The Tower of Pisa is stable and is gradually reducing its iconic tilt. Since 2001, the bell tower, one of the most famous monuments in the world, has lost about 4 centimeters of its tilt, thanks to consolidation work carried out by an international committee coordinated by Michele Jamiolkowski in the 1990s.
The tower is doing even better than predicted by the committee, the surveillance group led by Salvatore Settis, Carlo Viggiani and Donato Sabia, who have been monitoring the monument for the past 17 years, said last week.
“What counts the most is the stability of the bell tower, which is better than expected,” said Nunziante Squeglia, a professor of geotechnics at the University of Pisa who works with the monitoring group. “Since consolidation work started, the tower has reduced its tilt by 0,5°, which corresponds to roughly 4 cm.”
The consolidation work consisted mainly of a system of pipes and augers that subtracted ground from the opposite side of the tilt, inducing the tower to straighten. At the time, the work was intended to prevent the collapse of the monument; in 1990, when it was closed to the public for the following 12 years, the tower’s tilt was increasing by 1,5 millimeters every 12 months. In 1995, when the work had already started, the Tower began to move until engineers managed to block it.
Oscillations now vary between 1 and 2 millimeters a year.
The Tower of Pisa, which is the bell tower of the city’s Cathedral, began tilting during construction in the 12th century, due to inadequate foundation on ground that was too soft to properly support the structure's weight (there used to be a river in the area; the name Pisa is Greek for ‘marshy land’). The tilt increased in the decades before the structure was completed in the 14th century. Efforts to stabilize the tower began with the international committee in the ‘90s.
No worries though, the 58-meter-high tower will not become straight; the effects of the consolidation work are destined to stop, and the Leaning Tower of Pisa will continue leaning.
