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| Ministry of Environment |
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| Terrain |
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Surface Expression (Landforms)
Surface expression describes the configuration (three dimensional shape) of the land surface. It is generally used to indicate small landforms that are not shown by the contours of the topographic base of the terrain map. Some surface expression terms (v, b, w) indicate that the shape of the land surface is related to the configuration of the buried landscape upon which the surficial material lies.
Slope steepness is usually not shown explicitly on terrain maps. However, it is included in the definitions of surface expression terms and it may also be determined from the spacing of contours. On some detailed terrain maps (e.g. 1:20000 scale), slope steepness is indicated in an expanded terrain unit symbol.
One to three surface expression terms are applied to a surficial material. The use of two or three symbols implies that there is a mixing of discrete forms and not a combination of forms. For example, gFG hbr indicates that both ridges and hummocks of glaciofluvial gravel are present within the terrain unit. Where two or three symbols are used together, they are written either in order of importance or in alphabetical order with no order of importance implied (see map legend).
Description of Commonly Used Terms and Map Symbols
| moderate slope, apron |
a |
a slope of 10°-35° with a unidirectional surface. |
| blanket |
b |
a mantle of material that reflects the topography of underlying unit and is > 1m thick. |
| cone(s) |
c |
a fan-shaped surface with slope > 10°. |
| fan(s) |
f |
a fan-shaped surface with slope of 2°- 10°. |
| hummock(s) |
h |
steep-sided hillocks that are irregular or rounded in plan; slopes > 10°. |
| gentle slope |
j |
a slope between 2° and 10° with unidirectional surface. |
| rolling |
m |
elongated rises and depressions that are parallel in plan; slopes < 10°. |
| plain, level |
p, l |
level or gently inclined unidirectional surface < 2° for p; < 5° for I. |
| ridge(s) |
r |
narrow, elongated hills with slopes > 10°. |
| steep slope |
s |
steep slopes > 35°. |
| terrace(s) |
t |
step-like topography; consisting of scarps and horizontal surfaces. |
| undulating |
u, m |
u, m gently sloping hillocks that are irregular in plan; slopes < 10°. |
| veneer |
v |
a layer of material that reflects the topography of the underlying unit and is < 1m thick. |
| mantle of varible thickness |
w |
a layer or discontinuous layer of material of variable thickness. |
| thin veneer |
x |
a very thin layer of unconsolidated material about 2-20 cm in thickness. |
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