The fact that rippled travertine exists along the ceilings of the aqueduct channels indicates that they operated at capacity, the researchers said. Using the travertine deposited in immediate contact with the original aqueduct mortar, researchers conclude that when the aqueducts were first turned on, the water flowed through at a rate of about one meter per second – fast enough to flood a football field within an hour – much faster than previously hypothesized. “Since few researchers had ever recognized these structures as ripples before, no one had used the power of the shape of a ripple, together with fluid mechanics principles, to produce this kind of reconstruction,” Garcia said. The geometries of ripples along the vertical walls of the aqueduct are identical to those along the floors – evidence that the mechanisms that form crystal growth ripples are not dependent on gravity.Ĭonvinced that the structures are ripple marks that reflect flow, Garcia and his team measured the ripple geometries to reconstruct the volume and velocity of water flowing through the aqueduct during ancient Roman times. While the complex processes controlling travertine crystal growth ripples are distinctly different from those controlling sediment transport ripples, the researchers said they are visually similar. However, Fouke’s team posits that the Anio Novus travertine crystals precipitated, grew and accumulated in the flowing water of the aqueduct – independent of the forces of gravity and aided by the shape and biochemical composition of microbial colonies – to form what they call “travertine crystal growth ripples.” “The theory is that water or wind can move loose sediment into wavelike shapes that slowly advance and are influenced by gravity to form the familiar asymmetric ripple shapes we see along riverbanks, dunes and in the ancient sedimentary rocks deposited in these environments.” “A geologist will tell you that the only way to form ripples is through fluid shear and gravity-dependent sediment transport,” Fouke said. and study co-author – worked with their teams to meticulously measure the geometry of the rippled layers of the Anio Novus travertines to make an unusual interpretation. Once we realized the similarity between Subiaco and Yellowstone waters, we knew we had the knowledge base and experience required to start unraveling the history and mystery of the last flow of the Anio Novus, the longest and most significant of the ancient Roman aqueducts.”įouke and Marcelo Garcia – a civil and environmental engineering professor at the U. “We’ve also identified fossil microbes and plant debris in the dark layers of the Anio Novus travertine deposits. “The Subiaco waters are chemically similar to the waters of Yellowstone National Park, where waterborne microbes form mats and biofilms that play a critical role in the shape and structure of the famous stepped travertine features of Mammoth Hot Springs,” Fouke said.
His group has worked extensively to reveal the geologic history of layered mineral formations – yielding inferences to life on Mars via Yellowstone to coral reefs in Australia – and even inside the human body. However, travertine with similar layering forms in ancient aqueduct systems occurs worldwide, regardless of regional climate or operation.įouke’s specialty is interpreting how microbes thriving in mineral-rich waters influence the crystalline architecture of travertine and other similar mineral deposits in nature. Previous studies have proposed, without evidence, that the layers in the Anio Novus travertine are the result of changes in flow rate initiated by seasonal change or engineering methods put in place by the Romans, the researchers said.
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