Rome’s Relationship with its Geology: the Tiber River and Tuff

The Creation of Rome

Over 220 million years ago, what we know as Rome today was submerged under the Tethys Sea which connected the Indian and Atlantic oceans. After millions of years of dynamic tectonic plate movement, volcanic activity and sediment deposit, Rome was raised above the water. Explosions from the volcanoes on the northwest and southeast corner of Rome produced large pyroclastic deposits in the region (Figure 1), consequently narrowing the Tiber River, and shifting it west on its path towards the Tyrrhenian Sea. Consolidated volcanic ash created plateaus of tuff along the floors of Rome, providing hills above the floodplain of the Tiber where it had previously been flat (Figure 2). 20,000 years ago, man first began to occupy the region of Rome and nearly 3,000 years ago the Roman Republic began (De Rita et al 2013).

The natural resources in the region of Rome are unquestionably useful in creating a civilization, supporting an Empire and sustaining its success. Whether intentionally chosen or not, Rome is a city built in the right spot. Yet the success of the ancient Roman empire and its visible fingerprint across time is not simply a matter of being in the right place. Ancient Roman engineers dedicated themselves to understanding the environment they inhabited, and proceeded to apply this knowledge within their designs. At the fall of the Roman Empire, the population of Rome dramatically decreased. In the Middle Ages Rome began to repopulate, but the care to understand its nature was not made a priority (Morabito 2022). From ancient Rome to the present, the interaction between Rome and its natural environment has marked changes. This paper will explore the evolution of these relationships by using the examples of the Tiber River and the popular building materials: tuff and travertine.

The Water Artery of Rome

The city of Rome is cut through by the snaking Tiber River, which has transitioned from the imperative lifeline for a growing ancient city to a often ignored divider. The Tiber River flows along a depression caused by the pulling apart of the Earth’s crust, leading it west of Rome until it deposits into the Mediterranean Sea. It meanders from the North to the South of the city of Rome, carrying river sands and sediments. At times of excessive rain water intake, the Tiber swells tremendously, and throughout history has flooded its plains bringing layers of alluvial soil to the base of Rome’s seven hills (Aldrete 2007).

The Tiber River was imperative to the operations of the ancient Romans, serving as its means of transportation, waste management and source of water. Transport of goods was restricted by the technology of the period, thus access to flowing water made imports and movement easy in the city. Basilicas, simply called buildings today, were decorated with marble imported along the Tiber from Egypt and Greece. Wild animals made their way to the Colosseum through transport along the Tiber (Lanna 2022). Travertine from local quarries entered Rome through barges along the Tiber (Pacifici 2022). The Tiber also made it possible to move unwanted things out of Rome, such as wastewater from latrines and buildings via the Cloaca Maxima canal. Although vital to ancient operations, the Tiber also brought troubles to Rome. The Tiber’s frequent floods required strategic planning so the floodplain was only used for facilities that could be cleaned easily post flood such as theaters, temples and army training facilities. Residential homes and businesses were placed above on the tuff hills (De Rita et al 2013).

When Rome began to grow again after the fall of the Roman Empire, preventative measures were implemented to reduce the damage of floods, thus making the humans’ plan for the area ruling over the river’s effects. During the growth in population in the Middle Ages, residential structures were constructed on the floodplain of the Tiber. When the Tiber flooded, its effects were much more devastating than they were in ancient times, as seen in Figure 3. After the great flood of 1870, flood walls were constructed along the Tiber’s banks to protect the city’s infrastructure from further damages (Aldrete 2007). The poor choice to move onto the floodplain has a ripple effect that is noticeable on today’s infrastructure. At the time of the floodwall’s construction, many buildings’ floor levels were below the river crest during flooding. As a result, in several places along the Tiber the floodwalls rise above the ground level, as seen in Figure 4. This article, entitled “The Past, Present and Future of Flood Control in Rome,” provides more details on the history of flood control in the city. Since the construction of the floodwalls, the devastation of floods has greatly decreased in Rome but the city has essentially turned its back on the Tiber. In the summer months, a few booths are set-up to serve food and sell souvenirs; however, the majority of the year its graffitied banks are speckled with few users (Rankin 2022). Figure 5 demonstrates the bank’s lack of use as no human activity is visible: rather than utilizing the natural benefits of the Tiber, modern time has neglected this natural resource.

The Ancient Romans knew well the trade off between the natural benefits of a river access and the risk posed due to flooding. This predicament is not unique to the city of Rome as many cities are next to water. Rome provides a glimpse at the history of human interaction with our natural resources. At one point, what the Tiber naturally did controlled the use of land and limited human mobility in the area. However, as technology advanced new measures could allow human thriving on the unlikeliest of places, like the floodplains of a river.

The Building Blocks of Rome

Two of the most abundant building materials local to Rome are tuff and travertine: both were imperative to ancient construction, and over time have become less utilized in the city, despite their abundance. Travertine is created over thousands of years by the deposition of calcium from slow moving water down a gradient. The deposit closest to Rome and used since the ancient Roman period brings waters from the hills of Siblini to the Aniene River, which eventually feeds into the Tiber. Under the weight of the soil above, this calcium is compressed into a strong and durable stone shown in Figure 6 (Pacifici 2022). Tuff is a result of the Alban and Sabatini volcanic hills that erupted until 3,500 years ago. These explosions left large deposits of volcanic ash primarily consisting of rocks, glass and crystals on the floor of Rome. Through compression, these deposits became tuff, and are popularly called the “Seven Hills of Rome.”

Ancient Romans utilized tuff and travertine heavily in their construction, and grew to understand particular benefits of each stone and applied them strategically. As early as the sixth century BC, Romans began to use soft tuff in construction. Over the following centuries the mining for tuff expanded and the quality of tuff used increased gradually. Travertine became a popular building material as early as 121 BC, so that by the first century BC the Romans had gained “extensive practical knowledge” about the material properties of tufts and travertine (Jackson et al 2005). Evidence of their understanding can be found in the selection of stone for buildings. The Temple of Portunus, pictured in Figure 8, was rebuilt in the first century BC and is a fantastic example of the diverse use of stones. Tufo Lionato makes up the walls, podium and half columns. Alternating travertine and Tufo Lionato blocks reinforce the corners of the walls and travertine is used as a facing for the podium. Tuff, available in greater abundance and lighter than travertine, make up the bulk of the structure, but key supportive elements incorporate travertine. Marble and travertine were used heavily in ancient Roman construction, and while they added a decorative element over the brick or tuff walls, they also served to protect the structure from deterioration. Tuff is porous and absorbs a lot of water, which in turn weakens it significantly. Ancient Romans protected their structures from deterioration due to rain, floods or other weathering forces by applying a stone or stucco as protection. Figure 9 provides a clear example of the ancient process. Over time, nearly every ancient Roman building has had the façade stripped by time or people, so it is necessary to use your imagination to see the structure as it once was.

Since the time of Ancient Rome, the importance of travertine and tuff has decreased in Roman construction, though the presence of these stones are still clear throughout the city and under it. Under the neighborhood of Monteverde, a network of tuff mines were rediscovered and mapped by Roma Sotterrannea as seen in Figure 10. Here, you can watch a Linea Verde video on the Monteverde Caves. The mine was originally used in ancient Roman times for building material, and in the 1870s with the boom of population growth more stone was required for new infrastructure. The mine was greatly expanded using explosives lodged into the tuff. This automatic work nearly cleared any original marks from the ancient Roman picks (Morabito 2022). Though abandoned as a mine for tuff, the cave has been used for several other purposes throughout the years. Pottery, dishes and other home goods are scattered about remnants of the mines’ use as both a shelter during air raids in WWII (see Figure 11), and a dumping ground (see Figure 12). Piles of soil and rock throughout the mine point to its more modern use as a dump. Now, paperwork is being processed to open the space for public tours.

 

Though modern development now relies on fabricated building materials like steel and concrete, travertine and tuff remain in and around Rome. Excavated ruins, like the Roman Forum, provide a glimpse into the use of these stones by the Ancient Romans. The Pacifici Quarry, founded in 1938 an hour drive from Rome supplies travertine stone for various purposes internationally including building façades and bathroom tiles. Tuff caves and deposits are underneath the layered city floor, just like the Monteverde cave.

Rome as it Stands and will Continue

Rome offers an insight into mankind’s relationship to its natural environment. Rome has access to water and an abundance of building stone suitable for durable construction. In Ancient times, these resources were critical to the city’s growth and well developed infrastructure. As time and technology progressed, the local natural phenomena held less restraint on what was possible in the city. Floods that once restricted construction could be blocked by high walls, stones that once were required for sturdy construction could be replaced with fabricated metal beams. Rome continues to hold in both hands the old and new, and it creates the blend of a city unique to itself, just like a piece of travertine.

References

Aldrete, Gregory S. Floods of the Tiber in Ancient Rome. Johns Hopkins University Press, Baltimore, 2007. doi:10.1353/book.3303

De Rita, D., Heiken, G., and Funiciello, R. The Seven Hills of Rome: A Geological Tour of the Eternal City. Princeton, Princeton University Press, 2013.

Jackson, M. D., Marra, F., Hay, R. L., Cawood, C., and Winkler, E. M. “The Judicious Selection and Preservation of Tuff and Travertine Building Stone in Ancient Rome.” Archaeometry, vol. 47, 2005, pp. 485-510.

Lanna, S. Tour of Roman Forum and Colosseum, 2 Sept. 2022.

Morabito, A. Tour of Monteverde Cave, 13 Sept. 2022.

Pacifici Cava, Tour of Travertine Quarry, 16 Sept. 2022.

Rankin, T. Sustainable Rome Tour, 31 Aug. 2022.