Valley Orientation Research Articles

Geomorphic History Determined by a New Glacial History Paradigm and Topographic Map Interpretation, Towanda Creek Drainage Basin, PA (USA)

Pennsylvania’s Towanda Creek drainage basin geomorphic history is determined by using a recently proposed geology and glacial history paradigm (which predicts massive and prolonged southwest oriented continental ice sheet meltwater floods flowed across Pennsylvania) when interpreting previously unexplained topographic map drainage system and erosional landform evidence. The new paradigm explains most of the region’s erosional landforms including barbed tributaries, drainage divides, through valleys (valleys crossing drainage divides), water and wind gaps, valley orientations, entrenched meanders, through valley and gap floor elevations, regional ridge crest elevations, upland area elevations, and intervening lowland elevations. The new paradigm suggests the present-day northeast-oriented Towanda Creek drainage basin formed as immense and prolonged southwest-oriented floods first lowered a low relief surface (now preserved if preserved at all by the region’s highest elevations) in the area between the present-day northeast-trending Blossburg and Barclay synclinal uplands and also to the south of the Barclay synclinal upland. Those floodwaters after flowing across the present-day northeast-oriented Towanda Creek drainage basin flowed in a southwest direction through the now southwest-oriented Lycoming and Loyalsock Creek drainage basins and then to and along a now northeast oriented West Branch Susquehanna River valley segment before continuing in a southwest direction along what is now the Allegheny Front. Headward erosion of today’s southeast-oriented North Branch Susquehanna River valley segment between Pittston and Athens, Pennsylvania captured and reversed the beheaded southwest-oriented floodwaters to create the northeast-oriented Towanda Creek drainage system seen today.

Modelling the Contributions of Riparian Vegetation and Topography to Stream Shade Using LiDAR and Conventional Digital Elevation Data

ABSTRACTStream temperature is widely considered the master variable in stream ecosystems. One of the key drivers of diel and seasonal stream temperature variability is the solar radiation received at the stream surface, which can be influenced by shading associated with both larger scale topographic features and riparian vegetation. In this study, a stream shade model was developed that uses LiDAR point cloud data to model shading by riparian vegetation, including canopy overhang, and conventional elevation data to model stream shading by topography. The model was applied to a dominantly north–south oriented river flowing in a floodplain within a mountain valley. When compared with shade interpreted from PlanetScope visual imagery, the model predicted stream shade at the point scale with 92% agreement. Sources of error were attributed to pixel and azimuth band size, which can be refined within the model arguments, although at the cost of increased processing time. The shade model was re‐run after virtually rotating the reach by 90° and 270° clockwise to evaluate the effect of valley orientation. Peak reach‐wide sunlight exposure occurred approximately 2 h later in the day when the stream reach was rotated 90°, and produced greater shading from mid‐morning to mid‐afternoon. Further work should test the model on smaller streams using ground‐based oblique or drone‐based photography to provide ground‐truthing, particularly to assess the accuracy of predicted shade below over‐hanging vegetation.

The interplay of lithology, tectonics and climate in the morphology of Corsica

The morphology of the landscape on the island of Corsica in the western Mediterranean Sea is transient with a clear topographic asymmetry. The geology of the island can be divided into two units – Hercynian Corsica and Alpine Corsica – with contrasting lithology, climate and structural controls between them. We used topographic analysis to assess the influence of each of these factors on landscape form. Disequilibrium in the landscape is illustrated by analysing χ and Gilbert metrics, which indicate active migration of the drainage divide, along with a new metric that quantifies tributary heights above the main stem channel. The climate in the region has fluctuated dramatically from the Messinian salinity crisis through to Quaternary glaciation. However, analysis of the size and distribution of knickpoints across the island does not reflect specific base-level changes. Instead, the basement structures control valley orientation and the conditioning of the landscape by glaciation exerts strong controls on drainage evolution.

Study on the impact of valley orientation on solar radiation shading of roofs in western Sichuan

Solar energy is a commonly used renewable energy source in buildings. In the high-altitude mountainous regions of western Sichuan, solar energy resources are abundant, but the complex and variable terrain significantly affects the shading of solar radiation on building roofs. In the mountainous regions of western Sichuan, towns located in valley terrain are the most prevalent, accounting for as much as 42.14%. Therefore, based on the mountainous solar radiation estimation method, this study estimates the direct radiation shading rate and diffuse radiation shading rate for building roofs in the valley towns of western Sichuan. The research delves into the analysis of the impact of valley terrain characteristics on the shading of solar radiation on building roofs. The study reveals that, for a specific valley town, the orientation of the valley has a more significant impact on the shading of direct radiation compared to its impact on diffuse radiation. When the town's orientation approaches an east-west direction, both direct and diffuse radiations are less affected by terrain shading.

High‐intensity bird migration along Alpine valleys calls for protective measures against anthropogenically induced avian mortality

AbstractThe Alps are a natural barrier for avian broad‐front migration in Central Europe. While most birds that approach the Alps are deflected and circumvent the mountains, some choose to make the crossing. Here, they are funnelled and channelled in valleys, leading to high bird densities. Many Alpine valleys are suitable locations for wind farms, potentially creating a conflict between wind energy production and bird conservation. Collisions can be reduced by temporarily shutting down wind turbines. This however requires timely coordination, either by locally monitoring migration intensity or by extrapolating and forecasting migratory fluxes from other sites. However, little is known about the timing and intensity of bird migration in valleys of the central Alps, especially during spring migration. This study presents a 2‐year quantification of avian migration across the Alps. We collected terrestrial radar data at three sites: two located in Alpine valleys and one in the lowland, close to the northern foothills of the Alps. We found high migration traffic rates (MTR) during both migration seasons in the Alpine valleys, with outstanding numbers of migrants during the spring season. The strong alignment of the flight directions with the main orientation of alpine valleys highlights the importance of valleys and the connected passes in channelling migratory fluxes through the Alps. However, extrapolating migration intensities and forecasting peak migration events for inner Alpine sites is difficult, likely due to how migratory patterns and activity are influenced by the complexity of the local topography and the associated dynamic wind and weather conditions. Instead, we call for year‐round on‐site monitoring of migration intensities and strategies tailored to the local context to reduce the risk of bird strikes at wind turbines in the Alps.

Source Determination of Debris Avalanche Deposit based on the Morphology and Distribution of Hummocky Hills on the Northeastern Flank of G. Sundoro and G. Sumbing, Central Java, Indonesia

The presence of hummocky hills as a typical product of debris avalanche deposits is prominently visible in the northeastern flank of G. Sundoro and G. Sumbing, Temanggung, Central Java. In an attempt to better understand the past behavior of both G. Sundoro and G. Sumbing, we identify the source of the debris avalanche deposit. Interpretation is performed on the basis of the assumption of two possible sector collapse sources, i.e., G. Sundoro and G. Sumbing. The Sumbing source scenario is assumed as freely spreading type considering 1) distribution of the hummocky hills are relatively on the northeastern flank of the volcano, and 2) the present crater structure on the summit of the volcano which is opening to the northeast. The Sundoro source scenario is assumed as valley-filling type considering the distribution of the hummocky hills are relatively on the eastern flank of Sundoro extended to the far distal area and bounded by older high topography of G. Sumbing and North Serayu Mountains. The source identification was done on the basis of field observation of the deposit lithological characteristics combined with image analysis, including hummocky hills morphometry, displacement angle, and spatial distribution. Image analysis identifies approximately 645 hummocky hills ranging from 1,851 mz to 623,828 mz and average of 23,482 m2. Petrographic analysis of 5 representative block lava samples shows variation of olivine basalt, pyroxene andesite, to hornblende andesite. The results show that big size hummocky hills dominate the western side, while small size on the east. Displacement angle varied following the valley orientation with typical downslope topography. These suggested that the hummocky hills were originated from G. Sundoro as a valley-filling debris avalanche deposit.

Morphology and genesis of the Yaselda glacial valleys in Belarus

Geological mapping revealed the oldest Yaselda (Don (on the territory of Russia), Sanian 1 (on the territory of Poland)) generation of valleys in the Quaternary strata. Valleys are widespread in marginal and inner zones of the Yaselda glaciation area. They are located in the pre-Yaselda lowlands, in the areas of deformable deposits that lie above the more hard rocks protrusion and in fault systems. The distribution of glacial valleys is depends on the radial-sectoral structure and dynamics of the Yaselda glacier, which predetermined both the common and regional features of the valley regularity and morphology. The common features are the location in lobed sectors, occurrence in heterochronous ice marginal complexes, the predominance of polygenetic valleys. The regional features include isolated position, submeridional and meridional orientation, smaller size and weak expression of valleys in the maximum phase relief, the predominance ofvalleys of glacial exaration and extrusion and tunnel valleys. Valleys of the younger (Novogrudok) phase are located in the marginal complexes of the Middle Neman, Naliboky and Middle Berezina ice lobes and tongues. Valleys are characterised by connection with the belt of marginal highlands, sublatitudinal large-festoon ordering on the area of the lobes and a fan structure in the tongues, large size and maximum depths, clear expression in relief. Here, mainly polygenetic basins and trough valleys, extrusion valleys and subglacial tunnel valleys have been established. Basins arose simultaneously with the advance of outlet glaciers and are the result of exaration and glaciotectonic overthrusts of substrate rocks in the territory of the Belarusian anteclise and lowlands enveloping from the north. Their formation became possible at the regressive stage, when the readvances of the ice lobes led to the extrusion of a large amount of bed material and its accumulation in the basin borders. Trough valleys arose due to the wedging of outlet glaciers into paleovalleys or selective linear erosion along zones of structural weakening. In areas of rock bed, they were formed by plucking and abrasion, and in areas of soft substrate – by plucking, removal of thrust blocks. Numerous extrusion valleys appeared due to the extrusion in the Meso-Cenozoic deposits from under the glacial tongues into the marginal zones during the glacial retreat phase. Tunnel valleys originated as a result of canal erosion of sediments during rapid outbursts of water from subglacial lakes established for the glacier reduction phase. Most of the large valleys are of polygenetic origin.

Physisorption of trichloroethylene and tetrachloroethylene on novel zeta arsenene nanotubes – A first-principles study

The structural stability of novel ζ-arsenene nanotubes (ζ-AsNT) is studied based on the density functional theory framework and is used as a base material for the detection of trichloroethylene and tetrachloroethylene vapours. The formation energy of ζ-AsNT is found to be −4.321 eV/atom and the energy band gap is 0.304 eV. Besides, the changes in the electronic properties of ζ-AsNT are explored with regard to the projected density of states, charge transfer, and electron density difference. The bandgap energy decreases for hollow site orientation to 0.205 and 0.204 eV for trichloroethylene and tetrachloroethylene vapours and increases for the valley and top site orientations. The adsorption energies were maximum for the valley site orientation of target molecules onto ζ-AsNT (01.165 and −1.513 eV for trichloroethylene and tetrachloroethylene, respectively). Moreover, the target vapours trichloroethylene and tetrachloroethylene are physisorbed on ζ-AsNT enabling the recycling of base substrate for continuous operation. The average energy gap changes vary from 18 to 32.9% depending on adsorption sites. The variation in the average energy gap owing to adsorption of trichloroethylene and tetrachloroethylene indicates the chemo-sensing nature of ζ-AsNT. The current report lays the inroads in the development of a new sensing element for the detection of chloroethylene molecules.

Discordance analysis on a high-resolution valley network map of Mars: Assessing the effects of scale on the conformity of valley orientation and surface slope direction

Fluvial valleys incised into planetary surfaces display morphologies, geometries and orientations that can be used to understand their controlling processes. Comparisons between valley orientations and topographic surface slope direction have been used to understand how Martian surfaces have evolved (Luo and Stepinski, 2012; Black et al., 2017); however, new insights from terrestrial studies have revealed that the slope needs to be defined on a scale commensurate with the length of valley (Lipp and Roberts, 2020). We propose and test a new map-based framework for interpreting the difference between Martian valley orientation and surface slope direction (discordance) at varying spatial scales. Valleys and inverted channels were manually mapped in a latitudinal strip from pole to pole between 20°E–20°W using High/Super Resolution Stereo Colour Imager images (15 to 25 m per pixel). The orientation of incisional valleys, associated with fluvial activity, were compared with topographic slope direction at varying scales (463 m, 1 km, 10 km and 50 km). High-resolution mapping resulted in ~1.5 times the density (0.02 km/km2 on average) of the previous valley map (Hynek et al., 2010), which raises the possibility that water volumes necessary to carve valleys were greater than previously thought. The distribution of valleys is similar to previous valley maps, however there are areas where valleys were identified that have previously remained undetected in low resolution images. The scale over which one compares valley orientation to surface slope direction has a clear effect on the apparent conformity between Martian valley orientation and topographic slope direction, with smaller valleys conforming more closely with smaller scale topography. To account for scale we perform discordance analysis with the spatial scale of surface slope direction varying based on valley length. When scale is accounted for, there is a greater conformity between valley orientation and surface slope direction, however only ~38% of valleys display conformity, indicating other sources of high discordance. We find that the source of the high values of discordance are likely a result of a combination of valley immaturity, attesting to the arid nature of the Late Noachian – Early Hesperian climate, but also the palaeolake outburst and, possible, subglacial origin of some valley networks. Considering a large proportion of valleys do not display conformity with topography, we suggest that a discordance analysis of the kind reported here is an important preliminary to any hydrodynamic analysis that relies on topographic information.

Incision and aggradation phases of the Amazon River in central-eastern Amazonia during the late Neogene and Quaternary

The development of the Amazon River as a transcontinental drainage has been narrated in terms of the sedimentary record in western Amazonia and in marine offshore areas. However, little is known about the landscape changes in central-eastern Amazonia, which is considered a former water divide prior to the establishment of the Amazon as a transcontinental drainage. In this study, we carried out geomorphological and sedimentary facies analyses of fluvial deposits associated with the Amazon River in central-eastern Amazonia. Additionally, extended range luminescence ages and sediment provenance data are used to help to improve the chronostratigraphic framework of the study area. Erosive scarps bound the Amazon River valley in the study area, where higher elevation upland terrains (locally called ‘terra firme’) are sustained by older and resistant bauxitic-lateritic paleosols that cap the Cretaceous sandstone bedrock. Two abandoned fluvial terraces (T3 and T2), representing lower elevation terra firme, and the active floodplain (T1), collectively record the incision and aggradation phases of the Amazon River in a NE-SW oriented valley since the Late Miocene. The T3 is intensely dissected and has weathered deposits with surface elevations between 30 and 50 m above sea level (a.s.l.). These deposits are composed of gravel with boulders, coarse sand, and locally grey mud rich in organic matter. Quartz thermally-transferred optically stimulated luminescence (TT-OSL) dating allows us to determine the oldest Quaternary ages reported for fluvial terraces associated with the Amazon River. Depositional ages for the T3 deposits range from 944 ka to 2.3 Ma. The T2 deposits form a flat area with surface elevations between 25 and 30 m a.s.l. These deposits comprise fine to medium sand interbedded with mud and locally coarse sand and mud alternations forming inclined heterolithic stratification. Feldspar post-infrared infrared (pIRIR290) luminescence ages indicate an incision and aggradation phase leading to deposition of the T2 from 557 to 140 ka. The T1 represents the active floodplain with a surface elevation lower than 25 m a.s.l. These deposits are composed of moderately to well-sorted silty fine sand and greyish mud. OSL sensitivity measurements suggest that deposits from all terraces are formed by a mixture of Andean and shield-cratonic sediments, which are similar to the sediments transported by the modern Amazon River. The fractures in the Paleozoic to Cretaceous bedrock that comprises the higher elevation terrain incised by the Amazon River in central-eastern Amazonia lead to differential fluvial erosion, shaping the current NE-SW and NW-SE valley orientation. The T3 and T2 terraces record the progressive incision of the Amazon River valley since the Late Miocene, leading to poor preservation of fluvial deposits in comparison with western Amazonia. Here in central-eastern Amazonia, fluvial activity has been locked into a narrow fluvial valley in comparison with a wide area in western Amazonia. The stratigraphic scenario with a limited accommodation space favoured the recycling of terraces within the Amazon River valley. The restricted distribution of deposits associated with the Amazon River in central-eastern Amazonia is attributed to the uplift behaviour and high erosional resistance of the Paleozoic and Mesozoic bedrock forming a high elevation plateau. During the Pleistocene, the T3, T2 and T1 deposits record at least three main phases of incision, which promoted the abandonment of floodplains and formation of new lowland terra firme areas.

Thermally and Dynamically Driven Atmospheric Circulations over Heterogeneous Atmospheric Boundary Layer: Support for Safety Protocols and Environment Management at Nuclear Central Areas

Ilha Grande Bay is located in Angra dos Reis, Rio de Janeiro State, Brazil. The area is characterized by different land cover, complex topography and proximity to the Atlantic Ocean. These aspects make it susceptible to thermally and dynamically induced atmospheric circulations such as those associated with valley/mountain and land/sea breeze systems, among others. The Almirante Álvaro Alberto Nuclear Complex (CNAAA) is located in this region, with a total of two nuclear power plants (NPPs) in operation in the Brazilian territory, Angra I and Angra II. Therefore, knowledge of local atmospheric circulation has become a matter of national and international security. Considering the importance of the meteorological security tool as a support for licensing, installation, routine operation and nuclear accident mitigation, the main aim of this study is the development of combined strategies of environmental statistical modeling in the analysis of thermally and dynamically driven atmospheric circulations over mountainous and coastal environments. We identified and hierarchized the influence of the thermally and mechanically driven forcing on the wind regime and stability conditions in the coastal atmospheric boundary layer over the complex topography region. A meteorological network of ground-based instruments was used along with physiographic information for the observational characterization of the atmospheric patterns in the spatial and time–frequency domain. The predominant wind directions and intensity are attributed to the combined action of multiscale weather systems, notably, the valley/mountain and continent/ocean breeze circulations, the forced channeling due to valley axis orientation, the influence of the synoptic scale systems and atmospheric thermal tide. The observational investigation of the combined influence of terrain effects and meteorological systems aimed to understand the local atmospheric circulation serves as support for safety protocols of the NPPs, contemplating operation and environmental management. The importance of the study for the adequacy and skill evaluation of computational modeling systems for atmospheric dispersion of pollutants such as radionuclide and conventional contaminants can be also highlighted, in order that such systems are used as tools for environmental planning and managing nuclear operations, particularly those located in regions over mountainous and coastal environments with a heterogeneous atmospheric boundary layer.

Topographic Map Analysis of the North Platte River-South Platte River Drainage Divide Area, Western Larimer County, Colorado, USA Eric Clausen

The United States Supreme Court settled legal disputes concerning four different Larimer County (Colorado) locations where water is moved by gravity across the high elevation North Platte-South Platte River drainage divide, which begins as a triple drainage divide with the Colorado River at Thunder Mountain (on the east-west continental divide and near Colorado River headwaters) and proceeds in roughly a north and northeast direction across deep mountain passes and other low points (divide crossings) first as the Michigan River (in the North Platte watershed)-Cache la Poudre River (in the South Platte watershed) drainage divide and then as the Laramie River (in the North Platte watershed)-Cache la Poudre River drainage divide. The mountain passes and nearby valley and drainage route orientations and other unusual erosional features can be explained if enormous and prolonged volumes of south-oriented water moved along today’s north-oriented North Platte and Laramie River alignments into what must have been a rising mountain region to reach south-oriented Colorado River headwaters. Mountain uplift in time forced a flow reversal in the Laramie River valley while flow continued in a south direction along the North Platte River alignment only to be forced to flow around the Medicine Bow Mountains south end and then to flow northward in the Laramie River valley and later to be captured by headward erosion of the east-oriented Cache la Poudre River-Joe Wright Creek valley (aided by a steeper gradient and less resistant bedrock). Continued uplift next reversed flow on the North Platte River alignment to create drainage routes seen today. While explaining Larimer County North Platte-South Platte drainage divide area topographic map drainage system and erosional landform evidence this interpretation requires a completely different Cenozoic history than the geologic history geologists usually describe.

Valley Orientation of Electrons and Excitons in Atomically Thin Transition Metal Dichalcogenide Monolayers (Brief Review)

The main aspects of physical phenomena associated with the optical orientation of the spin and valley degrees of freedom in transition metal dichalcogenide monolayers and in van der Waals heterostructures based on them have been briefly reviewed. Owing to features of the band structure and spin–orbit coupling in such systems, circularly polarized light induces optical transitions in different valleys K+ and K– of the Brillouin zone; consequently, the optical orientation of charge carriers and excitons is accompanied by their valley polarization. The main features of the band structure of transition metal dichalcogenide monolayers, excitonic effects, and results of theoretical studies of the valley orientation of excitons and electrons at one-photon absorption have been reported. The linear–circular dichroism and valley orientation of free charge carriers and excitons at multiphoton absorption have been studied. Effects associated with the trigonal symmetry of monolayers, including the inversion of valley polarization at two-photon transitions and the second harmonic generation, have been discussed. The considered theoretical models have been illustrated by experimental data.

Inverted dune swales, Hunder, Ladakh, India

ABSTRACT The Hunder Dunes occur in the Shyok valley, Ladakh region, north-western India. These barchanoid and transverse dunes consist of sand reworked from the seasonally exposed beds of the river. Wind direction is strongly uni-modal from the northwest and is controlled by valley orientation. We observed small (10–20 m long, 5–10 m wide, and up to 1.5 m high) ellipsoidal mesas in the swales between dunes, composed of sand deflated from the Shyok River system. The mesas have a tiered, wedding cake appearance with concave upper surfaces. We interpret these mesas as inverted swale deposits consisting of stacked cycles of sediment. The cycles range from 40 to 50 cm in thickness and are composed of a from bottom to top, deposits of prior dunes, high energy fluvial deposits with climbing ripples, pool sediments with symmetrical wave ripples, and desiccation-cracked mud drapes over the ripples indicating final drying out of the pool. Up to four cycles of deposition were present in the mesas. The inverted swales are being both exhumed from beneath and buried underneath migrating dunes. Inverted swale deposits provide a record of historical depositional processes and biological communities active at the site.

Salt‐induced crestal faults control the formation of Quaternary tunnel valleys in the southern North Sea

Tunnel valleys are major features of glaciated margins and they enable meltwater expulsion from underneath a thick ice cover. Their formation is related to the erosion of subglacial sediments by overpressured meltwater and direct glacial erosion. Yet, the impact of pre‐existing structures on their formation and morphology remains poorly known. High‐quality 3D seismic data allowed the mapping of a large tunnel valley that eroded underlying preglacial delta deposits in the southern North Sea. The valley follows the N–S strike of crestal faults related to a Zechstein salt wall. A change in downstream tunnel valley orientation towards the SE accompanies a change in the strike direction of salt‐induced faults. Fault offsets indicate important activity of crestal faults during the deposition of preglacial deltaic sediments. We propose that crestal faults facilitated tunnel valley erosion by acting as high‐permeability pathways and allowing subglacial meltwater to reach low‐permeability sediments in the underlying Neogene deltaic sequences, ultimately resulting in meltwater overpressure build‐up and tunnel valley excavation. Active faults probably also weakened the near‐surface sediment to allow a more efficient erosion of the glacial substrate. This control of substrate structures on tunnel valley morphology is considered as a primary factor in subglacial drainage pattern development in the study area.

A multivariate statistical method for susceptibility analysis of debris flow in southwestern China

Abstract. Southwestern China is characterized by many steep mountains and deep valleys due to the uplift activity of the Tibetan Plateau. The 2008 Wenchuan earthquake left large amounts of loose materials in this area, making it a severe disaster zone in terms of debris flow. Susceptibility is a significant factor of debris flows for evaluating their formation and impact. Therefore, there is an urgent need to analyze the susceptibility to debris flows of this area. To quantitatively predict the susceptibility of the area to debris flows, this study evaluates 70 typical debris flow gullies, which are distributed along the Brahmaputra River, Nujiang River, Yalong River, Dadu River, and Ming River, as statistical samples. Nine indexes are chosen to construct a factor index system and then to evaluate the susceptibility to debris flow. They are the catchment area, longitudinal gradient, average gradient of the slope on both sides of the gully, catchment morphology, valley orientation, loose material reserves, location of the main loose material, antecedent precipitation, and rainfall intensity. Following this, an empirical model based on the Type I quantification theory is established for susceptibility prediction for debris flows in southwestern China. Finally, 10 debris flow gullies upstream of the Dadu River are analyzed to verify the reliability of the proposed model. The results show that the accuracy of the statistical model is 90 %.

Tunnel valleys of the central and northern North Sea (56°N to 62°N): Distribution and characteristics

The analysis of buried tunnel valleys in the North Sea can provide information about the past configuration and dynamics of the Scandinavian and British ice sheets and the processes by which sediment and meltwater were transported at the ice-sheet base. However, little is presently known about the distribution and characteristics of tunnel valleys in the Norwegian sector of the North Sea. Here we use an extensive database of 3D seismic and high-resolution magnetic data to map >2200 tunnel valleys in the Norwegian and British sectors of the North Sea between 56°N and 62°N. With the exception of the deep Norwegian Channel, in which evidence for tunnel valleys is absent, the geological setting of the North Sea is interpreted to have been conducive to tunnel-valley formation and preservation because of its poorly consolidated substrate and shallow water depths. The highest density of tunnel valleys is located in the central part of the North Sea where Quaternary sediments are thickest. The extreme length of some of the tunnel valleys, which are up to 155 km long, supports theories that tunnel valleys form in stages rather than catastrophically. Detailed analysis of the orientation of tunnel valleys and their relative age relationships within four representative subareas shows that tunnel-valley orientation varies significantly across the central and northern North Sea and between different generations of valleys. This suggests that the pattern of subglacial meltwater drainage in the central and northern North Sea was different between each deglacial event in which tunnel valleys were formed.

Age determination for valley networks on Mars using tectonic-fluvial interaction

Two areas on Mars in the old Thaumasia region were analysed, where interaction between fluvial and tectonic landforms provided conditions to improve age estimation for valley network formation. An Earth analog terrain was also involved in this work at Villány Hills (Hungary) for reference and to see the relations in tectonic-fluvial interaction. On Mars such interaction was observed by morphology (parallel curvatures of neighbour valleys) and by the comparison of statistical analyses of the fluvial and tectonic lineaments’ azimuthal orientation. While in the case of Mars the fluvial network elements’ distribution closely follows that of the tectonic elements’ distribution, in the case of the Earth the connection is weaker. The comparison gives an interesting example for tectonic landforms controlling fluvial valley orientations, occasionally producing resembling features in valley tracks, influencing the sediment transport and the locations of deposits.Because the tectonic faults crossed a much larger area than the fluvial valleys they influenced, crater size frequency distribution based ages could be better measured with them. Using this approach, we found the minimal age of the fluvial network formation to be around 3.7 Ga (or up to 3.9 Ga). This result demonstrates that the small, scattered, and poorly integrated valleys might also have formed at the same period as the larger, branching systems with well determined ages: around the Noachian/Hesperian transition. Thus valley network formation even in the case of small, non-integrated systems might not necessarily extend into the early or middle Noachian ages and might have happened at a potential climatic optimum around 3.7 Ga ago. However the most difficult task remains the exact dating of old and small valleys at other locations on Mars, to confirm this possibility.

Geomorphometric analysis and terrain evaluation for environmental management in the Kurseong hill subdivision of the Darjeeling district, West Bengal, India

Kurseong hill subdivision of the Darjeeling district, West Bengal, is associated with complex geomorphic set-up stemmed from form–process interaction on varied slope, relief, elevation, aspects, ridge–valley orientation, density and frequency of drainage, dissection, ruggedness and topographic wetness over different stratigraphy of geological rocks having different hardness. This complexity provides ample scope to evaluate the terrain and categorize the terrain into different sensitivity zones according to land utilization point of view so that different terrain segments can be classified into different grades and therefore can be rationally utilized and managed for sustainable use. Therefore, the present paper takes an attempt to evaluate the terrain sensitivity of the Kurseong hill subdivision based on multi-criteria analysis method to identify different grades of terrain according to their ability to hold and sustain the pressure of land utilization for settlements, agriculture and other land uses. Terrain sensitivity evaluation of the Kurseong hill subdivision has been done on the basis of the study of hard rock geology, some selected geomorphometric parameters derived from 3-arc-second SRTM digital elevation data as well as SOI toposheets having RF of 1:50,000 and the existing land use factors after necessary ground truthing on some selected sites. The procedure adopted for multi-criteria analysis is 1 km2 grid-based rating value assignment algorithm of the selected parameters and determination of different classes of sensitive terrain and their gradation according to the capacity of the terrain to withstand present pressure of land utilization. Some measures for rational land utilization and management have also been proposed for optimal land use planning for the study area.

Characterizing Alpine pyrogeography from fire statistics

In this paper, we describe current fire characteristics in the Alpine region using a ten-year forest fire record at the third and lowest resolution of the European Classification of Territorial Units for Statistics (NUTS3). To this purpose, we performed hierarchical clustering based on the Bray-Curtis dissimilarity index on five pyrogeographic metrics. This resulted in three main geographically well-distinguished clusters (Southern, Northern, and Maritime Alps) and two small groups of outliers. From a geographic point of view, we found a clear differentiation between the high fire density on the southern slope of the Alps and the substantially lower proportion of burnt areas registered in the north. The most relevant climatic (e.g., frequency and length of drought periods), environmental (e.g., vegetation types, mean elevation and predominant orientation of valleys), and socio-economic (e.g., population density and educational level) drivers for the described clusters of fire characteristics were also identified. The proposed pyrogeographic characterisation may represent an important baseline for detecting future shifts in fire occurrence or anomalous fire seasons.