Western Wall not about to crumble, experts say after stone comes crashing down
search
Visual tech could detect rock movement and prevent harm

Western Wall not about to crumble, experts say after stone comes crashing down

Hebrew University academics emphasize that while constant monitoring and a early warning system are necessary, the monumental Herodian-era site should stay open to the public

Amanda Borschel-Dan is The Times of Israel's Jewish World and Archaeology editor.

Daniella Goldberg stands later on Monday, July 23, 2018, at the site where a large chunk of stone dislodged from the Western Wall in Jerusalem Old City that day, at the mixed-gender prayer section. The boulder fell close to where she was praying. (Yonatan Sindel/Flash90)
Daniella Goldberg stands later on Monday, July 23, 2018, at the site where a large chunk of stone dislodged from the Western Wall in Jerusalem Old City that day, at the mixed-gender prayer section. The boulder fell close to where she was praying. (Yonatan Sindel/Flash90)

A 2,000-year-old piece of stone crashed down from the Western Wall on Monday, but the sky is not falling, said Hebrew University experts.

In the Davidson’s Archaeological Park on Monday morning, a large, 220-pound (100-kilogram) block from the Western Wall was dislodged and tumbled down onto an egalitarian prayer platform near Robinson’s Arch. As captured in dramatic footage, Daniella Goldberg, 79, was the sole occupant of the site at the time. Unharmed, she told Israel’s Hadashot TV news that she “tried not to let the incident distract me from my prayers.”

The stone, which landed close to Goldberg and damaged the platform, fell from a Herodian-era section of the Western Wall, which is made up of massive limestone blocks quarried 2,000 years ago in what is now the city’s Ramat Shlomo neighborhood.

Speaking with The Times of Israel on Tuesday, Earth Sciences Prof. Simon Emmanuel and archaeologist Dr. Eilat Mazar both emphasized that rocks crumbling from the Western Wall is “very rare.” But there is a need for serious and continuous checks around the wall’s perimeter.

Israel Antiquities Authority professionals assess damage at the Robinson’s Arch section of the Western Wall after a stone fell on July 23, 2018. (Hannah Estrin)

While the Robinson’s Arch egalitarian prayer platform remains closed to the public since the incident, neither academic saw a need to shutter the entire archaeological site or the Western Wall Plaza at this time.

Their view stood in contrast to the analysis of an archaeologist who visited the site on Monday afternoon and warned that the entire Western Wall is a “danger zone.”

After noting multiple cracks in other stones on both sides of the Western Wall — both at the traditional prayer plaza and in the area of the egalitarian plaza — Zachi Dvira, head of the Temple Mount Sifting Project, said the public should stay away. These stones “could immediately fall on the heads of people,” said Dvira, who is completing a PhD on the recorded archaeology of the Temple Mount.

Archaeologist-activist Zachi Dvira examines what he said was damage to a mound of ancient dirt atop the Temple Mount, June 18, 2018. (Amanda Borschel-Dan/Times of Israel)

Another immediate rock fall is not so likely, insisted Emmanuel, who in July 2014 published an article in the peer-reviewed journal Geology based on laser-driven data taken from the Western Wall Plaza called “Limestone weathering rates accelerated by micron-scale grain detachment.”

“Erosion a slow process. It doesn’t usually happen catastrophically like this,” said Emmanuel. The last well-publicized instance of a rock falling from the Western Wall came in 2004. “The fact that now and then a rock falls off of it — well, that’s the nature of weathering in buildings,” he said.

Daniella Goldberg (left), with Culture Minister Miri Regev, inspects the damage caused by a large stone that dislodged from the Western Wall in Jerusalem Old City on July 23, 2013, at the mixed-gender prayer section. The boulder fell close to where Goldberg was praying. (Yonatan Sindel/Flash90)

Tthe 2014 study is based on data taken from non-invasive lidar laser scans of 20 meters of the men’s section of the Western Wall that were commissioned by the Israel Antiquities Authority. Emmanuel found that according to their micro-crystal makeup, some of the building rocks are less strong than others and less resistant to weathering.

In Emmanuel’s study, because he could not take samples of the Western Wall itself, he examined rock from massive Second Temple-period quarries in Ramat Shlomo, a northern neighborhood of Jerusalem, that is the origin for most of the ashlar, dressed, building blocks.

Hebrew University Earth Sciences Prof. Simon Emmanuel. (courtesy)

After studying the limestone under an atomic force microscope, he discovered that there were two types of limestone in the quarry, depending upon what section the rock was taken from.

In research and experiments performed with co-author Yael Levenson, Emmanuel’s team concluded that the stone with larger crystals is stronger and more resilient to climate and water damage.

“We find that extreme erosion rates in fine-grained micritic limestone blocks are as much as two orders of magnitude higher than the average rates estimated for coarse-grained limestone blocks at the same site,” write the authors in the article abstract.

Visible cracks can be seen in stone all along the Western Wall, said Emmanuel, from the main area to Robinson’s Arch. In the case of Monday’s fallen rock, said Emmanuel, what is interesting is that it appears to belong to the large-crystal form of limestone.

“I looked at images of the rock that fell the other day and, ironically, it seems to be the other [larger] mode — the rock that would seem to be more resilient,” said Emmanuel. He added, “it’s not a one-to-one relationship” and there are a variety of factors at play in rock erosion.

A microscope image of Jerusalem limestone made up of tiny crystals. (photo credit: Dr. Simon Emmanuel/Hebrew University)

In terms of why a piece of this particular stone fell, there are several possibilities. One is water seeping through the soil fill behind the wall. Another is the vegetation and its root systems growing within the wall itself. “It throws a spanner in simple explanations and experiments,” said Emmanuel.

A third explanation is touched on by both Emmanuel and archaeologist Mazar: Hundreds of years ago, during the Byzantine period, a horizontal line about 30 centimeters (one foot) deep was dug into the wall. “The line would have weakened stability and made the rock more prone to falling off,” said Emmanuel.

Noted Mazar, the piece of the stone that chipped off the Herodian block was about 30 centimeters deep.

“It surely helped cause the damage,” said Mazar, who edited and compiled the archaeological reports from the original excavations of the Western Wall following the Six Day War, which were directed by her grandfather, Prof. Benjamin Mazar. “The whole stone course [row] above and below this line should be carefully monitored,” she said.

Archaeologist Dr. Eilat Mazar at a reception in Jerusalem’s King David Hotel on June 10, 2018. (courtesy)

A fourth explanation is also offered by Mazar: renovations and projects on the Temple Mount itself.

“We need to find out what is happening on the other side” of the wall, she said. While the use of tractors, trucks and heavy machinery is forbidden there, “every time they use an industrial tool — even for drilling — it influences the wall below,” Mazar said.

In general, the Herodian building is massive and relatively stable, she said. But there are sections that need closer inspection and preservation, especially in the southeastern corner of the wall, located in the Davidson’s Archaeological Park.

“All must continue as normal,” said Mazar. But more, and continuous, monitoring is necessary for all places along the wall where the public visits — not only in the prayer plazas.

Part of the Western Wall showing highly eroded stones alongside well preserved ones. (photo credit: Dr. Simon Emmanuel/Hebrew University)

Emmanuel also emphasized the need for new and immediate monitoring systems, as well as a more complete survey of the status of the stone itself. His data comes from lidar scans, which he said is very precise — but very expensive and extremely time-consuming.

The IAA, said Emmanuel, had planned a scan the southern and eastern sections of the Temple Mount walls, but it was not completed. Likewise, the area of the Western Wall where the rock fell was not scanned.

That is a scientific loss, indicated Emmanuel. “If I would have chosen where to scan, I would have scanned there. [The Robinson’s Arch site] is less messed about by people and there is less actual man-made damage. The rocks are better preserved,” he said.

The earth scientist suggested using relatively cheap and non-intrusive high-resolution cameras and computer algorithms to analyze visual input in real time to sense the slightest movement.

“If you look at the footage, there was a bulge before the fall. Had there been a proper warning system, it could have picked it up in time,” he said.

Emmanuel’s lab is also looking into preservation methods and technology for these ancient blocks. He said, however, because the technology is still at its beginning phases — and there is an unwillingness of the Israeli authorities to test it on such a sensitive site — this avenue has not yet been pursued at the Western Wall. (Standard renovations, such as those that were undertaken in 2009 to replace the mortar of the Ottoman-period upper courses in the Western Wall Plaza, are being implemented by the IAA.)

“The powers that be at the Western Wall are afraid of changing things — and rightly so. It may do more damage than prevent it,” he said. The same can be said for removing the vegetation — caper plants in particular — that freely grows on the wall.

“No one knows where to point the finger. Removing the caper plants may help, but it also may cause more damage,” he said. Emmanuel said there hasn’t been enough research on what vegetation removal would do in this kind of situation. Without further study of the wall in general, he wouldn’t jump to give any particular recommendation at this time.

Daniella Goldberg stands close to the spot where a large stone dislodged from the Western Wall in Jerusalem Old City on July 23, 2013, at the mixed-gender prayer section. The boulder fell close to where Goldberg was praying, damaging the platform. (Yonatan Sindel/Flash90)

For its part, the IAA told The Times of Israel on Tuesday that it is not rushing to create quick fixes.

“The survey will take time,” said the IAA spokesperson. “This isn’t the type of thing that you do from moment to moment.”

Emphasized Emmanuel and Mazar, with this monumental Herodian wall, there is likely no immediate emergency.

“Look, the wall stood for 2,000 years. That’s a pretty successful engineering project in anyone’s kind of book,” said Emmanuel.

Times of Israel staff contributed to this report.

View of the place where a large chunk of stone dislodged from the Western Wall in Jerusalem at the mixed-gender prayer section on July 23, 2016. (Yonatan Sindel/Flash90)
read more:
comments