Page 30 - Fundamentals of Geomorphology

WHAT IS GEOMORPHOLOGY? 13

the measurement of rates and in the understanding FORM
of the physical basis of tectonic and geomorphic pro-
cesses have revitalized it as a field of enquiry. It is The two main approaches to form in geomorphol-
a stimulating and highly integrative field that uses ogy are description (field description and morphological
techniques and data drawn from studies of geomor- mapping) and mathematical representation (geomor-
phology, seismology, geochronology, structure, geodesy, phometry).
and Quaternary climate change (e.g. Burbank and
Anderson 2001). Field description and morphological
Submarine geomorphology deals with the form, mapping
origin, and development of features of the sea floor.
Submarine landforms cover about 71 per cent of the The only way fully to appreciate landforms is to go
Earth’s surface, but are mostly less well studied than into the field and see them. Much can be learnt from
their terrestrial counterparts. In shallow marine envi- the now seemingly old-fashioned techniques of field
ronments, landforms include ripples, dunes, sand waves, description, field sketching, and map reading and map
sand ridges, shorelines, and subsurface channels. In the making.
continental slope transition zone are submarine canyons The mapping of landforms is an art (see Dackombe
and gullies, inter-canyon areas, intraslope basins, and and Gardiner 1983, 13–20, 28–41; Evans 1994).
slumpandslidescars.Thedeepmarineenvironmentcon- Landforms vary enormously in shape and size. Some,
tains varied landforms, including trench and basin plains, such as karst depressions and volcanoes, may be rep-
trench fans, sediment wedges, abyssal plains, distributary resented as points. Others, such as faults and rivers,
channels, and submarine canyons. are linear features that are best depicted as lines. In
Planetary geomorphology is the study of landforms other cases, areal properties may be of prime concern
on planets and large moons with a solid crust, for exam- and suitable means of spatial representation must be
ple Venus, Mars, and some moons of Jupiter and Saturn. employed. Morphological maps capture areal properties.
It is a thriving branch of geomorphology (e.g. Howard Morphological mapping attempts to identify basic
1978; Baker 1981; Grant 2000; Irwin et al. 2005). landform units in the field, on aerial photographs, or
Surface processes on other planets and their satellites on maps. It sees the ground surface as an assemblage of
depend materially on their mean distance from the Sun, landform elements. Landform elements are recognized
which dictates the annual receipt of solar energy, on as simply curved geometric surfaces lacking inflections
their rotational period, and on the nature of the plane- (complicated kinks) and are considered in relation to
tary atmosphere. Observed processes include weathering, upslope, downslope, and lateral elements. They go by a
aeolian activity, fluvial activity, glacial activity, and mass plethora of names – facets, sites, land elements, terrain
wasting. components, and facies. The ‘site’ (Linton 1951) was
Climatic geomorphology rests on the not uni- an elaboration of the ‘facet’ (Wooldridge 1932), and
versally accepted observation that each climatic zone involved altitude, extent, slope, curvature, ruggedness,
(tropical, arid, temperate for example) engenders a dis- and relation to the water table. The other terms were
tinctive suite of landforms (e.g. Tricart and Cailleux coined in the 1960s (see Speight 1974). Figure 1.6
1972; Büdel 1982). Climate does strongly influence geo- shows the land surface of Longdendale in the Pennines,
morphic processes, but it is doubtful that the set of England, represented as a morphological map. The map
geomorphic processes within each climatic zone creates combines landform elements derived from a nine-unit
characteristic landforms. The current consensus is that, land-surface model (p. 169) with depictions of deep-
owing to climatic and tectonic change, the climatic fac- seated mass movements and superficial mass movements.
tor in landform development is more complicated than Digital elevation models lie within the ambits of land-
climatic geomorphologists have on occasions suggested form morphometry and are dealt with below. They have
(cf. p. 389–90). greatly extended, but by no means replaced, the classic