Apologies for the title, but when I worked out where I was going to ride today, I knew what one of the themes would be: geology. My brother will tell you I’m no geologist (he is), but you can’t fail to notice it round here. There are extraordinary formations virtually wherever you look: not only are there very dramatic examples of different rocks and rock formations and upheavals, but so much of it is exposed too (sometimes because large chunks of mountains have simply fallen off).
Actually, today’s ride was so entertaining that it will be split into two posts. The ride from Die went up the Roanne valley to St-Nazaire-le-Désert, turned left along the D135 over the Col des Roustants to La Motte–Chalancon, and then back to the D93 at Luc-en-Diois to get back to Die. The D135 stretch was new to me, and not quite what I had planned. In the end it quite took my breath away, and as the col is at 1028m, it earns itself a separate post for the stretch along the D135.
So, the two stretches either side. The Roanne valley is certainly worth a visit. I think it’s safe to assume from the size of the boulders in the river, and the unstable-looking cliffs overhead that they must have come from, that this dramatic geological scenery changes more quickly than we tend to be used to in Britain (at least when humans aren’t doing the changing). If you do visit, you’ll also notice the very extensive anti-rockfall works after St-Benoit-en-Diois: one assumes that the road maintenance engineering managers round here understand their geology in great detail, as it varies enormously even in short distances.
At the other end of the ride is the mind-boggling portion of regular vertical strata of alternating layers of mudstone and limestone near La Charce. I see they’ve put some information boards there now, and are encouraging people to stop and investigate. It’s well worth the effort.
Perhaps in some of these photos you might get one or two flavours of Provence: the ride passes through into Drôme Provençale, and apart from the cypresses, particularly in a normal year the area does often look distinctly more arid than the Diois area.
I’ll link a route map in due course.