Overview
ISO 710-7:1984 - "Graphical symbols for use on detailed maps, plans and geological cross-sections - Part 7: Tectonic symbols" is an International Organization for Standardization (ISO) document that defines a standardized set of graphical symbols specifically for representing tectonic phenomena on large‑scale geological maps, plans and cross‑sections. Published as part of the ISO 710 series (developed by ISO/TC 82, Mining), this part focuses on strata, faults, joints and schistosity; folds and monoclines; and lineations and axes. The standard includes four symbol tables and fourteen illustrative figures to guide consistent depiction.
Key topics and requirements
- Principle of representation: Symbols describe the observed (existing) state, not genetic interpretations.
- Planes and lineations:
- Planes are shown by their traces on the reference plane (single or thicker lines depending on type).
- Lineations are represented by projections (compound line of alternate dots and dashes) with added modifiers to indicate origin and orientation.
- Certainty levels: Symbols can be varied to indicate certain, probable or possible existence/orientation of features.
- Fault types and modifiers:
- Basic and additional symbols for normal faults, reverse faults/overthrusts, strike‑slip faults, and mixed types (combinations of symbols).
- Use of short lines, triangles, or right‑angled ticks to show dip direction, hanging‑wall/footwall relationships and movement sense (sinistral/dextral).
- Slopes and inverted strata: On plans, slope is shown with arrows; inverted strata use curved arrows to indicate overturned orientation; dip angle may be annotated in degrees or grades.
- Folds and monoclines: Symbols for crest/trough lines, axial planes and fold axes; additional inked symbols (diamonds, triangles) indicate anticlines/synclines and their certainty.
- Tables & figures: Table 1 (basic symbols), Table 2 (special planes), Table 3 (slopes), Table 4 (folds/monoclines), plus 14 illustrative figures.
Practical applications and users
ISO 710-7 provides a unified visual language for geological mapping and technical documentation. Typical users and applications include:
- Field geologists and structural geologists preparing maps and cross‑sections.
- Mine planners and mining engineers producing mine plans where fault geometry and lineations affect design and safety.
- Civil and geotechnical engineers documenting ground conditions for infrastructure projects.
- Cartographers and GIS specialists implementing standardized symbol sets in map products and digital layers.
- Academic researchers and consultants ensuring consistent representation in reports and publications.
Using ISO 710-7 improves clarity, reduces misinterpretation of structural data, and supports interoperability between maps, technical drawings and GIS databases.
Related standards
- ISO 710 series - Part 1 (General rules) and Parts 2–6 (representation of sedimentary, magmatic, metamorphic rocks, minerals and contact/metasomatic rocks). These parts should be consulted together for comprehensive graphical symbol guidance.
