Volcanoes of the world

Ever since our distant ancestors roamed the Earth, volcanoes have been feared for death and destruction they bring, wreaking havoc on a local, regional and occasionally global scale. Major number of volcanoes are located in developing countries and are poorly studied. But now volcanologists, from around the world are keeping vigil on world's active volcanoes, aiming reducing disasters in populous world.

Around 50 volcanoes erupt every year - during 2021, January to June, 12 volcanoes have erupted in seven countries – Indonesia four, US three, and one each in Iceland, Russia, France, Nicaragua, and Costa Rica, in addition, in Barren Island - uninhabited, volcano, Andaman Sea, India small ash emissions were seen in satellite images in February 2021; some of which like Mediterranean island of Stromboli - are constantly active, while others like Etna and Vesuvius in Italy or Krafla & Hekla in Iceland may not have erupted for years or decades.

The most concerning volcanoes are those who have not erupted for century or more like Hood, Shanta in western US along with hundreds of dormant volcanoes in Southeast Asia - India has such few, Central, South America and around Pacific Rim. It is likely that next big eruption will occur at a volcano which has demonstrated no activity during historic times. These gigantic explosive eruptions eject thousands of cubic kilometres of debris into the atmosphere devastating the surrounding regions and dramatically modifying global climate. At TOBA, Indonesia, this type of eruption has occurred about 74,000 years ago. Analysis of frequencies of such eruptions suggest that they occur, on an average, twice every one lakh years, so there should be another along anytime soon. Volcanoes are not randomly distributed but occur mainly along well-defined chains, hundreds to thousands of kilometres long. They exist in chains around the Pacific Ocean, in the Caribbean, through Europe's Mediterranean countries and along the eastern half of the African continent. Beneath the oceans, volcanic ridges rundown the middle of the Atlantic, through the Indian Ocean and around the rim of Antarctica. The whole planet has a network of volcanoes. The hard crust of Earth's surface layer from about 100 km thick, is composed of a set of large and small plates. These lithosphere-rigid outer layer of Earth, plates move across the Earth's surface, interact along their boundaries, diverging, converging or slipping past each other. These plate boundaries are the sites of volcanic activity.

Looking at major volcanic eruptions, Asia teems with the most explosive and dangerous volcanoes. In Indonesia - having highest concentration, during 1815, eruption of Tambora volcano, the biggest eruption since ice age, resulting in 12,000 deathss from direct effect and 80,000 starved or succumbed to diseases as crops died and water was contaminated.

In Europe, concentration of biggest and deadliest volcanoes is there in Italy. In Vesuvius volcano,the most recent eruption was in 79 CE. Flourishing towns of Pompeii and Herculaneum were buried from the sight by pyroclastic flows. Stromboli is one of the most active volcanoes on Earth. It has been active for last 2000 years and its lava is visible from long distances at night, it is known as the 'Lighthouse of Mediterranean'.

In 1912, Novarupta volcano (considered extinct) Alaska, erupted - a black cloud settled over 10,000 sq. km, removing all traces of sunlight for three days. Noxious gases filled the atmosphere, is reported to be the largest eruption of last century. Mt. St. Helens, US, which has been quiet for 100 years became active in 1980. A landslide exposed pressurized magma within volcano, triggering a massive blast and pyroclastic flows that devastated 600 sq. km including prime Douglas Fir forest. In 1985, Ruiz volcano, Colombia erupted and pyroclastic flows were spewed over the ice cap, they were hotter than 900 degrees Celsius, rapidly melting the ice. A wave of 40 m high mudflow swept through the town of Armero killing over 35,000 people.

In the Caribbean, the worst volcanic disaster, St Pierre town of Martinique island - the Paris of West Indies, was wiped out from the face of the Earth within 2-3 minutes. The Mt Pelee volcano - the bald mountain erupted in 1902, gigantic volcanic explosion like a blast from shotgun, driven by volcanic gases, glowing clouds of molten fragments and superheated steam flowed down the flanks of Pelee, battering town by hurricane force and flattening buildings in seconds, killing 29,000 people. Volcanoes are being monitored and the first volcano observatory was established on the slope of Vesuvius volcano in 1847. As such volcanologists are continuously monitoring more than 600 world's active also most dangerous volcanoes and are saksham enough to predict eruption with remarkable precision, accordingly contingency plan like evacuation and other measures are activated so as to minimize human and other impending losses. Mostly known for destruction and deaths, volcanoes accrue some benefits as well in many parts of the world the solidified lavas are used for building purposes. Volcanoes are also an immense source of cheap power. In Iceland volcanically-derived hydrothermal power heats the glass houses which keep the population in fresh fruits and vegetables. Volcanic scenery is often spectacular and attract tourists in some parts of the world. The volcanoes of Iceland, Hawaii, New Zealand and Canary Islands of Spain accrue major economic benefits to their regions through attraction of large number of tourists.

(The author is a retired

IFS officer)