Fischer, C. y Bahamondez M. Moai. Environmental Monitoring and Conservation Mission. 2011

8/3/2019 Fischer, C. y Bahamondez M. Moai. Environmental Monitoring and Conservation Mission. 2011

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http://www.eisp.org/3793/

Conservation Repor t Season I

Moai. Environmental Monitoring and Conser vation Mission

Dr. Christian Fischer and Ms. Monica Baham ondez P.

Mar ch 8-16, 2011

Introduction

The main objective of this mission, carried out with the assistance of Cristin Arvalo Pakarati, was to

evaluate the status of the environmental monitoring equipment illegally removed in 2010 and to re-

install it on site for a measurement campaign of seven months to November 2011. In addition,

another objective was to complete the building of the fence on the site to ensure safety around both

equipment and excavated areas and to avoid potential damage from cattle and horses. Finally, a few

meetings in relation to the project were also organized with different people on the island.

The course, actions and results of the mission can be summarized as follows:

1. March 8: Testing of the environmental monitoring system

A close inspection of the condition of the environmental monitoring system showed that the different

components (sensors, cables, data logger, solar panel, power) were not visibly damaged, apart from

some marks left on the stainless steel mounting pole when it was illegally removed from its base. The

cable connections to the data logger were still secured and the cables and sensors looked intact. The

environmental monitoring system was then temporarily assembled outside the Mana Gallery andtested. Data were collected during the whole day and the results indicated that all the different

sensors were working as expected. It was therefore decided to re-install in the next days the

equipment on site in Rano Raraku. A visit was also paid to CONAF were we briefly met with Enrique

Tucki and Irene Arevalo.

1. March 9: Field work in Rano Raraku

After a general survey of the site, I collected information about the conservation state of the

excavated parts of the statues while Cristin started with the building of the fence and later buried the


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toki found during the excavation of statue RR-001-156 in February. At the end of the day, some

excavation supplies left on site in February were taken back to the Mana Gallery.

The visual examination of both statues, complemented by photographic documentation, clearly

shows that the excavated parts are overall much better preserved than the exposed parts; a fact

further supported by the exceptional quality and conservation state of the petroglyphs (Fig. 1). In

comparison to the exposed areas, the tuff material does not show

Fig. 1: General aspect of the dorsal side of statues RR-001-157 (left) and RR-001-156 (right);

photographs by C. Fischer.

flaking or major losses of material through weathering. This obvious difference in the conservation

state was not really a surprise and, from a conservation point of view, strongly supports the decision

to backfill after the excavation has been completed and fully documented. However, close

examination of the dorsal sides of both statues shows that the upper section of the part that was

buried is in fact less well-preserved than the lower section. This is particularly visible on the neck and

shoulders of statue RR-001-156 and the arms of statue RR-001-157 (Fig. 2) and could indicate that

these parts were exposed at some point in the past. Correlations with previous excavation levels and

soil stratigraphy now in process should shed more light on these differences. In terms of

conservation, these upper parts will also be treated, but the question of extending the application of


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the product down to the bottom of statue RR-001-157 is still under discussion and a final decision

will be taken in May.

Fig. 2: Weathering features showing erosion and material losses in the upper section of the excavated

parts. Left: left arm of RR-001-157; right: shoulder level of RR-001-156 (photographs by C. Fischer).

1. March 10 : Field work in Rano Raraku

Before heading to the site, some additional wood was purchased for the building of the fence. With

the help of Dario, the main tasks carried out during this day consisted of building and installing the

fence, putting in place the concrete block for the weather station and preparing the small surface

trenches to bury the cables of the different sensors. Upon our return from Rano Raraku, we briefly

met with Sonia Haoa Cardinali and Lilian Gonzalez Nualart and agreed on a visit to Rano Raraku on

Saturday March 12.

1. March 11: Lithic Analysis Project and Field work in Rano Raraku

Rafael Paoa Rapu joined us for this working day which gave me the opportunity to discuss with him

the outlines of the lithic analysis research project assigned to him by Jo Anne Van Tilburg inFebruary. The goal of this project, which builds upon Rafaels well-developed interest in lithic

analysis, is to use the toki collection previously excavated and fully described by EISP as the core of

an intensive scientific analysis and sourcing study. He will initiate that study in May by training in

the use of the projects portable XRF equipment. The work will extend to the location and study of at

least two basalt quarries. We anticipate that this work will be in occasional cooperation with the

survey team directed by Sonia Haoa Cardinali and Lililan Gonzalez Nualart and under the

supervision of his current university study, and with the cooperation of CONAF. It is further

anticipated that additional toki will be collected during the July excavation season. These toki will be


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registered by EISP in the same manner as the previous, but additional location information will be

recorded as needed to facilitate the lithic analysis.

The environmental monitoring system was re-installed on site inside the fenced area (Fig. 3). In

order to accommodate the outline of the excavation around the statues, the position of some of the

sensors was changed compared to last years layout. It concerned primarily the surface temperature

sensor that was on the dorsal side of statue RR-001-156 and which is now temporarily located in

front of statue RR-001-157, to the right of the other sensor, and records the surface temperature of

the almost permanently shaded area under the chin (Fig. 3). When statue RR-001-157 will be

backfilled, it is planned to move this sensor on the dorsal side of that statue. Protected with an

adequate fence, the third surface temperature sensor was again installed in front of the inclined

statue RR-001-158 located a few meters east of RR-001-157 to collect reference or comparative data

on an untreated statue (Fig. 3). For the moisture and temperature sensors buried in the soil, one was

again installed about two meters behind statue RR-001-157 and the others between its front and the

main station (a detailed map with the location of each sensor will be provided later).

Fig. 3: Environmental monitoring system with the new fence (left); the two surface temperature

sensors in front of statue RR-001-157 (center) and the one for the reference data (right); photographs

by C. Fischer.

1. March 12: Visit to Rano Raraku with Lilian Gonzalez Nualart

The purpose of the visit was to evaluate and discuss the various options currently under

consideration by CONAF for the protection of the interior of Rano Raraku. Several suggestions

concerning the improvement of the access pathway and other issues have been made to Lilian, but it

could only be re-emphasized (as many other people did before) that the first priority remains a

solution preventing the access of cattle and horses to the area with the statues, probably by the


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installation of a fence, and that potential available resources and any future actions should be

directed toward this goal.

1. March 14: Meeting with Tahira Edmunds (morning) and visit to the museum(afternoon)

The objective of the meeting with Tahira Edmunds was to give her a short training on the software

used to download the data from the weather station. After a brief introduction of the environmental

monitoring system and its components, the software was installed on her computer and we went

through the procedure to be followed for the downloading of the data in preparation of the on-site

training scheduled for the next day. A copy of the software was also left to her in case of computer

failure.

In the afternoon, I went to the museum, later joined by Cristin and Rafael who had returned from

Rano Raraku, to check the quality of the remaining water-repellent product (Wacker BS290) that

what used during the Tongariki conservation campaign and that has been stored at the museum for

several years. After some difficulties, the 200 liters barrel could be finally opened and showed to

contain still about 100 liters of product. The liquid looked fine though a bit hazy and a sample was

taken for evaluation. After dilution with iso-propanol, a quick test on a piece of tuff indicated that the

product had retained its water-repellent properties despite the long storage time. Based on these

results, it was decided to use part of this product together with a new one that will be supplied by

Monica Bahamondez P. from Chile for the application of the protective treatment.

1. March 15: Field work in Rano Raraku

The last day, Cristin and I went to the site with Rafael Rapu and Tahira Edmunds (Fig. 4). While

Cristin and Rafael were finishing a few tasks (burying of the extra cable length next to the concrete

block, site cleaning, fence verification, photography), I gave Tahira some explanations concerning the

function of the different sensors and the location of the moisture and temperature sensors buried in

the soil and completed her training. Then, we carried out a real situation test and she could

successfully download the data on her computer. For the next months, it was decided that she will go

to the site every two weeks to collect the data from the weather station.


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Fig. 4: Last day on the site (from the left to the right: Rafael Rapu, Cristin Arvalo Pakarati and

Tahira Edmunds; photograph by C. Fischer).

In conclusion, with the re-installation of the environmental monitoring system following its illegal

removal by vandals in 2010 and the re-fencing of the excavated areas around the statues, it can be

considered that the initial objectives of the mission have been achieved. Moreover, important

observations could be made and valuable information collected for the preparation of the

conservation treatment phase of the two statues scheduled in May 2011. And last but not least, all of

the individuals and agencies who have contributed to the success of this mission are herewith

gratefully acknowledged.

Field Crew:

Cristin Arvalo Pakarati

Rafael Paoa Rapu, Student Intern

Tahira Edmunds

Digital copies provided to CONAF, CMN Rapa Nui, and EISP Archives 1 April 2011


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R e la t ed p o s t s :

1. Sustainable Archaeology on Easter Island 2. Field Season I3. Field Season II4. Field Season III5. Conservation Report Season II

Posted on April 6th, 2011 by EISP Staff | Category: 2000s, Conservation Reports, Featured Articles |

The content of this website is copyrighted by Jo Anne Van Tilburg/Easter Island Statue Project, unless otherwise noted.Welcome, Visitor! EISP Collaborators and Staff: Log in

http://www.eisp.org/3844/

Conservation Repor t Season II

Environmen tal Monitoring and Conservation Mission

Dr. Christian Fischer and Ms. Monica Baham ondez P.

May 14- 26

Introduction

The main objectives of this mission, carried out with the assistance of Cristin Arvalo Pakarati,

Rafael Paoa Rapu and Vaiheri Tuki Haoa, were firstly, to apply the protective treatment on statuesRR-001-157 and RR-001-156 currently being excavated by EISP and secondly, to start the Toki

Sourcing Project by analyzing the elemental composition of the toki found during the excavation

using a portable X-ray fluorescence spectrometer.

1. Activities sum mar y

During the course of this mission, the various tasks and actions were organized as follows:

Mon. 16: Meeting with Susana Nahoe at CONAF. Preparation of equipment andmaterials and visit to Rano Raraku (CAP, CF).


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Tue. 17: In the morning, meeting with Governor Carmen Cardinali and councilmembers (MB, CAP, RPR, CF). In the afternoon, carrying of equipment and materials

to the site, installation of platforms and ladder, retrieval of the buried toki and

training of RPR on the operation of the handheld XRF spectrometer (MB, CAP, RPR,

CF).

Wed. 18 Sat. 21: Field work in Rano Raraku: application of the protective treatment(MB, CF, CAP) and analysis of about 170 toki with the portable XRF (RPR, VTH, CF).

Mon. 23: Cleaning of the site and removal of equipment and materials (CAP, CF). Tue. 24: Collection of XRF data on basalt fragments embedded in the statues, basalt

outcrops and ancient quarries around Rana Raraku and Tongariki and along the north

coast between Poike and Anakena (CF, CAP).

Wed. 25: Collection of XRF data on basalt outcrops and ancient quarries along thesouth coast between Maunga Toa Toa and Maunga Orito (CF, CAP).

2. Conser vation of statue s RR-001-157 and RR-001-156

2.1 Gener al contex t

The vandalism act perpetrated against the site in April 2010 has required a profound revision of the

original projects planning. Although the decision was taken to continue with the project, the

methodology initially implemented for the conservation treatment needed to be reconsidered due to

the budgetary, technical and timing constraints created by this regrettable event. After a careful

evaluation of the different options, it was decided to limit the conservation treatment to the

application of a protective treatment as water remains the major factor responsible for the

deterioration of the statues. Such an approach also permitted to proceed with minimal equipment for

the application, using only a ladder without having to put back a bulky scaffolding (fig. 1).

From a technical point of view, this choice obviously represents a compromise with all the

uncertainties and limitations attached to it. On the other hand, in term of feasibility, this approach is

much closer to a methodology, this pilot conservation project will contribute to define, that could be

applied at a larger scale, e.g. to complete the treatment of a large number of statues in a relatively

short time frame and at a reasonable cost, a final objective which should remain a priority for the

preservation of the statues on the island.


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Figure 1: Conservation intervention and application of the protective treatment (photographs by

VTH).

2.2Protective treatment

The conservation intervention has consisted in the application of a protective treatment using a

silicone concentrate of silane and siloxane (BS290, Wacker) diluted in a solvent, similar to white-

spirit though less pure but available in Chile, containing a mixture of paraffinic, olefinic, cyclo-

paraffinic and aromatic C10-C14 hydrocarbons (Aguarras Mineral). BS290-based water-repellent

solutions were successfully used in the past for the treatment of the Hanga Kioe and Tongariki

statues (Roth, 1990; Bahamondez and Valenzuela, 2004).

Two water-repellent formulations were used for the protective treatment:

- A solution of BS290 at a concentration of 15% (V/V) diluted with Aguarras Mineral.

- Cave Clear-S: a ready to use solvent-based water repellent available in Chile (the product actually

contains BS290 diluted with Aguarras Mineral).

After some preliminary trials with the brush, the different products were applied with a portable

sprayer following a wet-on-wet application methodology until saturation of the surface was observed.

The water-repellent solution at 15% was primarily used for the treatment of the exposed, and most

weathered, parts of the statues. Once treated with the solution at 15%, the surface was sprayed with

pure solvent in order to increase the penetration depth of the active product followed by a final

application of Cave Clear-S. On the excavated parts of the two statues which are in much better

condition, only Cave Clear-S was applied.


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On the back of the head of statue RR-001-157 which has suffered major losses of tuff material

through flaking, a pointing mortar, prepared by mixing a partially reacted ethyl silicate with a fine

powder of yellowish volcanic tuff, was applied in some areas along the edges created by these losses.

On the backside of both statues, a few loose surface fragments were also reattached with Paraloid B-

72.

For the treatment of the two statues, about 50 liters of the solution at 15% and 40 liters of Cave Clear-

S were applied as well as 30 liters of pure solvent. Based on a rough estimation of the surfaces to be

treated, 14 and 16 m2 for respectively the exposed and excavated parts, the amount of product applied

per square meter was on average:

- solution at 15%: 3.5 l/m2 pure solvent: 2 l/m2 Cave Clear-S: 1.25 l/m2

These relatively elevated values are directly correlated with the high absorbing capacity of the

weathered volcanic tuff, a material for which the porosity can reach 40% and more. The high

consumption per square meter also indicates, indirectly, that the treatment was carried out to a

sufficient depth with respect to the thickness of the weathering layer which can be estimated to a few

centimeters. However, important variations in the absorbed amounts were observed during the

application, primarily caused by the petro-physical heterogeneity of the volcanic tuff (e.g. between

the fine and coarse-grained layers) as well as by differences in the degree of weathering (e.g. strongly

weathered areas on the top of the heads, whitish hydrated silica crusts with low porosity). Although

the solvent evaporation and drying of the statues will take several weeks or even months, after the

application of the water repellent products, the effectiveness of the protective treatment was almost

immediately visible with water droplets literally running away from the treated surfaces when water

was poured onto the statues. Finally, it should be mentioned that the weather conditions during the

mission, though not bad, were far from being optimal, with time to time strong winds and light rains

that some days notably complicated the conservation treatment.

For the completion of the conservation work, the last phase of intervention is planned for December

2011 or January 2012 and will primarily consist in a general assessment of the situation after the

statues were left to dry and stabilize for several months, the removal of the remaining lichens and

algaes and other cleaning actions, color retouching and adjustments and, if necessary, additional

treatment of the areas previously colonized by the lichens.

2.3Decay on the back of the head of statue RR-001-156

The decay on the back of the head of statue RR-001-156 is important and particularly visible in the

lower proper right part that shows major losses of material (fig. 2). The upper part is apparently in


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much better condition, but the hollow sound produced by knocking the surface has indicated that this

area is also affected, with a real risk of losing a large and thick piece of tuff by detachment, something

that could happen anytime. Obviously, this structural problem is the result of an advanced

weathering stage, but has been also enhanced by the orientation of the natural bedding in the tuff,

slightly inclined with respect to the vertical position of the statue, creating thus potential planes of

de-cohesion (fig. 2). Besides, on some statues located on the external slopes of Rano Raraku, the

same causes have already led to a complete loss of the back of the head.

From a conservation point of view, a possible solution would be to secure the area at risk by inserting

two or three stainless steel pins fixed with epoxy glue. However, following discussions with other

experts about the appropriate methodology, it has been suggested that such an intervention, though

relatively easy to implement, would benefit from a detailed and quantified assessment of the

extension of the damage and it has finally been decided, for now, to postpone the conservation

intervention. A precise picture of the spatial distribution and size of the voids underneath the surface

could be obtained by analyzing the area with a ground penetrating radar unit (GPR) equipped with a

high frequency antenna and the possibility to carry out GPR measurements will be explored for the

next mission.

Figure 2: Decay on the back of the head of statue RR-001-156 and schematic visualization of the area

sounding hollow (dotted circle) and of the bedding planes (arrows). Photographs by CF.

3. The toki sourcing project

The goal of this project is to use the toki collection previously excavated and fully described by EISP

as the core of an intensive scientific analysis and sourcing study. More importantly, this project

provides also a unique opportunity for Rafael Paoa Rapu to be involved in a scientific study using a


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state-of-the-art portable XRF instrument and to further develop his interest and expertise in lithic

analysis. For this purpose, a technical and safety training on the operation and handling of the XRF

instrument (Niton XL3t 980 GOLDD+) was given to Rafael by C. Fischer. During the excavation of

statue RR-001-157, more than 300 toki and toki fragments were found and subsequently reburied

in a one meter deep hole in square 30 for storage (Van Tilburg and Arvalo Pakarati, 2010). The first

task was to retrieve the toki and to clean them thoroughly with water, at least the surface to be

analyzed, to minimize errors in the XRF readings due to contamination by soil deposits. Although the

toki were fully documented after the excavation, in order to avoid an on-site time consuming

identification and matching procedure, each toki was again photographed, measured and labeled

with a reference number also used for the XRF data file. Vaiheri Tuki Haoa joined the team to help on

these tasks allowing Rafael to focus on the XRF measurements (fig. 3). Thanks to their dedication

and patience, about 170 toki could be analyzed during this field season.

Figure 3: Documentation and XRF analysis of the toki by Rafael and Vaiheri (Photographs by CF).

A preliminary analysis of the data collected with the portable XRF has shown that elements such as

Zr, Ca, K, Rb and Ti are particularly interesting to investigate compositional variations among the

toki. For example, on a bivariate plot of Zr vs. Ca (fig. 4), it can be observed that most data form a

well-defined cluster with intermediate Zr and Ca values indicating that about 85% of the analyzed

toki are made with the same type of basalt. Another cluster, representing about 13% of the toki,

with low Ca and high Zr can also be distinguished while only a few artifacts belong to a group with

high Ca and low Zr. Moreover, the comparison of the Zr values with previously published

geochemical data (Baker et al., 1974) suggests that the basalt of the toki from the main group is a

mugearite; a result in agreement with earlier analyses carried out on a few toki (Baker, 1993). The

second cluster with a higher Zr content corresponds most likely to a benmoreite whereas the low-Zr

basalt could be either an alkalic basalt or a hawaiite. In general, the concentration variations

observed for Zr and Ca and other elements are consistent with the increasing differentiation index


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(e.g. from alkalic basalts to benmoreites) that characterizes the numerous lava flows associated with

late eruptive phases of the Terevaka volcano (Vezzoli and Acocella, 2009).

Figure 4: Bivariate plot of Zircon vs. Calcium concentrations in 168 toki analyzed with the portable

XRF.

For the identification of potential raw material sources, additional XRF measurements were taken on

some of the volcanic rocks found on the island. This first field survey has included the analysis on

several statues of basalt fragments embedded in the volcanic tuff as well as the analysis of lava flows

and ancient known quarrying sites located on the south and north coasts of the island (fig. 5). The

field data need still to be processed and will be compared with the ones obtained for the toki. It is

expected that the interpretation of the XRF results and the analysis of the toki characteristics

(shape, dimensions), combined with surface archaeological evidence (e.g. mining pits, associated

debitage), will allow a precise identification of the raw material sources and provide useful

information about the extraction and manufacturing processes of these tools and the organization of

their distribution.


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Figure 5: Analysis of basalt fragments embedded in the volcanic tuff and basalt outcrops with the

portable XRF (photographs by CAP).

Collaborators :

Cristin Arvalo Pakarati (CAP)

Rafael Paoa Rapu, student intern (RPR)

Vaiheri Tuki Haoa (VTH)

References

Bahamondez M. and Valenzuela P., 2004. Conservacin de los moai del Ahu Tongariki, Centro

Nacional de Conservacin y Restauracin / DIBAM, Report, 19 p.

Baker P.E. , Buckley F. and Holland J.J., 1974. Petrology and Geochemistry of Easter Island, Contr.

Mineral. and Petrol., 44 , 85-100.

Baker P.E, 1993. Archaeological stone from Easter Island, Geoarchaeology: An International Journal, 8 ,

2, 127-139.

Roth M., 1990. The Conservation of the Moai Hanga Kioe : Methods and Consequences of the

Restoration, Courier Forsch.-Inst. Senckenberg, 12 5, 183-188.

Van Tilburg J.A. and Arvalo Pakarati C., 2010. Preliminary Report: Phase 2 Excavation Field

Season, 15 October to 22 November 2010,Easter Island Statue Project Conservation Initiative.


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Vezzoli L. and Acocella V., 2009. Easter Island, SE Pacific: An end-member type of hotspot

volcanism, GSA Bulletin, 12 1, 5/6, 869886.

R e la t ed p o s t s :

1. Field Season I2. Field Season II3. Field Season III4. Conservation Report Season I5. Field Season IV

Posted on July 11th, 2011 by EISP Staff | Category: 2000s, AIA Partnership, Conservation, Conservation Reports, Featured Articles |

The content of this website is copyrighted by Jo Anne Van Tilburg/Easter Island Statue Project, unless otherwise noted.Welcome, Visitor! EISP Collaborators and Staff: Log in

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Fischer, C. y Bahamondez M. Moai. Environmental Monitoring and Conservation Mission. 2011