Volcanoes - Extreme Events: A Physical Reconstruction and Risk Assessment - page 209

eruptions also leave distinct signatures in the landscape. Lavas, pyroclastic and
ash deposits are preserved for thousands to millions of years. Vegetation commu-
nities are also affected by these events. Records of volcanic activity can thus be
stored in pollen records. Each of these methods of reconstructing past volcanic
activity is discussed below.
Archaeological evidence
Archaeological studies of prehistoric populations and settlements can
be very useful in determining the nature and timing of volcanic events. Used
together with other techniques such as stratigraphic investigations, petrographic
analysis and geological dating it can help create a more complete picture of erup-
tion events. Archaeological evidence that can aid the identification of prehistoric
volcanic eruptions ranges from ceramic artefacts to the burial and preservation
of entire cities by pyroclastic materials.
The burial of ancient buildings has provided evidence of the timing and inten-
sity of a number of volcanic eruptions. The Cuicuilco pyramid in Mexico was
covered by a 10--15 cm thick layer of ash and partially buried by a lava flow when
theXitle volcano erupted around 1670 years BP. In this instance, the archaeolog-
ical evidence along with radiocarbon dating was able to show that the pyramid
was still populated at the time of the eruption (Gonzales et al ., 2000). Also in
Mexico, communities were forced to flee the area of Tetimpa in western Puebla,
during a pumice fall event that buried buildings, activity areas and agricultural
fields when the Popocatepetl volcano erupted between 200 and 50 BC. The event
appeared to occur suddenly as many large and heavy household goods were left
behind (Plunket and Uruneuela, 2000). A similar situation involving the burial
of pre-Hispanic cultural features in the Canary Islands by volcanic debris helped
to identify the age of the AD 1677 eruption of the San Antonio volcano. Here
theGuanches peoples, thought to have originally come from North Africa, dis-
appeared shortly after the occupation of La Palma Island by the Spanish in the
last decade of the 15th Century. Pottery, petroglyphs, post-hole circles and other
foundations of Guanche dwellings were buried by the eruption. While eruptions
had occurred during or before occupation of the area by these peoples, the only
volcanic units that overlie the Guanche remains were those of the 1677 eruption
(Day et al ., 2000).
The Minoan city of Akrotiri was covered in volcanic material around 1500 BC
following the eruption of Thera (Santorini). It should be noted that this is the
date most commonly applied to this eruption although it is not certain as ages
as old as 1648 BC have been suggested (Doumas, 1990). Thera lies just to the
south of the Cyclades Islands, 110 km north of Crete in the Mediterranean Sea.