How dangerous are volcanoes?

Around 1000 degrees hot lava, explosions, burning streams – volcanoes are dangerous, no question. Fortunately, it is now possible to predict roughly where an eruption will occur, and when it is imminent, a distinct volcanic tremor will alert those in the area. With modern science, this means that it is usually possible to evacuate in time and fewer and fewer people have to die from volcanic eruptions. Nonetheless, they are beasts. They are fire-breathing dragons that simply roll over houses and fields as if nothing were there. They have a destructive power that we humans cannot fight. We can only deal with the dangers emanating from volcanoes and avoid personal injury. Anything man-made, volcanoes will just shave away if it gets in their way.

Volcanic eruptions

Volcanic eruptions sound like a very unlikely event, almost like an asteroid falling on someone’s head. But it’s not that rare: around 50 of the active volcanoes erupt every year. Some, like Stromboli in Italy, are always active, while in other regions like the Pacific Fire Belt, volcanic eruptions are commonplace. Usually these are not big, spectacular eruptions, but a little spit, a little ash, a little lava. Nevertheless, people fall victim to them again and again: in the large outbreaks, but also in smaller ones again and again. The reason for this is that the area surrounding volcanoes is very fertile and is therefore often settled – if an eruption comes as a surprise to the population, it can be too late to get to safety.
About 300,000 people have died in volcanic eruptions since 1700, 25,000 of them in the 1980s alone. Even if the predictability is getting better: large, massive outbreaks claim more and more victims in heavily populated regions.
The immediate dangers of a volcanic eruption lurk less in the outflowing lava, which is usually quite slow. High numbers of victims cause pyroclastic flows from which one cannot escape. Lava and gravel landslides caused by collapsing craters can also bury entire towns. Mud avalanches, called lahars, composed of water, volcanic ash, and gravel, can bury large regions around a volcano under mud. And last but not least, stored gases can be released explosively.

How close is too close?

Volcanoes can make an interesting spectacle. In Iceland you can see the relatively harmless volcanoes very closely, in Guatemala hiking routes to the crater rim of active volcanoes are part of the normal tourist excursion program, and tours of Mount Etna are very popular. Especially gentle, effusive and long-lasting erupting volcanoes are suitable to look at. But caution is always required: If a volcanic area is closed, there are reasons.

Sudden or predictable?

Volcanoes don’t usually erupt as a surprise. Although it is almost impossible to know the exact time beforehand, the signs before a volcanic eruption become increasingly clear.
In the days and weeks before a volcanic eruption, earthquakes accumulate, in the days immediately before there can be several hundred in one day. They become swarms that come closer and closer to the earth’s surface, approaching the point of the eruption. These earthquakes can be measured and represent a clear warning signal. Just before an eruption, small, long-period earthquakes accumulate into volcanic tremors, a constant vibration that accompanies the magma rising through the eruption.
The rising magma not only makes the earth tremble, but also swells it up: a clear deformation can often be measured on the slopes of an approaching volcanic eruption. In addition, the temperature increases due to the hot, approaching magma. Furthermore, escaping gases indicate that an eruption is imminent.
Years in advance, one can see that radiant heat will increase as volcanic activity increases. An evaluation of satellite images showed in 2021 that the temperature can rise by up to half a degree, indicating that something can happen here. This new finding can help to monitor the currently most active volcanoes in a more targeted manner in the future.

Earthquakes rising to the surface before the volcanic eruption on La Palma on September 19th, 2021

Monitoring active volcanoes

In about 70 volcano observatories, the activities around volcanoes are observed intensively. Especially those that pose a great danger, such as Vesuvius in Europe, are continuously monitored.

In addition to monitoring, human action is required above all: what should happen if scientists predict an outbreak? How seriously this is taken and how early an evacuation is made can mean the difference between a manageable problem and an enormous humanitarian catastrophe.

Travel to volcanic regions

Volcanoes often announce their activities well in advance. If a volcano is observed particularly intensively, there is usually interesting activity there. In that case, it’s a good idea to follow the latest news and see if contingency plans are activated in a region. This usually happens well before a real risk arises, but it is intended to put the population on the alert.

If there are clear signs of an approaching eruption, holidaymakers should consider leaving the area. If you stay: As calmly as possible, simply do what is ordered by the local authorities.

Volcanic gases

Air measuring stations around a volcano regularly sound the alarm: sulphur, particles, CO2 and too little oxygen – right next to a volcano the air gets thin for people. That’s why volcanologists who go near a lava flow wear appropriate gas masks, against which any FFP2 mask is airy, and of course goggles that fit tightly to the face. And if they come very close still protective suits…. A walk to an active lava tongue without such protection and the appropriate knowledge should definitely be avoided.

CO2 (carbon dioxide)

CO2 is produced with every combustion, as well as with a bubbling volcano in rough quantities. It is the gas that is known to be the fuel of the impending climate catastrophe – and the gas that every human being produces when we breathe. CO2 is heavier than air and can form a layer on the ground where it can accumulate in harmful concentrations. This can happen in the basements of breweries, but also in depressions on the rims of active volcanoes.

SO2 (sulphur dioxide)

SO2 can combine with water to form sulfuric acid. This is particularly dangerous where lava meets large amounts of water – eg when it enters the sea, when it rains or when it comes into contact with groundwater. The poison, which is highly harmful to humans, should not be inhaled – one of the reasons why the area around active volcanoes is often closed even when there is no longer any danger to be seen. Volcanologists only approach the critical zones with gas masks.

Acid rain can form from the released sulfur dioxide, which can rain down far from a volcanic eruption.

H2S (hydrogen sulfide)

The smell of rotten eggs that you can smell around volcanoes is due to the hydrogen sulfide in the air. The smell indicates an incipient unhealthy concentration of this extremely toxic gas, which fortunately rarely causes harm to humans when it occurs in nature: one automatically tries to escape the smell.

Creeping Death: Gas Leaks from Crater Lakes

Gases of volcanic origin can kill people in very unpredictable ways. CO2 can accumulate at the bottom of crater lakes. If it doesn’t combine with the water, it can lie underneath as a gas bubble and explode out in a volcanic tremor. One such event in Cameroon in 1986 killed 1700 people who were poisoned by C02 seeping down the hillside.
Individual victims demand volcanic gases when researchers or interested parties are exposed to excessive levels without protection. The only dead in the Ausbuch of Teneguia on La Palma in 1971 was a photographer who died in the hospital from symptoms of poisoning.

Volcanic Ash

“Lava ash? Yeah, we’re familiar with that here… (laughs) I mean, imagine coming home with your hair and face covered in ashes. Before you take a shower, you first clean up the ashes in the bathroom, then you get rid of them from your hair. There’s still a little bit left, but at least the ashes don’t trickle into your food anymore. And before you go to sleep, you shake the ashes out of your bed… after picking the last grains out of your teeth….”
(Lidia, Los Llanos, La Palma)

Every volcanic explosion is accompanied by ash. The resulting cloud can stretch several kilometers high and be carried hundreds to thousands of kilometers. Extreme amounts of ash can remain in the atmosphere for weeks and months and slow down the entry of the sun’s rays, causing short-term climate changes in large regions.
Volcanic ash can therefore not only affect the immediate vicinity of a volcano, but also large airspaces: When Eyjafjallajökull in Iceland erupted in 2010 – some still remember – the entire northern European airspace came to a standstill for several days because the ash cloud was not with the safety of the engines was compatible.
Small ash particles are like glass, incredibly sharp. These particles can become unhealthy for humans.

Quiz 4: How dangerous are volcanoes?

Welcome to the fourth Knowledge review: Volcanic Dangers

Good luck! You can repeat as often as you like.