Scientists believe that the eruption of Indonesia’s Toba supervolcano around 74000 years ago caused a global cooling of 3-5 degrees Celsius for several years, as well as a massive loss of plants and wildlife. 1 Researchers talk about a volcanic winter. 2 Can this also happen during the eruption of other supervolcanos? And how can a supervolcano eruption alternate climate? In this blog post, I´ll search for answers to these questions after looking at general facts about volcanic eruptions. A supervolcano eruption could it trigger a volcanic winter?
By the way, the featured image for this blog post is not the Toba supervolcano, but the Yellowstone. It´s one of the few photos I didn’t take myself but found on Pexels.
Why do volcanos erupt?
To dive into this topic I´ll look at the reasons why volcanos erupt in the first place. The temperature within the earth’s mantle is so high that rocks melt and turn into magma. As discussed in my last blogpost about the formation of volcanos, the melting can occur when tectonic plates are separating or one plate descends beneath the otherone. Because magma is lighter than surrounding rock, it can rise and flow within magma chambers. Volcanos erupt when magma pushes through the surface. At this point we talk about lava. Lava is a term used to describe erupted magma. 3 4
Why are some volcanic eruptions explosive and others not?
If a volcano erupts explosively or not makes a huge difference in its danger. The composition of the magma determines whether or not a volcano erupts explosively. During an eruption where the magma is thin, it simply flows out of the volcano. This is because gases can previously escape from the magma when it is light. People can easily escape from these types of eruptions, making them less dangerous. 3
Gases cannot escape as easily in the case of thick magma. This increases the pressure within the volcano, causing an explosion through which the gases can escape. Explosive eruptions are menacing and can cause many deaths. 3
The environmental consequences of a supervolcano eruption
The size of a supervolcanic eruption is determined by the amount of material emitted by the volcano. When “at least 400 km3 of bulk material” (Global Challenges Foundation, s.a.) is ejected, an eruption is classified as a supervolcano eruption. Ash and dust can kill residents nearby and destroy agriculture. 1
But the interesting part is that the climate of the entire planet can become colder for a while. This sounds odd at first but the explanation is quite simple. Sulfate aerosols are liberated through the eruption and create a layer in the mid-atmosphere called the stratosphere. They reflect sunrays and cool the planet. Because of the amount of sulfate aerosols emitted, super-eruptions such as the Toba eruption might cause volcanic winters that can influence evolution. 2
You can learn more about the consequences of supervolcano eruptions in the video below, where Science Time talks specifically about the Toba eruption mentioned in the beginning.
I found it fascinating that the Toba eruption around 74000 years ago may have caused a bottleneck effect and thus altered the human population. 5 If you’re unfamiliar with the term. The bottleneck effect describes the loss of various gene variants in a population as a result of a catastrophic event. This means that some gene variants become extinct while others multiply. As a result of the bottleneck effect, a population becomes less diverse. 6
Conclusion
Let´s sum up what we´ve learned in this blog post and answer the question: “Could a supervolcano eruption cause a volcanic winter?”: Volcanos erupt when magma pushes through the surface. We deal with a supervolcanic eruption when 400 km3 of bulk material is ejected. This can have various consequences for our lives and the environment. Researchers name the possibility of a volcanic winter as a result of a sulfate aerosol layer in the stratosphere caused by the eruption. There is also the chance that an eruption in this dimension can influence genetic diversity. What do you think? Is it likely that we experience a volcanic eruption in our lifetime that alters genetic diversity?
References:- Global Challenges Foundation, s.a. Supervolcanic eruption. Available at: https://globalchallenges.org/global-risks/supervolcanic-eruption/ [4.12.2022].
- Osipov, S., Stenchikov, G., Tsigaridis, K., LeGrande, A.N., Bauer, S., Fnais, M. and & Lelieveld J., 2021. The Toba supervolcano eruption caused severe tropical stratospheric ozone depletion. Communications Earth & Environment.
- USGS, s.a. How Do Volcanoes Erupt? Available at: https://www.usgs.gov/faqs/how-do-volcanoes-erupt [4.12.2022].
- BBC, s.a. The Big Question: Why do volcanoes erupt? Available at: https://www.bbc.co.uk/newsround/44100737 [4.12.2022].
- Science Time, 2020. Yellowstone Supervolcano VS Toba Supervolcano. Available at: https://www.youtube.com/watch?v=-H050L8ilCQ [4.12.2022].
- National Geographic, s.a. Genetic Bottleneck. Available at: https://education.nationalgeographic.org/resource/genetic-bottleneck [4.12.2022].