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Exploring the Darker Side of Everything

The Devastating Long-Term Effects of Krakatoa

Written by Olivier Guiberteau 


In August 1883, a volcanic island located in the Sunda Strait, between the islands of Java and Sumatra in Indonesia began to tremble violently. The mighty beast had last erupted several centuries before but had remained at peace for some time. But as the shaking intensified and with loud booming explosions now echoing across the ocean, it was clear that this volcano, known as Krakatoa, was nearing the point of no return. 

What came next was devastation on an unimaginable scale. Tens of thousands died, either through the ash and lava erupting from Krakatoa or the tsunamis that tore out in all directions from one of the largest volcanic eruptions in history. 

And yet, this was just the beginning. The Krakatoa eruption, which came with a force of 200 megatons of TNT making it around 10,000 times more powerful than the atomic bomb dropped on Hiroshima, sparked a devastating chain of events around the world and caused climate chaos that few regions escaped. The events that began in August 1883 had a dramatic effect on the planet that lasted for years and which we are still learning about today. 


Today, this fiery monster known as Krakatoa is, in fact, a group of four islands collectively known as the Krakatoa Archipelago. It is comprised of Lang and Verlaten, two islands that were thought to have emerged after an eruption long before 1883, Rakata, which was once the much larger island of Krakatoa which was decimated in 1883, and Anak Krakatau (Child of Krakatoa) which emerged demon-like in 1927 from the caldera created in 1883 – a caldera being the hollow area that is left after a volcano empties its magma chamber during an eruption. 

The island of Krakatoa once measured 9 km (5.6 mi) long by 5 km (3.1 mi) wide and included three volcanic cones, Rakata, measuring 820 meters (2,690 ft) in height to the south, Danan, reaching 450 meters (1,480 ft) in the center of the island and Perboewatan the shortest at 120 meters (390 ft) to the north. 

Previous Eruptions


This has long been considered one of the most active and tempestuous volcanoes around and even before 1883, it has seen numerous eruptions that possibly had global impacts. 

It is difficult to gauge eruptions as we go back in time, but a good one to start with is the 535 AD eruption, which some argue may have been even more powerful than its 1883 younger brother. It’s therefore perhaps not surprising that around that exact time the world experienced what is known as a volcanic winter. 

The volcanic winter of 536 AD has been defined as the most dramatic and longest cooling period the Northern Hemisphere has seen over the past 2,000 years. Summer temperatures dropped by around 2.5 C (4.5F) across Europe and there was a wide catalog of observations from around the world, including a blue-ish and weakened sun in Rome and a dry dense fog that hung over the Middle East and China. 

What has been called ‘the year without summer’ led to widespread droughts, famines, and death around the world, and considering the Plague of Justinian, which tore through the Mediterranean Basin, Europe, and the Near East killing perhaps between 30 and 50 million started just five years later, it’s fair to say that this may well have been the very worst time to be alive – certainly in and around Europe. 

Krakatoa was given the perfectly apt name ‘fire mountain’ by local people and there were scores of further eruptions over the centuries, which have been recorded, with sketchy accuracy it must be said, as being in 850, 950, 1050, 1150, 1320, and 1530 AD. We don’t know a great deal about these eruptions, and because of that, we can probably assume that they were at least on the smaller side. 

The last well-documented eruption before 1883 came in 1680 AD, but even here most of the damage was consigned to the archipelago itself and there were probably few if any, effects felt around the world. 



Still years before significant geological equipment capable of reading seismic activity, there is scant reliable information on the years building up to one of the most dramatic explosions humans had ever witnessed. By some accounts, the preceding years had seen intense seismic activity in the Krakatoa area, with several earthquakes recorded, some of which were felt as far away as Australia.   

On 19th May 1883, steam began venting from the Perboewatan cone, followed by eruptions of ash that reached 6 km (20,000 ft) in height. A month later, a series of loud explosions were heard and a resulting dark cloud of ash hung ominously above the island for several days. On 26th June, as an easterly wind picked up, the ash cloud was blown clear to reveal a chilling sight – two great columns of ash now rising steadily out of the bowels of the island. 

Six weeks later, a Dutch official visited Krakatoa and reported an ash layer about 0.5 m (1 ft 8 in) thick covering the entire island, with almost all of the vegetation dead, leaving on the sad stumps of trees remaining. For those in the area that had even the faintest understanding of volcanic activity, it was now a question of when, not if, Krakatoa would erupt. 

As August progressed, seismic activity intensified, and by the 26th August, Krakatoa had reached its paroxysmal phase on the Volcanic Explosivity Index. That’s a 5 out of 8 if you’re new to the VEI, with an 8 being a ‘Mega-colossal’ – which may as well be goodnight, and thanks for coming for most of the world. By 2 pm that day, the eruptions had become almost constant, with pieces of hot pumice – volcanic rock – up to 10 cm (4 in) in diameter landing on the decks of ships up 20km (12 mi) away. Later that evening, a small tsunami hit Java and Sumatra and it became clear that Krakatoa was now at its tipping point.    


This bubbling, brooding monster finally reached its crescendo on 27th August as four enormous explosions fractured then blew the island of Krakatoa apart. The first, originating from the Perboewatan cone, came shortly after dawn at 5.30 am, resulting in the first tsunami of the day which barrelled north, devasting the town of Telok Betong, today known as Bandar Lampung. 

The second, at 6.44 am, erupted from the Danan cone, sending a tsunami east and west, while the third, and largest explosion occurred at 10.02 am. Thirty-nine minutes later, a massive landslide carved off half the Rakata cone, along with much of the island, leading to the final cataclysmic explosion. These four titanic eruptions came in the space of just over five hours and one of the greatest natural disasters in human history was now underway.   

Over the following 48 hours, the eruptions at Krakatoa would cause carnage in the immediate region and well beyond. The tsunamis that emanated out from the island after each explosion were recorded to have reached heights of over 30 meters (98ft) – roughly the size of a seven-story building, while the Sunda Strait and parts of the Sumatran coast also had to contend with the pyroclastic flow from Krakatoa – the fast-moving current of hot gas and volcanic matter which can reach speeds of up to 700 km/h (430 mph). It’s believed that these pyroclastic flows that followed each explosion set off the tsunamis when several cubic kilometers of material entered the sea, resulting in the same amount being displaced and sending waves arching upwards.     

As I mentioned, the third explosion was by far the largest and has long been considered one of, if not the loudest, sound ever heard during recorded times. It was distinctly heard 3,110 km (1,930 mi) away in Perth, Australia, and also on the small island of Rodrigues near Mauritius, 4,800 km (3,000 mi) away. 160 km (100 mi) away from Krakatoa, the explosion was measured at 180 decibels, enough to shatter many an eardrum. This sound was so immense it circled the globe four times, while energy released has been estimated at 200 megatonnes of TNT – which is four times that of the Tsar Bomba, the largest nuclear bomb ever detonated, and at least 10,000 as powerful as what was dropped on Hiroshima at the end of World War II. 

Immediate Effects 

The immediate effects over the next 48 hours were horrific as Tsunamis thundered through communities with little to no warning. Though this has always been difficult to fully confirm, it has been reported that some of the Tsunamis circled the globe six times. The official death toll of the Krakatoa eruption was 36,417, though it’s likely to have been much higher. The towns of Teluk Betung and Ketimbang in Sumatra and Sirik and Semarang in Java were ravaged, Merak was destroyed by a wave measuring roughly 46 meters (150ft), while the entire population of 3,000 people on the small island of Sebesi died as a result. 

Further afield, ships were tossed into the air by the giant waves, killing or injuring many on board. The steamship Berouw was found nearly a mile inland on Sumatra, while tidal anomalies were recorded as far away as the English Channel Islands. 

Geographically, the area around the volcano had changed dramatically. Only around 30% of the island of Krakatoa remained, but by the 29th August, an eerie calm descended on the region, the seething giant once again lay at rest.  

Long Term Effects 

For some time there was a great deal of confusion as to whether Krakatoa continued erupting weeks, even months after its initial rupture. It’s not exactly clear why this view continued as many close to Krakatoa reported it to be calm and it wasn’t until Dutch geologist Rogier Verbeek, who had been a direct witness to the eruption, compiled a report, was it generally confirmed that the Krakatoa eruption had most definitely come to an end.   

But this was just the start. Now, it is worth highlighting that we still don’t know definitively what the long-term effects of this dramatic event have been. Even as recently as the last decade scientists have been uncovering possible links between our current climate today and the Krakatoa eruption. 

There are plenty of maybes and possibilities when talking about the long-term effects of the events of 27th August 1883, but it’s clear that its consequences spread around the world and endured over a lengthy period.  

Visual Effects

The Krakatoa eruption was followed by a bizarre and dazzling visual display that lasted for years. There were reports of both darkened skies and spectacular colors around the world. Sunrises and sunsets seemed to be the most dramatic periods as they appeared to be much more prolonged than usual with intense fiery colors burning in the sky. 

And it gets even weirder. Some reported stars and the moon glowing a deep green, while the sun had a bluey-green haze to it for some time. A recent suggestion by astronomers has queried whether the fiery sky in the background of Edvard Munch’s The Scream, which was painted ten years later, may have been inspired by the dazzling effects seen in the skies above Norway after the eruption.  



Volcanic Winter

Perhaps the clearest climatic change that came about after the Krakatoa eruption was the rather ominously named volcanic winter, an almost mythological-sounding event, but there have been roughly 11 or 12 of them over the last 3000 years or so. A volcanic winter occurs after a major volcanic eruption and typically sees global or at least hemispherical temperatures drop significantly. 

And this doesn’t necessarily mean just a single year. The volcanic winter that occurred after the Krakatoa eruptions lasted four years, and if anything, got worse with the winter of 1888 seeing powerful blizzards and record snowfall around the word. 

The year immediately after the eruption average Northern Hemisphere summer temperatures fell by 1.2C (2.1 F) – which might not sound too dramatic but when you think we’re talking about a possible 0.1C to 0.3C (0.18 – 0.54 F) increase per decade because of current climate change, a 1.2 C drop in a single year is staggering.

After a major eruption like this, huge amounts of sulfur dioxide are pumped into the stratosphere which leads to an increase in sulfuric acid concentration in high-level cirrus clouds. This means that cloud reflectivity increases dramatically, reflecting more sunlight than normal acting and acting as a solar radiation filter that cools the earth below. It’s thought that for the first full year after the event, only 87% of the sunlight that would have normally reached earth actually did.  

Floods, Droughts & Freezes

This is where things get a little more complicated when talking about the effects of the Krakatoa eruption because the following years saw plenty of natural disasters spiral around the world, killing many and destroying large swathes of land. Now, it would be tempting, and certainly convenient for this post, to blame every natural anomaly that occurred on the great volcanic blasts, but we have to be clear and say and it’s often impossible to differentiate what was the result of the eruption and what was down to one of several million other factors that contribute to natural disasters. It could be coincidental, but let’s just say that many of them were high-likely at least linked with Krakatoa in some way. 

There was widespread drought in many areas of the world. Baghdad for example saw not a single drop of rain the following year, while the American Plains saw devastating droughts that led to cattle farms being completely decimated. Severe droughts in Sichuan and Guizhou Province in China in 1884 and 1885 certainly killed many, but to complicate the statistics, this region of the country had been experiencing famines since 1879, so it’s not clear what the true effect was. There was also a major famine in the Java region of Indonesia, close to Krakatoa, the following year, but research had suggested that this may have been caused by landlords attempting to extract a greater harvest from the local peasantry.   

On the complete opposite side of the spectrum, China saw terrible flooding in the years after the eruption, particularly around the Yellow River, which burst its banks in 1887 and killed close to a million in the process – a tragedy that remains the most devasting flood in human history. We should point out that this region has a torrid history of floods that kill huge numbers, but enormous floods were also recorded in the U.S and Europe during the same period. Southern California experienced record rainfall and Los Angeles has never again seen rainfall like the year after Krakatoa. 

The years after the eruption there were no El Nino weather patterns – which isn’t always a guaranteed occurrence but the two may have been linked on this occasion – which exacerbated droughts in the Pacific region. The years after the eruption also saw some bone-chillingly cold years, with the winters of 1886 and 1888 being some of the coldest in living memory. The Great Blizzard, also known as The Great White Hurricane, was a ferocious storm that battered the U.S Northeast in March 1888, killing at least 400 people are causing $25 million in damage (around $7 billion today).   

Warmer Oceans 

But if you think that the Krakatoa eruption was all bad news then think again. In a bizarre, twisted, round-about way, the colossal volcanic blasts may actually have helped humanity. It was known for some time that the eruption had a dramatic cooling effect on our oceans but only recently has the full extent come to light.

Scientists in 2006 used several geological models to map out the effects of the Krakatoa eruption and found that the consequences were much more dramatic than first thought. They found that the volcanic cooling had penetrated deep layers in the oceans and the effect was enough to offset a large amount of anthropogenic rises in ocean temperature and sea level. In layman’s terms, the Krakatoa eruption helped to cool the oceans over almost a century which helped to counteract global warming and rising sea levels caused by humans. Leaving us with the potentially uncomfortably reality, that without one of the worst natural disasters in human history, humans might well be in a much worse situation right now.  

What’s Next?

It’s difficult to pinpoint the exact effects that were caused by the Krakatoa eruption in 1883, but it’s clear that for the next five years or so, the Earth’s climate was chaotic. Temperatures certainly dropped, which perhaps even worked in our favor when it came to the oceans, but the long-term damage around the world was seismic.

When we take into account the numbers that died through floods, failed crops production, and the freezing drop in temperature, the true figure of those killed as a result of the Krakatoa eruption could even run into the millions. 

We’ll finish this post on a slightly ominous tone, because, well, let’s be honest that’s probably why you’re here. Krakatoa may have been big, but it’s still not the largest eruption during recorded human history, with that award going to the 1812 eruption of Mount Tambora in New Zealand. And even that was likely to be at least seven times less powerful than the 10 to 20, we’re not entirely sure, supervolcanoes dotted around the planet. If one of these was to go off and a super-eruption was to take place, we can forget about extreme winters and excess rainwater, humanity’s problems are going to be much, much bigger. 

Covers.indd (geolsoc.org.uk)

Krakatoa’s signature persists in the ocean | Nature

The Volcanic Eruption of Krakatoa – The Atlantic

strange (stanford.edu)

Causes and consequences of nineteenth century droughts in North America (columbia.edu)

Krakatoa Volcano: Facts About Deadly Eruption | Live Science

1883 eruption of Krakatoa – Wikipedia

Krakatoa (sciencedaily.com)

The Sound So Loud That It Circled the Earth Four Times – Nautilus | Science Connected

Krakatau’s 1883 explosion caused years of climate chaos — Quartz (qz.com)

What were the long term effects of Krakatoa? – SidmartinBio

Krakatoa – Eruption, Causes & Impact – HISTORY

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