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Volcanoes and the Climate

Science has always fascinated me. This includes not only the ecological sciences, which I studied in school, but other endeavors, as well.

Mt. St. Helens is the most active volcano in the continental US. Its historic eruption in 1980, killed dozens but had almost no effect on the world's climate

Mt. St. Helens is the most active volcano in the continental US. Its historic eruption in 1980, killed dozens but had almost no effect on the world's climate

History of Climate Changes Induced by Volcanic Eruptions

It's been a while since a volcano has changed our climate by even the smallest amount. The last noteworthy episode occurred in 1991 when the Pinatubo volcano in the Philippines went off, eventually lowering atmosphere temperatures by a whole degree centigrade. This effect wore off in a year or two, but still, it is important to note the relationship between volcanic eruptions and climate.

On a grander scale, there were two very large volcanoes in the nineteenth century that were able to change the weather in a manner greater than the Filipino explosion that rocked the Pacific island in the last decade of the twentieth century. These monsters were named Krakatoa (1883) and Tambora (1815), and they both happened to be located within the island nation of Indonesia. Because the two are located close together in time and place, the aftereffects from each one often get confused. But for the record, Tambora was the stronger and bigger eruption, and also the one that brought the most profound climate changes.

The Valley of Ten Thousand Smokes was created by the Novarupta volcanic explosion. Today, the place is a popular tourist destination, located within the Katmai NP in Alaska

The Valley of Ten Thousand Smokes was created by the Novarupta volcanic explosion. Today, the place is a popular tourist destination, located within the Katmai NP in Alaska

An Alaskan Giant Goes Off

Pinatubo was not the biggest volcano to go off in the 20th century, for that honor belongs to the Novarupta volcano located on the Aleutian Penninsula of Alaska. In June 1912, this Alaskan monster underwent a V.E.I. 6 eruption that lasted for several days. Approximately, 36 cubic miles (30 times more than Mt. Ste. Helens) of debris was ejected into the atmosphere, but because of its northern location, this volcano had a lesser global effect than Pinatubo.

In 1991, the Pinatubo volcano in the Philippines erupted, sending enormous amounts of ash into the atmosphere

In 1991, the Pinatubo volcano in the Philippines erupted, sending enormous amounts of ash into the atmosphere

A Slight Drop in Temperature

During its spectacular eruption in 1991, Pinatubo ejected about three and a half cubic miles of material into the stratosphere. To atmospheric scientists, the most important portion of this event was not the ash, but the huge cloud of sulfur dioxide (SO2), which was emitted from the mouth of the volcano. It is estimated that the culprit cloud was 22 miles high, 684 miles long, and weighed 17 megatons. The ash quickly descended back to earth, but the sulfur dioxide stayed airborne as an aerosol. Furthermore, it is this mass of SO2 that was largely responsible for the one-degree temperature drop that occurred in the following year.

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Small volcanic clouds of sulfur gas at the surface can create highly acidic lakes, like the shown here at the Kawah-Ijen volcano in Indonesia

Small volcanic clouds of sulfur gas at the surface can create highly acidic lakes, like the shown here at the Kawah-Ijen volcano in Indonesia

The Biggest Cooling Factor

By far, the biggest cooling factor in a volcanic eruption is the release of sulfur, which travels high into the stratosphere in the form of SO2 (sulfur dioxide). After its ejection from the mouth of the volcano, the sulfur dioxide molecule combines with water to form sulfuric acid (H2SO4). The newly formed sulfuric acid exists in tiny droplets, which form a natural kind of aerosol spray which effectively reflects sunlight away from the earth, thus creating a cooling effect. Eventually, the drops coalesce and then fall back to earth. Nonetheless, in a large volcanic eruption, this cooling effect can last for several years.

This Icelandic volcano, called Eyjafjallajökull, erupts frequently because it is not covered by much ice or snow

This Icelandic volcano, called Eyjafjallajökull, erupts frequently because it is not covered by much ice or snow

Another Scenario

There is another scientific scenario, currently under discussion, which suggests that rising temperatures in the earth's atmosphere can affect a volcano that is covered in ice. This recently-developed line of thought applies mainly to places like Iceland, Alaska, and eastern parts of Russia, where many active volcanoes lie buried underneath an ice sheet.

It is suggested that if the layer of frozen precipitation is not too thick, then the melting of this mini ice cap might erase a natural plug to the volcano. The result could be a minor or middling volcano, which spreads ash and lava from the mouth of the volcano.

Volcanoes and Glaciation

There is growing evidence that a decrease in glaciation may be linked to an increase in global volcanic activity. In other words, if the overall land area covered by glaciers and ice sheets becomes substantially smaller, there may be more volcanoes erupting activity around the planet. This is relatively new scientific speculation, so coming to any definitive conclusion may be premature. Just to put things into perspective, here is another article, which puts forward the idea that when discussing climate and volcanoes, we should be looking at changes that occur over millenniums rather than decades or centuries.

Hacking the Planet

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2020 Harry Nielsen

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