Everything Everywhere Daily: History, Science, Geography & More - The Toba Eruption

Starting point is 00:00:00 74,000 years ago, the Earth suffered the greatest natural disaster that it's seen in the last several million years. A supervolcano erupted in what is today the country of Indonesia. In addition to completely changing the Earth's climate for years, it may have pushed a species known as Homo sapiens to the brink of extinction. Learn more about the Toba eruption and how it might have almost spelled the end of humanity on this episode of Everything Everywhere Daily. What if your perceptions about the past were wrong? The Thulein is a podcast that takes you back in time to uncover the parts of the story that may have gone unnoticed. It effectively turned day into night. And how it shaped the world now.

Starting point is 00:00:55 Time travel with us every week on the Thulein podcast from NPR. I've talked about several different volcanoes and volcanic eruptions in previous episodes. However, none of them come close, not even within an order of magnitude, to the eruption that I'll be talking to. about in this episode. To put things into perspective, there is a scale known as the Volcanic Explosivity Index, or VEI, which measures the power of volcanic explosions. The VEI is a logarithmic scale, so each unit on the scale is 10 times greater than what came before it. The current eruption of Mount Etna in Sicily, or the 2019 eruption on White Island in New Zealand, ranks a two on the VEI. The 1997 Sufriere Hills eruption on the island of Montserrat that caused two-thirds of the island to be permanently evacuated ranks a three.

Starting point is 00:01:51 The 2010 Ae Fiatra-Yakov-Tal eruption in Iceland, which caused a shutdown in international air travel, ranks a four. The Mount Vesuvius eruption in the year 79 that destroyed Pompeii, the 1980 Mount St. Helens eruption, and the 2022 eruption of the Hungatonga-Tonga-Hunggha-Hapai volcano all only rank a five on the VEI. The 1883 eruption of Mount Krakatoa and the 1991 eruption of Mount Pinatubo in the Philippines, both rank a six. Finally, the 1815 eruption of Mount Tambora in Indonesia, on which I've done a previous episode, and which was the greatest volcanic eruption in recorded human history, ranks a seven. There are, however, eruptions that are even more powerful than what was seen in Mount Tambora. These eruptions are known as supervolcanoes.

Starting point is 00:02:39 They are not only the most powerful of all volcanic, eruptions, but they are also correspondingly very rare. Geologists have estimated that over the last 130 million years, there have only been 40 super volcano eruptions that have ranked an eight on the volcano explosivity index. The last time such an eruption took place was 26,500 years ago on the North Island of New Zealand. The Taupo volcano exploded, which resulted in the creation of Lake Taupo, which today is a very nice place to visit. However, a much larger explosion occurs, approximately 50,000 years before that, Mount Toba. The eruption of Mount Toba wasn't just bigger. It is believed to have been the largest volcanic eruption in the last 25 million years.

Starting point is 00:03:25 Unlike the other volcanic eruptions I've covered in previous episodes, we have no eyewitness testimony of the eruption. If there were any eyewitnesses, they probably didn't survive to tell the tale. Tobah was the biggest eruption in human history, and by that I mean that the eruption took place when there were human beings on the planet, not that they were documenting any history. Toba is located on the northern part of the Indonesian island of Sumatra. Today, Lake Toba is a 100-kilometer-long lake that also happens to be the largest volcanic lake in the world, larger than Lake Taupo in New Zealand and Lake Yellowstone in Wyoming, both of which were also formed by supervolcanoes.

Starting point is 00:04:02 The eruption took place approximately 74,000 years ago. Based on the distribution of ash from the eruption, it's believed that it probably took place during the summer in the northern hemisphere, as monsoon winds during that time would explain the ash distribution. The eruption probably didn't occur in one single explosion. Like the Mount Tambora eruption, it most likely took place over about a two-week period. The amount of debris that was spewed out of Toba was incredible. The total amount ejected from Mount Toba,

Starting point is 00:04:32 was at least 2,800 cubic kilometers or 670 cubic miles, and it may have been as much as 50% more, according to some estimates. To put that into perspective, the total amount ejected from the Mount St. Helens eruption in 1980 was only about one quarter of a cubic kilometer. So this eruption would have been about 10,000 Mount St. Helens eruptions. It would have been enough to fill all of Lake Victoria with volcanic matter. And if the upper estimates are correct, enough to fill Lake Huron. It would have been three to five times the entire volume of Mount Everest. In previous episodes, I've spoken about how dangerous and deadly pyroclastic flows are. These are superheated clouds of gas and ash that travel at incredible

Starting point is 00:05:19 speeds from volcanoes. There is absolutely nothing you can do if you find yourself facing one. You can't outrun it, and you can't hide or take shelter from it. The area hit by pyroclastic flows from Mount Tobah was estimated to be over 20,000 square kilometers, an area the size of the nation of Belize. Most of the ash, which was ejected, was sent to the north and the west. Most of the area north and west of Sumatra is the Indian Ocean, which means that it would have made the sea in the area into a toxic pool. However, there was enough debris piled up on land that indicate just how incredible the eruption was. In the area of Sumatra, closest to the volcano, the ash deposit were 600 meters or 2,000 feet thick. Over in Malaysia, across the Strait of Malacca,

Starting point is 00:06:08 there were areas with 9 feet or 3 meters of ash. India and South Asia had it just as bad over a much larger area. Almost all of South Asia had a layer of ash at least 15 centimeters or 6 inches deep. In one part of Central India, the amount of ash was 6 meters or 20 feet deep. The ashfall is believed to have destroyed entire forests in India. There were even ash deposits discovered as far away as Lake Malawi in Africa. Researchers studying ice cores taken in Greenland and Antarctica have found a large spike in sulfate particles during this period. The incredible amount of ash that was sent into the atmosphere had enormous consequences

Starting point is 00:06:47 for the Earth's climate. If you remember back to my episode on the 1815 Mount Tambora eruption, it resulted in the year without a summer in 1816. There were freezing temperatures in July and August across much of the northern hemisphere as well as famine due to crop failures. The impact of the Tobah eruption would have been even more severe. Estimates are that global temperatures drop by three to three and a half degrees Celsius or five to six degrees Fahrenheit for several years, with a short-term drop in temperatures as much as 15 degrees Celsius or 59 degrees Fahrenheit. Some researchers think that the toba eruption may have reduced global temperatures for as long as 100 to even a thousand years.

Starting point is 00:07:30 Everything I just outlined isn't very controversial. There is debate as to the magnitude of the effect, but not that it happened. There's ample evidence of the toba eruption all over South and Southeast Asia, as well as a giant caldera in Sumatra, which can still be seen today. The controversy has to do with another theory that comes from the seemingly distant world of genetics. About roughly, the same time as the toba eruption, humanity seemed to have gone through some sort of genetic bottleneck. The genetic bottleneck can be explained if the population of humans around this point shrunk down to an incredibly low number, possibly as few as only 1,000 people. This theory became known as the Toba catastrophe theory. It was an elegant theory that linked together to known events,

Starting point is 00:08:18 the Toba eruption, which had a huge impact on the planet, and the genetic bottleneck that humanity seemed to have gone through at roughly the same time. The implication is that the toba eruption and its aftermath would have killed off almost all of humanity. After all, if the much smaller tambora eruption caused the problems that it did, then certainly the much larger toba eruption would have been even worse. The theory, mainly due to its simplicity and elegance, gained popularity in the 1990s and early 2000s. However, research afterward challenged the theory and indicated that it wasn't just incorrect, but it might have been the total opposite of what really happened. For starters, not all volcanoes are the same. The type of magma that they emit has different

Starting point is 00:09:01 chemical compositions. In particular, the magma has different abilities to carry sulfur. More recent studies on the magma emitted from the toba eruption show that it was much lower in sulfur content than the magma from the Tambora eruption in 1815. This is important because it's sulfur particulate matter in the atmosphere, which is responsible for blocking and reflecting sunlight that lowers the temperature. This means that while the Tobah eruption undoubtedly influenced the Earth's climate for years, it might not have been as bad as the sheer quantity of material ejected would indicate. Other damage to the theory came from archaeological evidence found in Africa. The Tobah eruption left a layer of debris across Africa that left a

Starting point is 00:09:42 very unique signature in the stratigraphic record. This is handy for archaeologists because it serves as a marker. Anything below this level occurred before the toba eruption and anything after this level occurred after the toba eruption. If the toba catastrophe theory is true and the eruption did result in the near extinction of humanity, then we should expect to see a gap of at least several thousand years of little to know human activity after the eruption, as it would take that long for humanity to repopulate. However, that isn't what the archaeological evidence shows. In fact, it shows just the opposite. There was an increase in human activity after the eruption. The same thing was found in India, which was hit even harder than Africa. After the toba eruption, there were more

Starting point is 00:10:26 animal rains and more evidence of toolmaking. Moreover, there is no sudden drop in populations of Neanderthals or any human population across most of Eurasia or Africa. So if the tobo eruption didn't result in a massive decrease in humans, what explains the bottleneck that genetic is find in genetic human history. A genetic bottleneck is basically a decrease in genetic diversity within a gene pool. It can result from a decrease in population, so linking the Tobah eruption to this wasn't a ridiculous idea. However, genetic bottlenecks can occur in other ways. One is through a phenomenon known as the Founder Effect. As humanity spread out from Africa, they separated into different groups that became isolated from each other. These small groups would have had limited

Starting point is 00:11:11 genetic diversity amongst their group, as they were distanced from the larger human genetic pool found in Africa. Thus, the genetic bottleneck is more a reflection of the fragmentation of human groups after they left Africa, rather than as a massive reduction in the population of humans, which almost resulted in their extinction. The toba catastrophe theory is still being debated, and there are still proponents of it, but it holds much less sway than it did even 10 years ago. Nonetheless, regardless of how the Toba eruption may have impacted humanity, it was still one of the largest volcanic eruptions ever. While there is no indication that there are any super volcano eruptions on the horizon, you also can't say that it is impossible. The odds of an eruption of this magnitude occurring in our lifetimes is very, very, very small, but it also isn't zero.

Starting point is 00:12:01 The eruption of Mount Toba, 74, 7,000 years ago, shows that no matter how devastating and destructive a volcano can be, there's always the the potential for something worse. The executive producer of Everything Everywhere Daily is Charles Daniel. The associate producers are Thor Thompson and Peter Bennett. I just want to thank everyone, including the show's producers, who support the show over on Patreon. If you'd like to support the show, just head over to patreon.com, which is currently the only place where you can get show merchandise.

Starting point is 00:12:32 Also, if you want to talk to other listeners about the show, head over to our Facebook group or Discord server, both of which have links in the show notes.

Everything Everywhere Daily: History, Science, Geography & More - The Toba Eruption

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