Dormant or Extinct? How to Tell if a Volcano is Safe

Copyright (c) 2008 Mary Smith

The Auvergne is the stunning and seemingly tranquil region found in the heart of France. It is a lush, fertile landscape characterised by crater lakes and big skies. Its spectacular scenery was formed thousands of years ago by a powerful combination of volcanic eruptions and glacial activity. It has been compared to the English Lake District but with one very important difference - the mountains of the Auvergne are dormant volcanoes.

The 'Parc Naturel Régional des Volcans d'Auvergne', contains France's largest concentration of recently active volcanoes. The volcanoes of the Auvergne are still classed as recently active rather than extinct even though there have been no eruptions since just after the last ice age. Indeed, volcanic activity was still occurring as recently as 3 500 years ago in the Chaine des Puys.

The main volcanic areas are known as the 'Massifs' and there are four of them - Chaîne des Puys (highest peak - Puy de Dôme, 1465m/4792ft high), - Monts Dore (highest peak - Puy de Sancy, 1886m/6188ft high), - Monts du Cézallier (highest peak - Signal du Luguet, 1551m/5089ft high) - Monts du Cantal (highest peak - Plomb du Cantal, 1855m/6086 ft high)

They are considered to be the most spectacular and popular of the volcanoes situated in the Auvergne. It is worth asking ourselves if the thousands of tourists who visit these magnificent, sleeping giants each year actually realise that we still have 5 000 years to wait before they will be officially classified as extinct.

These, as well as several other volcanoes, were created from one monumental volcano which is thought to have measured up to 3000 metres in height. The region is of eminent interest to geologists who make up a sizeable percentage of the Auvergne's tourists per year. The volcanic activity has created an array of elaborate formations which consists of solidified lava flows filling valleys to result in dammed streams and rivers which form lakes and waterfalls of rock. The lava flows in the Auvergne are thought to only be rivalled by similar formations situated in Alaska and New Zealand. Glaciers and peat land can also be found in the region as well as a wide variety of plants and animals.

The Chaîne des Puys extends for 40 km north to south. Just west of the city of Clermont Ferrand, it lies on a granite plateau at an altitude of 900metres. It is characterised by the linear positioning of 80 volcanoes, all taking different forms.

How can you actually tell if a volcano is dormant or extinct? Volcanologists study and classify volcanoes according to their activity. With special instruments they can determine if pressure in the volcano is building up. They check to see if the top of the volcano is plugged with cooled lava. There are three different classifications of volcanic activity: active, dormant or extinct. An active volcano is one that has erupted recently or might erupt soon. Active volcanoes are watched very closely so people and animals in the area can be moved to a save place.

The official classification of a dormant volcano is as follows - it has been quiet for some considerable time ( even thousands of years) but still exhibits some signs of activity. When the magma seeps back under the earth's crust or the vent is blocked by hardened lava ( the plug) then the volcano is referred to as dormant. Volcanoes can be dormant for hundreds, even thousands) of years. Then suddenly a volcano will erupt again. The eruption is usually very violent. The plug of a dormant volcano stops the magma from rising. Then pressure under the plug builds up, so the plug gives away and a large eruption is caused. The volcano is then classified again as an active volcano.

An extinct volcano is one that has not erupted for thousands of years. Sometimes it is hard to tell if a volcano is dormant or extinct. They will be listed as dormant until volcanologists are sure there will be no more eruptions. Even then, it has been known for 'extinct' volcanoes to erupt unexpectedly.

For the moment, the volcanoes of the Auvergne provide a spectacular summer and winter holiday destination; whether skiing, hiking, biking, rock-climbing or hang-gliding the volcanic landscape provides physical challenges and breathtaking vistas. The volcanic nature of the area causes numerous forms of springs, including hot, whose water is particularly rich in minerals. People often come for a 'cure' (to 'take the waters') as it is thought to have healing properties.

You can never really tell if a volcano is extinct, even if you are equipped with all the science and the instruments. The geographical history of the Auvergne has been nothing if not dramatic; spectacular volcanic eruptions and an Ice Age have combined to create the stunning landscape of this beautiful region. Let's enjoy it while we can!