Research Article: GIS-based landform classification of Bronze Age archaeological sites on Crete Island

Date Published: February 21, 2017

Publisher: Public Library of Science

Author(s): Athanasios V. Argyriou, Richard M. Teeuw, Apostolos Sarris, John P. Hart.

http://doi.org/10.1371/journal.pone.0170727

Abstract

Various physical attributes of the Earth’s surface are factors that influence local topography and indirectly influence human behaviour in terms of habitation locations. The determination of geomorphological setting plays an important role in archaeological landscape research. Several landform types can be distinguished by characteristic geomorphic attributes that portray the landscape surrounding a settlement and influence its ability to sustain a population. Geomorphometric landform information, derived from digital elevation models (DEMs), such as the ASTER Global DEM, can provide useful insights into the processes shaping landscapes. This work examines the influence of landform classification on the settlement locations of Bronze Age (Minoan) Crete, focusing on the districts of Phaistos, Kavousi and Vrokastro. The landform classification was based on the topographic position index (TPI) and deviation from mean elevation (DEV) analysis to highlight slope steepness of various landform classes, characterizing the surrounding landscape environment of the settlements locations. The outcomes indicate no interrelationship between the settlement locations and topography during the Early Minoan period, but a significant interrelationship exists during the later Minoan periods with the presence of more organised societies. The landform classification can provide insights into factors favouring human habitation and can contribute to archaeological predictive modelling.

Partial Text

During the Middle Minoan period of the Bronze Age period in Crete, there appears to have been a widespread increase of sites in low elevation areas suitable for arable farming. Systematic archaeological surveys across eastern and central Crete have examined the settlement dynamics and in all cases highlight a generalised population movement from high elevation areas with limited arable land to lower elevation areas, particularly plains favourable to cultivation and efficiency in irrigation [1]. Most of the studies hypothesized that this population movement tendency was caused by economic and political reasons but only a few of them considered the possibility that this tendency could be a result of environmental conditions and resource exploitation [2,3,4]. Mountainous sites at higher elevations (~600–800 m) seem not to attract further exploitation during the Middle Minoan (and were rarely re-occupied permanently during the later Minoan periods). That was perhaps due to the development of new practices for intensive agriculture which could not be applied in steeply sloping terrain [1]. As a result, people relocated to lower elevations (~300 m) and plains, which have high agricultural and irrigation potential to support population growth, as in Kavousi and Vrokastro districts [5,6].

Crete is located in the southern part of Greece and has a significant archaeological heritage. Evidence from stone tools reveals human presence on the island of Crete as early as 130,000 years ago. However, evidence for modern human presence dates to 10,000–12,000 years ago and it was not until the Neolithic period (8500–4900 BP) when the first signs of advanced agriculture appeared in the Aegean, to open the way for the subsequent emergence of the Minoan civilization (5,600 to 3,000 BP), which is considered as the birthplace of the earliest “high culture” in Europe [35,36,37] (Fig 1A). The Phaistos, Kavousi and Vrokastro districts were selected as case study sites because of their rich archaeological heritage (Fig 1B). The information derived from past archaeological surveys is sufficiently detailed for the analysis of variations in settlement locations during the Minoan periods [6,33,38]. Earlier prehistoric geomorphological conditions were not considered in this methodological framework, as a freely-available Digital Elevation Model (DEM) of recent years is being used in the analysis: further research is needed to determine palaeo-geomorphological features of the study region. In general, the landscape of the study region has remained stable since the earliest phases of human settlement, with the main terrain features being formed in the Pleistocene (i.e., mostly within the past 2 million years) [39]. Regarding palaeo-climatic conditions, at present no conclusive observations exist for Crete from Bronze Age to the present. The role of climatic fluctuations during that period is in general an unexplored field, although a few studies have attempted to evaluate climatic changes with societal developments in areas around eastern Mediterranean [40,41]. [34] reviewed existing indirect measurements of palaeo-climate, so-called climate proxies (e.g. stable isotopes, fossil microshells), with few climatic fluctuations (drought or wetter conditions) being observed in Crete during the Minoan period. As [34] describes, the existing data is unevenly distributed, with some periods having one or two proxies and others by seven or eight. That highlights the importance of integrating climate and environmental history because a relationship between minor Alpine glacial advances in Europe and periods of extreme weather in the Aegean seems to have existed in the study region [39].

During Early Minoan, in the case of the Kavousi-Vrokastro district, the settlements are preferably established on heterogeneous landscapes and many are found at higher elevations with complex rough terrain, mainly hills and ridges [6]. The Mirabello Bay area consists of small coastal valleys: most of the settlements seem to be placed on slopes rather than on the best (flat, lowland) agricultural land [42]. The site pattern was defensive, providing lines of sight between the settlements and out across the Mirabello gulf. Thus the Vrokastro site pattern may be in some accord with [43] suggestion that “people were forced to look for their safety in barely accessible places”. During this period it seems there was a dichotomy between occupying low-lying coastal sites and upland locations, indicating a tendency of the population to occupy diverse types of terrain, seeking to gain control of water sources and sites with the greatest visibility [6]. The evidence for settlement hierarchy during this period has been doubted [44], with clusters of settlements found around the arable coastal basins and not around large settlements.

This study has quantified the spatio-temporal variations of Early, Middle and Late Minoan settlement locations in the landscapes of Crete. A general trend is observed during the Early to Middle Minoan, with the population moving inland in search of arable land, most settlements initially being located within 1.5 km of the coast. During the Middle Minoan, there was an increase of settlements over low-gradient slopes, upper slopes and mesas in hilly terrain, where they remained during the Late Minoan, probably because of their strong defensive advantage (Fig 6).

During the last decade the quantification of landform types has attracted the interest of the geoinformatic research community, with various studies using GIS-based approaches. The evaluation of geomorphometric datasets can be integrated with GIS techniques, highlighting the information within the interlinked geographic data. The extracted information can be particularly useful for landform classification, as this case study of Crete has illustrated. Such information is useful when linked to geospatial data about the distributions of archaeological sites over space and time.

 

Source:

http://doi.org/10.1371/journal.pone.0170727

 

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