An interlocking spur, also known as an overlapping spur, is one of any number of projecting

ridge A ridge is a long, narrow, elevated geomorphologic landform, structural feature, or a combination of both separated from the surrounding terrain by steep sides. The sides of a ridge slope away from a narrow top, the crest or ridgecrest, wi ...

s that extend alternately from the opposite sides of the wall of a young,

V-shaped valley A valley is an elongated low area often running between hills or mountains and typically containing 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 a ve ...

down which a river with a winding course flows. Each of these spurs extends laterally into a concave bend of the river such that when viewed either upstream or from overhead, the projecting ridges, which are called ''spurs'', appear to "interlock" or "overlap" in a staggered formation like the teeth of a zipper.Jackson, JA, J Mehl and K Neuendorf (2005) ''Glossary of Geology.'' American Geological Institute, Alexandria, Virginia. 800 pp. While similar in general appearance, the mechanism behind the formation of interlocking spurs is different from that behind

meander A meander is one of a series of regular sinuous curves in the Channel (geography), channel of a river or other watercourse. It is produced as a watercourse erosion, erodes the sediments of an outer, concave bank (cut bank, cut bank or river cl ...

s, which arise out of a combination of lateral erosion and deposition. Interlocking spurs are formed as either a river or stream cuts its valley into local

bedrock In geology, bedrock is solid rock that lies under loose material ( regolith) within the crust of Earth or another terrestrial planet. Definition Bedrock is the solid rock that underlies looser surface material. An exposed portion of bed ...

. As it entrenches its valley, it preferentially follows and erodes zones of weaknesses within the bedrock that typically consist of intersecting sets of

joints A joint or articulation (or articular surface) is the connection made between bones, ossicles, or other hard structures in the body which link an animal's skeletal system into a functional whole.Saladin, Ken. Anatomy & Physiology. 7th ed. McGraw- ...

. This process creates a zig-zagging

fluvial A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...

valley that "interlock" or "overlap" in a staggered manner. If the river valley is subsequently subject to glaciation,

glacial A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...

erosion widens the V-shaped valley and removes the ends of the interlock spurs projecting into the valley. As a result, the ridges are truncated to form ''

truncated spurs A truncated spur is a spur, 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, wa ...

''.Thornbury, W. D. (1954) ''Principles of Geomorphology.'' John Wiley and Sons, Inc. New York. 618 pp.

References

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Geomorphology Fluvial landforms {{geomorph-stub