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Photo: Sebastián Crespo Photography / Getty Images
What are volcanoes?
Volcanoes are openings on the surface of the earth from which molten rock, known as magma, emerges from the earth's interior together with gases.
Once the magma is on the surface of the earth, it is called lava.
The large volcanic cones with the typical circular craters are known.
However, volcanoes can also be columnar or bowl-shaped.
The cause of volcanism is, on the one hand, plate tectonics: when tectonic plates diverge or meet, the magma below can push upwards.
On the other hand, they can also occur within a plate at so-called hot spots.
Most of the volcanoes are along the Pacific Ring of Fire, from the South American west coast to Alaska and Japan to Indonesia.
What is the significance of volcanic eruptions for the climate?
Volcanoes with violent, explosive eruptions, the gas and ash particles of which reach the stratosphere, can cause global climate change.
In particular, the sulphate particles formed from volcanic sulfur dioxide linger in the atmosphere for several years and absorb some of the solar radiation.
The stratosphere warms up, but at the same time the reduced radiation leads to a cooling of the earth's surface.
The effects of the Pinatubo outbreak in the Philippines in 1991 could still be measured a few years later.
In the summer of 1992, the eruption caused the globally averaged, ground-level air temperature to drop by around 0.5 degrees Celsius.
As a rule, however, these cooling effects only have a short-term effect and, due to fluctuating volcanic eruptions, are also very irregular.
In contrast, even small eruptions emit not only water vapor but also carbon dioxide as a significant greenhouse gas into the atmosphere.
However, this warming influence on the climate is currently of little importance.
An estimated 0.3 billion tons of carbon dioxide are emitted annually by volcanoes, which corresponds to only about one percent of man-made CO2 emissions.
Since the beginning of industrialization, the average volcanic activity on earth has not increased significantly, so that the increase in CO2 levels in the atmosphere and the resulting climate changes cannot be attributed to volcanic eruptions.
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