Climate Change, Earthquakes, and Volcanic Eruptions

How might climate change affect eruptions from Osorno volcano in Chile and vice versa?

Source: Ilan Kelman

Are climate change and tectonic processes linked? We must examine both directions: volcanic eruptions and earthquakes changing the climate and climate change affecting earthquakes and eruptions.

Volcanic eruptions and earthquakes changing the climate?

Volcanic eruptions have affected the climate throughout the eons. If eruptions are big enough, their emissions circle the globe and block some sunlight for a few years, which can cool the climate. After Mount Pinatubo erupted in the Philippines in 1991, the world had a short period with a small cooling effect, before human-caused climate change took over again.

Farther back, after the Tambora volcano erupted in Indonesia in 1815, “the year without a summer” became a common refrain around the world. The cold, wet, rainy summer of 1816 around Geneva kept people indoors, so a group of English tourists was said to have exchanged ghost stories to pass the time. This tale, challenged as apocryphal, continues that one member, Mary Wollstonecraft Shelley, wrote Frankenstein solely due to inspiration from the volcano-induced situation.

Geological history reveals many volcanic eruptions around the same time as dramatic climatic shifts. Chief among these are flood basalts spewing out lava to heights above most houses covering areas larger than many countries. In each specific case, whether climate change or an eruption came first, and any feedbacks between the two, are subjects of perpetual discussions and ongoing research.

Irrespective, a single earthquake, even if coming from one of these massive volcanic eruptions, has little scope for significantly impacting the long-term process of climate. In contrast, tectonic processes over geological time periods build and destroy continents, mountains, and other landforms, representing a major input into changing the climate locally and globally.

Climate change affecting earthquakes and volcanic eruptions?

Within human lifetimes today, we are causing a rapid and substantive shift in the climate. Could this climate change affect earthquakes and volcanic eruptions? Too frequently, any major environmental event is pounced on as presumed evidence of climate change’s apparent devastation.

It is not just media exaggeration or random tweets. After Hurricane Maria pummelled Dominica in the Caribbean in 2017, the country made a big splash by setting the goal to be the “the world’s first climate-resilient nation." Their 2018 law mentioned how becoming climate-resilient would make Dominica “better able to withstand future hurricanes, earthquakes and other natural disasters."

Irrespective of the importance of avoiding the term “natural disaster,” being resilient certainly assists in dealing with any peril, so it makes sense to focus on resilience without highlighting specific environmental hazards. Dominica should aim to be “the world’s first disaster-resilient nation," rather than highlighting one environmental change, that of climate. The country’s law never addresses the question of how earthquakes and climate change might affect each other.

Sea-level rise from climate change is a possible influence on tectonic processes. Differences in sea level redistribute the amount of seawater over fault lines, changing earthquake frequencies and other traits. Similarly, the pressure from water over an undersea volcano affects eruption frequency and some aspects of eruption magnitude.

Land-based volcanoes are similarly influenced by any ice over them. When an ice age tightens its grip over the planet, massive ice sheets trek towards the equator, pushing down continents. As this happens, it could increase seismic and volcanic activity.

Then, the glaciers rest over volcanoes, increasing the pressure which magma must punch through for a volcano to erupt. When the ice age ends with the glaciers retreating, the release in pressure lets the stoppered volcanoes explode with their associated earthquakes. Meanwhile, the continents continue to rebound as the glaciers vanish, adding further influences on earthquake characteristics.

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This provides lessons for the current possibilities of the Greenland and Antarctic ice sheets melting due to climate change and raising sea levels considerably. As this ice becomes water, huge masses would be redistributed at the global scale, changing patterns of earthquakes and volcanic eruptions. How much and to what extent is not really known, especially regarding changes to big tremors and eruptions compared to smaller ones.

Additionally, some volcanoes explode violently, as Mount St. Helens in Washington state did in 1980. Others allow lava to flow down their slopes like rivers, as with much of the activity from Mauna Loa on the island of Hawai’i. Changes in the balance between these types of eruptions under different climate change scenarios are not well-understood.

One other factor is that detailed statistical analysis shows that volcanic activity changes with the seasons. As climate change alters or shifts seasons at a global scale, a chance exists of volcanoes and related earthquakes responding with their own season-related changes.

Continual connections

So, yes, tectonic processes change the climate, and climate change affects earthquakes and volcanic eruptions—in many ways, over many timespans, and over many extents in area. This intricate dance among the land, ocean, and atmosphere is not surprising. Irrespective of scientific specialisation, we know how inextricably all aspects of the planet are interconnected.

The key is avoiding adverse effects of these changes on another major part of the Earth: life, including human beings.