Built On Salt: The Leaning Tower of Bad Frankenhausen
What does the campanile at Pisa have on the leaning tower of Frankenhaus in Germany? A church steeple in the eastern German town is slanted at an impressive angle. But it could disappear soon because no one knows what will happen to the subsiding earth beneath it and rescue efforts have fallen short.
It looks so harmless. The Elisabeth spring winds its way quietly through the park in the center of Bad Frankenhausen, a spa town in the eastern German state of Thuringia. It meanders gently next to mini-golf courses and an empty public swimming pool. Despite its peaceful outward appearance, the spring may soon be responsible for toppling a 2,600-ton colossus. The Elisabeth spring is leaching the earth from beneath the town, and in some places the ground has become dangerously unstable. The most obvious sign of this instability is the steeple of the Church of Our Beloved Ladies by the Mountain.
As far back as 1640, historical documents reported that the church's steeple was slanting. Since then, the 56-meter-high (183 foot) structure has been further subsiding to the northeast. "The last time we measured it, the displacement at the top of the tower was 4.44 meters (14.5 feet) -- in other words, 4.8 degrees," says Tobias Scheffler, head of the surveying department at the Magdeburg-Stendal technical college. "Which means the tower is more crooked than the leaning tower of Pisa." The tourist attraction in the Tuscan city only has a slant of about 3.9 degrees to the southwest.
Together with colleagues at the Freiberg University of Techology's Mining Academy, Scheffler regularly measures the massive stone structure. To do this he has set up a network of around a dozen measuring points, which he uses to determine the degree to which the steeple is tilting. And each year, he and his colleagues determine that the tower is leaning by yet a few additional centimeters. "But it's not a uniform process," Scheffler explains, "it is dependent on what is happening underground."
The Ground in Bad Frankenhausen Just Opens Up
Rainy days can be particularly treacherous because the extra water also washes the plaster out of the ground. Most of all, though, it is the subterranean salt deposits beneath the city that are causing problems. They date back 250 million years to a time when an ocean slowly dried up here under the heat of the primordial sun. Salt layers meters high remained to be covered with sand, gravel and clay later on. Then, around 95 million years ago, the Kyffhäuser hills rose here. Bad Frankenhausen is located on the edge of the range. And where the hills rose, the ground formed cracks and water started to find its way into the deeply buried salt deposits.
Springs started to flow and they brought with them geological problems for the region -- including sinkholes, which occur when subterranean hollows collapse. "We have to deal with a massive amount of leaching," says geologist Frank Rey, a soils expert who has been researching the leaning church tower since the mid-1960s. According to Rey's calculations, the springs at Bad Frankenhausen carry away around 250 tons of salt each day. "I don't even want to think about the implications," the geologist quips.
Bärbel Köllen knows only too well what the porous underground means. The resolute city councilor heads an association that is trying to save the church. At the end of a long, linden tree-lined avenue she waits at the gates of the gothic church. At the moment nobody is actually allowed in, but today Köllen is making an exception.
An unusual sight awaits people who pass through the church's doors. One can look straight up into the cloudless sky and directly at the leaning tower, because the church has been without a roof since 1961. It was removed when it fell into disrepair and has never been replaced. Art treasures, the pulpit and the baptismal font are all long gone, and grass is growing in the nave. Earlier, concerts were given here as well as open-air services under a blue metal crucifix, but they are no longer permitted today. A yellow sign posted right next to the church bears warns: "Danger Area -- Danger of Collapse."
- Part 1: The Leaning Tower of Bad Frankenhausen
- Part 2: 'Time Is Getting Short'
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