What is a Volcanic Eruption?

A volcanic eruption is an explosive release of hot gas, ash, lava, and rocks from a volcano. It occurs when magma from deep within the Earth’s crust rises to the surface, accumulating pressure and creating instability. The powerful force released from the magma’s expansion can cause devastating destruction, including widespread outages, mudslides, floods, and contamination of drinking water. The hazardous effects of volcanic eruptions can also cause serious health issues, such as burns, respiratory illnesses, and injuries from falls. Volcano eruptions are measured in terms of the sheer output and their consequences. Large eruptions can affect the global climate and have major economic consequences, such as loss of infrastructure and income.

Worst Volcanic Eruptions Chart

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What are the Different Types of Volcanic Eruptions?

1. Explosive Eruption

An explosive eruption is a major volcanic event characterized by a rapid release of high-pressure gases, ash, and other volcanic materials. It is one of the most powerful and devastating natural events that can occur on Earth and is rated on the Volcanic Explosivity Index (VEI) on a scale of 0 to 8.

Explosive eruptions are often accompanied by pyroclastic flows, which are fast-moving currents of hot gas and rock that can reach speeds of up to 700 mph and reach temperatures of up to 1000°C. These flows can travel up to 100 km away from the eruption site and can cause extensive damage to property and landscapes.

Other features of an explosive eruption include: high ash plumes, intense seismic activity, volcanic gases and lightning, lava fountains, pyroclastic density currents, and lahars (mudflows). All of these can cause extensive destruction and disruption to human life. Furthermore, the volcanic gases and ash particles released during an explosive eruption can have a global impact, causing a reduction in global temperatures and changes in the climate.

2. Effusive Eruption

An effusive eruption is a volcanic eruption that is characterized by the slow, relatively gentle release of lava, as opposed to violent, explosive eruptions. This type of volcanic activity is usually associated with basaltic magma and produces low-silica lava, which is more fluid than other types of lava.

Generally, effusive eruptions are less hazardous than explosive eruptions because they produce relatively few volcanic bombs, pyroclastic flows, and other hazards. However, they can still prove to be destructive, especially if they are of long duration.

Examples of effusive eruptions include the eruption of Novarupta, or Katmai, in 1912 and the eruption of Mt. Pinatubo in the Philippines in 1991. Both of these eruptions released large quantities of lava and ash, although the ash from the Mt. Pinatubo eruption had a much greater impact as it cooled the global climate for several years.

3. Paroxysmal Eruption

A paroxysmal eruption is a type of volcanic eruption that is characterized by an explosive release of magma and associated gases in a short period of time. It is different from a typical volcanic eruption in that it is much more violent, with the sudden release of gas and magma taking place in a matter of seconds or minutes, rather than hours.

Paroxysmal eruptions can produce massive amounts of ash and debris, some of which may be shot into the stratosphere and remain suspended for months or even years. They can also cause huge amounts of destruction, as the high-speed ejecta and intense heat can level buildings and vegetation over a wide area.

4. Effusive-paroxysmal Eruption

An effusive-paroxysmal eruption is a type of volcanic eruption that is characterised by a sudden and violent release of magma and volcanic ash and gases from the vent of a volcano. Effusive-paroxysmal eruptions are usually associated with stratovolcanoes, the most dangerous type of volcano due to their steep slopes, which can generate mudslides, pyroclastic flows, and huge amounts of ash and lava. Such eruptions are highly destructive, with catastrophic effects on the local environment and its inhabitants.

Characteristics of an effusive-paroxysmal eruption include: a large, sudden release of magma and ash and debris, loud noises caused by the violent expansion of gas, flash flooding and lahars, massive pyroclastic flows of ash and pumice that can move at speeds up to 450 km/h, and the potential to cause global cooling by impacting the Earth’s atmosphere.

5. Strombolian Eruption

Strombolian eruptions are characterized by moderate to high-level explosive activity that ejects incandescent lava and volcanic bombs into the air. They typically occur in a single vent but can be accompanied by lava flows and pyroclastic flows. The explosions can reach up to 500 meters in height and the ejecta can be thrown up to several kilometers away. Strombolian eruptions occur at a low pressure, typically lasting from several minutes to hours.

Vulcanian eruptions are characterized by powerful gas-driven explosions and can reach heights of 1,500 meters or more. They are often preceded by an increase in seismic activity and the emission of large plumes of ash and steam. Unlike Strombolian eruptions, Vulcanian eruptions can continue for several days and are very dangerous. The ejecta from Vulcanian eruptions can reach velocities of several hundred meters per second and can travel up to 10 kilometers away.

6. Vulcanian Eruption

A Vulcanian eruption is a type of explosive eruption characterized by the ejection of dense dark ash clouds. It is one of the most powerful types of eruption and is classified as a 6 on the Volcanic Explosivity Index (VEI). Vulcanian eruptions are caused by the sudden release of pressure from magma build-up, creating a violent and explosive eruption. Vulcanian eruptions can last from a few seconds to several hours and are very dangerous due to the huge amounts of hot ash and gases that can be released.

The main characteristics of a Vulcanian eruption include a distinct explosive activity, with a loud rumbling sound, a thick grey-black cloud of ash, and the ejection of large rocks and pyroclastic material. Additionally, Vulcanian eruptions produce a fast moving and hot pyroclastic flow, an intense ground shaking, and can cause strong winds and rain. The ash ejected from Vulcanian eruptions can travel long distances and can cause significant damage to vegetation and infrastructure, while the intense heat and ash can cause respiratory problems in humans.

7. Submarine Eruption

A submarine eruption is an explosive volcanic eruption that occurs underwater, usually at the surface of the ocean. These eruptions are usually characterized by powerful blasts that produce large quantities of ash, lava, and steam. Submarine eruptions can generate waves of water up to 10 meters high, which can carry debris long distances and cause massive destruction to nearby coastal areas. They also produce a great deal of heat and pressure that can trigger tsunamis and seismic activity. Submarine eruptions can also cause environmental damage due to the release of toxic gases and acid rain. Additionally, they can produce large amounts of sediment and lava, which can be dispersed over the ocean and onto nearby land.

The Worst Volcanic Eruptions in History

1. Krakatoa, Indonesia, 1883

The magnitude of the Krakatoa volcanic eruption of 1883 was a VEI of 6, which is the highest level of volcanic explosivity index. The eruption devastated two-thirds of the volcanic island on which it stood, located near Sumatra in Indonesia. It also shot five cubic miles of lava into the air, as far as 50 miles, and created a global veil of ash that decreased the planet’s temperature by several degrees. In addition, tsunamis caused by the eruption killed around 36,000 people.

2. Mt. Tambora, Indonesia, 1815

The Mount Tambora volcanic eruption of 1815 was a catastrophic event that ranks among the worst volcanic eruptions in history. The magnitude of the eruption was VEI 7, the second-highest rating on the Volcanic Explosivity Index. This level of eruption is classified as “super-colossal” and is incredibly destructive. The volcano erupted explosively, sending 12 cubic miles of gases and ash into the atmosphere. This dust and ash spread across the sky, blocking out the sun and plunging many areas into darkness. It also triggered towering tsunamis and drenched the surrounding islands in ash.

This impact caused an estimated 90,000 people to die due to related food shortages. The enormous ash cloud created by the eruption blanketed the skies of the Northern Hemisphere for many months, and the global impact extended far beyond Indonesia. Crop failures, famine, and disease spread to Europe and North America, with devastating effects. The catastrophic devastation and far-reaching impacts of the Mount Tambora eruption have earned it a place among the worst volcanic eruptions in history.

3. Mt. Vesuvius, Italy, 79 AD

In 79 AD, the mighty Mount Vesuvius in Italy erupted with devastating consequences. On August 24th, Vesuvius unleashed ash, mud and toxic gases that asphyxiated some 2,000 people in the nearby city of Pompeii. A torrent of volcanic debris cascaded on the settlement, burying it beneath a blanket of ash and taking only fifteen minutes for Pompeii to disappear. Roman author Pliny the Younger witnessed the eruption and described it as having “sheets of fire and leaping flames.” This makes Vesuvius possibly the first formally documented volcanic eruption in history.

The eruption of Vesuvius was catastrophic and had a lasting impact on the region. Thousands of lives were lost and the cities of Pompeii and Herculaneum were completely destroyed. The ash and pumice left deposits over 660 feet thick at the foot of the mountain, while tropical storms created vast mudslides out of the volcanic ejecta. The cities were eventually rediscovered in the 18th century and new discoveries about the last days of Pompeii and Herculaneum are still being made to this day.

4. Santa Maria Volcano, 1902

The magnitude of the eruption of the Santa Maria Volcano in 1902 was a VEI 3, which is the third largest on the Volcanic Explosivity Index. The violent explosion occurred in Guatemala, producing a column of ash and dust 28km tall, and creating 5.5km3 of pyroclastic debris over the course of 19 days. It is thought to have cost more than $1 million in damages, and is estimated to have killed up to 5,000 people. The eruption left a large crater, nearly a mile across, on the volcano’s southwest flank.

5. Mount Pinatubo, Philippines, 1991

The eruption of Mount Pinatubo in the Philippines in 1991 was a classic explosive eruption, ejecting more than 1 cubic mile (5 cubic kilometers) of material into the air and creating a column of ash that rose up 22 miles (35 km) in the atmosphere. It was the second largest volcanic eruption of the 20th century and ranked a 6 on the Volcanic Explosivity Index (VEI), the second-highest rating in the index. In comparison, the eruption of Mount Tambora in 1815 was the largest ever recorded by humans, ranking a 7 (or “super-colossal”) on the VEI. Mount Pinatubo’s eruption caused global temperatures to drop by about 1 degree Fahrenheit (0.5 degree Celsius), while Mount Tambora’s eruption caused the death toll to be estimated at 71,000 people.

6. Nevado del Ruiz, Colombia, 1985

The 1985 eruption of Nevado del Ruiz in Colombia was a devastating event that cost an estimated $1 billion and resulted in the loss of over 25,000 lives. The eruption was classified as a VEI 3, meaning that it released between 10 and 100 megatons of sulfur dioxide and between 100 and 1000 megatons of ash into the atmosphere. The eruption sent an immense wave of mud and ash down the mountain, burying much of the nearby town of Armero and leaving 1,000 people dead in the town of Chinchiná. The mudflows reached as far as the Pacific Ocean, 75 miles away, and was thought to have had a global impact on climate.

7. Laki, Iceland, 1783

The Laki volcanic eruption was a series of lava flows and explosions that occurred in 1783-1784 in what is now Vatnajökull National Park in Iceland. The eruption registered a VEI of 4 and released a huge amount of toxic gases, including sulfur dioxide, which caused acid rain and global temperatures to drop. The gases poisoned crops and killed 60 per cent of Iceland’s grazing livestock, while the accompanying famine killed over 10,000 people, roughly a quarter of the country’s population at the time. The eruption had far-reaching effects, with death and famine reported in the UK and Egypt.

The Laki eruption is considered one of the worst volcanic eruptions in history due to its devastating consequences. Its emission of toxic gases and the ensuing famine inflicted severe losses on Iceland’s population and caused severe disruption across Europe and even beyond. In addition, some environmental historians believe the resulting famine may have been a catalyst for the French Revolution.

8. Mt. Thera, approx. 1610 B.C.

Mt. Thera, approx. 1610 B.C., is thought to have been the site of the strongest explosion ever witnessed, with the energy of several hundred atomic bombs released in a fraction of a second. Though the Minoan inhabitants of the Santorini archipelago likely sensed the imminent eruption and evacuated, the event still had devastating consequences, with tsunamis and temperature declines caused by the massive amounts of sulfur dioxide it spewed into the atmosphere altering the climate and disrupting the culture. Additionally, Mt. Etna, the largest volcano in Europe and the site of the forges of the God of Fire according to Greek mythology, has been active over the past 2,000 years, with its eruptions becoming more frequent since 2018. The most recent eruption, on 21 September 2021, was the cause of a 9km cloud. Comparatively, the 1815 eruption of Mt. Tambora in Sumbawa, Indonesia, was one of the most powerful in 500 years, with a VEI of 7, and claimed the lives of up to 120,000 people and caused global crop failures and famine.

9. Changbaishan Volcano, 1000 AD

In 1000 AD, the Changbaishan Volcano, otherwise known as the Baitoushan Volcano, was dormant. Located on the border of China and North Korea and measuring approximately 750 miles (1,200 kilometers) away from northern Japan, the volcano was considered inactive even though gas emissions were reported from the summit in 1994.

However, in 1702, the Changbaishan Volcano erupted in what would be considered one of the most violent eruptions in recorded history. The eruption spewed volcanic material as far away as northern Japan, creating a large caldera nearly 3 miles (4.5 km) across and a half-mile (nearly 1 km) deep at the mountain’s summit. This peak was the site of South America’s largest volcanic eruption in recorded history, and the explosion sent mudflows as far as the Pacific Ocean, 75 miles (120 km) away, and appears to have affected the global climate. Ash from the explosion buried a 20-square-mile (50-square-km) area to the mountain’s west, which remains blanketed to this day. The mountain also filled with the waters of Lake Tianchi, or Sky Lake, a popular tourist destination both for its natural beauty and alleged sightings of unidentified creatures living in its depths.

The 1600 cataclysm damaged the nearby cities of Arequipa and Moquengua, which only fully recovered more than a century later. Fortunately, such eruptions are rare, occurring every 50,000 or 100,000 years. The last one, the Toba Caldera (Indonesia), killed 60% of the population on earth 70,000 years ago. The most violent eruption registered in history was that in the La Garita Caldera in the United States, which occurred 2.1 million years ago and formed a 35 x 75 km crater. The biggest supervolcano on Earth was discovered in 2013: the Tamu Massif, with a 4 km height and a 640 km width, a submarine shield volcano located in the Pacific Ocean, east of Japan.

So, in 1000 AD, the Changbaishan Volcano was inactive and its last eruption had occurred in 1702.

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Effects of Volcanic Eruptions on People and the Environment

1. Death and injury

The catastrophic events of death and injury caused by volcanic eruptions can never be forgotten. From Tambora in Indonesia with 92,000 deaths due to starvation, to Krakatau causing 36,417 deaths by tsunami, to Mt. Pelee in Martinique with 29,025 killed by ash flows, the list of deadly eruptions is beyond comprehension. The eruption of Laki in Iceland in 1783 killed 9,350 people due to starvation, and Kelut in Indonesia in 1919 led to 5,110 deaths by mudflows. In more recent eruptions, Unzen in Japan caused 14,300 casualties due to volcano collapse and tsunami in 1792, while Galunggung in Indonesia killed 4,011 in 1882 through mudflows. Vesuvius in Italy has been the cause of thousands of deaths in 1631 and 79 AD due to ash flows and lava flows, while Papandayan in Indonesia resulted in 2,957 fatalities by ash flows and Lamington in Papua New Guinea claimed 2,942 lives.

2. Loss of property

Volcanic eruptions can cause extensive property damage. Natural landscapes and habitats can be destroyed by lava flows and lahars, while settlements, woodlands, and agriculture can be wiped out. Cultural property, such as buildings and monuments, can also be damaged or destroyed, as well as businesses and other economic activities that suffer due to the eruption’s aftermath. In extreme cases, entire villages and towns can be wiped out and human lives can be lost.

3. Food shortages

Volcanic eruptions can lead to food shortages due to the destruction of crops and food sources. This can be caused by a number of different factors, such as the release of toxic gases, ash, and other particles in the air, which block sunlight and prevent photosynthesis; the destruction of soil and vegetation due to intense heat and lava flow; and the disruption of agricultural and livestock production. The Tambora volcanic eruption in 1815 is an example of how such disasters can cause widespread starvation, as it caused the “year without a summer” in Europe and North America due to the abundant ash and sulfur in the atmosphere.

4. Disease and illness

Culture: Diseases and illnesses caused by volcanic eruptions can vary across different cultures. For example, some cultures may be more accustomed to living in close proximity to volcanoes, mitigating the health risks of living in such an environment.

Travel: Traveling to regions with active volcanoes can expose individuals to increased health risks, such as the inhalation of ash particles, the ingestion of contaminated water, and the disruption of air quality.

Early Modern: During the Early Modern period, diseases caused by volcanic eruptions were often misdiagnosed or not understood, leading to poor treatment and a higher death rate.

Medieval: In the Medieval period, volcanic eruptions often caused food shortages, leading to malnutrition and increased susceptibility to diseases.

20th Century: In the 20th century, widespread air travel brought increased awareness of the health risks associated with volcanic eruptions, such as air pollution, water contamination, and disease vectors.

5. Environmental damage

6. Disruption of infrastructure

Volcanic eruptions can have devastating effects on infrastructure, including causing power outages, mudslides, floods, auto crashes, wildfires, and contaminating drinking water. Buildings and roads can be damaged by the force of the eruption, or by the ash, lava, pyroclastic flows, and lahars that are often associated with it. In addition, landscapes can be transformed by the lava flows and lahars, while woodlands and agriculture can be destroyed. Finally, the economic effects of an eruption can be quite severe, leading to businesses suffering and economic activity decreasing.

7. Climate change

Volcanic activity can have a significant effect on climate change. When a volcano erupts, it ejects large amounts of ash and other materials into the atmosphere. This aerosol cloud, which can stay in the atmosphere for months or even years, can cause cooling on the planet by reflecting the sunlight away from the Earth’s surface. This cooling effect can lead to changes in the global climate, including changes in weather patterns, ocean circulation, and air temperatures. Additionally, the volcanic aerosols can also cause acid rain, which can also have an impact on climate change.

8. Earthquakes

Volcanic eruptions can cause powerful earthquakes that can have devastating effects. These earthquakes can cause extensive damage to buildings, roads, and other infrastructure, as well as trigger landslides and tsunamis. In addition, the ash and dust particles from eruptions can cause respiratory problems, as well as disrupt air transportation. Additionally, the gases and ash released into the atmosphere can have an impact on global climate. For instance, the eruption of Mt. Pinatubo in 1991 cooled the Earth’s surface by over half a degree Celsius for several years. Finally, magma chambers (which are 1,000 times larger than regular chambers) can form huge craters, drastically changing the climate of the areas around them. Fortunately, these super volcano eruptions are rare, occurring every 50,000 to 100,000 years.

9. Tsunamis

Tsunamis caused by volcanic eruptions can have devastating effects, both immediate and long-term. In the short-term, the waves can cause extensive damage to coastal towns and cities, inundating them with water and devastating the local infrastructure. In addition, the tsunamis can sweep away people and animals, and cause extensive flooding in inland areas. In the long-term, the tsunamis can result in damage or destruction of important coastal ecosystems and habitats, causing economic and ecological disruption. The eruption of Japan’s Mount Unzen in 1792 caused a massive landslide and tsunami, killing an estimated 15,000 people. Similarly, the eruption of Krakatoa in 1883 triggered a 140 foot tall wave which killed 34,000 people. The ash and dust particles left in the atmosphere can also have an effect on global temperatures, leading to crop failures and famine. All in all, tsunamis caused by volcanic eruptions can have devastating impacts on the environment, economy, and communities.

10. Ash and debris flows

The effects of ash and debris flows from volcanic eruptions on people and the environment can be devastating. Volcanic ash and debris flows can cause damage to property, destroy landscapes and natural habitats, and cause immense destruction in the immediate vicinity and beyond. Ash from large eruptions can affect climates globally, leading to crop failure, famine, and disruption of the local economy. Lava flows can cause buildings and other structures to collapse and can even bury entire villages. Pyroclastic flows can cause roofs, trees, and other structures to be crushed, while mudflows can cause floods and landslides, wiping out whatever is in their path. In some cases, ash and debris flows can cause loss of life, as was seen in the 1815 eruption of Tambora in Indonesia, which caused an estimated 92,000 deaths due to starvation. In other cases, such as the eruption of Mount Pelee in Martinique in 1902, the ash flows killed an estimated 25,000 people. In both cases and many more, the effects of ash and debris flows have been catastrophic.