewage treatment, transport and communications — would all be crippled within days. "Disruption to the supply of medication, for diabetes sufferers, for example, would have a near-immediate and grave impact," Kappenman says. "Ironically, it is the most developed regions of the world, with the most interconnected power grids, that would be affected most severely."
Meanwhile, satellites are also likely to be knocked out, forcing ships and aeroplanes to resort to old-fashioned methods of navigation and severely reducing our capability to forecast the weather. A CME tends to be channelled towards the Earth's poles, meaning that latitudes above 40 degrees (ie everything north of Lisbon or San Francisco or south of Wellington or Concepcion) are most at risk. Predicting CME events is difficult but they tend to coincide with the Sun's most active periods. "We have just started the new cycle and over the next few years, will observe more and more CMEs," Brekke says.
Asteroid impacts
Roughly every 1,000 years, the Earth is hit by a smallish asteroid — 50 metres wide or so. Although only pebbles, compared to the six-mile-wide rock that did it for the dinosaurs, they still pack a punch. On June 30, 1908, a 30-metre asteroid is thought to have slammed into the Tunguska River in Siberia.
The explosion — equivalent to around two megatonnes of TNT — caused a shock wave that flattened forests covering an area of roughly 400 square miles and killed herds of reindeer and other animals. If a similar asteroid were to hit a highly populated region of Earth, the devastation would be immense. Thankfully, the chances are very slim (most of the Earth's surface is water or sparsely populated) but even an impact in a remote area could have grim consequences: "An unannounced impact in some areas of the world, where tensions exist, might be mistaken for a nuclear strike and invite retaliation," warns Donald Yeomans, manager of Nasa's Near-Earth Object Programme Office in California.
Magnetic-field reversals
Every so often, movements deep within the iron core of the Earth mean that the planet flips its magnetic field; south becomes north and north becomes south. The last reversal was 780,000 years ago and there are signs that another could be on its way soon. "The strength of the Earth's magnetic field has decreased by nearly 8 per cent in the past 150 years," says Nils Olsen of Denmark's National Space Institute. "In some regions, it has decreased by 10 per cent in just 20 years." The process takes several thousand years and while it is under way, we lose the protective magnetic field that normally shields us from the worst of the solar weather.
Life on Earth appears to have sailed through previous reversals unharmed, so we don't expect the next one to be a direct threat but there could be some disruptive side-effects from the extra pummelling the upper atmosphere will receive. Coronal mass ejections will penetrate further, increasing the chances of month-long power cuts across entire continents. Satellites would degrade more quickly and flying in an aircraft could become an exceedingly risky activity. "The increased radiation from high-energy particles that astronauts, aeroplane passengers and pilots will experience during a weaker magnetic field is a major concern," Olsen says.
Earthquakes
As events in Haiti, Chile and China have demonstrated recently, earthquakes can be devastating. Usually, the impact is contained within the region they shake but, occasionally, they reverberate around the world. In March 2010, Taiwan was struck by an earthquake of magnitude 6.4. There were no deaths and few injuries but a number of buildings and bridges were damaged and the Tainan Science Park — a major global supplier of computer memory chips and LCD televisions and monitors — had to be shut down for a few days. Fortunately, these businesses were running again quickly and none of us noticed the blip in supply — but we might not be so lucky next time.
"When the next big earthquake hits the San Francisco Bay area in California, it could potentially end chip supply from some of the Silicon Valley manufacturers for a few months," says Peter Sammonds, a geophysicist at University College London. In this case, the impact would be felt globally as supplies of specialised chips, such as those used in hospital equipment and banks, became scarce. On a less serious note, some of us might lose signals in our smart phones and have to do without Facebook and Google for a while.
Volcanoes
The recent fireworks on Iceland may just have been a taster of what is to come. "Increased earthquake and volcanic activity over the past ten years suggest Iceland might be entering a more active phase," says Thorvaldur Thordarson, a volcanologist at the University of Edinburgh. Periods of high activity in the past have produced monsters such as the 1783 eruption of Laki, which killed more than half of Iceland's livestock and led to a famine that wiped out about a quarter of the human population.
Across Europe, the thick haze choked people and suppressed temperatures, causing thousands of deaths. Rice harvests failed in Japan and the monsoon was weakened in Africa and India. Thordarson thinks modern society is better equipped to deal with such an eruption but the disruption to our lifestyle and economy could be severe — flights might have to be grounded for five months or so. Based on historical patterns, Thordarson and his colleagues estimate that Iceland's active phase will last for another 60 years or so, peaking between 2030 and 2040. Hold on to your hats: We could be in for a bumpy ride.
Three of the scariest
Bubbling under
Landslide Research suggests that part of the Canary Islands is due for a major landslide. If this happens, it could generate a tsunami that may break undersea cables and inundate the east coast of the US.
Methane burp
The release of a pocket of the greenhouse gas methane hydrate from the ocean floor could cause a dramatic acceleration in global warming, as has happened in the past.
Cosmic rays
An increase in the level of cosmic rays reaching the solar system — perhaps from a nearby star exploding — could trigger an Ice Age, perhaps leading to a mass extinction of life on Earth. Those volcanoes don't look so bad now, do they?
