Morphometric Analysis on the Size, Shape and Areal Distribution of Glacial Cirques in the Maritime Alps (Western French-Italian Alps)

The morphometry of 432 glacial cirques in the Maritime Alps (Western French‐Italian Alps), studied over several years of fieldwork, was analysed with the use of a geographical information system. Some of the parameters automatically evaluated from digital elevation models required an objective and relatively new definition. In particular, cirque length was measured along a line that, from the threshold midpoint, splits the cirque into two equivalent surfaces; cirque width was automatically drawn as the longest line inscribed in the cirque and perpendicular to the length line. Significant correlations were found among the different factors and parameters analysed. In particular, cirque shape analysis showed that cirques develop allometrically in the three dimensions, i.e. more in length and width than in altitudinal range. Nevertheless cirques of the Maritime Alps have a regular, almost circular shape (mean L/W value = 1.07). The correlations among length, width and area are all very high (r²= 0.8–0.9). In terms of size, cirques show a wide range in area from 0.06 to 5.2 km² with a mean value of 0.4 km². The largest cirques are found on SSW‐facing slopes and at high elevations. Small cirques can be found at all altitudes but all those at high elevation are part of compound cirques at the main head valleys. Most cirques (37%) are characterized by a northern aspect; NE and SW are also frequent directions.     

Hummock corridors in the south‐central sector of the Fennoscandian ice sheet,morphometry and pattern

Subglacial conditions strongly influence the flow of ice‐sheets, in part due to the availability of melt water. Contemporary ice sheets are retreating and are affected by increased melting as climate warms. The south Swedish uplands (SSU) were deglaciated during the relatively warm Bølling‐Allerød interval, and by studying the glacial landforms there it is possible to increase the understanding of the subglacial environment during this period of warming. Across the study area, vast tracts of hummocks have long been recognized. However, recent mapping shows a pattern of elongated zones of hummocks radially oriented, hereafter referred to as ‘hummock corridors’. Morphometric parameters were measured on the hummock corridors using a 2 m horizontal resolution digital elevation model. Corridor width varies between 0.2 and 4.9 km and their length between 1.5 and 11.8 km. A majority of hummock corridors are incised in drumlinised till surfaces. The pattern of hummock corridors shows a clear relation to the overall ice‐flow. Further, hummock corridors do not follow topographic gradients, and in at least one place an esker overlies hummocks on the corridor floor. The lateral spacing of hummock corridors and corridor morphology are similar to tunnel valleys, eskers and glaciofluvial corridors reported elsewhere. Such relationships support a subglacial genesis of the corridors in the SSU by water driven by the subglacial hydraulic gradient and that hummock corridors are forms that can be identified as tunnel valleys and glaciofluvial corridors (GFC). Ages were assigned to hummock‐corridor cross‐sections from a deglacial reconstruction of the Fennoscandian Ice Sheet. By comparing the frequency of corridors per age interval with climate variations from a Greenland ice core, we hypothesize that an increase in the number of corridors is related to the Bølling‐Allerød warming, indicating a higher rate of delivery of surface melt water to the bed at this time. Copyright © 2017 John Wiley & Sons, Ltd.     

Dynamics of salt marsh margins are related to their three-dimensional functional form

The three-dimensional configuration of sedimentary landforms in intertidal environments represents a major control on regional hydrodynamics. It modulates the location and magnitude of forces exerted by tidal currents and waves on the landform itself and on engineered infrastructure such as sea walls or coastal defences. Furthermore, the effect is reflexive, with the landforms representing an integrated, long-term response to the forces exerted on them. There is a strong reciprocal linkage between form and process (morphodynamics) in the coastal zone which is significantly lagged and poorly understood in the case of cohesive, vegetated sediments in the intertidal zone. A method is presented that links the geometric properties of the tidal flat–salt marsh interface to the history and potential future evolution of that interface. A novel quantitative classification scheme that is capable of separating marsh margins based on their functional form is developed and is applied to demonstrate that relationships exist between landform configuration and morphological evolution across a regional extent. This provides evidence of a spatially variable balance between self-organized and external controls on morphodynamic evolution and the first quantitative basis for a quick assessment procedure for likely future dynamism. © 2019 John Wiley & Sons, Ltd.     

Geomorphic process signatures reshaping sub-humid Mediterranean badlands: 2. Application to 5-year dataset

Badland landscapes exhibit high erosion rates and represent the main source of fine sediments in some catchments. Advances in high-resolution topographic methods allow analysis of topographic changes at high temporal and spatial scales. We apply the Mapping Geomorphic Processes in the Environment (MaGPiE) algorithm to infer the main geomorphic process signatures operating in two sub-humid badlands with contrasting morphometric attributes located in the Southern Pyrenees. By interrogating a 5-year dataset of seasonal and annual topographic changes, we examine the variability of geomorphic processes at multiple temporal scales. The magnitude of geomorphic processes is linked to landform attributes and meteorological variables. Morphometric differences between both adjacent badlands allow us to analyse the role of landform attributes in the main geomorphic process reshaping landscapes subjected to the same external forcing (i.e. rainfall and temperature). The dominant geomorphic process signatures observed in both badlands are different, despite their close proximity and the same rainfall and temperature regimes. Process signatures determining surface lowering in the gently sloping south-facing badland, characterized by lower connectivity and more vegetation cover, are driven by surface runoff-based processes, both diffuse (causing sheet washing) and concentrated (determining cutting and filling, rilling and gullying). The steeper, more connected north-facing slopes of the other badland are reshaped by means of gravitational processes, with mass wasting dominating topographic changes. In terms of processes determining surface raising, both mass wasting and cutting and filling are most frequently observed in both badlands. There is a clear near-balanced feedback between both surface-raising and -lowering processes that becomes unbalanced at larger temporal scales due to the thresholds overcome, as the volume associated with surface lowering becomes higher than that associated with raising-based processes. Rainfall variables control surface flow processes, while those variables associated with low temperature have a significant relation with mass movement-based processes and other localized processes such as regolith cohesion loss. Finally, our results point out that morphometry (slope and connectivity) together with vegetation cover are key factors determining geomorphic processes and associated topographic changes. © 2020 John Wiley & Sons, Ltd.     

Power law or power flaw?

Since its introduction by Svensson in 1959, the power law curve y = ax^b (where x and y are horizontal and vertical direction, respectively) has been widely used in morphological analysis of glacial trough cross-profiles. The numerical constants a and b are obtained by a linear regression analysis of the logarithmic form of the power law curve (ln y = ln a + b ln x). The value b then gives a measure for the form of the cross-section. However, over the years this form of the power law has endured a lot of criticism. This criticism is well founded, since this particular form of the power law is not suitable for curve fitting in morphological analyses. In this paper a general power law is proposed, of the form y − y₀ = a|x − x₀|^b (where x₀, y₀ are the coordinates of the origin of the cross-profile). A unique and unbiased solution for this equation is obtained with a general least-squares method, thereby minimizing the error between the cross-profile data and the curve, and not between the logarithmic transform of the data and its regression line. This provides a robust way to characterize trough cross-section forms. © 1998 John Wiley & Sons, Ltd.     

基于图像识别的5个不同产地克氏原螯虾(Procambarus clarkii)形态差异分析

为了解江苏、江西、湖北、上海、河南5个地区克氏原螯虾（Procambarus clarkii）的形态差异和获取快速、有效的形态鉴别方法,本研究采用传统形态测量法和地标点法来分析各产地形态差异。结果显示：（1）克氏原螯虾雌雄群体相对扭曲主成分分析,前三个主成分累计贡献率分别为79.96%、67.21%,传统形态测量法前三个主成分累计贡献率分别为76.77%、82.70%,两种方法均表明其形态差异主要体现在头胸甲及腹部部位;（2）聚类分析将克氏原螯虾5群体聚为两支,上海、河南、江西、湖北群体聚为一支,江苏群体单独聚为一支。（3）地标点法雌雄群体综合判别准确率分别为100%、94%,传统形态测量法综合判别准确率均为56%。以上研究结果表明不同产地间克氏原螯虾具有一定的形态差异,且地标点法区分不同产地克氏原螯虾群体差异性效果显著,这将有利于克氏原螯虾生产和选育过程中群体的鉴别及外形特征的快速获取。     

New formulae for estimating lava flow volumes at Mt. Etna Volcano, Sicily

 A new data set of Etna lava flows erupted since 1868 has been compiled from eight topographic maps of the volcano published at intervals since then. Volumes of 59 flows or groups of flows were measured from topographic difference maps. Most of these volumes are likely to be considerably more accurate than those published previously. We cut the number of flow volumes down to 25 by selecting those examples for which the volume of an individual eruption could be derived with the highest accuracy. This refined data set was searched for high correlations between flow volume and more directly measurable parameters. Only two parameters showed a correlation coefficient of 70% or greater: planimetric flow area A (70%) and duration of the eruption D (79%). If only short duration (<18 days) flows were used, flow length cubed, L³, had a correlation coefficient of 98%. Using combinations of measured parameters, much more significant correlations with volume were found. Dh had a correlation coefficient of 90% (h is the hydrostatic head of magma above the vent), and  , 92% (where W is mean width and E is the degree of topographic enclosure), and a combination of the two , 97%. These latter formulae were used to derive volumes of all eruptions back to 1868 to compare with those from the complete data set. Values determined from the formulae were, on average, lower by 16% (Dh), 7% (, and 19% . Received: 30 November 1998 / Accepted: 20 June 1999