•
What is a geological map ?
• A geological map gives information on the
superficial layers of the earth’s crust. The
geological formations are listed according to
their composition (lithology), their age
(stratigraphy) and their structural position
(tectonic). They are placed on a topographic
base (map) using different graphic elements
• A
geologic map
is an illustration of a
huge volume of geologic information.
Using a geological map, a geologist can
show the
distribution of rock bodies
at
the surface of the Earth and
geologic
• How are geological maps made ?
• The essential condition for establishing a geological detail map is a precise field survey, based on numerous measurements and observations. The topographic base is generally taken from maps at a scale of 1:10'000, such as those of the comprehensive cadastral plans.
• The field geologist determines the rock type according to various criteria and measures its orientation. All data are transcribed onto the map and in a field notebook. Besides the natural or artificial outcrops, data from bore
holes or important test holes are taken in consideration.
• In the case of a doubtful rock identification, complementary investigations are carried out in the laboratory on samples of these rocks.
• At the end of the field survey, the geologist establishes an original draft at a scale of 1:25'000 and constructs some geological sections across the
studied sector. He also writes an explanatory note that generally contains numerous illustrations.
