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Supervolcanoes in the Ancient World

The views expressed are those of the author and are not necessarily those of Scientific American.

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Supervolcanoes are volcanic eruptions thousands of times more powerful than normal volcanic eruptions.  These types of eruptions cause significant local ecological disturbances and have profound effects on global climate.  On the scale of geological time they occur quite frequently.

Volcanologists categorize eruptions by the amount of volcanic ash ejected upon eruption using the Volcanic Explosivity Index (VEI).  The VEI consists of 8 levels, with VEI-8 eruptions considered “supervolcanic eruptions” ejecting 1000 cubic kilometers of ash or more.

Lake Toba

Lake Toba

Throughout human history our species has encountered one known supervolcanic eruption.  This eruption occurred at Lake Toba in Indonesia approximately 74,000 years ago, potentially causing a genetic bottleneck and slowing human expansion into Asia and Australia.  However, VEI-7 eruptions (eruptions ejecting 100 cubic kilometers of ash) have occurred with relative regularity (4 in the past 2,000 years).

I recently interviewed University of Texas paleoecologist Dr. Robert Dull to discuss past major eruptions in human history.  Dr. Dull studies climate change on millennial scales of time and discovered evidence that a major volcanic eruption occurred around 536 C.E. at Lake Ilopango in modern day El Salvador.  He believes that this eruption is responsible for the well-documented extreme global weather events in 536-537 C.E. throughout the northern hemisphere.

I believe that understanding how major eruptions effected human civilization in the past will give us an opportunity to prepare for these eruptions in the future.

Cadell Last: How large was the Lake Ilopango eruption?

Robert Dull: The Lake Ilopango eruption was a magnitude 6.9 eruption.  The magnitude scale is more accurate that the VEI.  Classifying the eruption as a 6.9 is obviously more precise than labeling it 6 or 7.  But it was nearly a VEI-7.  However, it wouldn’t take many new data points for that estimate to go up.  The more samples we collect the better we will be able to figure out the full volume of the eruption.  The magma volume was approximately 39 cubic kilometers.

Cadell Last: Are there estimates on how many people were directly killed as a result of the Ilopango eruption?  If so, how were they estimated?

Robert Dull: Between 40,000-80,000 people died during the Lake Ilopango eruption.  We used population density assumptions based on settlement patterns in the area.  Some of the original density estimations indicated that there were 72 people per square kilometer near the volcano.  However, I choose to be more conservative and estimate that there were 20-40 people per square kilometer.  Since the eruption affected an area of 2,000 kilometers this indicates that 40,000-80,000 people died in the greater El Salvador region.

Cadell Last: Lake Ilopango was very close to the Maya civilization.  Would the entire Maya civilization have been effected by this eruption?  And do we know that this eruption caused the “Maya Hiatus” during the Classic Period?

Robert Dull: The entire Maya civilization would have been effected.  The entire southeastern Maya highland certainly would have been directly affected.  This area was the source of a lot of ceramic types and major obsidian quarry sites.  There were a few towns that were completely wiped away.  However, we don’t know as much as we could know about the Maya Hiatus.  Our findings will spur a lot more research into this.  We know that the Maya Hiatus started around 534 C.E. and then lasted for 30 years.  These are rough dates but what we know is that this eruption happened right in the middle of the Classic Period.  During this time monumental architecture came to a halt.  Political alliances changed.  One of the most exciting findings is that this eruption coincides with the fall of the largest Mesoamerican city: Teotihuacan.  Teotihuacan was a Aztec city with a population of 200,000 people and it fell around 550 C.E.  We need to better understand how their alliances with the Maya may have contributed to this collapse.

Cadell Last: Do researchers know why this eruption did not end the Maya Classic Period?

Robert Dull: There were big shifts of power in the Maya lowlands.  What seems to have happened was that some regions benefitted and some regions lost out.  All cities had a dusting of ash, but some were only covered in about a centimeter of ash.  I believe there must have been refugees to a large center of largely unaffected cities in the northern half of the Yucatan Peninsula.  I think future research will tell us a lot more about the role of these refugees in the later Maya Classic Period.

Cadell Last: What is your stance on the connection between the Lake Ilopango eruption (536 C.E.) and the Plague of Justinian (541-542 C.E.)?

Robert Dull: It’s certainly plausible.  The plague did break out after the volcanic eruption.  A global dust vale from the eruption lasts for 18 months in the northern hemisphere during this time.  That lasted for two summers.  This period of time was also an anomalously cold period.  On the whole climate change could have allowed the event to take place.

Cadell Last: There was a VEI-7 eruption in Indonesia in 1815.  The Tambora eruption.  From the historical record, what do we know about the main parallels and differences between the climatic effects of the 536 eruption and 1815 eruption?

Robert Dull: Tambora is the best analogue to the Lake Ilopango eruption.  They were eruptions that shook the world.  They produced similar effects.  In the case of Tambora it produced The Year Without Summer in 1816.  In the case of Ilopango it produced the years without summer: 536-537 C.E.  You don’t store food that lasts for two years.  In the northern hemisphere you grow it in the summer and save it for the winter.

Cadell Last: Considering how dangerous these eruptions are, have paleoecologists and volcanologists discovered and accounted for all potential supervolcanoes?  Is there any possible way that volcanologists will be able to predict the next supervolcanic eruption?

Robert Dull: No we can’t predict when the next supervolcanic eruption will occur.  There are known supervolcanoes that have repeatedly erupted.  For example, Yellowstone has erupted three times in the last two million years.  That is something that we should be concerned about.  Of course, Yellowstone is being monitored but we have no way of predicting when it will erupt next.

Pinatubo ash plume

Pinatubo ash plume

I believe that Dr. Dull’s research can teach us a lot about how major volcanic eruptions effect human civilization.  It is clear that eruptions at or near the scale of VEI-7 have the ability to destabilize civilizations and even alter global climate for multiple years.  Also, research by other paleoecologists has shown us that VEI-7 eruptions happen with surprising regularity on scales of thousands of years.  Therefore it would be prudent to identify high-risk volcanoes and prepare for such events.

The danger a VEI-8 eruption poses is even higher.  They may pose just as significant a threat to our existence as asteroids do.  In my opinion there are too many hypothetical situations to know exactly how a VEI-8 eruption would impact our global civilization today.  However, it is conceivable that what occurred locally in Mesoamerica in 536 C.E. could repeat itself globally if we encountered a VEI-8 in the near future.

Finally, I would like to add that I am not trying to be an alarmist.  However, if we would like to create a stable global civilization, we must properly prepare ourselves for natural events that occur on larger time scales than we are accustomed to thinking about.

Cadell Last About the Author: Cadell Last is an evolutionary anthropologist (MSc.) with a background studying chimpanzee sleeping patterns and the emergence of human bipedalism. He is currently working on an animated science channel with PBS Digital Studios and merging anthropological and cybernetic theory with the Global Brain Institute. Follow on Twitter @cadelllast.

The views expressed are those of the author and are not necessarily those of Scientific American.

Comments 8 Comments

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  1. 1. sethdayal 2:27 pm 04/17/2013

    One of the dangers of a society that depends on solar power.

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  2. 2. Joshua B 3:09 pm 04/17/2013

    Really?… Did you ever consider the massive impacts to transportation and food production. Solar Power would be the very least of our issues.

    I really appreciated the article and it was a good read. I didn’t realize that these types of eruptions were that common. I have heard about Yellowstone and even saw the Discovery Channel movie, that was, a hypothesized documentary? I thought that anything that would have effect on such a large regional scale were very rare, but the effects would be tremendous.

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  3. 3. cadelllast 4:53 pm 04/17/2013

    @sethdayal – I actually think that is a fantastic point. If we transition to a global energy economy dependent on mostly solar – we also need to have developed technologies to prevent supervolcanic eruptions.

    @Joshua B – Thanks! Since doing research on supervolcanoes I have also been surprised by their frequency. I’m not sure if I’m aware of the Discovery Channel documentary, but I have watched a BBC “docu-drama” about what would happen if Yellowstone erupted next week.

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  4. 4. M Tucker 6:24 pm 04/17/2013

    Hmm, prepare for a VEI-8, like Lake Toba about 74,000 years ago, the one responsible for the near extinction of all humans. How much food and water do I need in my bunker to survive that? When that day comes we will remember it as Ben Dover Day…kiss your ass goodbye.

    Our only chance is to not be here. Off planet living. If we can get through the next 50 to 90 years with a “stable global civilization” maybe we can work on living in space. So far we have not demonstrated political will or the global cooperation necessary to do either.

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  5. 5. Acoyauh2 7:42 pm 04/17/2013

    “Teotihuacan was a Aztec city with a population of 200,000 people and it fell around 550 C.E.”

    Goodness gracious, no!

    Teotihuacan pretated the Aztecs and hence had no relationship – ethnical, linguistical or other – with them. During the time (550 C.E.) the Nahua people were a band of wandering nomads just leaving their native Aztlan up North. They did not arrive to their founding site at the Anahuac valley until circa 1280 C.E.
    No, not all natives in Mexico were Aztecs, dude…

    However, I do find it interesting that it has been confirmed that Teotihuacan did suffer a serious ecological collapse around 550 C.E. – a circumstance that Cacaxtla took advantage of, forming an alliance with neighbors Cholula and the up-and-coming Xochicalcas to invade and give them the coup the grace and burn the city to the ground.
    Interesting to analyze whether the same climatic emergency that affected Teotihuacan presured the neighbours enough to move against the neighbourhood bully.

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  6. 6. RSchmidt 9:19 pm 04/17/2013

    @Joshua B, sethdayal is a denier troll. He doesn’t care about where people get their food during an extinction event, just that they keep pumping gas.

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  7. 7. way2ec 2:44 am 04/18/2013

    Acoyauh2, thank you. Dr. Dull should offer a correction. When the Aztecs, then but nomadic hunters building on the mud flats of Lake Texcoco came upon the ruins of Teotihuacan they thought the gods had built the place, or so I was taught. There is also a theory that if the semi-divine ruler/priests were ever to lose “favor” with the gods, be unable to balance the forces of nature which included the sacred power of “place”, the rest of the pyramid power scheme would collapse, the people would abandon a place and/or turn upon the ruling elite. To lose faith in the divine leadership at the same time as dealing with an eco-collapse would be the end of the world as they knew it. It wouldn’t necessarily be the same as anarchy.

    Using the “small scale” and “short term” events such as Hurricanes Sandy and Katrina don’t offer much in the way of our ability to “prepare”. To “prepare” for a volcanic eruption at a global scale across all geo-political boundaries would require multinational and global corporate cooperation that I just don’t see happening. If the global production of food was at risk for a year or TWO? If entire governments and regimes are at risk of collapse? Coping with the floods of refugees even here in the Americas would be a nightmare. No, with 7 billion people and counting, a disruption of food production on a global scale would be a “tipping point”. Global communication systems would only inform where the most need would be and who were the least affected. Global transportation systems would be taxed moving refugees, not food stuffs… how could you deny your own “local people” food supplies required to get “everyone” through for a year or two? What could you ship and for how long could you ship food to other parts of the world if the effects to global food production are just that, global in scope. At less than a global scale where some parts of the world could export foods, like mentioned in this article, many new “alliances” would be formed with the rich and powerful, military, and agribusinesses becoming the “winners”, leaving how many millions, or billions, to “live off the land”.

    At a smaller scale we might include the eruption of Thera or Santorini, thought by some to “explain” the 10 plagues of Egypt. Reading Exodus and extrapolating the consequences of a volcanic eruption with global impacts to 7 billion people is enough to boggle the mind, how would we “prepare”? Perhaps if the Mayan books hadn’t been torched by the Spanish we could read their version of an exodus, the end of their known world, or the world as they knew it when Ilopango blew. But wasn’t the Spanish conquest of the New World an even greater apocalypse, complete with plagues, but without ever being able to “let the people go”? Perhaps instead of a lesson in preparedness, the peoples of Mexico might offer lessons in survival, in picking up the pieces and rebuilding, and I suspect that some of the best places to survive a global scale volcanic disruption would be in those tiny communities of indigenous people in remote places in Mexico.

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  8. 8. jtdwyer 3:01 am 04/18/2013

    It seems the Toba eruption – human genetic bottleneck hypothesis was oversold in documentaries on the Discovery Channel & Science Channel, etc., produced primarily in the 1990s, and has become well entrenched in the popular culture. I know I certainly bought into it for years.

    However, there seems to be quite a bit of evidence that argues against the proposal, including an unbroken chain of archaeological tool samples in India both before & after the eruption, the survival of Neanderthals until 20,000 years ago and remarkably, right in Toba’s back yard, the survival of Homo floresiensis (the Hobbit) on the Indonesian island of Flores until ~10,000 ya. The genetic analysis based only on Mitochondrial DNA and Y-chromosone is also questioned. Please see
    - it includes many references on both sides.

    No doubt large eruptions may have had a tremendous impact on regional populations throughout the history of human development.

    As to whether today’s enormous population, now at least 7 times larger than has ever existed in the history of the Earth prior to 1800 – so dependent on fragile modern infrastructure, could survive a supervolcano eruption – I have very serious doubts…

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