Chris Butterworth’s Blog Part II

Having spent Monday afternoon learning about wind-blown dust on Comet 67P, Titan, and Mars, I again did another 5-hour volunteer shift on Tuesday morning, this time standing in for the student volunteer who was late for the session on the Proterozoic accretion of the North American continent.  In the first talk, “United Plates Revisited,” Dr Paul F. Hoffman described the feedbacks between subduction-induced mantle flow and the rise of magma, speculating on which came first.  On Tuesday afternoon I went to the session on the Pluto, Charon, and the Kuiper belt.  This was held in the large room 2A/3A and was well-attended.  In a talk called “Pluto is the new Mars,” Jeffrey M. Moore, chief geologist on the New Horizons mission, described the rich diversity of geological features found on Pluto, including the weird convection polygons made of nitrogen.  This seems to be an active process.  After loading up the vans on Wednesday morning I got to see part of the session on impact cratering, the most interesting of which was about the mathematical modelling of surface roughness versus age of the crust of Mercury.

Wednesday’s “Lunchtime Enlightenment” talk was by Claudio Margottini of the Geological Survey of Italy, and was titled “Geosciences Save UNESCO Heritage.”  Margottini is the author of 300 publications, having worked in many institutions, including the Italian Atomic Energy Commission.  He explained the role of the United Nations Educational, Scientific and Cultural Organization in the preservation of cultural heritage.  Following the 1972 convention to protect cultural and natural sites, there is now a list of 1,031 sites, many of which are threatened by war, collapsing infrastructure, pollution or natural hazards including volcanoes, floods, erosion, wind, fire, vegetation, and landslides.  76% of the sites are exposed to at least one geohazard.

Margottini’s first example was the pair of Buddha statues blown up by the Taliban in Bamiyan, Afghanistan.  I was disappointed to learn that UNESCO is not allowed to rebuild structures except using the original blocks, so the statues have gone forever.  UNESCO is instead shoring up the cliffs and the sides of the alcoves which used to contain the statues.  The stone is siltstone and conglomerate, which takes in water and becomes unstable, so the drills used to insert bolts into the walls are air-cooled instead of water-cooled.  Local labor is used, paid about $3 per day, which presumably includes danger money for the risk from landmines.  UNESCO tries to develop preservation skills in local populations, and this became a recurring theme in the other examples.

Another site is Petra in Jordan, where the royal tombs are in danger from erosion, rockfalls, slides, and cracks.  A 3D laser scan has been made of the monuments, and a large block which fell in 2015 had already been identified as a risk.  Monitoring systems connected by wi-fi are now in place to warn of blocks which are starting to shift.  Local people have been trained to climb the cliffs and remove these threats to passing tourists.

An integrated monitoring system has also been installed at Machu Picchu in the Peruvian Andes, which was considered to be at risk of sliding off its mountain along downhill-dipping beds.  Analysis of data from interferometry, lasers, GPS, and optical satellite images concluded that the monument would not slide.

In Akapana, Bolivia, there used to be a pyramid.  Unfortunately the stone cladding was removed centuries ago to build houses, and an earthen core was left behind.  This was itself at risk of disappearing under the action of soil erosion and sliding.  UNESCO made a geomorphological map of it and diverted water away from it using gabions (baskets of rocks, as seen lining the Arkansas River).  They used compressed earth consisting of straw, mud and cactus juice to give the mound a water-resistant overcoat to prolong its life.

UNESCO has helped stabilize leaning minarets in two parts of Afghanistan, Jam, where a river bank had to be shored up, and Herat, where steel ropes and buttresses were put in place to prop up a group of minarets after a local river had flooded and undermined their foundations.

In Kogurio, North Korea, a mound containing a tomb was being eroded by rainwater, so UNESCO provided a waterproof cover to protect it.

Rain was also causing erosion of the rock churches of Lalibela, Ethiopia.  These are carved out of solid basalt scoria containing montmorillonite, which unfortunately swells when it gets wet, causing the host matrix to crumble.  UNESCO has built scaffolding and roofs above the churches to protect them.  These are not very pretty, and Margottini says the churches now look like gas stations.

After he had finished his presentation, I asked Margottini if anything was being done to restore Palmyra, the ancient city in Syria partially destroyed by ISIS.  He said UNESCO had made a model of the gates, using a 3D printer.