Modern techniques in illustration and recording in geology

Advances in technology have enabled new methods in the acquisition and recording of field data in geology and its presentation within publications. These techniques compliment, rather than replace, traditional field observations. This chapter describes the use of photogrammetry and aerial drone surveys in constructing three-dimensional models of geological features, which provide valuable data when combined with field notes on lithology. Digital methods in the analysis and processing of images are discussed together with methods in digital drawing and painting to produce publication-ready diagrams for Earth Science. Photographs for use in publications should be corrected to ensure optimal contrast and brightness.

Drawing schematic diagrams

Schematic diagrams are invaluable in Earth Science in the communication of concepts in both publications and teaching. These diagrams can also be used during fieldwork to help develop interpretations of structures, palaeoenvironments, and geological processes. This chapter describes methods used to create block diagrams of structures and landscapes, surface diagrams of folds and faults, and process diagrams used to summarize interpretations of a wide range of processes. Schematic diagrams can and should be included in field notes. Process diagrams represent a cartoon of interpretative thoughts. Four worked examples of schematic diagrams are provided to illustrate their uses and construction.

Landscape sketches

Drawings of landscapes are often used to record large-scale geological structures in Earth Science. This chapter describes how to draw geological features exposed within landscapes with a focus on the methods used to produce accurate and detailed field sketches. The tactics in drawing large fields of view, landscapes with significant topography, and vegetated landscapes with sparse outcrops are described. Three worked examples of landscape field sketches are provided to illustrate how best to record tectonic structures and volcanic features exposed over topography. Topographic features such as ravines and ridges can be added as lines to add additional value. Common mistakes considered include insufficient detail and schematic vegetation.

Drawing three dimensions

Natural outcrops of rock often have significant topography that makes them difficult to record in field sketches. This chapter describes the methods used to draw outcrops in three dimensions. The concepts of perspective and its influence on the appearance of strata are described as well as the tactics that can be used to simplify the drawing of natural outcrops. Three worked examples of field sketches are included in the chapter to illustrate how best to record the geology exposed on surfaces with significant relief. These include sketching of large three-dimensional outcrops and drawing of coastal cliffs. Common mistakes in drawing outcrops with relief are described.

Drawing folds

Folds record the deformation of strata and reveal the tectonic processes by which the Earth’s crust has evolved. In this chapter the techniques used to create field sketches of folds are described together with the important features of these structures that need to be recorded. Careful observation is needed in drawing fold structures prior to drawing to identify the trace of the fold axial planes on the outcrop. The importance of the fold axial plane in the geometry of fold structures is stressed. Two worked examples of field sketches of simple folds are given to illustrate the tactics involved in observing and drawing these structures.

Drawing hand-specimens of rocks and crystals

Rocks and minerals are naturally occurring solid materials that make up planetary bodies such as the Earth and are highly diverse. This chapter describes how to record the mineralogy and petrology of rocks using drawings and includes methods used to graphically record hand-specimens of rocks and crystals. Four worked examples of drawings of hand-specimens are included to illustrate techniques and the important features to record. Practical advice on how to identify rock types and minerals is also given. The outline of the specimen is important since it guides the placement of other features. The petrology must be simplified to make drawing practical.

Drawing sedimentary outcrops

Sedimentary rocks are the commonest rocks found on the surface of the Earth’s crust and record much of the history of both our planet and life on Earth. This chapter describes how to draw outcrops of sedimentary rocks in the field and the most important features of these rocks to record and describe. The stratigraphy and interpretation of sedimentary rocks is also considered in the chapter and includes a description of common sedimentary structures. The use of sedimentary facies in evaluation of depositional environment is introduced. Five worked examples of field sketches of sedimentary outcrops are given to illustrate how to make accurate and detailed observations of sediments. Examples include how to draw unconformities, sedimentary structures, lithologies, and graphic logs.

Drawing igneous outcrops

Igneous rocks are a fundamental component of the Earth and are commonly encountered during geological fieldwork. This chapter describes techniques used to draw field sketches of intrusions and volcanic features, such as lava flows, volcanic craters, and pyroclastic sequences. The most important features of igneous rocks to record are discussed. Recording the nature of contacts is particularly important in drawing igneous outcrops, in particular cross-cutting relationships that relate to emplacement timing. Four worked examples of field sketches of igneous geology are provided to illustrate concepts in their description in during fieldwork. These include the summit crater of Vesuvius, lava flows from Mount Etna, and pyroclastic deposits from Santorini.

Geological cross-sections

Geological cross-sections are graphical representations of the distribution of rock units in vertical planes cut through landscapes. Cross-sections extrapolate the boundaries between rock units above and below ground. This chapter provides practical advice on how to create geological cross-sections through the interpretation of maps with an emphasis on recognizing the key features that reveal the orientation of boundaries and structures. Topography lines can be sketched with reasonable accuracy rather than transferred from maps. The use of sketch cross-sections as an interpretative diagram is introduced, and examples given to illustrate how these can be used in field notes to assist in the analysis of geological structures.

The methods of drawing

Drawing and illustrating in Earth Science has a fundamentally different focus to artistic illustration and requires different techniques. The methods used in drawing geology are described in this chapter, including the basic techniques of general drawing and those methods that are specific to geology. The chapter examines which outcrops should be drawn and introduces three rules that should be applied to every field sketch. The methods to ensure field sketches of outcrops are accurate and detailed are described, with practical advice on how to apply line style, colour, and shading in geological diagrams. Finally, aspects of drawing such as posture and position are described that will help improve the quality of sketches.