216 Ozark Hall
University of Arkansas
Fayetteville, AR 72701
The PETRA PROJECT
ARCHITECTURAL DETERIORATION, CULTURAL HERITAGE MANAGEMENT,
and ENVIRONMENTAL CHANGE
The University of Arkansas PETRA PROJECT is an ongoing project established in 1990 to assess and record various aspects of landscape change in the classical period city of Petra, Jordan. Aspects include deterioration influences and rates for limestone and sandstone architecture and rock, cultural heritage management issues for the UNESCO World Heritage site and region, urban planning and local Bedouin studies (Bdoul) in Wadi Musa and Umm Sayhoun, and prehistoric and historic environmental landscape change and influences. Under the supervision of Professor Tom Paradise, University of Arkansas graduate students in the Department of Geosciences and the Environmental Dynamics PhD Program participate in various components of the research project, completing theses and dissertations while conducting valuable fieldwork in Petra and the region.
Now after more than 100 million voters have chosen Petra, Jordan as one of the NEW SEVEN WONDERS of the WORLD, it is imperative that this ongoing research project continue as tourism will dramatically increase, infrastructure will become increasingly strained, and the environment in and around Petra will be impacted drastically. This magical yet sensitive site needs increased research so that its stewardship may continue now and in the future.
Evidence indicates that Petra has been occupied since 3000 BCE, and Greek, Roman and Aramaic records mention Nabataean culture in the region since 500BCE. However, it was the sacredness of Mount Hor (or Jebel Haroun) that deir closeupbrought early notoriety to Petra since it was the reputed burial site of Aaron, the brother of Moses. Many believe that Bedouins have occupied and roamed the region long before Moses’ arrival about 1250BCE, or later when Rome annexed the region in 104AD as Felix Arabia Petraea. This hidden Valley passed into legend with the passage of time and remained unknown until the 19th Century, when in 1812, Johann Burckhardt visited the Valley surreptitiously dressed as a Bedouin traveler wishing to sacrifice a lamb at the mountaintop tomb of Aaron. Since the earliest days of the Nabataean civilization, followed by Roman invaders and partners, then raided by Crusaders, defended by Sa’aladin, the hidden valley of Petra was unknown to outsiders. Researchers did not ‘discover’ Petra until the early 1900s, when historians, geographers and archaeologists extensively studied and surveyed Petra and its monuments, tombs, buildings, tells, and temples.
Petra is a crescent-shaped Valley confined by high fault-bound sandstone walls that may have been the home to more that 50,000 people 2,000 years ago with more than 500 known tombs, structures and monuments. The unique architecture of Petra represents an interesting melding of indigenous Nabataean, Hellenistic, Roman styles, uses and decoration. Since sandstone represents a common building material and a dominant landscape component across the region and its structures have a known exposure (roughhly 2,000 years old), Petra represents an ideal outdoor laboratory for sandstone deterioration research since (i) the structures (ie tombs, temples) were carved during known periods, (ii) many of the structures were hewn and have not been moved, (iii) restoration has been recorded and/or is visible, (iv) the sandstone has been extensively studied and is relatively consistent in lithology. Petra’s two primary formations are the Cambrian Umm Ishrin and Cambrio-Ordivician Disi sandstones and represent one of the oldest, most widespread and relatively unaltered sandstones units on Earth.
Although the PETRA PROJECT was initiated in 1990 with a focus on architectural deterioration and stone decay, over the years it has expanded to included aspects of the cultural and social landscape, and cultural heritage management. Originally the research looked at climatic influences on rock weathering, however it became apparent that visitors were accelerating the rock breakdown faster than nature had in 2,000 years -- humans and their effects were added to the investigation of the architecture and landscape. At first, variations in sandstone lithology were correlated to environmental variables like aspect, moisture, sunlight (insolation), slope, and biotic coverage (lichens, plants). Later, other variables were studied including respiration and humidity from tourists, and visitor frequency across the Valley. Various research components follow that have been investigated so far:
Petra Theater Sandstone Study
This study examined 26 variables related to surface recession that created a statistical matrix of nearly 14,000 data points creating the largest sandstone weathering data set known. 526 baseline recession measurements were taken across the Theater (in a stratified random scheme) and related to 26 variables that included aspect (220 degrees of coverage), insolation (mjoule/m2/yr), matrix lithologic constituents (calcium, iron, manganese, silica), clast lithologic components (siliceous, calcareous), lichen genera and coverage, and daily & annual shadowfall.
Sandstone matrix constituents of iron and silica were found to decrease overall sandstone weatherability, while calcium matrix components were found to increase deterioration in areas that receive more than 5500 megajoules/square meter/year of solar radiation — a typical southern aspect in mid-latitude, arid regions. Moreover, when iron matrix concentrations exceed 4-5% (by weight), original stonemason dressing marks are still clearly evident, indicating a nearly unweathered state in 2,000 years. Surface recession rates for sandstone in the Roman Theater were determined to range from 15 70mm per millennium on horizontal surfaces to 10 20 mm/millennium on vertical surfaces.
Monument Surface Recession Aspect Study
While the Theater study explains significant sandstone weathering relationships and hierarchies, it created more questions and Petra’s monuments and quarries afforded new research opportunities. So, quarries and monuments across Petra - like the Blocks of Djinn - were studied for surface recession relationships to aspect. Insolation was found to have the greatest effect on weathering on southwestern and southeastern aspects (and not southern faces as is often discussed), indicating that insolation may be most influential in sandstone weathering when in tandem with increased wetting-drying and/or heating-cooling cycles.
Al-Khazneh Anthropogenic Deterioration Study
As tourism grew in Petra and the, studies into anthropogenic influences on sandstone deterioration are warranted and the Khazneh (Treasury) represents the perfect sites due to its popularity. Over a five-year study with Arkansas graduate students Mick Frus, Mohammed Salem, and Chris Angel, it was found that interior surfaces have dramatically receded due to visitor touching, leaning and rubbing, as much as 40mm in less than 50-100 years (period of increased tourism). This indicates that a 4 by 3 meter wall area has lost a volume of sandstone of approximately one half cubic meter in these 100 years from 0.5 to 2m above the floor indicating surface recession from human contact .
Visitor Mapping Study
(Synoptic Tourism Cartography)
In the Summer of 2003, Mo Salem, a graduate student in Geography and Dr. Paradise recorded and assessed each visitor that entered and exited Petra in the hopes of determining tourist movement through the Park. Recording each tourist that entered Petra through the main gate (Bab as-Siq), to then pass the Khazneh and Theater, they mapped the tourists' movements throughout the valley and their use of related infrastructure. Their exit was also recorded as to where they walked, why, and how quickly. This extensive study is invaluable in cultural site management -- determining what resources they use and when, where they are in the Valley and how fast they move, how quickly they leave and by what route is fundamental in management research. Maps were then created for each portion of the Valley and City during various times of the day to determine how many visitors are where and where. This research and mapping project has been studied and utilized in Petra's new Park Management Plan.
Umm Sayhoun Digital Mapping Study
Over the Summer of 2007, graduate student Chris Angel and Dr. Paradise digitally mapped the Bdoul Village of Umm Sayhoun using satellite imaging, flyover photography, ground-level imagery, GIS and computer cartography. Since the village was created in the early 1980s, it is a unique opportunity to assess a new city of 2000 residents since its creation. Aspects of urban morphology, materials and construction, perception of space, and topophilia are addressed. The Bdoul clan of Bedouins were forced to relocate in 1984-1985 when the new designation of the UNESCO title as a World Heritage Site was implemented on the Valley of Petra and its surrounding area -- so how does a previously semi-nomadic clan create a permanent city? This important baseline study has strong implications now that Petra has been designated as the one the NEW SEVEN WONDERS of the WORLD.
Urn Tomb and Al-Khazneh Chamber Humidity Study
Weathering studies have shown that wetting and drying cycles accelerate deterioration, however little is known about human-induced moisture changes affecting deterioration of stone architecture; humans contribute to ambient humidity through respiration, transpiration, perspiration. So, comprehensive interior and exterior humidity measurements were made in Petra’s most celebrated structures, al-Khazneh and Urn Tombs in conjunction with data on visitor numbers and frequency over a ten-year period (1998-2008). This study found that small visitor groups entering the tomb chambers caused interior relative humidity increases of 5% to 15%. Statistical correlations of determination (r2) explained that correlations increased dramatically when the tourist numbers were compared to relative humidity in the chambers both simultaneously (r2=0.007, 0.136), and to fifteen minute delays (r2=0.707, 0.895). These relationships indicate that it takes ten to twenty minutes for human respiration and transpiration to contribute to relative humidity in chambers of this volume (2,000-3,600m3) – an important finding regarding the possible anthropogenic acceleration of architectural deterioration. Further research in these popularly visited tombs will continue, in addition to more chamber humidity measurements across Petra.
Historic Cartography of Petra
The popular, touristic, and scholarly maps of Petra represent the current structure footprints of Petra and not the contemporaneous structure and monument locations and footprints. For instance, Byzantine, Roman and Nabataean structures are cartographically represented alongside each other. So however similar in space, there are nearly unrelated in time. So the Arkansas team of cartographers, GIS technicians, and geographers including graduate students Chris Angel and Daniel Snyder, are currently taking advanced GPS readings to merge with ground-level structural measurements, isohypsometry (DEMs), and historic data to create an innovative time series of Petra's urban morphology over time from the Neolithic period of Umm al-Biyara, to Nabataean and Roman city, to the Byzantine and Crusader sites, to the new locations of Petra's new structures and infrastructure.
GIS and Map Construction of the Valley and Surrounds
As a part of a large collaborative project with UNESCO, the American Center of Oriental Research (ACOR), the Petra National Trust (PNT), the Jordanian Department of Antiquities (DofA), and the Petra Development & Tourism Regional Agency (PDTRA), the University of Arkansas is working to facilitate the creation of a new, extensive geographic information system (GIS) that will combine elements and layers of elevation, hydrography, imagery, infrastructure and energy, geology and soils, demographics, structures, etc. After our 2011 field season in Petra, this year represents the first year to merge and meld these layers and data planes into one cohesive and up-to-date GIS, all in the hopes of creating a strong and effective management and sustainability tool for the Valley and local environment - inshallah.
The PETRA FLOOD
Research since 2010 has identified a number of features (i.e. bedrock scoring, perched alluvium, absent architectural features) that indicate the city center of Petra may have been inundated by catastrophic flood(s). Extensive flood deposits have been excavated and identified in and alongside the Colonnaded Street Shops indicating flood surges may have reached 3-5m in height. Roman-Byzantine coins found below and above the paleo-flood alluvium dates the possible disaster to the 4th century, indicating that it may have followed the earthquake swarms of the 3-4 century which have razed the effective Roman-Nabatean flood abatement structures such as dams, weirs and cisterns. A flood of this magnitude would have abruptly halted all operations in the city for months to years, and may have facilitated the downfall of Petra’s Golden Age.
PETRA’s ARCHITECTURE and URBAN FORM
Earth-Sun Relationships, Alignment, and Orientation
Research since the 1990s has continually divulged relationships between solar marker days (solstice, equinox) and the alignment and orientation of Petra’s most prominent structures and monuments. Many of Petra’s tombs and buildings are displaying such relationships with inner-chamber illumination and penetration on these marker days (only), and/or with structural alignments with sunset and sunrise paths intersecting at prominent horizon sites such as Jebel Haroun, Umm al-Biyara, and true west and east pathways. Important structures, such as the Royal Tombs, show such solar-architectural alignments. This ongoing landmark research is changing the way we look at Petra’s urban morphology, architecture, and religion/cosmology.
So, what are we learning in Petra?
in the physical landscape:
* that in architectural deterioration research, the old foci of extrinsic vs. intrinsic influences has proved significant in Petra;
* the utilization of petrologic microscopy is valuable (i.e. backscatter microprobe, scanning electron, transmission electron);
* that aspect plays an underrated role in the decay of sandstone architecture by influencing wetting & drying and freezing & thawing cycles;
* that anthropogenic effects on stone decay and environmental degradation and denudation may be under-evaluated and/or overlooked;
* that high frequency & low magnitude agents (i.e. particle disaggregation, human foot-tread, human-induced moisture, etc.) may influence sandstone landscape development more than conventionally accepted episodic occurrences like rockfalls and spalling;
in the cultural landscape:
* that humans represent an underestimated impact influence on sensitive landscapes often representing the most influential single factor;
* the importance of strong and progressive infrastructure on cultural site management and stewardship can never be underestimated or overfunded;
* and that all share-holders (social, environmental, economic, cultural) must be integrated and included in all decision-making policies in effective cultural heritage management.
* that the Sun plays a fundamental role in Petra's architecture and urban planning, possibly indicating its role in its cosmology and religion.
** Click to watch an 2008 TV interview with Dr. Paradise and the the ongoing Petra Project.
For more information on this ongoing project, you may contact Dr. Tom Paradise at
University of Arkansas, Department of Geosciences
113 Ozark Hall, Fayetteville AR USA 72701
479-575-3159 (telephone), email@example.com (email)
The Petra Sandstone Deterioration Project has been funded by a number of agencies including the US National Science Foundation, Jordanian-American Fulbright Program (JACEE), USAID, USIA-USIS, NMERTP,
American Center of Oriental Research (ACOR), the Petra National Trust, the King Fahd Center for Middle East & Islamic Studies at the University of Arkansas, and the Hashemite Kingdom of Jordan.