Truncated spurs
Encyclopedia
A truncated spur is a geologic formation created under specific conditions which result in a ridge of land with its end cut off. It occurs when ridge spurs
Spur (mountain)
A spur is a subsidiary summit of a hill or mountain. By definition, spurs have low topographic prominence, as they are lower than their parent summit and are closely connected to them on the same ridgeline...

, which were formed in a mountain
Mountain
Image:Himalaya_annotated.jpg|thumb|right|The Himalayan mountain range with Mount Everestrect 58 14 160 49 Chomo Lonzorect 200 28 335 52 Makalurect 378 24 566 45 Mount Everestrect 188 581 920 656 Tibetan Plateaurect 250 406 340 427 Rong River...

ous area by river action, have been (or are still being) truncated by the action of ice
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...

 or active fault
Active fault
An active fault is a fault that is likely to have another earthquake sometime in the future. Faults are commonly considered to be active if there has been movement observed or evidence of seismic activity during the last 10,000 years....

ing.

Glaciation

Before glaciation, relatively immature rivers display a pattern of interlocking spur
Interlocking spur
An interlocking spur is a natural geographical feature that occurs in the upper course of a river in which downward erosion is the dominant force determining the river's course...

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 are found in between truncated spurs as the 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.

Truncated spurs can be found in mountainous regions. The Mer de Glace
Mer de Glace
The Mer de Glace is a glacier located on the northern slopes of the Mont Blanc massif, in the Alps. At long and deep, it is the longest glacier in France.-Geography:...

, 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.

Active faulting

Truncated spurs are also formed by active faulting, especially normal faulting, producing characteristic triangular facets, sometimes known as a 'flat irons', at the mountain front. These landforms provide evidence for recent fault movement and are used in seismotectonic
Seismotectonics
Seismotectonics is the study of the relationship between the earthquakes, active tectonics and individual faults of a region. It seeks to understand which faults are responsible for seismic activity in an area by analysing a combination of regional tectonics, recent instrumentally recorded events,...

analysis.
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