Geology

The knowledge of the geology of an area requires mapping through field surveying, sampling, laboratory analysis and processing of the data using existing classification systems. One of the crucial points of geology mapping is the scale of the map.  

Aim of the method/technique	The aim of the geological mapping is to derive a geological map presenting the various geological formations. Geological information can be used for environmental studies such as understanding basic properties of the formed soils, the hydrology of an area, and land and environmental vulnerability to degradation. Geology is used as a parameter in land use planning for agricultural areas and environmental impact assessments. Natural hazards such as landslides and slope stability is highly related to the stratigraphy of the geological formations.
Scale – spatial and temporal	At European level the implementation of geological mapping is delegated to the official national Geological Surveys. As example of a national level, the Geological Map of Italy (scale 1:100,000), is currently the only official geological map of the country, whilst the CARG project is currently working on the completion of the new Geological Map at 1:50,000 scale, which is the common used scale. The National Geological Surveys of EU countries  provided the geological synthesis for the European Map at 1:1,000,000 scale, as required by European Directive INSPIRE (May 2007). Following the INSPIRE Directive the "One Geology-Europe” project has been implemented to identify and share digital geological data across Europe. The information of the existing geological maps is usually not enough for detailed studies of land degradation processes. In such cases, field surveys are conducted by observing the geological materials on existing cuts. As an example, the geological map of Crete (Figure 1) presents the geological parent materials of the uppermost earth geological layer that affects soil characteristics.   Figure 1. Geological map of Crete characterized as parent material of the existing soils (Source: LEDDRA project)
Brief description	Based on the Geo-referenced Soil Database for Europe (Finke et al. 1998), the following categories of geological materials are distinguished: •    Consolidated clastic sedimentary rocks (conglomerate, sandstone, claystone, siltstone, etc.). •    Calcareous and non clastic siliceous sedimentary rocks and sulphates (limestone, marl, evaporates, chert, etc.) •    Igneous rocks (acid to intermediate plutonic rocks, acid to intermediate volcanic rocks. Basic plutonic rocks, basic volcanic rocks, ultrabasic rocks, pyroclastics rocks). •    Metamorphic rocks (non calcareous metamorphic such as gneiss, mica schist, calcaric metamorphic such as marble). •    Unconsolidated alluvial deposits (marine and estuarine deposits, fluvial and lacustrine deposits, lake deposits). •    Unconsolidated glacial deposits (glacial drift. glaciofluvial deposits, etc.). •    Eolian deposits (loess, eolian sands). •    Residual and redeposited materials (slope deposits, redeposited clay, etc.) •    Other rocks and deposits (organic material, anthropogenic deposits).
Data requirements	The data required for compiling a geological map of an area are a topographic map and aerial photographs. Geological data for studying land degradation processes or land vulnerability to degradation are required for the uppermost geological layer, considered as parent material of existing soils.
Main applications in cropland and forests & shrubland regions	The geological characteristics of an area are used for assessing: (as) the vulnerability of the land to land degradation and desertification, (b) the soil characteristics such as nutrients availability, amount of rock fragments, etc., (c) the crop production, (e) the ability of an ecosystem for recovering after a strong disturbance such as forest fire, (f) the resilience of an ecosystem under specific land management practices, (g) the density of drainage system, (i) the presence of ground water, etc.
Strengths and weaknesses	The classification of geological materials presented above can be adequately used for assessing land degradation processes and land capability for crop production. Some of the limitations are related to lack of uniformity of existing classification systems and existing data. Furthermore, geology mapping requires many field observations by geology experts. Also the lack, in some cases, of digital mapping support requires a complex work of digitization and geo-referencing.

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