Petra Project
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:
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.
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.
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.
(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.
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.
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.
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.
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.
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.
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?
* 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;
* 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.
For more information on this ongoing project, you may contact Dr. Tom Paradise
University of Arkansas, Department of Geosciences
117 Ozark Hall, Fayetteville AR USA 72701
479-575-4359 (telephone), paradise@uark.edu (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.