How can volcanoes impact us?

How do volcanoes affect people's lives? Izzie Clarke spoke to seismologist Lucy Jones from California Institute of Technology and author of The Big Ones - How Natural Disasters Have Shaped Us. First Izzie asked Lucy what happened in Pompeii....

Lucy - We all have the image that everyone was buried in their homes and died because we found those corpses when Pompeii was excavated. But actually the eruption began with what’s called the Plinian eruption where the gases and ash head high up into the atmosphere. It turned everything black; it terrified people, and we know that about 90 percent of the people left during that period and survived.

About 10 percent said hey, rocks are falling on your heads, I’m staying in my home. And then were trapped there when what’s called the pyroclastic flow came through, which is when the gases lose the impetus up into the atmosphere. And as they’re heavier than air they flow down at tens of kilometres per hour, sweeping through and burning everything on touch.

Izzie - How do we know how many people this actually affected?

Lucy - The Romans had decent tax records and numbers of people that lived in the area and we can compare it with the number of corpses that were found in the excavation.

Izzie - Throughout the show we’ve also heard about these gases that are thrown out after an eruption, so how far can they travel globally? Does it only affect just the people near that eruption?

Lucy - Oh, absolutely not. It depends upon the explosive force of the volcano and how far up into the atmosphere they go. But as long as they aren’t just at the surface, like we’re seeing in Hawaii right now, they get up into the atmosphere, they travel over. And, in fact, in 1783 there was a massive eruption in Iceland. It was called the Laki eruption, and the gases that came out from there essentially poisoned all the crops and animals in Iceland. They were both fluorine and sulphide gases and the only thing to eat had to come out of the ocean. The whole country of Iceland came very close to extinction.

But then the gases travelled on and moved out over Europe, but now the gases were much more intense and concentrated. Our estimate is that 23,000 people died in the summer of 1783 just in the UK. Comparing death records of that summer with other summers, reports of a fever and burning throats and looking back it’s like okay, they were being poisoned by these gases in from Iceland. And then there were further deaths across Europe so they can travel a very long ways.

Izzie - Gosh. Are there any other knock-on effects? We heard about this global cooling so can that cause a big problem?

Lucy - Oh, it can be huge. Once you get out of the immediate Earth surface you get into the atmosphere, travel over to Europe. If it gets up into the stratosphere then it can travel around the world. In the stratosphere it’s much drier and, therefore, these particles, which actually are heavier than the air and in the lower atmosphere get washed out relatively quickly, can last for years up in the stratosphere.

Again, back in 1783, we had the poisons in the UK and in Europe, and then global cooling because these sulphide particles got up into the stratosphere and blocked the sunlight. It stopped the monsoons which depend upon a temperature differential of between the continents and the ocean. Without monsoons, the Nile didn’t flood and over 600,000 people starved to death in Egypt because of it. And, in fact, there were famines in both India and Japan that were partially caused by this that killed over 11 million people.

Izzie - Do we know what the likelihood is of having another eruption somewhere like this?

Lucy - The probability’s 100 percent. Just give us enough time. And, of course, whether it happens this year or next century - that’s a random distribution - there are many volcanoes around the world that are capable of doing this, that have done it in the past, and it’s absolutely certain that it will happen again.

Now, because of modern technology, if we instrument a volcano, we are much more likely to be able to predict that it’s happening. But you need the instruments, you need a warning system to communicate it. And, as we just saw in Guatemala, you’ve got to be able to get the warning to the people who are actually going to be affected and that takes time and sometimes you don’t have enough time.

We really need to be ready for that humanitarian crisis. We need to have resources to help people because it is going to be happening at some point.