Today in Geological History – March 28th; El Chichón

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When you think about climate changing eruptions from the last few decades you mind usually automatically jumps to Pinatubo. However there was an eruption which was almost as climate altering just 9 years previous.

El Chichón sprang to life in the spring of 1982, with no confirmed eruptions since 1360, many had believed it was extinct. Laying in Southern Mexico between the Trans-Mexican Volcanic Belt and the Central American Volcanic Arc it is actually quite far from any other regularly active volcanoes. Seismicity began to increase in the region around El Chichón from early in 1980 through to the end of 1981 but no extra monitoring or investigation took place as the volcanic complex was not believed to be a threat.

This was proved wrong however on the 28th of March seismicity increased dramatically although locals failed to realise they were experience volcanic tremors not the earthquakes often felt in the region. At 23.22 that night an eruption has decimated the lava dome which had grown in VEI 5 Plinian eruption. This initial eruption only lasted a few hours but flung nearly half a cubic kilometer of dense rock at a terrifying rate. The area was quickly and erratically evacuated but as things settled down over the next few days, with only small vulcain or phreatic episodes near the main vent, people began to return home.

However El Chichón was far from finished clearing his throat and on Sunday April 4th a much larger eruption begun. It began with a huge pyroclastic flow which surged down the flanks at speeds in excess of 100 km p/h. The village of Francisco Leon was completely buried killing about 1000 people. A further two Plinian eruptions occurred later in the day causing an ash column towering over the landscape at over 29km high.

By the time things really calmed down roughly 2000 people had lost their lives and 9 villages had been devastated. The new crater spanned a kilometer wide and 300 meters deep, this has since filled with water creating a highly acidic crater lake as seen below.

The area around the complex was predominantly agricultural land and with over 24,000 square kilometers were covered in thick ash, many crop plantations were completely lost, making this Mexico’s most costly natural disaster of recent history.

It was not just Mexico however that felt the effects of the explosions. Seriously high levels of sulphur dioxide and other volatiles were sent in to the atmosphere. This coincided with the strongest El Niño phase recorded which lead to some suggesting it was caused by the eruption, however no scientific link was ever made. The combination of the two saw dramatic effects on climate world-wide.

El Chichon was a huge wake up call around the globe, showing us that we need to pay closer attention to signs our planet give us, no matter what our preconceptions. Ignorance that a volcano has not be active for a few hundred year lead to seismic warnings being ignored which in turn lead to the loss of lives.

It also shows that for all our worry about climate change and anthropogenic emissions, the Earth actually has the upper hand regardless of our efforts; one simple eruption at the right latitude can effect the world’s climate for years and there is little we can do about it…..

Figure 1. http://jennysmexico.blogspot.co.uk/2012/01/mexicos-volcanoes-mesoamerican.html

Figure 2. https://curiousmatters.wordpress.com/2014/05/23/curious-facts-31-of-the-strongest-volcanoes-known-to-man/

Figure 3. http://www.john-daly.com/soi-temp.htm

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