Geoscience Reference
In-Depth Information
10
Making a
geological map
Tom W. Argles
10
10.1 Principles and aims
A geological map is one of the most important tools of a
geologist's trade. It shows how geological features (rock units,
faults, etc.) are distributed across a region. It is a two-
dimensional representation of part of the Earth's surface, scaled
down to a size that is convenient for displaying on a sheet of
paper or a computer screen. Information on the third
dimension is incorporated by means of strike and dip symbols
and other structural labels. Different rock units are usually
shown as different colours (and/or ornaments) and are overlain
on a topographic base map for easy location. Additional
information on features such as structure, lithology and
stratigraphy is also included, allowing interpretation of the
subsurface. Increasingly, geological mapping data are stored
with subsurface information in computer models that allow
more sophisticated visualization and manipulation in three
dimensions than is possible with traditional paper maps.
Geological maps are made for a variety of reasons and,
depending on the region, these are to:
record the position of particular geological features or
exposures;
help us understand the geological history of a region;
locate natural resources, and understand the best way to
exploit them;
identify potential hazards (e.g. faults, volcanoes, unstable
substrates, hazardous deposits);
gain insights into the immediate subsurface environment,
which governs soils, drainage, agriculture and ecosystems;
provide a base for constructing a detailed geological cross-
section to deduce and visualize strata below ground.
Geological mapping aims to distil data concisely onto a
topographical base map, producing a clear, detailed
