The small Romanian town of Costeşti is home to a one-of-a-kind rock group. Not content with the typical sedentary life of rocks, these bulging rocks slowly seep out, and may even appear to grow and move as if they were alive. That’s why it’s not surprising that these strange geological structures, known as Trovant, are also called “living rocks.”
Scientific studies investigating Trovans are scarce, but these strange rocks have attracted a large number of geologists and tourists over the years. These round rocks can be found in numerous places in the region north of the Romanian capital, Bucharest.
Trovans are thought to be blocks of sandstone with hard outer layers of sand, although there is some controversy regarding these rocks. These blocks are harder than the surrounding rocks and therefore can rise to the surface when the softer surrounding bedrock is eroded.
When it rains on the rock, the rainwater reacts with the mineral content of the concrete, seeping its interiors out and causing the rock to appear to expand.
Of course, since we’re talking about geology here, we have to point out that this actually happens really slowly. The rocks are estimated to have “grown” less than 5 centimeters in 1,200 years. In other words, it is not possible to record this event with a time-lapse video shot.
“Trovants are basically oval or spherical in shape, but they can come in a wide variety of shapes,” Florin Stoican, co-director of the Buila-Vanturarita National Park, told Radio Romania International in 2010. Seven million years ago there was a delta where the quarry is today. This delta contained sediments, particularly sandstone and siltstone, that were collected and transported from across the continent by a prehistoric river. Subsequently, various mineral substances melted into solutions circulating in this basin of gravel and sand.”
Stoican continued: “These minerals acted as cement and stuck together various sedimentary particles. Today, there are trovans of various compositions. Some are made of sandstone, others are made of gravel. In geological terminology, they are made of sandstone and conglomerates.”
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