Engineering Rome

The Geology of Rome and Its Use Throughout Time

“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. Volcanoes on the northwest and southeast corner of Rome narrowed the Tiber River, and shifted 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. 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).

Image 1.Geological map of Rome “showing the Monti Sabatini and Alban Hills volcanic rocks [and] travertine deposits within the Acque Albule basin near Tivoli” (Jackson et al, 487, 2005).
Image 2. From a vantage at Villa D’Este, the topography of the region of Rome is flat. Indistinguishable from this distance are the hills formed by volcanic activity.

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 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 brining layers of alluvial soil to the base of Rome’s seven hills (Aldrete, 2007).

“Ancient Romans and the Tiber”

Access to the Tiber River was imperative to the operations of the ancient Romans. 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, 8, 2013). In planning accordingly, the frequent floods of the Tiber were not devastating to the city or empire, and the Tiber was seen as an ally.

“The Misunderstanding of the Tiber”

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. 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 todays infrastructure. At the time of the floodwall’s construction, several buildings had floor levels below the flood height level. As a result, in several places along the Tiber the floodwalls rise above the ground level. 

Image 3. In front of Ponte Sublicio, the difference in height between the floor level of the bank’s buildings and the flood wall is greater than the height of the vehicles that pass in between.

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). Rather than utilizing the natural benefits of the Tiber, modern time has neglected this natural resource.

Image 4. Though beautiful in the morning light, the modern Tiber has few users besides the occasional fishermen or runner along its banks. 

“The Building Blocks of Rome”

Two of the most abundant building materials in ancient Roman construction are tuff and travertine. 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 (Pacifici Cava, 2022). 

Image 5. A block of travertine from the Pacifici quarry in Tivoli. The nearly horizontal lines give insight into the layering of calcium deposits that created this stone.

The Alban and Sabatini volcanic hills erupted until 3,500 years ago, leaving 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.” The constituents of volcanic ash greatly vary, so a wide range of tuff is present in and around Rome. Each variance of tuff has unique durability and strength, but in general the compressed ash is less durable and is weaker than travertine (De Rita et al, 2013).

Image 6. Tufo Lionato in a mine in Monteverde.

“Tuff and Travertine as used by the Ancient Romans”

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, rebuilt in the first century BC, utilizes Tufo Lionato for 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. 

Image 7. The Temple of Portunus, constructed in the first century BC, strategically uses Tufo Lionato and Travertine to maximize strength, durability, stability and cost.

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. Over time, nearly every ancient Roman building has had the façade stripped by by time or people, so it is necessary to use your imagination to see the structure as it once was. 

Image 8. At this bath house ruin in Ostia Antica, remnants of the marble façade that covered the brick structure are left. Similar methods were used to cover tuff structures within the city of Rome as protection from weathering and aesthetical appeal.

“Middle to Modern Age and the Rocks”

The Roman Forum gives thousands of tourists daily a glimpse of what the city of Rome looked like in its ancient period. Stripped of its stucco by time, marble by later residents and metal by looters, the tuff remains as a testament to what once was. However, beyond decoration these facades served the important role of preserving the poorly durable tuff from the effects of weathering. As much of the Roman Forum stands now uncovered, the rate of deterioration of the site is high (Jackson et al, 2005). 

Under the neighborhood of Monteverde, a network of tuff mines were rediscovered. Originally used in ancient Roman times for building material. In the 1870s, Rome required more materials to build infrastructure to keep up with the population growth. 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 dumping ground, and a shelter during air raids in WWII. 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.

Image 9. A map created by Roma Sotterranea shows the expanse of the Cave di Monteverde. Blue specks mark pillars present in the cave added to support buildings above ground around the 1970s.

 

Image 10. This tuff mine was used as a shelter during air raids in WWII, and several metal hooks with lights can be found along the ceiling pointing to how they illuminated their space.

Image 11. In the tuff mine, a speleologist from Roma Sotterranea points to the material dumped into the cave from a manhole above.

“Rome as it Stands and will Continue”

Modern Romans seem less inclined to lean into the benefits of their natural environment. The deep thumbprint mankind has left on Rome makes it feel more man made than natural. Even underground, the first several meters are more man-made, archaeologically significant locations than pure tuff or travertine deposits. Yet despite mankind’s established footing in Rome, care could be taken to understand, preserve and participate in the natural environment of the region once again. 

The two focuses of this paper offer a starting point to reunite Rome’s relationship with their environment. Reviving the Tiber seems like a significant step, making its walkways a place to visit and not just something to be crossed. Ancient Roman ruins that have been uncovered should have protection over them, especially exposed tuff, to preserve their integrity from weathering.

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

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