Each grain of sand that makes it up is a fraction of geological time. Porous and resistant, sandstone gathers water, gives shelter, lets itself be hollowed out, and maintains almost mysterious relationships with animals and humans. From the beaches of England to the Thar Desert, the film follows this rock and what it makes of those who live in contact with it.
Every grain of sand, says Matthew Bennett, has its story: its descent down a mountainside, its journey to the bottom of the ocean, then to the beach.
In the American West, it is iron oxide, mixed with the cement that binds the grains, that gives sandstone its red colour.It all begins with a handful of sand, on the beach at West Bay, in the south of England. At the bottom of a bucket, the sedimentologist Matthew Bennett reproduces what the ocean achieves on a grand scale: layers that settle, water that circulates and precipitates the minerals that cement them. Behind him, the cliffs were born at the bottom of the sea some 200 to 175 million years ago. He sees in them a book set upright. In the Moab desert, the marine biologist Tim Graham studies the potholes, those hollows where water collects in the rainy season. Branchiopods live in them; some of their eggs, left for more than 50 years on a laboratory shelf, hatched as soon as they were wetted. From these little holes are born, on a geological scale, canyons like Antelope Canyon.
More than 40 metres high, these cliffs were first a seabed, which geological forces raised up over time.
The bucket does not have the scale of an ocean floor, where layers are laid down over hundreds of kilometres, “but the basic physics is the same”.
500 million years ago, branchiopods were the most abundant crustaceans in the oceans, lakes and rivers.
The Navajos call it, in their language, “the place where water runs through the rocks”.At Mesa Verde, in Colorado, the ancestors of Kevin Maddalena, geo-palaeontologist and member of the Pueblo people, settled in the shelter of the sandstone some 1,500 years ago. A lintel there bears, by design, the fossilised remains of a riverbed. “It’s living history”, he says before these dwellings he refuses to call ruins. In southern Utah, the Moqui Marbles recall the dead who, in Hopi stories, play marbles to reassure their loved ones. At Fontainebleau, the geologist Médard Thiry shows two horses engraved near a crack from which water flows during long rains: life would disappear there only to rise again. In Edinburgh, the Stone of Destiny, taken by the English in 1296 and returned in 1996, does not look like much. Yet it makes legitimate kings, and Hugh Allison likes to think that “the stone perhaps has a claim on us”.
Moqui Marbles form only where there is sandstone: sand inside, a crust of iron and haematite outside.On the Californian coast, the marine biologist Michael Russell has spent 40 years observing sea urchins that scrape the sandstone with their teeth and hollow out a shelter in it. The rock, in return, determines their shape: the more crumbly it is, the deeper the holes and the larger the urchins. At Fontainebleau, sphagnum mosses have survived for 40,000 years thanks to the acidity of the sandstone alone. Humans seek the same fit. In Jaisalmer, the porous stone gives back coolness, and the historian Navneet Vyas compares the houses to desert igloos. In Moigny-sur-École, Francisco de Oliveira, the last quarryman in the area, listens to the block ring before splitting it. “And my heart goes to the stone”, confides a stonecutter in Jaisalmer. Learning to inhabit the Earth perhaps begins like this: listening to what shelters us before striking it.
Billions of urchins scrape these reefs: for Michael Russell, the rock they erode is measured “in millions of tonnes”, an “astonishing” figure.
The “golden city” owes its nickname to its yellow sandstone; on a caravan route linking India to Persia, silk and spices passed through it.
Stonecutters know how to read the stone: this block will go to the foundations, that one to the pillars or to sculpture.All sandstone, one day, returns to sand.