Auverne with OUGSME 2003

View of the Puys to the south of the Puy de Dôme. Mike in front of another outcrop to look at A photograph taken at the bottom of the Puy de Dôme of those in the group who decided to walk to the top. Exposure of trachyte along the pathway to the top (lower part of the Puy de Dôme). Nico described this particular outcrop as “fluffy” due to large amounts of gases trapped in the lava. Puy de Dome Elisabeth pointing out sulphur staining around an old fumarole in the crumbly, white trachyte during the walk to the top of the Puy de Dôme. Outcrop in profile. The pathway was nearing the top of the Puy de Dôme at this point, as can be seen from the views in the background. At the top of the Puy de Dôme: Nico with the geological map of the region explaining to the group the various large-scale features that can be viewed from the summit (e.g. alignment of the Puys in a general N-S direction, the horst/graben structure of the Limagne valley with its maars, and the mesa structures in the valley formed by lava flows protecting umderlying layers from erosion). At the top of the Puy de Dôme. The Temple of Mercury can be seen in the background. A road cutting on the way to the next locality. The pale coloured rock is the country rock covered by layers of volcaniclastic material (mainly tephra). The outline of the country rock looks superficially like a volcano, but this is purely incidental. The Gravenoires quarry: at this locality we looked at the differences in colour of the scoria (red close to the vent and black further away from the vent) and what the visible features in the dykes could tell us about flow direction (small shear zones, alignment of phenocrysts, etc.). The Gravenoires quarry: investigation of one of the dykes close to the central vent. A close up of the granitic basement rock at a road cutting upon which the Puys erupted. Puy de la Vache & Puy de Lassolas: both these Puys have been used to quarry scoria. We looked at the difference in colour of the scoria, the bombs and surface discolouration due chemical alteration on some bombs. Royat: Brenda, Frank and Mike supping the mineral waters (which smelled and tasted very sulphurous. This glass building in Royat is open to the public, who can wander in, pick up a plastic cup and choose from one of the continuously flowing taps the particular source of water they would like to try (each is named after the location where it surfaces). Blackbird’s rock (Roche Merle): view of the rock looking upwards at Mike on the top (approx 4 m high). Nico took us to see this rock, sitting all by itself in a green field, to demonstrate what can happen to a flow when it meets an obstacle. The block had been carried in the flow but, when it hit the obstacle it travelled upwards over the obstacle and ended up sitting on top of the flow (which was below our feet in the field). Bois de Charmes: a quarry where trachyte used to be mined. The quarry face with Brenda for scale. Parc des Volcans: lunchtime on the hike up to see Puy de Sarcouy. Frank and Germaine. Puy de Sarcouy: this was a trachyte quarry exploited by the Romans. They used the stone to carve sarcophagi. The lava of the Puy de Sarcouy is very viscous and evolved. As a result the Puy has very steep sides and a flattened top (as opposed to a crater-like depression). After struggling to the top, we discovered it was covered in flowers, here a pansy. On top of the Puy de Sarcouy: Frank and Dave recovering from the almost vertical ascent to the top. On top of the Puy de Sarcouy: Stuart and Nadine recovering. On top of the Puy de Sarcouy: harebell. A quarry on the north side of Puy de Sarcouy: a closer view of the surface weathering on a small piece of broken bomb. On top of the Puy de Sarcouy: pinks. Back at the gîte that evening, the most tremendous hail storm took place. Some brave souls ventured out to collect a few of them.

Slideshow Auvergne Trip 2003