Volcanoes and Human Population

The Calbuco volcano in southern Chile erupted for the first time in more than five decades, which in the global media was covered more for its visual spectacle rather than its perception as a major catastrophe. This can be partly explained with the low threat that Calbuco poses to larger numbers of people. As reported by the BBC, “authorities have declared a red alert and evacuated more than 4,000 people within a 20km (12 mile) radius”. This is a relatively low number as the volcano is situated in a sparsely populated, mountainous area. Natural events usually turn into natural disasters when they happen in more densely populated areas. The following map shows how human settlement patterns and the global distribution of volcanoes correlate by drawing a 100km radius around each of the world’s volcanoes and then projecting this data onto a gridded population cartogram. This equal-population projection results in some of these 100km risk zones around the volcanoes to become hugely visible, because there are large populations living in this area, while other volcanoes and their risk-radius become almost invisible due to the low number of people living there. Very often, these are the decisive differences between a volcanic eruption being a natural event (or even spectacle) and a natural disaster, which these events can become in the red-shaded areas of this map:

Map of volcanic risk zones on an equal-population projection
(click for larger version)

As the map above shows, similar to earthquake risk zones (as shown in this map which I published in a paper for the Journal of Maps) volcanoes are not always in the remotest places on the planet. Due to the rich and fertile volcanic soils they are in sometimes much more densely populated regions than in Southern Chile, such as the northern highlands of Ecuador on the same continent where its capital region Quito is home to over 3 million people in close vicinity to a number of volcanoes. Even higher populations near major volcanoes can be found in Mexico City and South East Asia (with Indonesia and the Philippines having tens of millions of people living near the numerous volcanoes there).

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