Spectacular eruptions, volcanoes

In 2010, the eruption of the Merapi volcano in the centre of the Indonesian island of Java paralysed airports and displaced thousands of people, and in April of that year, thousands of flights at European airports were grounded when ash from the Eyjafjallajokull volcano in Iceland became airborne.

In fact, volcanic eruptions are one of the most dangerous events on Earth that directly affect humanity.

Dangerous volcanic phenomena

When a volcano erupts, the threats to humans include pyroclastic flows, lahars, and volcanic collapses. The most dangerous volcanic event is a lahar, which is a fluid mixture of lava, ash, hot gas, and rocks that is over 1,000 degrees Celsius and flows at speeds of around 70 km/h. Pyroclastic flows usually flow so fast down a volcano’s slopes that people can barely avoid them. The second most dangerous volcanic phenomenon is lahars, which are volcanic rocks or ash deposited after a volcano erupts, mixed with flowing water. Because volcanic areas are usually devoid of trees and grass, and the sediments are unconsolidated, even small rainfall can cause lahars. It can travel tens of kilometres, usually at speeds of up to 100 kilometres per hour. Other volcanic threats to humans include damage from the collapse of a volcano’s summit or slopes, asphyxiation from hot toxic gases, and extreme weather events caused by ash rising into the atmosphere.

Volcanoes in history

Volcanoes are named after Vulcanus, the fire god of Roman mythology.

Vulcanus was ugly and lame, and as a volcano god, he was associated with blacksmiths, craftsmen, metals and metallurgy.

His forge was the volcano Etna on the eastern Italian island of Sicily.

In Greek mythology, he appears as Hephaistus.

The oldest recorded volcanic eruption in human history is the 693 BC eruption of Mount Etna.

Etna is the tallest volcano in Europe at 3,329 metres and is thought to have begun volcanic activity around 2.5 million years ago, and is known to have erupted over 200 times in its history.

Etna is a cone-shaped volcano with a circumference of 140 kilometres and a base area of 1,190 km2. One of the most well-known volcanic disasters is the eruption of Vesuvius, which occurred on 24 August 79 AD.

The eruption completely covered the ancient city of Pompeii on the shores of the Bay of Naples in southern Italy with ash.

The actual location of the city was unknown until 1599, when the ruins were accidentally discovered during the construction of an aqueduct, and excavation began, with two-thirds of the city now uncovered.

Volcanoes causing extreme weather

The year 1816 is the so-called ‘year without a summer’.

It was so cold that the entire planet was worried about the arrival of an ice age.

Why was 1816 so cold? It was due to the eruption of the Tambora volcano on the Indonesian island of Sumbawa on 5 April 1815. The Tambora eruption spewed out 150 km2 of volcanic ash and covered everything in a 40 km radius around the volcano in lava.

Hundreds of millions of tonnes of ash and dust also rose into the air, covering the sky, blocking out sunlight, and gradually travelling across the planet on air currents, bringing extreme cold and affecting crops, including snow and frost in Europe the following summer. Tambora had a Volcanic Explosivity Index of 7.

The Volcanic Explosivity Index is a measure of the intensity of a volcanic eruption based on the duration of the eruption and the amount of volcanic material produced, and ranges from 1 to 8, with each increase of 1 representing a 10-fold increase in explosive intensity.

The eruption of Indonesia’s Toba volcano about 74,000 years ago had a magnitude of 8, making it the most powerful eruption since the dawn of humankind.

There are other recent examples of volcanic eruptions that have lowered global temperatures. The 1991 eruption of the Pinatubo volcano in the Philippines was the second largest volcanic eruption of the 20th century, after the 1919 eruption of Alaska’s Nova Lupta volcano.

The massive eruption, with a magnitude of 6, wiped out about 100,000 km2 of farmland, destroyed 40,000 homes, and displaced 650,000 people.

Among other areas, the city of Angeles was the hardest hit, forcing the US base there to evacuate.

The Pinatubo volcano eruption released 10 billion tonnes of magma, with ash rising as high as 40 kilometres above the ground. The ash plume reached as far as the east coast of Africa, 8,500 kilometres away.

Between 15 and 20 million tonnes of sulphur dioxide (SO2) were ejected, which is believed to have stayed in the stratosphere of the atmosphere and blocked sunlight, causing the average global temperature to fall by 0.5 degrees Celsius by June 1992.

This is known as the Pinatubo effect, or global cooling by volcanic eruptions.

Living with volcanoes

Most of the world’s active volcanoes are now monitored.

This is to warn people in advance of the risk of an eruption so that damage can be minimised.

Changes in the amount or composition of gas emitted by a volcano, an increase in temperature due to the accumulation of new magma, a swelling of the volcano due to the accumulation of new magma inside the volcano, or a change in the pattern of seismicity in a previously quiet volcano can all serve as warning signs that a volcano is about to erupt.

Volcanoes have not always had a negative impact on humanity. Kilauea, the largest active volcano in the world, created the island of Hawaii by spewing lava. Jeju Island and Ulleungdo Island in Korea are also volcanic land masses.

Humans live on this land, and the substances such as potassium (K) and phosphorus (P) erupted by volcanoes fertilise the soil and help solve the food problem.

For this reason, 10% of the world’s population currently lives near active volcanoes, despite the danger. This is because of the benefits of volcanoes. Iceland, a country with more than 150 active volcanoes, uses volcanic heat to generate hot water for heating, grow crops, and generate electricity. Volcanoes are also attractive tourist destinations.

Tourists visit the volcano’s sulphurous hot springs and slather themselves in natural sulphurous mud.

It is said to be effective against osteoarthritis and skin diseases. Ash baths are also used to remove toxins from the body and disinfect the skin.

Pompeii’s amphitheatre, baths, and Temple of Jupiter have been preserved in their original state, making it a great cultural heritage and tourist resource.

Pompeii now attracts 2.5 million tourists a year. Living with volcanoes, this is where human interaction with volcanoes creates common ground.

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