Head Scars Research Articles

Glaciers, rock avalanches and the ‘buzzsaw’ in cirque development: Why mountain cirques are of mainly glacial origin

AbstractIt has been proposed that most cirques are source‐area depressions of large, deep‐seated rock‐slope failures. Yet the close relation between cirques and climate is convincing evidence of the dominance of glacial erosion, rather than rock‐slope failure, in mountain cirque development and distribution. Cirque floor altitudes have a lower limit that varies with snowfall by 1000 m or more between windward and leeward sides of mountain systems. Glaciation levels and equilibrium line altitudes implied by cirques vary in parallel with those for modern glaciers. Cirques are often found mainly on the poleward or leeward slopes of individual mountain ranges, as are modern small glaciers (because of solar radiation and wind effects on ablation and accumulation).Most rock‐slope failures (RSFs: rock slides, rock avalanches and gravitational deformations) do not involve the deep‐seated rotational movement that would produce a cirque form. Although some deep‐seated RSFs with arcuate head scars may be confused with cirques, identification as a glacial cirque is more confident as the floor is longer, wider and more gently sloping. Some scars from major RSFs may resemble poor or moderately developed cirques, but tend to have steeper floors, to be more scattered and closely related to geology, whereas glacial cirques develop on all rock types. Deep‐seated RSFs high on slopes can be associated with seismic shaking, but cirques develop without relation to seismicity. Degree of cirque development can be related to duration of exposure to glaciation. Often RSFs are found adjacent to cirques, or in glacial transfluences; only a proportion are well situated to develop into glacial cirques. Valley‐head cirques are continued down‐valley by glacial troughs. The ‘overdeepening’ (rock basins with reversed slopes) found in a large minority of cirques is not due to rock avalanching, fluvial or periglacial erosion.The RSF proposal should therefore be rejected in favour of the traditional glacial explanation, without any nivation stage being necessary. Rock‐slope failure is one of several possible ways of initiating hollows for glacier accumulation, as well as an ancillary process of cirque extension or widening through collapse of glacially oversteepened slopes.Headward extension of adjacent cirques on a ridge leads to displacement of the divide, sometimes by 2 km or more, lowering ridge and summit altitudes and producing the ‘glacial buzzsaw’ effect. Where a relatively lower snowline has led to cirque erosion on all sides of a mountain, cirque intersection lowers summits further. The buzzsaw hypothesis is not applicable, however, where remnants of a preglacial summit surface survive. © 2020 John Wiley & Sons, Ltd.

Attributions about persons with brain injury: The effects of knowledge and familiarity about brain injury

Primary objective: To determine how visible markers of brain injury interact with people's knowledge about brain injury to influence people's attributions for undesirable behaviours of a person with brain injury.Research design, method and procedures: Scenarios in Experiment 1 (n = 98) and Experiment 2 (n = 148) described an adolescent pictured with or without a head scar, who showed four behavioural changes. Participants rated two causal attributions for each behaviour: brain injury and adolescence. Experiment 1 varied information that the adolescent had a brain injury and Experiment 2 assessed participants’ familiarity with brain injury.Main outcomes and results: The presence of a head scar increased attributions to brain injury. In Experiment 1, participants not informed about the brain injury attributed the behaviours more to adolescence than to brain injury than informed participants. In Experiment 2, in the ‘no scar’ condition participants familiar with brain injury attributed the behaviours more to brain injury than those who were not.Conclusion: Markers of brain injury interact with people's knowledge about brain injury in shaping people's attributions for the behaviour of persons with brain injury. When people attribute sequelae of the brain injury to other causes, this may hinder appropriate treatment.

Attributions and Expectations for the Behavior of Persons With Brain Injury

To determine whether visible markers of brain injury shape people's causal attributions for the behaviors of the person with the injury and their expectations that those behaviors will persist for 5 years. Experimental scenarios described an adolescent boy with a brain injury (pictured either with or without a head scar) who showed 4 behavior changes relating to sleep, anger, self-confidence, and motivation. Victoria University of Wellington. University student volunteers (N = 249). For each behavior, ratings of attributions to either the brain injury or to adolescence and estimates that the behaviors would persist for 5 years. Attributions to brain injury correlated with expectations that the behaviors would persist. Participants attributed the behaviors more to the brain injury than to adolescence in the scar condition but not in the no-scar condition. Visible markers of brain injury such as scars are spurious markers of severity that shape attributions for actions of persons with the injury and expectations that problematic behaviors will persist. The results inform strategies for correcting misunderstandings about brain injury and enhancing rehabilitation.

Attributions for behaviours of persons with brain injury: The role of perceived severity and time since injury

Primary objective: The experiment determined first whether visible markers of brain injury shape judgements of severity of injury and time since injury; and secondly whether these two judgements predict attributions for undesirable actions performed by an adolescent with brain-injury.Research design: Scenarios presented a photograph of an adolescent, in one condition with a head scar and in a second condition with no scar. The adolescent was described as having suffered a brain injury and showing four behaviour changes, concerning sleep, anger, self-confidence and motivation.Methods and procedures: For each behaviour, students (n= 101) rated attributions to the brain injury and adolescence and estimated severity of injury and time since injury.Outcomes and results: With no scar, participants attributed the behaviours to adolescence more than brain injury, whereas with the scar they invoked both causes equally. With the scar they rated severity higher and time since injury shorter; severity predicted participants’ attributions for the behaviours.Conclusions: Visible markers of injury such as scars are spurious indicators of severity but they shape judgements of severity and attributions for actions of persons with brain injury. These results inform more accurate diagnosis and treatment for actions resulting from brain injury.

Submarine landslides in the Santa Barbara Channel as potential tsunami sources

Abstract. Recent investigations using the Monterey Bay Aquarium Research Institutes (MBARI) Remotely Operated Vehicles (ROVs) "Ventana" and "Tiburon" and interpretation of MBARI's EM 300 30 kHz multibeam bathymetric data show that the northern flank of the Santa Barbara Basin has experienced massive slope failures. Of particular concern is the large (130 km2) Goleta landslide complex located off Coal Oil Point near the town of Goleta, that measures 14.6-km long extending from a depth of 90 m to nearly 574 m deep and is 10.5 km wide. We estimate that approximately 1.75 km3 has been displaced by this slide during the Holocene. This feature is a complex compound submarine landslide that contains both surfical slump blocks and mud flows in three distinct segments. Each segment is composed of a distinct head scarp, down-dropped head block and a slide debris lobe. The debris lobes exhibit hummocky topography in the central areas that appear to result from compression during down slope movement. The toes of the western and eastern lobes are well defined in the multibeam image, whereas the toe of the central lobe is less distinct. Continuous seismic reflection profiles show that many buried slide debris lobes exist and comparison of the deformed reflectors with ODP Drill Site 149, Hole 893 suggest that at least 200 000 years of failure have occurred in the area (Fisher et al., 2005a). Based on our interpretation of the multibeam bathymetry and seismic reflection profiles we modeled the potential tsunami that may have been produced from one of the three surfical lobes of the Goleta slide. This model shows that a 10 m high wave could have run ashore along the cliffs of the Goleta shoreline. Several other smaller (2 km2 and 4 km2) slides are located on the northern flank of the Santa Barbara Basin, both to the west and east of Goleta slide and on the Conception fan along the western flank of the basin. One slide, named the Gaviota slide, is 3.8 km2, 2.6 km long and 1.7 km wide. A distinct narrow scar extends from near the eastern head wall of this slide for over 2km eastward toward the Goleta slide and may represent either an incipient failure or a remnant of a previous failure. Push cores collected within the main head scar of this slide consisted of hydrogen sulfide bearing mud, possibly suggesting active fluid seepage and a vibra-core penetrated ~50 cm of recent sediment overlying colluvium or landslide debris confirming the age of ~300 years as proposed by Lee et al. (2004). However, no seeps or indications of recent movement were observed during our ROV investigation within this narrow head scar indicating that seafloor in the scar is draped with mud.

Head scarring on male narwhals (Monodon monoceros): evidence for aggressive tusk use

The data presented here provide strong evidence that support the hypothesis that the narwhal's tusk is used during fights between mature males. Evidence of violent fighting among adult males includes high numbers of head scars, broken tusks, and a tusk tip embedded in a skull. Females and immature males had significantly fewer head scars, and immature males had a significantly lower incidence of broken tusks. Among mature males, scar number was positively related to body girth, tusk weight, and tusk girth, but not to tusk length or body length. Relating dominance to the pattern of many head scars on massive mature males with massive tusks is consistent with data from other species for which both anatomical and behavioural observations are available. The lack of significant correlations of tusk length with body length and body girth in mature males is not consistent with the hypothesis that dominance assessment is based on a display of tusk lengths.

The evolution of sexual dimorphism in the skink Eumeces laticeps: an example of sexual selection

Adults of the skink Eumeces laticeps are sexually dimorphic in coloration, body size, head size, and relative head size. Males have larger heads at a given body size than females and the divergence in relative head size is coincident with the size at which sexual maturity is reached. Although there were no differences between sexes in tail loss frequencies, there were substantial differences in frequencies of body and head scars, a consequence of aggressive male–male interactions. Prey size was correlated with body and head size and males tended to eat larger prey items than females. However, both sexes are capable of eating prey much larger than the mean or maximum size of prey found in stomachs, suggesting that resource partitioning is a consequence of sexual size differences rather than a cause. The heads of males at a given body size increase during the breeding season, and a combination of head and body size apparently determines the outcome of intrasexual aggressive encounters. Moreover, small males were never observed with females during the breeding season, and those males observed "guarding" females were significantly larger than males observed in the absence of females. We conclude that sexual selection accounts for many of the differences in morphological traits between sexes of E. laticeps.