The Pentagon and the Empire State Building are both decades old, but parts of the two iconic buildings are a whole lot older. About 340 million years old, to be exact, made by ancient microbes that predated the dinosaurs.
Oolitic limestone has been used in the construction of buildings all over the globe, including the Empire State Building and the Pentagon. The popular material is made up primarily of tiny, millimeter-sized spheres of carbonate known as “ooids.”
Now, a new study led by researchers at the Australian National University found that ooids are not made up of layers of sediments, as previously believed. Instead, they’re layer upon layer of mineralized microbes.
“We have proposed a radically different explanation for the origin of ooids that explains their definitive features,” Dr. Bob Burne, a co-researcher in the study, said in a press release. “Our research has highlighted yet another vital role that microbes play on Earth and in our lives.”
Oolitic limestone has been found all over the world, in the U.S., Europe, China and Australia.
Because the limestone is sturdy and lightweight, humans have been using it as a building material for millennia. Along with the Empire State Building and the Pentagon – both made with Mississippian oolitic limestone – the stone has been used in the construction of Buckingham Palace, St. Paul’s Cathedral, the British Museum and much of the city of Bath in England.
The researchers found their mathematical formula for analyzing the limestone’s ooids in an unlikely place: neuroscience.
“Our mathematical model explains the concentric accumulation of layers, and predicts a limiting size of ooids,” said Dr. Murray Batchelor, a co-researcher from ANU. “We considered the problem theoretically using an approach inspired by a mathematical model developed in 1972 for the growth of some brain tumors.”
The team’s research has been published in the journal Scientific Reports.
Image credit: Australian National University