How Volcanoes Affect The Atmosphere

Chris - Now Janet works on the nuts and bolts of volcanoes, but you're interested in what comes out of them. Tell us about your work.

Tamsin - I started off looking at atmospheres, and now I'm looking at the effect volcanoes have on our atmosphere. Like Janet, I go out into the field and take measurements of volcanoes.

Chris - So you have to wander around on erupting volcanoes?

塔姆——不t erupting in the sense that most people think of with a big erupting lava column, but erupting with gas coming out of them.

Chris - Have you never been caught with your pants down so to speak. You've never been really close?

塔姆——不, I've had ash falling on my head but never had anything bigger, which is fortunate really. I try to avoid that.

Kat - What kinds of gases come out of volcanoes and are they very smelly?

Tamsin - There's often fire and brimstone. You can see the fire in the crater below you. The brimstone, which is actually sulphur, creates a lot of sulphurous gases. This is the egg smell that some people think of when they think of volcanoes. This is hydrogen sulphide. Sulphur dioxide is a more major component of the volcanoes I work on. You also get acid gases such as hydrogen chloride and hydrogen fluoride.

Chris - Pretty nasty.

Tamsin - It is. A colleague went up wearing a pair of spectacles and his glasses got etched by the hydrogen fluoride, so this shows you how corrosive these gases are.

Chris - I was lucky enough to be in Japan around Christmas of 2001 and I went to Mount Fuji. If you climb up adjacent to Mount Fuji, you can see hot springs there. They absolutely stink of bad eggs! There's also a big sign which says, although it's very loosely translated from the Japanese, if you stop noticing the smell of hydrogen sulphide, that's a bad sign. This is presumably because once it reaches a certain level, it just abolishes your sense of smell.

Tamsin - Basically yes. There's a window in which we are sensitive to the smell of hydrogen sulphide. Once it gets above that window, that's when it starts to become quite toxic.

Chris - But why is analysing some of these gases useful to science. What can it tell us about science and how volcanoes actually work?

Tamsin - It can tell us all sorts of things. I think the interesting thing is the different length scales on which volcanoes influence the environment. The local effects in places in the South Pacific include residents showing signs of fluorosis, such as discolouring of their teeth. The fluorine levels in the water that they drink are about ten times the World Health Organisation recommendations. There are also global effects. For example, after the Pinatubo eruption it shot up sulphur dioxide into the upper atmosphere, such as the stratosphere and ozone layer. This created an aerosol vale that went all around the planet and reduced the temperatures.

Chris - By reflecting sunlight back into space.

Tamsin - Yes exactly.

Chris - Because we also had some wonderful sunsets. I remember in 1991, when Mount Pinatubo erupted in the Philippines, these beautiful orange sunsets every night for the whole year.

Tamsin - Even the moon looked yellow because of all the small particles up in the stratosphere. After a bigger eruption such as the Tambora eruption in 1815, people painted some beautiful paintings. It has some beautiful aesthetic effects as well as negative effects.