Geoscience deals with the geology and subsurface of the earth and involves thinking in 3D. Geological maps are 2D efforts to convey 3D renditions of the subsurface that have tended towards cartoon-like conceptual sketches. Insufficient data and inherent complexity is frequently the cause of such poor understanding and representations. However, modern data collection techniques, coupled with powerful computer generated imagery, have greatly improved our ability to convey and better understand what lies beneath our feet.
[caption id="attachment_32647" align="alignright" width="300"] Du Noyer - old red sandstone[/caption]
Early geological maps were based on direct observation of rock and soil formations, usually as surface exposures in mountains, rivers, quarries and with limited underground exposures in road cuttings, caves, tunnels and mines. Ireland’s early geological mapping was carried out on a systematic scale from the mid-19th century, primarily driven by the search for coal and minerals.
The Geological Survey of Ireland (GSI) systematically mapped the entire island with field sheets on a scale of 1:10.560 (six inches to one mile), used to produce one inch to one mile maps. These maps and field sheets (now scanned and online) can still be accessed and are incredibly detailed and accurate.
Among the best examples of early mapping are the field sheets of George Victor Du Noyer (1817-1869) who often illustrated the rear and blank spaces of the sheets with beautiful sketches of the detailed geology or scenery.
The limited nature of surface exposure requires geologists to extrapolate and interpret to imagine and project what conditions exist at depth. Geoscientists now have, at their disposal, a vast amount of additional data to supplement visual observation. Geochemistry provides information of the chemical composition of soils and rocks. Samples can be taken from the surface, and with the help of drills from the subsurface, often to considerable depths. Geophysical data on magnetic, radiometric and density factors of the earth can be collected remotely by aircraft and satellite.
Satellite imagery has added greatly to our understanding of the earth and its processes, particularly for large scale structures or mapping in remote regions. An example of integrated data collection in Ireland is the Tellus project currently being carried out by GSI across Ireland. This involves the collection of airborne geophysical data using low flying aircraft and ground based geochemistry gathering stream and soil samples on a systematic basis.
Another example of data sets is the mapping of groundwater resources which supply approximately a third of Ireland’s water. The vulnerability of groundwater to pollution is determined by the amount of cover over the water bearing horizon (known as aquifers). Understanding the role of groundwater in flooding and flood management is central to GSI’s service to local authorities and the OPW.