We think it inert. Yet granite is alive, at a pace that is not ours. Root of the mountains and bedrock of the continents, it crumbles to form our soils, hold water, feed forests. To follow this rock around the world is to measure what life owes to the stone beneath its feet, and what this stone says about us.
Born in the depths, from the slow cooling of a magma that never reached the surface, granite only sees the light of day through the play of tectonics and erosion. A few tenths of a millimetre a year, over tens of millions of years, are then enough to wear away a mountain. On the Aiguilles de Bavella, in Corsica, the climber Stéphanie Bodet feels that, as she rises, “you also go back to the origin of the world”, and that she is connecting “to a temporality that is not that of humans”. At the foot of the Bitterroot Mountains, in Montana, Tim Wheeler, a geologist turned biologist, watches lichens open up the rock grain by grain. Nearly 20,000 samples to document this infinitesimal work, on the scale of the nanometre and of millennia, from which soils are born.
For Stéphanie Bodet, granite is “anything but monotony”: a whimsical being of varied forms, which has “a little something of the magician”.
On granite, you caress the rock in search of a hold: “you feel as if you’re dancing on the rock”, says the climber.
On a single sample of granite, Tim Wheeler counts some twenty species of lichen, mixed with algae and cyanobacteria.
Their colours betray acids: secreted by the lichen, they dissolve the minerals, including feldspar, rich in potassium and calcium.
Rain, more acidic than the rock, breaks granite along its cracks into blocks that grow rounder with time: this is how boulder fields are born.In Namibia, in the Erongo massif, the granite boulder fields have shaped even the feet and claws of Agama planiceps, and drawn for lions and leopards a landscape of attractions and fears. The San have lived there for more than 40,000 years. Before the paintings of his ancestors, Moses !amace reads “a book”: “It is thanks to this that I know where I come from.” In Brittany, for 6,500 years people have gathered at the foot of a stone to mourn their dead; at Carnac, 4,000 menhirs, some of them reaching 6 metres and 40 tonnes, were raised to leave a mark on the wall of time. In Dambach-la-Ville, the winemaker Florian Beck finds the texture of the rock in his wines, and turns the obvious on its head: it is also terroirs that shape people.
Granite already protected his ancestors; among these rocks, Moses !amace, a San, feels “protected”, “as if I were at home”.
In this avenue, the eroded faces of the stones all turn inwards, staged for whoever walked there; some blocks were cut on islands.
In Brittany, granite is everywhere, in every landscape as in every building, and people seem to have agreed to let it shape them.
Virtually indestructible, granite makes up a large part of the continental crust and the roots of mountains.
On the Frankstein grand cru, granite comes to the surface; its micas, white and black, break down first and release the minerals that the vine sends to the grapes.In the Sierra Nevada, the hydrologist David Dralle and his companions discover that, as it breaks down, granite becomes a sponge into which trees sink their roots to survive. A few hundred metres apart, two different granites make a bare slope or a dense forest. And against all expectations, the forests best supplied with water are the most vulnerable to drought: those that have learned to live with little hold out better. In Namibia, François Theart points out that you cannot protect a species without protecting the place that keeps it alive. A rock may seem inert, a soil nothing more than a factor of production; Florian Beck sees in it “a whole ecosystem” that “carries us”. By crumbling to welcome life, the bedrock of the world makes our planet habitable. Landing is perhaps, first of all, taking the time to look at it.
Everywhere, granite gives flavour to the living.