With an estimated ejecta volume of 160 km3 (38 cu mi), Tambora’s 1815 outburst was the largest volcanic eruption in recorded history.

And a powerful earthquake – 5.8 in magnitude – hit within miles of the volcanic peak on July 31, 2016. Is another mega-eruption imminent?

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On July 31, 2016, a strong (M5.8) and shallow (10km) earthquake hit really close to Mount Tambura, Indonesia, a volcano responsible for the largest volcanic eruption in recorded history in 1815.

Scary? Yes! Based on evidence from the geologic record, the chances of another eruption the size of Tambora occurring somewhere on Earth might be around 10% in the next 50 years and more likely than not, it will be from a volcano in Indonesia. We might think that Tambora is an isolated incident from the past, but volcanoes think otherwise. Another Tambora will happen, and there is a decent chance that it could be in our lifetime. Whether or not we’re prepared for it is another story, but we can be sure that we haven’t seen the last of eruptions of this magnitude.

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The 1815 eruption at Indonesia’s Tambora was a blast that altered global climate for years afterwards and has been fingered as the trigger of revolutions and migrations. Over 70,000 people perished directly from the event and hundreds of thousands more may have died due to disease and famine that could be linked to the effect Tambora had around the world.

No eruption in any of our lifetimes have come close to the size and impact of Tambora and once volcanic eruptions get this big, it can sometimes be difficult to really grasp just how large of a geologic cataclysm it was.

How much stuff came out?

The eruption of Tambora produced 175 cubic kilometers of volcanic debris (mostly ash and other tephra). 175 cubic kilometers is ~ 38 cu mi. How much is that? You could bury the state of Rhode Island in 183 (55 meters) feet of ash or Singapore in 805 feet (245 meters) of ash.

Those 175 cubic kilometers of volcanic debris is worth about 50 cubic kilometers of magma (so about 3.5:1 ratio of debris to magma). 50 cubic kilometers puts Tambora in the same class as the eruption of Mazama/Crater Lake in Oregon ~7,700 years ago. Compare that to the biggest eruption of the 20th century, the 1912 eruption of Katmai in Alaska, and you’d find that Tambora erupted 3.8 times more magma and 2.9 times more volcanic ash and debris. You can look at the mass of the magma as well.

How fast did that come out?

Tambora erupted an amazing amount of volcanic material and it did in a very short period of time. The whole eruption may have lasted no more than ~3 days. At its peak, it may have been erupting material at 300-500 million kilograms per second! The Horseshoe Falls at Niagara, at peak times, have 168,000 cubic meters of water passing over it per minute. Using the density of water (1000 kilograms per cubic meter), that works out to 2.8 million kilograms per second. So, the eruption of Tambora emitted, by mass, 178 times more per second than Niagara can handle.

Is that all?

Magma isn’t the only thing that came out Tambora during the 1815 eruption. When magma rises it releases gases that are dissolved in it. In a cataclysmic eruption like Tambora, that volcanic aerosols are catastrophically released. During the 1815 eruption, the volcano released 60 Tg (teragram, or 1012 grams) sulfur, 100 Tg chlorine (as HCl) and 70 Tg fluorine. That’s ~262,000 Saturn V rockets worth of sulfur and fluorine and ~437,000 of chlorine — all erupted over the span of only a few days. The amount of sulfur released by Tambora was 6 times more than the 1991 eruption of Pinatubo but only 58% of the sulfur released in the 1783 eruption of Laki in Iceland. It was all these aerosols, especially sulfur, that caused the vivid sunsets and cooled climate seen around the world for years after the eruption.

This animation shows global surface temperature anomalies in the years following the eruption:

All that ash

The eruption had two main phases: an initial Plinian eruption followed by voluminous pyroclastic flows of hot volcanic debris roaring down the slopes of Tambora. The Plinian phase produced an ash plume that was ~33 kilometers tall, possibly peaking at 43 kilometers tall. Plume heights like that reach well into the stratosphere, meaning the ash and volcanic aerosols could be moved around the globe quickly in the winds.

That plume and the following pyroclastic flows spread ash across the region. How much ash and how far has been tricky to reconstruct, even for an eruption that occurred only 200 years ago. Over 500,000 square kilometers around Tambora was covered with at least 1 centimeter of ash — that’s like covering all of Spain or 2 Oregons with a centimeter of ash. Double that number likely received at least a dusting of ash, so something like the entirety of Colombia or 2 Californias. In Banyawangi, over 400 kilometers from Tambora (roughly the distance between Las Vegas and Phoenix), 23 centimeters (9 inches) of ash fell. That is more than enough, especially mixed with any rain, to collapse roofs.

Big explosion means big energy

An explosive eruption like Tambora releases huge amount of energy. This eruption was 33 billion tons of TNT. That’s 2.2 million Little Boys (the first atomic bomb). Tambora, in the span of a few days, released about the same amount of energy as the consumption of the entire United States in one year (or ~ 1/4 of the entire world’s annual energy consumption!). Tambora was ~1200 times more powerful than the 2004 Indonesian M9.3 earthquake.

The consequences

Before the eruption in 1815, Tambora was a volcano that might have been 4,300 meters (~14,100 feet) tall. One of the biggest results of the 1815 eruption was the generation of a caldera — a large depression caused by the volcano falling in on itself after emptying its innards during the eruption (see the image at the top). The Tambora caldera is ~1.2 kilometers deep, so the volcano lost at least a few kilometers of elevation in a matter of maybe a day. The total volume of the caldera is ~36 cubic kilometers, which is pretty close to the total volume of magma erupted (50 cubic kilometers), so most of the hole that was created during the eruption is the missing magma that is now spread out as the ash across southeast Asia.

The explosion was heard on Sumatra island more than 2,000 km (1,200 mi) away. Heavy volcanic ash falls were observed as far away as Borneo, Sulawesi, Java and Maluku islands. Most deaths from the eruption were from starvation and disease, as the eruptive fallout ruined agricultural productivity in the local region. The death toll was at least 71,000 people, of whom 11,000–12,000 were killed directly by the eruption.

The Tambora cataclysm in art, science, agriculture and epidemics:

The eruption caused global climate anomalies that included the phenomenon known as “volcanic winter”. 1816 became known as the “Year Without a Summer” because of the effect on North American and European weather. Crops failed and livestock died in much of the Northern Hemisphere, resulting in the worst famine of the 19th century.

Get prepared, it could also occur closer than where you live!

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