Volcanoes of Auvergne, France

One of the main attractions of the Auvergne in France in terms of a walking holidays is the interesting and varied volcanic forms which remain intact in the Puy de Dome area. Perfect volcanic cones, domes and circular lakes cover the Auvergne plateau creating a spectacular landscape, unique in France. The Chaîne de Puys is very recent in geological terms dating from about 70,000 to less than 8000 years ago. Here we take a look at the different types of volcanoes that you'll come across on our guided walking holiday in the northern Auvergne and our multi-centre independent walking holiday in Auvergne. This explanation is limited to the Chaine de Puys and does not include the more complex and older stratovolcanoes of the Puy de Sancy or Cantal mountains further south.

Strombolian volcanoes

This is the most common type of volcano found in the Chaîne des Puys of Auvergne, France.

Named after the Stromboli Volcano in Sicily, these volcanoes are continuous in their eruptions. When they are active, there can be several eruptions per hour, building a cone relatively quickly (in as little as a few weeks) as the lava and volcanic rocks slide down the scree slopes, which stabalise at angles of 30° - 35°. This creates gently slopes for walking paths to ascend the rim. The crater contains constantly boiling molten lava and, from time to time, the volcano ejects a column of gas and rock.

The lava is hot - more than 1000°C - causing the air to separate from the lava. As the lava rises so the air bubbles grow with the reduction in pressure until the air explodes at the surface throwing lava into the air. Towards the end of the eruption, when there is little gas left the lava escapes in large flows from the volcano. Sometimes this can generate the collapse of the cone. The Puy Pariou and the Puy de Cone in Auvergne are two examples of this type of volcano with the later ejecting a huge quantity of lava at the end of its activity creating lava flows 130m deep at 1.5km from the volcano.

Puy Pariou in Auvergne on walking holiday in France

Domes or Pelean volcanoes

This type of volcano takes its name from the tragically famous Montagne Pelée on the island of Martinique. The lava is at lower temperatures, typically 800°C and is extremely viscous. Eruptions are separated by long intervals. The magama builds up slowly and the gas in its interieur finds it difficult to escape. They begin with a preliminary phase characterised by emissions of smoke and ash, followed by an enormous explosion as the gas escapes.

There after the lava accumulates in place, as it is not liquid enough to flow away. Sometimes the dome can no longer support the pressure of this build up and it gives way causing a magmatic cloud containing cinder, ash and blocks to flow down its flanks at 200km/h in what is know as a pyroclatic flow.

In the Auvergne, the Puy de Dome, which dominates the Chaîne des Puys, is a magnificent example of a Pelean volcano. Its flanks are often very steep and the surrounding slopes contain much pyrocastic flow debris.

puy de dome volcano in French Auvergne guided walks

Crater lakes

A maar or crater lake is a circular crater dug into the earth. These volcanoes generally vary from 100m to 1.5km in diameter and are often incredibly circular. They often create lovely short circular walks. The explosion which creates these craters is not due to the magma itself but due to its interaction with water, such as a lake or underground water table. The water is vaporised by the magma causing an explosive build up of gas. A constant water supply ensures this type of eruption during the life of the volcano. Sometimes the situation changes, such as when the lava fills the lake and a more normal strombolian eruption follows.

An example of this type of volcano in French Auvergne is the Lac Pavin. This volcano has created the deepest lake in the Auvergne at 92m. It is also the youngest of the volcanoes in the Auvergne and maybe as young as 6000 years old.

lac Pavin in Puy de Dome in France on guided walking holiday

 

More information about the Auvergne region

Take a look at our article about the historic villages of Orcival and Besse in the French region of Auvergne

Guided walking holiday in Auvergne - Independent centre based walking holiday in Auvergne - Independent walking tour of Puy de Sancy

Other French regions

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