Some aspects of drumlin geometry

Reed, B. Cameron; Galvin, Cyril; Miller, John P.

doi:10.2475/ajs.260.3.200

Cited by 45 publications

(19 citation statements)

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“…In Figure 7A the apparent drumlin axes are marked; the orientations have been measured and the results are shown as a histogram in Figure 7B. A normal symmetrical distribution of orientations is produced; this agrees exactly with the orientation measurements on real drumlins reported by Reed and others (1962).…”

Section: Orientationsupporting

confidence: 76%

“…In this equation I is the length of the drumlin, k is a dimensionless number which effectively indicates the width of the drumlin, p and 9 are the two variables. Reed and others (1962) Each method has advantages and disadvantages, but the Chorley method appears to be the more useful. The disadvantages of the Chorley method arc that it only operates in two dimensions and the equation is in polar coordinate form which is perhaps more difficult to manipulate than the more common rectangular coordinate system which is used by Reed and others.…”

Section: Shapementioning

confidence: 99%

“…The distribution of drumlins has been investigated in two ways. A random model has been devised and the distribution of drumlins in the model field has been compared with the observations of Reed and others (1962) and Vernon (19G6), and drumlins in real fields have been subjected to nearest-neighbour analysis.…”

Section: Distributionmentioning

confidence: 99%

“…Each of these larger drumlins counts as one so more coordinates are plotted until 12 distinguishably separate drumlins arc formed; this is the model distribution and spacing measurements can be made and compared with real fields. Reed and others (1962) made perpendicular and parallel measurements which are difficult to define and make.…”

Section: Random-placement Modelmentioning

confidence: 99%

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The Formation and Shape of Drumlins and their Distribution and Orientation in Drumlin Fields

Smalley

Unwin

1968

J. Glaciol.

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AISSTKACT. If glacial till contains more than a certain minimum boulder content, it is dilatant and requires a much larger stress to initiate shear deformation than to sustain il. If the stress level at the glacierlerrain interface drops below a certain critical level, or the till reaches its critical boulder-content density, then the till beneath the glacier packs into stable obstructions. These are shaped into streamlined forms by the giacier and are found distributed at random i" drumlin fields. Due to drumliii coalescence there is a normal distribution of drumlin axes about the direction of ice movement. RESUME. La formation rt mor/jlurlogir de drumlins et four repartition cl orientation en champs de drumlins. Si mi argile a blocaux contient plus d'une certaine quantite minimum de blocaux. il est dilatable et exige une plus grande tension pour debuter line deformation par cissaillement que pour 1c soutenir. Si le niveau de tension entre le glacier et le terrain descend au-dessous d'un certain niveau critique, ou si l'argile a blocaux atteint sa densite critique de blocaux, alors l'argile a blocaux au-dessous du glacier s'agglomere et forme des obstacles stables de formes carenees et distributes au hasard en champs de dnmihns. A cause de leur coalescences, les axes des drumlins s'alignem avec la direction ciu mouvement glaeiaire en une repartition normale.

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Section: Orientationsupporting

confidence: 76%

Section: Shapementioning

confidence: 99%

Section: Distributionmentioning

confidence: 99%

Section: Random-placement Modelmentioning

confidence: 99%

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The Formation and Shape of Drumlins and their Distribution and Orientation in Drumlin Fields

Smalley

Unwin

1968

J. Glaciol.

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“…It contains two identifiable suites of features interpreted as 'classically shaped' drumlins, namely of approximately leminscate or elliptical footprints (e.g. Chorley, 1959;Reed, Galvin, & Millier, 1962). The drumlins mark the presence of flowing ice during these time periods, broadly west to east during the LGM and north to south during the YD.…”

Section: Study Areamentioning

confidence: 99%

Manual mapping of drumlins in synthetic landscapes to assess operator effectiveness

et al. 2014

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Mapped topographic features are important for understanding processes that sculpt the Earth's surface. This paper presents maps that are the primary product of an exercise that brought together 27 researchers with an interest in landform mapping wherein the efficacy and causes of variation in mapping were tested using novel synthetic DEMs containing drumlins. The variation between interpreters (e.g. mapping philosophy, experience) and across the study region (e.g. woodland prevalence) opens these factors up to assessment. A priori known answers in the synthetics increase the number and strength of conclusions that may be drawn with respect to a traditional comparative study. Initial results suggest that overall detection rates are relatively low (34-40%), but reliability of mapping is higher (72-86%). The maps form a reference dataset.

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Spatial organization of drumlins

Clark

Ely

Spagnolo

et al. 2017

Earth Surf Processes Landf

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Ice-sheets flowing over soft sediments produce undulations in the bed, typically of metres in relief, of which drumlins are the most abundant and widely investigated. Consensus regarding their mechanism of formation has yet to be achieved. In this paper we examine the spatial organization of drumlins in order to provide an improved description of the phenomenon and to guide hypotheses of their formation. We review the literature highlighting contradictory findings regarding drumlin spatial organization and then use this to motivate our study based on a large sample (42 488) of drumlins from Canada, Britain and Norway. Are there typical arrangements in drumlin positioning and are they organized in a regular spatial manner (patterned) or are they distributed randomly? We recognize that drumlin fields are inherently patchy and therefore apply inhomogeneous spatial statistics in order to study their distribution. This shows that whilst drumlins are occasionally randomly placed, their main state is non-random. They exhibit a strong and statistically significant signal of regularity across lengths scales of 100 to 1200 m. We conclude that patterning is a near ubiquitous property of drumlins. This finding of regularity demonstrates spatial self-organization in the bedforming process with drumlins as an emergent manifestation of sub-glacial sediment mobility. Kilometre-scale interactions between drumlins must occur as they evolve, or interactions may arise as a consequence of growth or migration. Hypotheses or models are required that can explain the regular spacing of drumlins. We highlight three suggestions for such self-organization: instability in the coupling of ice flowsediment flux-bed shape; local feedback between sediment mobility and relief; and coarsening by growth or migration.

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Some aspects of drumlin geometry

Cited by 45 publications

References 0 publications

The Formation and Shape of Drumlins and their Distribution and Orientation in Drumlin Fields

The Formation and Shape of Drumlins and their Distribution and Orientation in Drumlin Fields

Manual mapping of drumlins in synthetic landscapes to assess operator effectiveness

Spatial organization of drumlins

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