A Geologist’s Guide To Finding Ancient History Embedded In Buildings

The buildings all around us contain meteorites, fossils, and billion-year-old stones. Why don’t we ever notice them?

Our cities are mostly made up of stone, but many of us don’t think of the billions of years of geological history each stone represents. When Ruth Siddall walks to work every day as part of her job as a geologist at the University of College in London, though, she travels back through time, just by paying close attention to the granite, ilarvikite, and other stones that surround her.


That’s an experience Siddall wants to share with others. As a resource for the many geological wonders of the capital, she’s put together a project called London Pavement Geology, recently highlighted by Hyperallergic, which allows visitors to drill down to see details, pictures, and even the history of the stones that most Londoners ignore every day–whether that’s a rare piece of meteorite-blasted granite, or a sidewalk paver swimming with fossilized ammonites.

Screenshot of the London Pavement Geology website.

To many people, the stones that surround us are anonymous, abstract materials. But to Siddall, these materials tell rich archeological stories.

For example, by just sitting down at a London pub where the bar is made of granite instead of marble, she can tell when it was built, and what clientele it catered towards at the time. “In the 1890s, there was an explosion of working-class pubs in London,” she tells me. “Working-class people didn’t want their pubs to use marble, like the Ritz, but they still wanted a material that was nice, and bright, and shiny. At the same time, the first railway lines were built from London to Scotland, so they began shipping polished granite down from Aberdeen, which revolutionized what London pubs look like.”

Other stones tell different architectural histories. While many stones have been used in London construction for centuries, certain rarer stones are of a very definite place and time. For example, the post-modern buildings of the 1980s were marked by the bright, unusual stones of the masonry. These stones came from countries like Brazil and China, where they’d been used in construction for centuries. It was only with the refinement of the diesel engine in the ’60s and ’70s that it became practical to transport these stones away from their native quarries, and ship them internationally.

Then there are the rare stones. One of Siddall’s favorite buildings is the unassuming Irongate House, an office block built slightly north of the Tower of London in 1978. Architecturally, it falls somewhere between dullness and being an eyesore, but geologically, it’s constructed of a fantastic material: slabs of Parys granite imported from South Africa that were hit by a meteorite about 2.7 billion years ago. The granite has all these beautiful black veins running through it–the melts generated by this huge astronomical impact. “I doubt the architects who built it were very interested that it has extraterrestrial glasses embedded in it, but I sure am,” says Siddall.

Asked what the most fantastic geologic discovery she’s made in London’s construction materials, though, and Siddall crosses her fingers. She says she can’t quite prove it, but there’s a fossilized bit of bone embedded in a block of Portland Stone, about 30 feet up from the ground. “I’d need a ladder to confirm, she says, “but I’m pretty sure it’s from a dinosaur!”

A chunk of possible dinosaur’s bone at St. Maraget’s.

A dinosaur bone is a rare fossil indeed, but others are more common. For example, in many places throughout London, Siddall says, you can find Jura marble, a type of marble quarried in Bavaria that commonly contains many impressive, photogenic fossils. This type of marble is so common in London, she says, that if you ever go into a Tube station or a shopping mall, you’ve got the shells of calcified prehistoric creatures beneath your heel.

Siddall hopes that the London Pavement Geology site will inspire people to look more closely at the stones that they see every day, but ultimately, that’s not her real goal. “I see this as an important resource for architects and historians in the future, as well as stone and building conservators,” she says, citing her own background helping restore Westminster Abbey and various Roman-period sites in the Mediterranean. Still, even Siddall has to admit she’s partly in it just for the joy of it. “I’d be lying if I said some of my motivation wasn’t purely geek,” she laughs.

[Cover Photo: Samuel Zeller via Unsplash]