St. Francis, Giotto and Geology

By Ann C. Pizzorusso

St. Francis of Assisi (c.1181-1226) and Giotto (c.1270-1337), would change the history of religion, art and ecology. Some 800 years later, geologists would examine the limestone used to construct the Basilica of St. Francis at Assisi and would discover the secret behind the extinction of the dinosaurs.

Central Italy, spliced by the Apennine Mountains, has some of the most complex geology in the world. It is no wonder, therefore, that those living in the region would have seen natural catastrophes and unusual rock formations. As a result, nature’s vicissitudes were often associated with divine or satanic forces. With the arrival of St. Francis, a radical change in perspective toward the natural world was presented. He set forth the unorthodox philosophy that all things in nature should be respected, as they were creations of the Almighty.


St. Francis’ ideas influenced the artist Giotto, who revolutionized art history by adding perspective, three-dimensionality and natural elements in his religious scenes. By removing sacred figures from Heaven and placing them in an earthly landscape, he separated them from their abstract, unapproachable representation in Byzantine art (which was the artistic style of the era). Giotto’s works are distinctive because they portray daily life in a pastoral manner, thus minimizing the difference between the sacred and profane.

It was perhaps Giotto who deserves the most credit for disseminating the ideas of St. Francis as the general populace was illiterate. Seeing frescoes which depicted sacred scenes in landscapes that were familiar, changed their way of thinking – the Creator was indeed present on Earth. The trees, plants, animals and rocky landscapes that were depicted were suddenly perceived as divine gifts. Even today, as an unexpected benefit of Giotto’s accurate rendering of landforms, geologists can identify the rock type and possibly the exact location depicted. In fact, it would be discoveries in the pink Scaglia Rossa limestone–depicted in Giotto’s frescoes as rose-colored buildings and used to construct the Basilica of St. Francis at Assisi–which would revolutionize the history of geology.


In order to understand the influence of Giotto on art, religion, ecology and geology, several of his frescoes (out of many) will be analyzed.

Nativity Scenes

Francis organized the first living recreation of the Nativity (presepe in Italian), on Christmas day 1223, in a limestone grotto at his monastery at Greccio. He had to obtain papal permission to use an ox and an ass in the program to avoid the charge of novelty. After the townspeople had assembled with their animals, Francis led a celebratory mass. Bringing the message of Jesus’ birth down to Earth allowed the congregants to understand the humble manner in which He was born.

Fig. 1. Limestone grotto at the monastery at Greccio, the site of the first Nativity scene organized by St. Francis in 1223. The limestone outcrop was used as an altar until it was replaced by another when the Pope visited. The fresco depicting the original Nativity scene is from the 14th century. Photo credit: Ann C. Pizzorusso.

If we look at the depiction of the Nativity in art history, we can see that its representation in Byzantine art (first part of the 14th century) shows Jesus’ birth in a cavern in a landscape replete with rocks, mountains and trees. However, the Byzantine style, lacking perspective and scale, portrayed the figures and landscape elements one-dimensionally.  Further, the gold leaf background, a symbol of grandeur, placed the scene in Heaven, not on Earth. This technique created a psychological distance between the sacred events and the viewer, evoking a reverential experience.

Fig. 2. Nativity by Andrei Rublev. First half of the 14th century. Note how the work lacks perspective and appears one-dimensional. State Tretyakov Gallery, Moscow, Russia. Wikimedia Commons.

Giotto, who is considered the father of Renaissance art, broke with the static iconography of Byzantine representation. In his frescoes depicting the life of St. Francis in the Basilica at Assisi and other churches, he acknowledged Francis’ love of nature by including realistic landscapes in each work. In his portrayal of the Nativity he reproduced the geomorphology of central Italy and added shepherds and their flocks to demonstrate that in the midst of our everyday lives there is a divine presence.

Fig. 3.  Adoration of the Magi, Giotto, 1305, Scrovegni (Arena) Chapel, Padua.  In October 1301 comet Halley was seen in the skies of Europe.  The historian Giovanni Villani described it as having “great rays of fumes behind.” Giotto, working on the Scrovegni frescoes must have seen it and remembered it in enough detail to use it as the model for the star of Bethlehem. The European Space Agency named its probe to Halley’s comet “Giotto” in honor of the enlightened artist.
Fig. 4.  Nativity, Giotto (1303-1306) at the Scrovegni (Arena) Chapel, Padua, Italy. Source: public domain – Wiki Commons.

Here, Giotto uses an upthrust block in the background to provide shelter for the newborn who rests upon an elevated formation of bedrock in the foreground. As always, he sets the divine event in the context of daily life. Giotto also deftly incorporated light into his scenes to illustrate the gift of divine life and miracles.

Fig. 5. Nativity scene by Giotto (ca 1297-1300).  St. Francis upper church, Assisi, Italy. Note the change from the outdoor manger to an indoor public church. Wikimedia Commons.

A differing portrayal of the Nativity occurred in the 14th century, when it changed from a cavern, to a kataluma an inn or guest room, a diversorium which might be an inn, a capanna, a cabin, or a tettoia, a hut with a canopy, all of which were common in medieval cities. These were public places where people gathered to rest and talk. They became the new churches, humble and unpretentious, according to the reform principles of the Franciscans.

The abandonment of the desert and the grotto has a precise theological justification. By placing Jesus’ birth in a city, not in the wilderness, the mystery of His divine nature would be seen by all. The newborn is often placed in the foreground on the earth, underlining His human character, or on a sheet – evocative of the shroud. In this manner, when the faithful looked down, they would have understood the humility of the divine birth. From an etymological standpoint, the word “humble” can be taken to mean “attached/close to the ground” (in Latin, humus).


St. Francis Receiving the Stigmata

Fig. 6.  St. Francis receiving the stigmata by Giotto (1318) Bardi Chapel, Santa Croce Basilica, Florence, Italy – Wikimedia Commons.

St. Francis received the stigmata of Christ in the grotto of the monastery at LaVerna in 1224. Giotto places St. Francis on a block of limestone which has been weathered and uplifted. A cleft in the side of the cliff is evocative of the form of Christ’s wounds. St. Francis slept in the cave and the falcon above it woke him for his nightly vigils.  The church in the foreground is made of gray limestone, indigenous to the area. Flora and fauna are sparse, adding tension to the miracle in progress.  The Franciscans believed that mountains were an integral part of the sacred ritual.  And so, for 800 years, pilgrims have been flocking to this shrine to pray, heal and give thanks.

St. Francis Gives His Mantle to a Poor Man

Fig. 7.   St. Francis gives his mantle to a poor man (1297-1299). Basilica of Saint Francis, Assisi, Italy – Wikimedia Commons.

In this fresco, Francis gives his mantle to a stranger. This act occurred privately, with no one to witness this act of generosity.  Francis would eventually give away all his earthly possessions and adopt the simple sackcloth which is even today, the habit of the friars.  Francis is on a road leaving a city and moving toward a church, indicating his changing life. Giotto depicts the town realistically, from its hilltop location, chosen for security, to the typical medieval wall with entry gates to the city. The buildings are pastel-colored, indicative of the local building material; lightly colored limestone. The enormous sections of overturned rocks, gorges and crevices are the result of the historic and ongoing seismic activity in the area. The scene would be familiar to the faithful who would recognize the landscape, architecture and of course the religious message.

The Dream of Joachim

Fig. 8.   The Dream of Joachim by Giotto (1304-1306). Scrovegni (Arena) Chapel, Padua, Italy – Wikimedia Commons.

St. Joachim, husband of Ann and father of the Blessed Virgin Mary had reached an advanced age without having a child.  This was considered a sign of God’s wrath.  When Joachim went to the synagogue to offer a sacrifice, he was cast out.  He went into exile in the mountains, where Giotto has created a barren landscape, indicative of the childless marriage.  The rocks are upthrust and there is scarce vegetation.  The shepherds are the only ones Joachim will see in this forsaken landscape.  The hut (or refugio) is made of indigenous limestone, mined in the area and identifiable by its color. In the midst of this desperate situation, an angel appears who will announce that Ann is with child.

Rewriting Geological History

Fig. 9. The pink-streaked with white Scaglia Rossa limestone was mined at the Mt. Subasio quarry and used to construct the St. Francis basilica at Assisi – Wikimedia Commons.

As noted previously, the Scaglia Rossa limestone was used in the construction of the Basilica of St. Francis in Assisi. But amazingly, this limestone would provide astounding information for geologists. Some 65 million years ago (Mya) a giant meteorite hit the Earth near the medieval city of Gubbio, sending smoke, dust and a rare element, iridium, into the atmosphere. The pollution blocked the sun which resulted in widespread plant and animal death, including the dinosaurs. High levels of iridium, indicative of a meteorite strike were found in the Scaglia Rossa strata dating to 65 Mya, connecting the meteor impact to the extinction of the dinosaurs.

The Basilica of Saint Francis in Assisi – photo by Peter K Burian / Wikimedia Commons

After 800 years, we still live with the revolutionary ideas of two people born in central Italy, have bequeathed us. St. Francis changed man’s view of nature and started the environmental movement. Yet his words and influence would have likely been lost if it were not for Giotto who depicted Francis’ ideas in his frescoes.

Unbeknownst to Giotto, his accurate portrayal of geologic formations would allow today’s geologists to analyze the frescoes from a scientific perspective. We know that Giotto’s pastel-colored buildings and churches were not flights of fancy, but reflected the colors of the actual building materials. In fact, the Basilica of St. Francis, with its pink limestone would end up being the key to understanding the extinction of the dinosaurs. And so, central Italy seems to be an area where one can explore art and religion by looking at Giotto’s frescoes and unlock the Earth’s mysteries while walking in the footsteps of St. Francis.

Ann C. Pizzorusso is a geologist and Italian Renaissance scholar. After many years of doing virtually everything in the world of geology—drilling for oil, hunting for gems, cleaning up pollution in soil and groundwater, she turned her geologic skills toward Leonardo da Vinci and other Italian artists. Click here to view Ann’s website. Her latest book is The Gems of Dante’s Divine Comedy.