Excursions
Witnesses of volcanism in Cantal
and on the way, some places steeped in history
IGN maps at 1/25,000: 2434 Riom-Bort OT, 2534 Monts du Cézallier OT, 2435 Monts du Cantal OT.
Getaway in July and August on Wednesdays
and on request in other periods, from May to October
accompanied by Francis Humbert:
06 83 20 80 18 - effache75@gmail.com
This escapade is preceded in July and August, on Monday evening at 9 p.m., by a conferencee “Cantal Volcanoes” at the Lac de Menet holiday village, in the lakeside building, near the pontoon.
FREE ENTRANCE
Departures: To9:15 a.m. from Champs sur Tarentaine to Menet then at 10 a.m. from Menet,
fairground square. Comments on Menet's trachyte extracted from quarries
local; its use in the regional built heritage.
Plan a picnic
Return via Riom ès Montagnes:7 p.m. approximately, towards Menet and Champs.
Depuis Champs : à la sortie de Champs, la D22 longe la rive gauche de la Tarentaine.
From Champs: route towards Menet via D 22 then D3, then D205. Traces of the glaciations in Cheyssac,
evocation of volcanism along the Sumène valley including Chastel-Marlhac, Milhac.
From Menet: D36 towards Riom ès Montagnes. Evocation of the bridge of death, then D678 towards Trizac.
La D22 traverse ensuite Cheyssac ; ce lieu témoigne de la débâcle glaciaire d’il y a environ 10 000 ans : socle rocheux râclé apparent, blocs erratiques de diverses natures, murets de pierres sèches. La “Table” de Chastel-Marlhac et les orgues de Milhac, à l’arrière-plan, permettent d’évoquer le volcanisme de la marge nord du massif cantalien.
scle strié, blocs erratiques
de Chastel-Marlhac
scle strié, blocs erratiques
La D3 à gauche vers Riom-ès-Montagnes suit la vallée de la Sumène, ainsi que la D205 que l’on prend à droite vers Menet. À gauche du pont sur la Sumène, au lieu-dit Le Gué Large, ancien moulin à huile.
À Menet : commentaires sur l’usage traditionnel de la “Pierre de Menet” : bâtiments civils et religieux, symposium de sculpture, chemin des pierres.
À partir de Menet : D36 vers Riom ès Montagnes, puis D678 à droite vers Trizac.
1st step
At the edge of the D678, before the bridge over the Cheylat, beyond a cliff representing the northeastern end of the Trizac planèze, a tree trunk burned by the last basalt flows (-4 Ma). Take nothing.
2nd step
Vast panorama from the D678 between Valette and Trizac (Parc des Volcans sign): about ten volcanoes in northern Cantal belonging to the Sumène-Dordogne domain (between - 10 and - 6.5 Ma). West, North and East horizons. Chronology of the installation of the buildings that make up the landscape.
À Trizac, approvisionnements, et visite possible de l’église : maçonneries en tuf et en trachyte ; manque de verticalité de piliers ; chapiteaux ; retables ; vitraux ; dans une vitrine, orfèvrerie et statues d’époque romane. Bulletin explicatif à disposition.
3rd stage
picnic stopover
On leaving Trizac, D678 towards Mauriac, then D30 left towards “Cases en pierre” representing theremains from the village of Cotteughes (Xeau XIVesiècles). Reading the sign at the entrance to the site. Presentation from the DRAC study during excavations in 1990. Vegetation: Beech, Meadowsweet, Aconit wolfsbane, Gentians, Veratre. Boundary between wooded valley and summer meadows. Burons of summer pastures.
4th step
D30 toCol d'Aulac: Basalt flows from the Planèze de Trizac, panorama over the Mars valley. View of the ridges: Puy Violent, Roc des Ombres, Puy Chavaroche, Puy Mary. Sources of Maronne and Mars. Altitudes, dating of eruptions and other phenomena: collapse of the stratovolcano, spectacular erosion during the glaciations. Coffee in the panoramic restaurant
The D30 descends towards the Mars Valley, crosses severalflows of the supra-cantalian basalts from various powers (- 4 to - 6 Ma), separated by old ferralitic soils, baked in contact with them.
5th step
Same route, limit between the first basalt flows from the Trizac planèze (- 6 Ma) and the products of the collapse of the Cantal stratovolcano, megablocks and matrix (- 8 Ma). Altitudes. Lespinasse stream fed by the abundant basaltic aquifers of the Trizac planeze. Evocation of sports practices (canyoning) at the waterfalls of this stream on a recent panel. Nature of the vegetation according to the constitution of the sides of the road: steep and rocky (basalt cliffs) from the Col d'Aulac, less steep and earthy (products of collapse) from this point down into the valley.
6th step
same road,megablock in a lahar,streaked by glacial erosion ; particle size of products of collapse.
7th step
At the foot of the D30, D12 on the right towards Le Vaulmier: on the left,megablocks scattered in meadows of themars valley (- 8 Ma). In Espinouze,contact between megablocks of several hundreds or even thousands of m3 and granite base; characters of the contact sole. Waterfall of Espinouze stream, scree, granite arena (disintegration of the granite by infiltration water). Evocation the exploitation of granite in the Vaulmier quarries, and the use of this material in the buildings of the Mars valley.
8th step
D 12 towards Le Falgoux then D37 towards the Col de Néronne: overhanging the D12, hugepanel chaos laminate from La Peubrélie, - 8 Ma
9th stage
At the Col de Néronne, path to the Buron d’Algour:baked ferralitic soils by a basaltic flow 4 to 5 Ma ago). Sampling. Valley of the Maronne, Puy Violent. Evocation of the continuity of the planezes before glacial erosion. Then D680 towards the Pas de Peyrol, possible stop at the roc du Merle: panorama towards the Mars valley, scree of the infracantal basalts of the La Franconèche volcano; probable limit of the stratovolcano.
10th step
Beyond Pas de Peyrol, D17 towards Aurillac; before reaching the Col de Redondet, view of thevalley of Mandailles and theheart of the massif : Puy Griou (- 6.5 Ma), and in the distance, Plomb du Cantal (- 2.8 Ma). Burning clouds of Puy Mary. U-turn after 1 to 2 km after observing thestrata of stratovolcano still in place (- 9 to - 8 Ma) crossed by a more recent dyke. Possible research, in damp ditches, Aconite Napel (August flowering), one of the most beautiful flowers of our flora.
11th and 12th stage
Return to Pas de Peyrol, then D680 and at Col de Serre, D62 to Riom ès Montagnes. At the exit of the village of Claux, career of a mason:infracantal basalts, - 10 Ma, and furtherSartre waterfall : crossing of a flow of this same basalt by the small Rhue.
13th and final step
Rest time at the church of Cheylade, details of the vault painted in the 18th century, unique in France. Evocation of the ceiling of the neighboring oratory of the former Sartre castle, of which photo presented. Via Riom-ès-Montagnes, return to Menet. In Saint Hippolyte, mention of the possible excursion to La Font-Sainte; in Apchon, evocation of the necks, the church and its altarpieces. The return to Champs by the D3 reaches a remarkable point of view at the Fleurac rest area.
Other possible steps:
Trizac church; Marilhou waterfalls (picnic possible); Saint-Vincent-de-Salers; source mineral from Fouilloux; recognition according to their biotope, the season of their flowering and fruiting, of plants present along the route (Meadowsweet, various species of Gentians and Aconite, Red Elderberry, Blueberries, Houseleek, Sorbier, etc.).
Retour à Menet : traverser Riom puis D3 vers Bort ; à la sortie de Riom, D678 vers Trizac puis à droite D36 vers Menet. Évocations : (1) de la légende du pont de la mort construit au début du XXe siècle, franchissant la Sumène audessus du ravin de La Clidelle, (2) du château et de ses célèbres occupants, (3) du moulin (céréales, huile, carderie), et de l’émergence d’eau minérale au pied du ravin.
Retour à Champs par la D3, puis juste avant le rond-point de La Baraquette, petite route à gauche vers Fleurac et stationnement à l’aire de repos, Au-delà d’un premier plan, vestige des glaciations, point de vue remarquable vers la vallée de la Sumène aux environs de Saignes, et vers la marge nord du massif cantalien. Analyse du paysage.
Atteindre par la même D3 le rond-point de La Baraquette, d’où la D922 conduit à Bort.
Plusieurs points de vue vers les orgues phonolitiques de Bort (-6,5 Ma) : colonnes massives dominant la Dordogne, en limite d’une coulée longue de 1,5 km.
Peu avant le pont du centre-ville, la D679 à droite conduit à Champs-sur-Tarentaine.
