Volcanoes - Extreme Events: A Physical Reconstruction and Risk Assessment - page 211

undertaking petrographic analyses of the ceramics and a microprobe analysis of
glass shards in the ceramics and compared these with the results of tephra and
geochronological studies of the volcanic sequences in the highlands. The com-
position of major, minor and trace elements in the ceramics suggest that the
ash used is consistent with tephra from the volcanic area in the Guatemalan
highlands. The size analysis of the ash particles also indicated that the ash
was windborne (volcanic loess material). These comparisons along with observa-
tions on the present occurrence of ash fall in the Maya lowlands following the
AD 1982 El Chichon eruption suggests that ash may have been in abundance in
thelowlands between AD 600 and 900. Comparisons of current wind patterns
with historic ash falls in Guatemala are also consistent with the direction of
airborne transportation and fallouts of the ancient deposits. The lack of such
deposits in the area today, however, suggests that any such deposits have been
subsequently removed most likely due to the rapid weathering processes in this
tropical climate.
The volume of ash used in the Maya lowland ceramics was greater than
1400 m 3 yr − 1 suggesting that there must have been considerably more outpour-
ing of ash from volcanic eruptions at this time compared to that which has
occurred over the past 550 years, or since historical records began in AD 1541
in Central America. This level of volcanic activity has not occurred during his-
torical times and the archaeological record in this instance suggests that the
Late Classical Period of Guatemala was dominated by active volcanism over a
period of around 300 years or the time span over which these ceramics were
made. Frequent volcanic activity also explains why settlements in the highlands
were diminished or abandoned during the same period (AD 600--900). Ford and
Rose (1995)havesuggestedthattheMayanlowland culture ceased at the end
of this period as the volcanic activity in the highlands diminished leading to a
reduction in soil fertility.
Besides ash used for ceramics, there are many volcanic products that have
been used in antiquity that can be used to potentially derive a long-term his-
tory of volcanism for a region. Products such as volcanic rocks for use as stone
tools, and for building and sculpture, for use as millstones and as additives
formaking cement can all be analysed to check for source area and geologically
dated to determine a chronology of eruptions. The Romans used pumice to form
hydraulic cements for use in marine and other architecture in the Hellenistic
Period around the 4th Century BC. They used pumice in this way in the Pantheon
in Rome to reduce its bulk density (Griffiths, 2000).
Although archaeological methods can be very successfully applied to investi-
gate and date prehistoric volcanic eruptions, it can provide an even more accu-
rate record of the impact of these eruptions on human settlements and culture.