A truncated spur is a

spur A spur is a metal tool designed to be worn in pairs on the heels of riding boots for the purpose of directing a horse or other animal to move forward or laterally while riding. It is usually used to refine the riding aids (commands) and to ba ...

, which is a ridge that descends towards a valley floor or coastline from a higher elevation, that ends in an inverted-V face and was produced by the erosional truncation of the spur by the action of either streams, waves, or glaciers. Truncated spurs can be found within mountain ranges, along the walls of river valleys, or along coastlines.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds. (2005) ''Glossary of Geology'' (5th ed.). Alexandria, Virginia, American Geological Institute. 779 pp. Thornbury, W. D., 1954, ''Principles of Geomorphology.'' John Wiley and Sons, Inc. New York. 618 pp. A faceted spur is also a spur that ends in a triangular face, known as a triangular facet, with a broad base and an apex pointing upward. As typically used in

geology Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...

, the triangular facet is usually a remnant of a fault plane and it and its associated faceted spur are the result of faulting. The term ''faceted spur'' is also applied to inverted-V rock faces formed by stream, wave, or glacial erosion and, thus, as a synonym for ''truncated spur''.

Formation

Truncated spurs

Before glaciation, relatively immature rivers display a pattern of

interlocking spur An interlocking spur, also known as an overlapping spur, is one of any number of projecting ridges that extend alternately from the opposite sides of the wall of a young, V-shaped valley down which a river with a winding course flows. Each of t ...

s. A valley glacier cannot avoid the interlocking spurs as a river can. As the valley glacier moves, abrasion and plucking erode the protruding tips of the spurs, leaving steep cliff-like truncated spurs.

Hanging valleys A valley is an elongated low area often running between hills or mountains, which will typically contain a river or stream running from one end to the other. Most valleys are formed by erosion of the land surface by rivers or streams over ...

are found in between truncated spurs as they join the main glacial valley from the side. It is common for waterfalls to form from them, where they fall into the main valley. Such truncated spurs can be found in mountainous regions. The

Mer de Glace The Mer de Glace ("Sea of Ice") is a valley glacier located on the northern slopes of the Mont Blanc massif, in the French Alps. It is 7.5 km long and deep but, when all its tributary glaciers are taken into account, it can be regarded as ...

, in the European Alps, is a valley through which a glacier currently flows. This is a geologically active process where the glacier continues to gradually erode the valley sides.

Faceted spurs

In the most typical usage of this term, faceted spurs are formed by active faulting, especially normal faulting that produces well-defined triangular facets along either a mountain front or edges of a rift valley. These triangular facets provide evidence for recent fault movement and are used in seismotectonic analysis.Bull, W. B., 2007, ''Tectonic Geomorphology of Mountains: A New Approach to Paleoseismology.'' Blackwell Publishing, New York, New York. 304 pp. Classic examples of faceted spurs can be found all along the Central Wasatch Fault, north-central Utah.Zuchiewicz, W. and J. P. McCalpin, 2000, ''Geometry of faceted spurs on an active normal fault; case study of the central Wasatch fault, Utah, USA.'' Annales Societatis Geologorum Poloniae, vol. 70, pp. 231-249.

References

Tectonic landforms {{Topography-stub