A character mélange of Jacques Tati, Zebedee, Tigger and a balletomane
to boot, comes close to describing the style and teaching methods of
another star in the OU geological firmament, one Nicholas Fournier,
leader of a most successful recent field trip on his home ground in
the Auvergne and Massif Central. Parted from his rub-out pen and drawing
board only to keep his fluid levels commensurate with his appetite (at
suitable intervals of course), and volubly fluent in three languages
but using mainly English, he made a good job of inculcating (Lat. to
ram down!) in us the various types of vulcanicity to be found within
a reasonable travelling radius of Clermont Ferrand.
Any apprehension I might have felt about Gîte accommodation
(and I admit to plenty), was quickly dispelled by the welcoming amorphous
group emerging from all parts of the European compass. Ever a survivor
and first to bag a bottom bunk, I would now cheerfully accept the sobriquet
‘the oldest Youth Hosteller in the business!’ Apart from
the geology interest we all had in common, the trip brought out in us
other elements of the OU membership; drinking and eating (in that order),
friendship, good conversations and expansion of our individual ‘mind
sets’.
The OUGS Mainland European branch has scant mention in run-of-the-mill
branch newsletters. Three years young now, it is a small branch of forty-three,
with members living as far north and east as Oslo and Moscow, and west
and south as Bordeaux and Athens. With the trip leader living in Oxford,
based at Milton Keynes and doing in research in Nicaragua, the treasurer
in Munich, trip-organiser in France and coordinator in Switzerland,
the eventual meeting of the group coming from Belgium, Germany, France,
Scotland and East Midlands was a logistic achievement to put us locals
to shame! As distances are vast, the AGM is a planned weekend ‘event’,
the main opportunity of a ‘get together’; who could resist
Brussels or Vienna as a venue?
Running concurrently with our generous consumption of wine and victuals
was some good ‘hard rock’ stuff when, to have the various
types of volcanic eruptions (‘explosive’, maar, phreatomagmatic,
‘effusive’ ‘etc.) and lava flow consistencies at immediate
recall at all times, was a distinct advantage. Nicolas, a.k.a. Nikki,
Nico (preferred) but never, under any circumstances in French company
or otherwise, Neek, (don’t ask!!) knew his stuff, that being his
PhD thesis. So we enjoyed excursions first to the northern part of the
Massif to the Puy de Dôme, (1465m) then moving on to Mont Dôre
and Puy de Sancy.
The Puy de Dôme is really a double dome, reaching a height of
550m. Consisting of highly viscous, acid, lava (trachyte, locally ‘domite’),
it emerged at different times from a magma chamber in the mantle, getting
stuck, in a somewhat constipated manner, as it cooled at the top of
the conduit. After the first explosive phase, as the lava was too viscous
to flow like a basic lava, it accumulated around the exit point to form
a dome covering the initial crater. Close to extensive remains of a
‘Temple de Mercure’, a nineteenth century discovery constructed
of lava blocks, of high place value even to the Romans who sanctified
the site, the needle-like man-made construction on the summit serves
as an early-warning system, radio mast, weather station and volcanic
research centre. In good visibility the volcanoes, roughly arranged
in line, the famous ‘Chaîne des Puys’, can be seen
extending over a wide area in a north-south orientation. Nico’s
opinion, and as recent research has it, sees this unusual number of
volcanoes in such close proximity and of widely varying ages as a result
of fissures and faulting, rather than of an underlying hot spot, an
earlier opinion now discredited as this widely researched area is always
providing new insights.
The whole area of the Massif Central, with much of France, was affected
by the Variscan (Hercynean) orogeny towards the end of the Palaeozoic
(570-245 Ma). Further faulting and rifting occurred in the Alpine orogeny
of the Tertiary (65- 1.64 Ma); its volcanic development spanned millions
of years ending only about 8000 years ago. Basically it is a horst,
underpinned at great depth by granitic crystalline rocks; Alpine folding,
uplift and downfaulting formed the escarpment and Limagne basin to the
east, later filled by Tertiary sedimentary material to a depth of 3000
m. To the west the Massif dips more gently into Aquitaine and the Dordogne,
the whole vast landscape shaped by later glaciation, river erosion and
changes in sea level. The Massif Central, although agriculturally poor,
is a ‘bocage’ area famed for cattle (Limousin and Charolais)
and cheeses (Roquefort) on the ‘planèzes’ (slopes).
The Auvergne produces much of France’s uranium for nuclear power;
the Cantal region, further south than our proscribed area, produces
tungsten. Around Limoges kaolin prompted the porcelain industry, now
in some decline.
Clermont Ferrand itself is ‘Michelin Tyre Country’, a
business emanating from the nineteenth century rubber invention of a
certain Mr. Mackintosh whose niece married a Frenchman of exceptional
entrepreneurial turn of mind. Situated on a butte on the edge of a maar
with many caves carved out over the centuries but now mostly used for
wine like the one we visited, its thirteenth century Gothic Cathedral
is built of extremely strong volcanic blocks quarried mainly from Volvic
(of the TV bottled water ad.). This made for a gloomy interior, but
enabled the nave to soar to a height of 300 ft. The statue in the cathedral
square is of Pope Urban I of the First Crusade ‘fame’ and
whose legacy still endures. Volvic supplied almost all of Clermont’s
building material until the end of the nineteenth century. Modern buildings
have used lighter materials and colours, relieving the rather austere
black of the lava. Strong yet with good carving qualities, this is commonly
used for lintels where basement blocks or local stone is used as facing
material.
We followed our leader, like the Pied Piper of Hamlyn, through the
intricacies, consistencies and vagaries of lava flows, domes, maars
and pumice ‘nappes’, ‘necks’ and sills, pleased
and awed in turn by dammed lakes and surprise caves. This last not always
from natural action of huge water/gaseous ‘bubbles’ but
a relict of masons quarrying the lava for sarcophagi in Puy Sarcoui.
Regarding caves, and deserving special mention here is the intrepid
band, (only five opted out), who camped out one night in a cave near
the Puys de la Vache and Lassolas. By all accounts they were mightily
sustained and rewarded after a three mile uphill hike in the dark, by
a fully comprehensive variety of liquid refreshment. Returning downhill
at the crack of dawn for early breakfast at the Gîte proved another
formidable task! One evening much excitement and comment ensued during
a terrific thunderstorm with hailstones like golf balls, the top of
at least one member’s car sustained damage. It must have been
international news as a friend over here heard all about it.
Our second stay was two nights in a beautifully converted barn, another
rural Gîte near Puy de Sancy and Mont Dôre. These volcanoes
founded on an older sequence of lavas, evolved over a period from 3
to 0.25 Ma .A major event occurred 3 Ma when 5 km3 of trachyte magma
erupted from the Mont Dôre area, pouring out in pyroclastic flows.
We saw a spectacular ignimbrite (pumice) deposit at Nappe de Ponce de
Rochefort-Montagne reminding me of that in Alaska in the Valley of a
Thousand Smokes left by the Katmai eruption of 1912. After driving up
to see La Dent du Marais, the backwall of a landslip induced by the
Tartaret eruption and soaring behind Lac Chambon, the lake provided
a restful morning’s swim. We spent the afternoon in the Chaudefour
Valley where several years ago, after prolonged heavy rain, holiday
makers were drowned at a camp site downstream by a horrendous flash
flood. The Massif du Sancy and Mont Dôre are extensive, covering
an area larger than the Puy de Dôme.
The end is in the beginning, and we had a jolly gathering for thanks,
gifts and much sampling of local viticulture products before dispersing
to spread the OU message across Europe once again, vowing to keep in
touch with people, courses and news by e-mail (its life blood, how else?)
and to make it to the AGM in Vienna in 2004. This must be the most attractive
of all geology AGM locations, just in time for the traditional Viennese
New Year Concert and seasonal performances at the Vienna State Opera
(but I betray my natural bent)! All power to your elbow, Mainland Europe
Branch; special thanks to all the organisers for their hard work, Elizabeth,
Annette, Monaco Mike and last but not least, Nico with his knowledge,
enthusiasm, dexterity, agility, volubility and supremely physical visual
aids!! Life-long learning at its best. Merci mille fois; enchantée
de faire votre connaissance!
By Mary Holborow
Glossary
pouzzolanes - friable volcanic cinders used in antiquity as
natural cement by the Romans, today in roadworks and for gritting roads
instead salt which would ultimately pollute the water table, and in
water purification (also, see mention of pouzzolane and pozzolana in
Kirsty’s account of Day 1).
eleutriation - new word for a layer of dust deposited after
‘dusty stuff’ has been disturbed!
‘eh....way...way’ (with actions appropriate to
steering a ‘deux chevaux’) - rising lava trying to exit
a conduit before blowing its top like a champagne bottle.
References
Auvergne
with OUGS Mainland Europe
Last modified on Tuesday, May 03, 2005 at 19:26