This news release is available in Japanese.
How does the Campi Flegrei caldera, or subsurface rock, near Naples, Italy, withstand more uplift than other calderas without erupting? A new study shows that the caprock underlying this particular caldera closely resembles ancient Roman concrete -- and that the rock's microstructures, characterized by intertwining fibrous minerals, lead to its exceptionally high strength. The findings help to explain how the caldera has been able to withstand tremendous deformation, such as the large uplift episode that began in 1982 and raised the town of Pozzuoli about two meters in just two years, prompting the evacuation of nearly 40,000 people, without erupting. (Many of the non-eruptive uplift events at the Campi Flegrei caldera have been three to six times larger than those observed at Yellowstone and Long Valley caldera, researchers note.) Tiziana Vanorio and Waruntorn Kanitpanyacharoen took a close look at two sediment cores that were drilled from the Campi Flegrei caldera just before the Pozzuoli episode and discovered the presence of fibrous minerals, finely interwoven with the matrix of the caprock, or hard rock overlying a softer rock. Their analyses suggests that basement rock about 1.9 miles (3 kilometers) beneath the caldera releases carbon dioxide, which reacts with seawater, lime, and other minerals -- including pozzolana, the unique volcanic product of the Campi Flegrei caldera -- as it rises. This chain of chemical reactions produces the same ductile, fracture-resistant material in the caprock that ancient Romans used to mix cement, according to the researchers. Their results suggest that ancient Romans might have been trying to mimic nature when they made their iconic concrete. They also imply that stronger construction materials for areas with high seismic hazard and self-healing materials for the storage of waste are within reach.
Article #20: "Rock physics of fibrous rocks akin to Roman concrete explains uplifts at Campi Flegrei Caldera," by T. Vanorio; W. Kanitpanyacharoen at Stanford University in Stanford, CA; W. Kanitpanyacharoen at Chulalongkorn University in Bangkok, Thailand.