~ELSEVIER loumlll ofVol=ology and GeotbennllI Rescon:h 66 (1995) 149-162

]oumalofvolcanology;]lidgeotJtennalresean:h

Volcanic ash in ancient Maya ceramics of the limestone lowlands:implications for prehistoric volcanic activity in the Guatemala

highlands

Anabel Ford " William I. Rose b

:I CORUMesoAmerican R~mrr:h Curler. Univ4rsiryofCaJifomia. S4nll1.Barbara. CA.. 93I06.USAIt DeparrmentofGt!ologic:al En.ginuring. Michigan Technological University. Houghton.. M/4993/.aSA

Received 24 M:uch 1994: :u:cepced 71uly 1994

Abst;act

In the spirit of collaborative research. Glicken and Ford embarked on the problem of identifying the source of volcanic ashused as temper in prehistoric Maya ceramics. Verification of the presence ofglass shards and associated volcanic mineralogy inthin sections ofMaya ceramics was straightforward and pointed to the Guatemala Highland volcanic chain. Considering seasonalwind rose patterns. target volcanoes include those from the area west of and including Guatemala City. Joint field researchconducted in 1983 by Glicken and Ford in the limestone lowlands of Belize and neighboring Guatemala. 300 km north of thevolcanic zone and 150 km from the nearest identified ash deposits. was unsuccessful in discovering local volcanic ash deposits.The abundance of the ash in common Maya ceranUc vessels coupled with the difficulties of long-distance procurement withoutdraft animals lead Glicken to suggest that ashfill into the lowlands would most parsimoniously explain prehistoric procurement;it literally dropped into their hands. A major archaeological problem with this explanation is that the use ofvolcanic ash occurringover several cenruries of the Late Classic Period (ca. 600-900 AD). To accept the ashfall hypothesis for ancient Maya volcanicash procurement. one would have to demonstrate a long span of consistent volcanic activity in the Guatemala Highlands for thelast halfofthe first millennium AD. Should this be documented through careful petrographic. microprobe and tephrachronologicalstudies. a number of related archaeological phenomena would be explained. In addition. the proposed model of volcanic activityhas implications for understanding volcanism and potential volcanic hazards in Central America over a significantly longer timespan than the historic period. These avenues are explored and a call for further collaborative research of this interdisciplinaryproblem is extended in this paper.

1. Introduction

Volcanoes have presented major hazards and impor­tant advantages to human populations who have livedin their vicinities (cf. Sheets. 1983; Sheets and Gray­son. 1979; Mooser et al.. 1958; Boserup, 1981). Obvi­ous hazards relate to the short-term repercussions ofviolent eruptions on local jnhabitants and have beenstudied with respect to particular archaeological sites[Ceren. EI Salvador ca. 260 AD (Sheets. 1983); Pom-

0377·0273/95/509.50 <0 1995 Else,i.r Science B.V. All rights reserved55DI0377·0273(94)00068·9

peii. Italy 79 AD (Jashemski. 1979); Sunset Crater.Arizona 1064 AD (Pilles. 1979); Thera. Greece ca.1625 (Kuniholm. 1990)] and modem populations[Nevada del Ruiz. Columbia (Voight. 1990); Paricu­tin. Mexico (Nolan. 1979)]. Advantages include thelong-term effects related to improved soil fertility(Williams and McBirney, 1979). and the access tovolcanic products. such as volcanic ash and obsidianfor use by prehistoric and modem societies. Indeed,manufactured goods from archaeological sites in the

150 A. Fard. W.l. RoselJournal o{Vo/canoiogyand GeotMrmal Reseort:h 66 (/995) 149-/62

vicinities of volcanoes traditionally use rbe productS oferuptions: volcanic ash in ceramics (Arnold. 1985. p.59: Shepard. 1956. pp. 164. 378-381). obsidian forcuaing implementS (G'lXiola and Clark. 1989) and asa semi.precious stone in jewelry, and orber extrusiverocks for building materials, stone implementS andabrasives.

In terms of volcanic hazard studies. archaeologyoffers vital information rbat can contribute to rbe exten­sion of time series data for activity patterns in volcanicregions and understanding rbe effectS ofvolcanic activ­ity on populations for which no historic record is avail·able. In Central America, rbere has been humanoccupation for several millennia, but historic docu·mentS star! with rbe Spanish conquest in rbe mid 1500s.VolcanologistS are conscious ofchanges in activity pat­terns of volcanoes - cyclic, monotonic and sequential- rbat operate in time scales much longer rban rbe 500years of "history" represented in Central America. Toaccurately interpret rbe activity record of a particularvolcano and rbe various hazards it may present tonearby inhabitantS, long·term time records are essen­tial. Archaeology offers rbe potential to illuminate rbeprehistoric chronological record. Archaeologicalinvestigations of sites buried by volcanic depositS canhelp date specific volcanic activity by association wirblocal eruptions. When volcanic ash, obsidian, or orbervolcanic productS are recovered from archaeologicalsites remote from volcanoes, questions of source andprocurement become important. Collaborationbetween volcanologistS and archaeologists has consid­erable potential for resolving such issues. Some ave­nues are pursued in rbe problematic case of the use ofvolcanic ash in ancient Maya ceramics (cf. Ford andGlicken, 1987).

The abundance of volcanic ash in common every­day utilitarian ceramic vessels used throughout rbeCentral Maya Lowlands (Fig. I) in rbe Late ClassicPeriod (600-900 AD), coupled with rbe problem ofash transport from at least 150 air lcm (nearest ashbeds) without draft animals, leads One to search foralternative explanations for procurement (cf. Arnold,1985. pp. 32-57). Glicken (pers. commun., 1983,1984) proposed that an ashfall into the lowlands wouldbest explain rbe procurement issue. But such an expla­nation is not without problems. In rbis paper, we presenta general picture of the archaeology of highland andlowland Maya regions, the specific problems of the

Late Classic Period in rbe Maya Lowlands. and a pre­liminary model of volcanism in rbe Guatemala High­lands that can account for most of rbe archaeologicaldata. We conclude wirb a call for frier collaborativeefforts to confirm or reject rbe model for highland vol­canic activity in rbe laner half of rbe first millenniumAD.

1.1. The archaeology ofthe Maya area

While rbe earliest occupantS of rbe Maya area dateback imo rbe Archaic Period before 2000 BC. it is rbedevelopment of sedentary agricultural groups of rberegion that is pertinent to the questions at hand. Earlyvillages in Highland Guatemala. around the active vol­cano vents. and on rbe Pacific slope to the southappeared during the second millennium BC and grewin size over time. The Maya Lowlands, situated on aCretaceous to Eocene limestone shelf to the noM ofthe highlands, were only sparsely settled at that timeby pioneering agriculturalists.

By 1000 BC agricultural settlements had been estab­lished rbroughout the region, including the highlandsand lowlands. Ceramics. used commonly by house­holds. become an important part of archaeologicalassemblages of rbese sedentary agriculturalists. Emer­gent complex and hierarchical societies appearedthroughout Mesoamerica during rbis era and by rbebeginning of the first millennium AD, the civilizationcentered at Teotihuacan in the Basin of Mexico wasexerting its power over all of Mesoamerica. InHighland Guatemala, complex societies were consoli­dating in the Valley ofGuatemala at Kaminaljuyu. Thiswas also the time ofexpanded settlement into rbe MayaLowlands and the establishment of lowland centers,such as Tika!.

The Early Classic Period (250-600 AD) marks theestablishment of dynastic hierarchies in the highlandsand the lowlands. Major centers and surrounding set­tlements are recorded at Karninaljuyu in the highlandSand Tikal in the lowlands. These independent societiesevolved in sophisticated organizations in the region,recognizable by the large public architectural feats oftemples, palaces and plazas that characterize theirmajor central communities.

The Late Classic Period (600-900 AD) marks asignificant change and contrast between the highlandSand lowlands. Where a long developmental period of

A. Furd. W./. Ros~ /Io"mal ufVolcanology aNi G~OtMmraiRu""",h 66 (/995/ /49-/62

>1:1

+N

I(J eon"", Moyo

Low<ondo~Volc.lnoec

Met vo&c:.nlc axis

o 50 100. . ,

•Rio Boc

eo",,"•

PACIFIC OCEAN

...

.""""'""-•Cobol

I."

151

Fig. I. The Maya area with the voIClnic highlands. ancient Maya lowlands. and O1l'C~otogiQ1 sites indicated. The inset shows the gener.:t1Mesoo.merie:ut~ (embr.u:ing modem Mexico. Guatem.aln and Belize) and arch~ological sites of the region. The numbered vofc:moes o:u-ethose included in TOlble 2.

growth was characteristic of both regions up throughthe Early Classic, this growth is arrested in the high­lands and accelerates in the lowlands. Highland centersdisintegrate, settlements atomize, and there appears tobe little growth or expansion of centers. At the sametime, the lowlands experience intense growth with res­idential settlement densities more than doubling to 200structures/km2• Centers of the lowlands witness sig-

niticant growth in public monumental architecture. Thelargest center of this period, Tikal, covered over 1 km2

and included more than 85 major public plazas. Tikalwas twice the size of the next largest center and fourtimes the size of its nearest neighbors (Adams andJones, 1981).

Coincident with the dramatic lowland growth is thewidespread use of volcanic ash as a temper, or aggre-

152 A. Ford. W.I. Ros~ / 10umal of Volcarwlogy and GftJtMmrtJI R~..an:h 66 (1995) 149-162

gale. in the fine ceramic wares in the region (Ford andGlicken. 1981; Jones. 1986: Shepard. 1939. 1942). Theuse of volcanic ash is prevalent not just in the few.limilCd. and highly decorated elice ceramic vessels(e.g.• vases). but also in general household utility ves­sels (cooking. storing and serving pots). In fact, 30­40% of Lace Classic ceramics are volcanic ash cem­pered (Ford and Glicken. 1987; Jones. 1986: Shepard.1939 Shepard. 1942). Thus. for approximately 300years during the Late Classic. volcanic ash wasdepend­ably available in sufficient quantities to use regularlyin the production of specific ceramic vessels used gen­erally by both commoners and the elite ofancient Mayasociety. The availability of volcanic ash is significantas a tempering agent for ceramics. Local limestonecarbonates are unstable when temperatures exceed85a-C. which is difficult to control in traditional open·air firing conditions employed by the ancient Maya.where volcanic ash is highly stable under the sameconditions (see Shepard. 1956. pp. 29. 158; Ford andLucero. in prep.).

The close of the Late Classic Period in the lowlandsis marked by the Classic Maya collapse e.g.• Culbert,W73. This event is documented most dramatically atthe center of Tikal where all monumental buildingceased and settlements were abandoned over a 100 yearperiod. The beginning of the Postclassic is documentedby relic sectlements and the scarcity of volcanic ashtempered ceramics in the lowlands (e.g.. Rice, 1987,pp.56, 107. 118). This same period witnesses growthofsettlements in Highland Guatemala and competitionamong highland centers. Highland centers of thePostcIassic Period are generally imposing and defend·able. In the lowlands. populations are low. growth islimited, and the settlements do not recover their earliergrandeur before the Spanish conquest of the NewWorld (Turner. 1990).

The significant aspect of this gloss of highland andlowland Maya prehistory focuses on the general datarelated to the Late Classic Period: (I) the atomizationofsettlements in the volcanic highlands; (2) the growthof settlements in the limestone lowlands; and (3) the

problematic use ofvolcanic ash in ceramics of the low.lands. When one seeks an explanation for the problemof lowland volcanic ash procurement in this context,the hypothesis of volcanic ashfall gains credibility.

1.2 A model o/volcanic highland hazards andlimarone lowland benefits

Slarting. as Glicken and Ford did. with the problemofvolcanic ash procurement for ceramic production bythe ancient Maya in the limestone lowlands during theLace Classic Period. it is obvious that ash was readily ,available based on the hundreds of ceramic pieces 'examined (see examples in Table I and Fig. 2). Giventhe evidence for volcanic ash availability, there shouldbe a reasonable' explanation as to its presence. Whilethe estimated overall amount of ash used in the low. i

lands during the 300 year Late Classic Period could beaccounted for by an eruption volume of less than.007km' (7X 10· mJ ), not a large figure by geologicalstandards. but phenomenal by archaeological stan­dards. The estimated use of volcanic ash in ancientMaya ceramics is no less than 1400 m'ly (based onFord and Glicken. 1987. pp. 491-492. 497). This, infact, is quite a large volume to regularly transport overlong distances from the nearest source of volcanic ash.approximately 150 air km away. especially withoutdraft animals. Otherexotics ofvolcanic origin importedto the area, such as obsidian. occur in very'small quan­tities and limited access (Ford. 1991; Rice, 1984; Sid·rys. 1976). Thus, the large quantities and widedistribution of the volcanic ash stands in contrast andmust be explained.

Given the constraints ofdistance and transportation,an explanation that included ashfall into the lowlandsis attractive. But again. while the overall volumes ofash are small in comparison to a major volcanic erup­tion, it is very unlikely that a single ashfall into thelimestone lowlands could account for the consistent useofvolcanic ash over a 300 year period. Human societiesfocus on short term planning, as modern occupationnear active volcanoes demonstrates. Storage and con,

Fig. 2. Photomicrogf:1ph of pottery frogmenc (il: 386A. b: 300A. c: 213A) from the Tlkal-Yaxha Intersitc:J.te3. This is J. typical textun: forMayJ. cemmics tempered with volc:mic ash. NotJ.ble is the brge volume percenl.llge of fine po.rticles e:JSily identifiabre as pyroclasts. All ashparticles :ue angul~. unweathered ilnd cl~rly pre5(:rved. suggesting they wen: collected as fresh ash for cern.mic temper. The phenocrystminerals are also easily identifiable ilnd large enough for microprobe analysis.

0.5

0.4

0.3

0.2

0.1

o mm

A. FIJrd. W./. Rost! / Jpurnul tlf Vo!cunl1lugy and Ceatilermul Research 66 11995) I~9-{62

c

IS3

1S4

Tobie IA genemI description of volcanic :Wi temper in thin sections of cer:unics from me TIlW-Yuba inrersite ar=..

C=Uog number Groin size crysmls Lidli ? Excavouion :m::a. runeper;odc.(estilllll[ed medion)

370A' Q.20mm b.hb absen' 5E Late Late Classic!iDe bowl%llOF' 0.2.:5 mm b.hb 3bsen< 3A Late Late Classic!iDe ....%130' OJSmm b.hb absen' ZA Late Classic!iDe bowlJOOAx 0'::0 mm b. hb. z a.zff? or cluster of:ash 3A LateOl!SSic!iDe bowlmA' 0.%0 mm b.hb presen' 44C !'mh. Late O=icline bowl/jor9398- 0.08mm b ruff'? or cluster of ash 44C !'mh. Late CI=icfine bowl/lcor386Ax 0.10 mm bhb present SA Ellrly Oassicfinejor410A, 0.40 mm b.hb absent 8A EllrlyO=icfine jor1930X 0.15mm b cuff? or cluster ofash ZA Late Preclassicfine Ig. bowlJ:z6A- 0.07 mm hy presen.. ;uso tuff? 630 Middle Precl=icbowl( omnge )3SS0' 0.07mm hy absent 41E Middle Precl=icbowl (omnge)

-: fine gntined. hornblende absent. biotite r.tte. hypersthene common.. med.illn gr:J.in size COl. 0.07 mm.-: coorse gr.tined. hornblende:1Ild biotice common~ hypersthene absent. medim1 grain size c:L O.U-O.40 nun.X: simil:1l' [0 the above ( .. ) but rn.ay be diffe~nL

Miner.U key: b =biotite. hb - hornblende, hy =0< hype~[henez=- zircon. lCernmic collections for this table are derived from the rese:1l'Ch ofandFord and Glicken (1987).

servation of goods rarely exceeds several years, evenwith critical products such as food scuffs. Therefore, itis difficult to imagine there would be volcanic ashstock-piling for ceramic production planned for cen­curies to come. This stockpiling would need to cover atime frame of at least twelve generations, far beyondany long-range planning ofmodern societies. To acceptthe ashfall hypothesis for procurement - a hypothesisIhat argues nO long-distance movement of materials,but rather the raw material arrives at your doorstep­one would have to propose the regular, cyclical influxof volcanic ash into the lowland region. Thus, thehypothesis we propose, argues Ihat the long-distancemovement of volcanic ash from highlands sources toIhe lowlands occurred naturally and frequently over a300 year period.

Because we know that significant ashfalls occurredin the Maya Lowlands following the 1982 EI Chichoneruption (Rose et aI., 1984, p. 163), we think Ihat

eruptions of similar size (about 0.5 km3) from eilher

E1 Chichon orotherneighboring volcanoes could, espe­cially if they occurred repeatedly, accountforlhe exten­sive availability of volcanic ash for use in prehistoricMaya ceramics. The current patterns of high levelwinds have been compiled from radiosonde recordscollected by meteorologists in Guatemala (Fig. 3).These data are consistent with patterns shown for his,toric ash fallout blankets in Guatemala and demonstrateash fallout mainly in a westerly direction for eruptionsin Ihe wet season months of May to November, and ina norlheasterly to easterly direction in the dry seasonmonths of December to April. These ash distributionpatterns would only be expected to carry ash eruptedfrom so~thern Mexico or western Guatemala to IheMaya Lowlands between December and April.

The hypothesis of regular ashfalls into Ihe limestonelowlands has implications for highland volcanic activ­ity (see Williams, 1960). The proposal of a model of

A. Ford. W./. Ros~ / }ollmm 0/ Volcanology and G~orJr~mrDi Research 66 (1995) 149-/62 ISS

December-April

w-

Calm: 9.6%

N

IMay-November

N

I

w-

calm: 13.2%

Fig. 3. Wind rose diagt<1l11 showing predominant winds aloft at .llEirudes between 10,000 and 50.000 feet at Guatemala City. 1ltis fig~ is ag:mphic representation of a ten-Ye<1r st<ltistical summuy ofbllUoon (rn.diosonde) measurements (two times a day) showing seasonal panerns.The length of black lines~ proportional to their frequency and they are e!ong;ued in the direction from which the winds come. Data <Ire fromthe Insticuto Nacionlll de Sismologin.. Vulc:mologia. Meceorologia. e Hidrologi:t. Guatemala.

volcanic activity in the highlands has a number ofimplications both geologically and archaeologically. Ifthere was a long period of consistent, regular volcanicactivity, with minimal periods ofrepose in the volcanichighland, this could help resolve the question of vol­canic ash procurement in the Maya Lowlands and set­tlement decrease in the highlands. The period ofvolcanic activity could begin with a relatively majorevent with a significant eruptive volume of dispersedtephra If there were successive eruptions with shortperiods of repose, the eruptive volume would be sig­nificantly less, particularly if the time span of the erup­tions embraced centuries.

Observations of volcanological systems character­ized by the eruption ofmagma of intermediate to silicacomposition provide a basis for understanding consid­erations of eruptive volume (V) and repose time (rR).

Evidence suggests a general power-law relationshipbetween volume and repose time (Smith, 1979; Speraand Crisp, 1981; Trial and Spera, 1990). In particular,the data suggest a relation of the form V=kxrj; withb=0.8 ±O.I and k= 3 X 10- 3 km3 a-b. For systems oftectonic setting and composition similar to those ofHighland Guatemala, the scaling suggests eruptive vol·umes of 0.02 km3 and 0.07 km3 for repose times of 10

and 50years, respectively. The actual average extrusionrates of active Guatemalan and Salvadoran volcanoesare estimated from field data and known dates. Fuegohas a rate of about 0.015 km3/y (Martin and Rose,1981) , Santiaguito's rate varies between 0.01 and 0.07km3/y (Rose, 1987a,b) and Izalco has a rate ofabout0.009 km3/y (Woodruff et aI., 1979). A period ofseveral hundred years of local volcanic activity inHighland Guatemala would create a hazardous envi­ronment in the vicinities of the active volcanoes, butcould promote benefits in terms of access to ash as anadditive for temper in ceramics and for enriching soilsfor agricultural production in distant locations, such asthe limestone Maya Lowlands.

In order to support the ashfall hypothesis, three majoravenues of evidence need to be pursued: (I) a petro­graphic analysis of Maya ceramics; (2) microprobeanalysis ofglass shards in the ceramics; and (3) tephra.and geochronological studies in the highlands. The firststage ofverification is the petrographic characterizationof volcanic ash in the ancient Maya ceramics of thelowlands. The characterization of the major, minor andtrace elements composition ofthe volcanic ash togetherwith the phenocryst assemblage could enable one todetermine the general volcanic source of the ash. To a

1$6 A. Ford. W.I. Ros<lJouma/ of vo/crm%rn ond GcotMmuU R4S<tUC1r 66 (1995) /49-162

TabJe2Peuogr:1phic d:lta on MexiQll and GwuemaJan volcanoes whichmiiht have produced tephr.l f:Illou' in me c:ol"nll Maya Lowlonds

Mineral key: pl- plagioclase. of =- olivine:. b::=o: biotite.cpx - clinopyroxene. hb = hornblende. mag""" magnetite.opx - orthopyroxene. qtz ""' qUllltZ., z". zircon. ap - apatHe.• Unlikely to have been a.ctive in the 600-900 AD period. based oncurrent descriptive datL

Refm:nc:e

Mm:adoandRose. 1992Rose. unpublishedGien;yc:ki. 1976Conway et al...1992Rose. 1987.. bHOllsor and Rose.1991Ralsor and Rose.1991HaIsor and Rose~

1991R~ unpublishedChesnee;:md Rose.1984Rose. unpublishedEggers. 1971Wunderman andRose. 1984

P!lenoayst plulses(approximare o<der of:Ii>ulIdanc:e)

pl. c:p•• opx. mag. 01. hb. bpl. 01. c:px. mag. hb. op.

pL c:px. opx. mag. hb. 01pl. 01. c:px. mag. op.pl. qrz. hb. b. mag. op., Z,

ap

I. EI OJicllon

Volc:mo

2. T<onueiuUn:'3. Nleow Ruir.'

4.T"""""

pL!Ib. c:px. mag. an. b. "II. Luhr .. oJ.. 1984sphpl.hb. c:px. mag. SP. ap. < QlpouJ. 1987pl.hb. c:px. mag. sp. ap. qrz. CaplWl. 1987

:pl. c:px. opx. 01. hb. mag.qrz

$. Tajumulc:o pL hb. opx. c:px. b. mag. 016. OJicobal" pI. opx. C:p;<. hb. mag7. Cerro Quemado pl. hb. mag. c:px. op•• b. 01.

qrzpl. hb. cpx. opx. 01. magpl. c:p'. hb. opx. mag. 01.qrzpl. c:p•• op•• mag. 01. hb.qrzpl. c:p•• opx. 01. mag

8. Santa Maria9. Son Pedro

1I. Addan

10. Toliman

12. AQlenango13. Fuego

I4.Agua1$.Pac:aya16. AmatitllUl

The bestcandidate volcanoes include EI Chichon. Taju­mulco. Cerro Quemado. Acatenango and Amatitlan(see Table 2).

The second line ofverification should include micro­probe examination of ancient Maya ceramics represen­tative of the full time range and regional lowlanddistribution. The microprobe examination should focuson the volcanic ash shards and the biotite as well. Bydetermining the major elemental composition of theglass shards. microprobe analysis would verify thenumber ofpotential volcanic ash sources involved andwould provide a baseline for the identification of erup­tion frequency. Ion microprobe. still in the experimen­Ial stages. could prove invaluable in the measure of

large extent. this has been accomplished (Ford andGlicken. 1987. pp. 485. 494-495). After a review ofthousands of ceramic pieces and hundreds of thin sec­tion examples of Maya ceramics from major lowlandsites. we identified the types of ceramics that had vol­canic ash tempering added to the clay paste and deter­mined that volcanic ash made up more than 20% of theceramic paste matrix of the ash tempered ceramic col­lections (see examples in Table I and Fig. 2). The ashand mineral assemblage (biotite, hornblende, hyper­sthene and zircon) all are consistent with GuatemalaHighland tephra (cf. Drexler et al.. 1980; Rose et al.,1981 ). The peU'Ographic analysis suggests the procure­ment of finely sorted vitric volcanic ash (see Shepard.1956, pp. 29-38). with grain sizes under 0.25 mm (seeTable I). well below the range of fine ash (Fisher.1961. p. 1411; see also Kittieman. 1979. pp. 63-70).This size range is indicative of windbome (volcaniCloess) particles distributed distal from the sourcevent(s). where particle size is inverse to the distancefrom the source (Kittieman. 1979. pp. 55-57).

Both Mexican and Guatemalan volcanoes couldpotentially erupt ashes that would repeatedly fall out inthe Maya Lowlands. The high level wind patterns sug­gest that volcanoes in either the highlands ofGuatemalaor the Chiapecan belt are positioned favorably for this(Figs. I and 3). A list of volcanoes in Mexico andGuatemala that are possible sources are presented inTable 2. We compared the mineralogical informationofthe potential volcanoes (see Table 2) with the phasesobserved in the ancient Maya ceramics (see Table I).Biotite is the mineral most frequently cited in ceramics.Biotite is not found in most of the potential volcanoesand, when present, is typically only a minor feature.The difference between the ceramic mineralogy andthe potential source volcanoes may be explained byatmospheric dispersion of the ash. which would beexpected to cause biotite flakes. with high surface arealmass and attendant high drag coefficients. to be pref­erentially carried farther than other. more equi­dimensional minerals. Thus. the conspicuous presenceof biotite. along with the vitric nature of the ash in theancient Maya ceramics (Shepard. 1939; Shepard.1942). suggests that the ash included in the ceramicshad undergone an air winnowing process. Given themineralogy of the potential source volcanoes (Table2) and focusing specifically on biotite. a number ofpotential sources are suggested for the ceramic tephra.

A. Ford. W.I. RoselJounuJlo!VolcllNJlogyandGoodwnruzl.Rnearch66Il995J 14<;-I6Z 157

= elements in biotite. as trace elements in phasesare more specific than glass. While the petrographicanalysis points generally to the Guatemllla Highlands.microprobe data would address the specific variety ofsources involved.

The finlll avenue of verification involves carefultephrachronologiclll and geochronologiclll srudies ofhighland eruptions focused specificlllly on the latterhlUf of the first millennium AD (cf. Self and Sparks.1979: Miller. 1985). The microstratigraphic data fromthe tephra sequences would address the eruption his­tories of the highlands by focusing on the depositionand frequency of eruptions and linking the sequencewith the archaeologiclll data from that region. Theresults of the geochronologiclll work covering the rel­evant time period would represent the most criticlllpiece of evidence to account for the archaeologicalpresence of volcanic ash in the limestone Maya Low·lands.

Among the biotite-bearing volcanoes in Table 2. sev­eral are known to have been active in the period of600to 900 AD. El Chichon has dated eruptions in the agerange of about 100 until about 700 AD. and may havebeen active repeatedly in this interval (Rose et aI..1984; Tilling et aI.• 1984). Tajumulco has no historiceruptions and nO known dated deposits in the period ofinterest. However. detailed field work has not beenconducted. so Tajumulco cannot be exclude as a pos­sibility. Cerro Quemado is known to have been quiteactive at about 800 AD (Conway et aI.. 1992) and thearea has a complex tephra stratigraphy which suggeststhat this activity could have continued for some time.Acatenango is known to have had a significant eruptioninvolving dacitic tephra at about 1300--1400 AD. basedon the discovery of pottery remains in the Alotenangoarea (southeast of the volcano) immediately underly­ing the tephra. There is a stratigraphy of mixed dacite/basaltic andesite ash layers that mantles the northernflanks of the volcano. indicating repeated activity.Although these layers are undated it is possible thatthey reflect activity in the 600--900 AD period. TheAmatitlan caldera has had an eruptive history ofseveralhundred thous~nd years, and has produced largeamounts of biotite-bearing tephra (Wunderman andRose. 1984). Most of its eruptions are much older thanthe 600--900 AD period. but there are young undatedmixed tephra south of Lake Amatitlan that could havebeen erupted in the critical period, and the dome com-

plex south of the lake could have been active withattendant ash eruptions at that time. In summary. exist­ing data are inadequate to resolve the specific sourcevolcano or volcanoes possibly responsible for the vol­canic ashes of the Maya Lowland ceramics. AU fivevolcanoes which carry biotite must be considered aspossible candidates. Of the existing chronologiclll dataOD eruptions. we know that both EI Chichon and CerroQuemado were quite active in the Classic Period. Also.E1 Chichon's ash shows a good mineralogiclll matchwith the ceramic data. Further. the 1982 eruption of EIChichon reminds us that winds can be expected to carryEI Chichon ash to the Maya Lowlands. as Fig. 3 dem­onstrates.

1.3. Implicarions ofrhe model

Volcanic hazard research is typically based on thecareful study of volcanic deposits to determine the styleof activity and to establish the chronology and fre­quency of activity. In many parts of the world geolog­ical field srudies are limited. which means that hazardsrudies are strongly influenced by records and descrip­tions ofhistoriclll activity. In Central America, the his­torical record begins in 1541. and it is important torecognize that 550 years of history is not long enoughto reflect the entire range ofactivity that volcanoes mayexhibit. Ifashflllis of biotite-rich ashes regularly blan­keted the Maya Lowlands in the years 600-900 AD,this represents a style of activity not experienced in thehistoric record. In the absence of volcanic hazard srud­ies based on the geologic record. the historic recordgoverns the public awareness of hazard. This is criticalbecause historic settlement in Central America isstrongly localized along the volcanic axis. Ifsignificantfllliouts were documented for the distant Maya Low­lands. the effects associated with the same eruptionsnear the volcano were clearly more severe. Should reg­ularexplosive activity recur, such as that proposed here,it is likely that large populations of the GuatemalaHighlands would be displaced. In this case, the archae­ological record may be able to reveal important aspectsofvolcanic hazards that have implications for the pres­ent and the future.

Volcanoes are most prominently known for theirhazardous impacts on populations, especially thosewithin the region of accumulation (e.g., Sheets, 1983;Rees, 1979; Rosi et aI., 1981; Voight, 1990; Warrick,

IS8 A. Foni. WI. RO$~IJoumaJ oIVolcan%gyandGcom.muUR~~h 66 (/995) 14~162

1979). At the same time. enhanced soil fertility is awell·recognized benefit of volcanic eruptions (WiI·liams and McBirney. 1979. p. 363). Recently. hazardplanning in regions of volcanic activity has becomeroutine even though periods oferuption may be outsidehuman memory. In times past, such long-range plan­ning was unknown. Hazard avoidance in terms of vol­eanic eruption was only on an emergency basis. Theancient Olmec abandonment ofthe Mexican GulfCoastin the Preclassic and the deslnJction ofPompeii in Italyare examples.

Evacuation and abandonment ofareas in the vicinityof active volcanoes are related to the experience ofdevastating eruptions and the reinforcement of thatexperience through periodic observation of similareruptions. Severe impacts are predictable in areasimmediately surrounding the active volcanoes ( <30lcm radius). Generalized impacts are not uncommon tosurrounding regions within 500 km (Thorarlnsson.1979. p. 126). Data from Iceland suggest that freshtephra and ash falls of30-50 cm caused complete aban­donment of permanent settlements while deposits of15-20 em caused short-term (up to 5 years)abandonments (Thorarinsson, 1979, p. 139). Theimpacts, no matter how extreme. will be short-termunless the periods of repose are brief. Extended periodsof repose would encourage resettlement, as observedin modern Michoacan after a decade long period ofactivity of Paricutin, Mexico (Nolan, 1979), in Iceland(Thorarlnsson, 1979), in the archaeological cases ofThera (Greece) and at Me. Vesuvius (Italy) (Santa­croce, 1987). On the other hand, risks of reoccupationof areas surrounding active volcanoes will be highwhere periods of repose are brief_ Thus, tephra fallsresulting in a 30-cm thick deposit (or thicker), withregular rates of accumulation as the result of frequent,periodic volcanism would render areas in the vicinityof active volcanoes inhospitable for settlement.

Settlements in the volcanically active GuatemalaHighlands have always been at some risk due to localvolcanism. Prehistoric, historic and modern groupswere faced with the same risk. In certain regions.archaeologists have demonstrated abandonment as aresult of volcanism (Sheets, 1983; Sheets, 1992).Thus, the marked change and reduction in highlandsettlements in the Late Classic could be accounted forby reference to local occupation risks due to volcanism.

While volcanic hazards are easily appreciated in theimmediate and short-term sense. benefits ofsoil enrich­ments with volcanic ash would be only recognized overthe long term. implying periodic. accumulative ashfaJlsthat would offset soil depletion and maintain produc.tivity, especially in regions where agricultural practiceswere widespread. Thus. for the lowland Maya subsis­tence system to be affected by volcanic ash fertilization.it would have to have regularly accumulated andreplenished the limestone lowland soils through peri­odic ashfalls occwring frequently at least within tenyear periods (see Williams and McBimey, 1979).Within the proposed period of heightened volcanicactivity in the Guatemala Highlands, lowland soilenrichment could be an outcome, especially if the fre­quent ashfaIls spanned several centuries.

Local environmental conditions of the tropical MayaLowlands have erased any potential evidence of vol­canic ash deposits that could aCCOunt for ash procure­ment and soil enrichment in prehistory. The CentralMaya Lowlands are typically divided into wet and dryseasons, with 2000 mm of rain per annum fallingmainly between June and Janu'ary. Weathering condi­tions are relatively rapid in the tropics, and high rainfall,high temperatures, and seasonal dehydration exacer­bate and accelerate the desalination and weatheringprocesses (Lowe. 1986, pp. 275-79). The rapid weath­ering process decreases only when rates of tephra accu­mulation occur regularly (Lowe, 1986). Without theregular addition of volcanic ash, the lowland environ­mental conditions would degrade any ashfaI! quickly,as Glicken and Ford witnessed in the region over aperiod less than twelve months after the 1982 El Chi­chon eruption that blanketed the region (Carey andSigurdsson. 1982). Soil studies in the region have char­acterized the pedology as locally derived and princi­pally composed of mollisols and vertisols of in situorigin (Cowgill et aI., 1966; Cowgill and Hutchinson,1963; Olson. 1969; Simmons et aI., 1959; Wrightet al.,1959).

Analyses of lake core sediments from the lowlandsindicate no distinct ash layers (e.g" Deveey et al.,1979). Glicken and Ford's field work in spring 1983 1

I Field soil collected <1nd analyzed in spring 1983 were focusedon (I) arc~ologiC';JJsurvey zones of the Belize River An:h~olog·icaI Settlement Survey (Ford and Fedick 1992); (2) n:uural sinksand ponds within che upper Belize River vaHey; and (3) stream ~d

river dr::linages of the New River. Belize River and Sibun Riversystems in Belize.

A. Ford. WI. RosolJo.nuJl o!Vo/catW/O/fY and Goodutrmal Research 66 (/995) /49-/62 159

consisted of an examination of river. stream and ponddeposits. as well as alluvial and general soils in thevicinities of the archaeological surveys in the BelizeRiver area (Ford and Fedick. 1992). Conducted withinone year of the 1982 EI Chichon eruption. Glicken'slaboratory analysis did not identify any evidence thatvolcanic glass or crystals representative of EI Chichonor other highland volcanoes were present in any catch­ments or deposits of the Maya Lowlands. Soil studiesfrom the specific Belize River area document local soildevelopmentand composition that substantiateGlickenand Ford's initial conclusions (Fedick. 1988. 1989;Jenkin et aI.• 1976). The lowland Maya soils are verydifferent from those adjacent to volcanoes. such asthose described for Thera (e.g., Betancourt et al..1990).

If the volcanic ash was collected as fallout in theMaya Lowlands and used as a tempering agent inceramics soon after the fallout, as we are suggesting,there is potential to gain remarkable information con­cerning ash dispersion and deposition. Data on distalashes are rarely preserved in any context and itsdescription is vital for accurate volume assessments ofexplosive eruptions. The study of ash material inarchaeologically dated pottery from the Maya Low­lands can provide information about distal fallout fromdeposits that are no longer preserved (Carey andSigurdsson, 1982). Thin sections of ancient Mayaceramics can yield data on particle size and shapes (seeFig. 2). of particular interest to those investigatingaonospheric fallout processes (Rose and Chesner,1987). In addition. petrographic studies allow for arobust quantitative description of the mineralogy of theashes for comparisons. Identification of source vol­cano(es) is possible by microprobe analysis of theglass and phenocrysts in the ancient ceramics. Thesedata could be, then, associated with similar data fromproximal volcanic deposits of potential source volca­noes. Given the archaeological ceramic chronology, theanalyzed data from the Maya ceramics will help vol­canologists to reconstruct prehistoric activity ofcertainvolcanoes, thus, expanding the knowledge of volcanicactivity in Central America. We conclude that petro­graphic and microprobe studies of the large number ofavailable ceramic materials from lowland Maya exca­vations have the potential of providing information oneruption histories, atmospheric fallout processes, andvolcanic hazards, and at the same time address the

procurementproblem for the use ofvolcanic ash by theancient Maya.

2. Conclusion

We have oudined a tentative model of volcanismsuggesting a centuries-long period ofvolcanism duringthe latter halfof the first millennium AD. This conceptwas originally proposed in collaborative discussionsbetween Glicken and Ford. Glicken could not acceptthat long-distance trade' accounted for the quantiry oruse of volcanic ash in the lowlands. He felt an ashfallcould best explain the use of ash in ancient Mayacerarirics. From the anthropological point of view, thisproposition would only be tenable if there had been adependable lowland source of volcanic ash during theentire time span of use. as the volcanic ash temperedceramics that were made and used by the ancient Mayathroughout the Late Classic Period (ca. 600--900 AD).To accept the direct ashfall hypothesis for the MayaLowlands. it is necessary to adopt a model of long­period volcanic activity in the Guatemala Highlands.Such a scenario would feature regular and periodictephra eruptions and ashfalls into the lowlands. Thevolume repose characteristics of such a system appearconsistent with volcanological observations at othervolcanic areas of the world.

The proposition ofregularashfalls into the limestonelowlands has implications for highland volcanic activ­ity. There are at least two volcanoes - EI Chichon andCerro Quemado - which are known to have beenactive in the Late Classic Period and could have pro­duced ashfalls into the lowlands. There are also severalother volcanoes which are candidates. based on the

" mineralogy of their erupted products and their location,but these volcanoes lack field descriptions and geo­chronological descriptions oftheir prehistoric deposits.Microprobe studies ofphenocrysts in the ceramics andash deposits of candidate volcanoes is needed to testcorrelations between the ash in the ancient Mayaceramics and specific Guatemala volcanoes. Strati­graphic/age date studies of the tephra at candidate vol­canoes is also needed to test for several other viablesource volcanoes. These potential volcanoes includeAcatenango, Tajumulco and recent Amatitlan tephras.

If the geological research could document a threecentury period of consistent, regular volcanic activity

160 A. Ford. w./. Ros~/ Joumai ofVolcQJtOiogyand~Re~etU'Ch 66 (1995) 149-162

in the Guatemala Highlands. this could account for anumber of archaeologically recognized occurrences;( 1) The presence ofvolcanic ash in Late ClassicPeriodceramics of the limestone lowlands. (2) the increasedsealement in the lowlands due to enhanced fertilityassociated with ash enrichment of soils. (3) the reduc­aon of sealements in the volcanic highlands. and (4)the Classic Maya collapse as a consequence of the ces­sation of volcanic activity. This hypothesis is bothsweeping and p=imonious. Harry Glicken began thiscollaborative venNre with archaeology. We now needother volcanologists that can advance this challengingproject.

Acknowledgements

Ford's long-standing interest in the problem of vol­canic ash in ancient Maya ceramics dates back over adecade when she first became familiar with petrographyand its relevance to archaeological research in the MayaLowlands. A number of persons from UCSB Depart­ment of Geological Sciences have helped to guide herqueries over these years. They include Mac Beggs. JimBoles. Harry Glicken and Frank Spera. Our ultimatecollaborative efforts are truly the result of HarryGlicken and the production of this volume commem­orating his research endeavors. Several individualswere helpful in the production of aspects of this paper.Connie Balzer aided in production of the map of thestudy area and Michael Conway assisted in the photosof the thin sections. Without the collaborative effortsof these schol=. the ideas presented here would nothave been spawned.

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