They’re everywhere, as a new map proves.

Look closely at London’s stone buildings and you’ll see the city is really a disaster site. The rock that much of England’s capital is built from is the residue of billion-year-old volcanic eruptions and tsunamis, of plants and animals flattened into gritty seams beneath layers of debris, and of earth warped by meteor falls. Now, an impressively detailed map (below) shows you exactly where to find the evidence of this turbulent prehistory.

Portions of London Pavement Geology's London rock map. (London Pavement Geology)

The London Pavement Geology project is a loving catalog of the many different types of rock to be found across the city. To be released as an app later this summer, it doesn’t just reveal the geological variety of the city’s building materials. In tracking down the seam of rick running through the U.K. capital, it also reflect key shifts in the city’s history.

Buildings as records of prehistoric events

For the non-geologist, the most immediately eye-catching part of the map tells you where to spot fossils, crushed shells, bones, and leaves embedded in the very fabric of London’s buildings. These are everywhere—somewhat unsurprisingly so, given that much of London’s building stone comes from Southern England’s Jurassic Coast, a Unesco World Heritage Site so named for its complete geological record of the Triassic, Jurassic, and Cretaceous periods. The limestone in this area has disgorged an incredible variety of fossils over the years (including the world’s first complete Ichthyosaur), and in the form of Portland Stone, its crushed shells have formed the foundation of many London buildings. This stonework by Green Park Tube Station, for example, is revealed on closer inspection as an infinity of oyster shells packed together with sediment.

Shell details in Portland Stone at London’s Green Park Station. (London Pavement Geology)

Not far away, the walls of the late-Medieval St Margaret’s Church also reveal the clear outline of a prehistoric reptile bone.

Reptile bone fragment in the wall of St Margaret’s Church, Westminster. (London Pavement Geology)

While finding these sea creatures crushed into the city’s walls is fascinating, they’re not the only compelling feature of London’s architectural geology. In fact, Ruth Siddall, a geologist at University College London and the co-creator of London Pavement Geology, seemed a little weary of fossils when she discussed the project with Citylab:

“Fossils are everywhere, and London actually has some much rarer materials to offer,” she says. Her favorite example is a building called Irongate House (below), which is made from rock hit by a meteorite three billion years ago; traces of the impact are visible in the black veins running across the stone.

Granite showing seams created by a meteorite hit, Irongate House, London. (London Pavement Geology)

Testaments to a globalizing London

As Siddall notes, there’s another thread running through London’s stone—a timeline of the city’s globalization. From the city’s founding by the Romans up to the early modern period, London building stone was mostly quarried in Kent, then brought by boat up the channel and along the Thames. After the Great Fire of London destroyed most of the city in 1666, London’s use of stone and brick shot up, in order to replace the less flame-retardant wood, plaster, and wattle buildings that had previously dominated the now-gutted city.

This time, the stone came from further down England’s coast, from the aforementioned Limestone quarries of Portland Bill. This stone became popular partly because new ideas about building aesthetics had been filtering into England from Italy. This Portland Stone had been used earlier throughout Italianate buildings by architect Inigo Jones, which derived from Italian Renaissance prototypes and formed the blueprint for post-fire designs from Christopher Wren and others. The sudden proliferation of Portland stone buildings in this period thus shows a city forging a more international style of non-religious architecture, using a local, flexible alternative to Italian marble.

The limestone of Inigo Jones’ Banqueting House provided an Italianate blueprint for London’s post-fire reconstruction. (Steve Cadman/Flickr)

Then in the late 19th century, Scottish and Scandinavian Granite suddenly started appearing across London, its polished surface providing sparkle to many of the city’s elaborate pubs. It started to appear because Scottish masons were the first to master the technique for cutting and polishing the material. Fast railways allowed the material to reach London quickly and cheaply, creating such a demand that Aberdeen stone polishers shipped stone across from Scandinavia to fill their orders. This elaborate finish is thus the expression of a faster, cheaper European transit network for goods. Without the railway and the steam ship, this granite wouldn’t have reached London in any great quantity.

London’s late 19th century Prudential Building has Scottish Granite Cladding on its ground floor. (Robert Cutts/Flickr)

The bedrock of postmodernism

Finally, at the end of the 20th century, the eclectic anti-purism of postmodernism clad London is a flood of novel exotic rock. Its flashiness was also a fitting visual expression of the global buccaneering of the finance companies whose offices it often graced. As Siddall put it to Citylab:

“In the 1980s, postmodern architecture was very flashy and plasticky and demanded bright colors, which encouraged export of fancy, brightly coloured stone from places like Brazil. These are these amazingly pretty coloured rocks. It reflects not just the vogue for Postmodern architecture but also the development of the diesel engine for shipping, which made it very cheap to import. It's now cheaper to bring granite from Brazil than from Cornwall.”

The changing building stone mapped by London Pavement Geography are thus a weathervane showing the city’s changing direction even today, when self-consciously austere brick is back in vogue. The stones are reflection not just of the historical record and changing aesthetic tastes, but of the economic shifts that made such changes possible. If anything, this makes the materials’ origin only more interesting and fantastical.

H/t Londonist

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