fulgurite morphology a classification scheme and clues to formation fulgurites are natural glasses formed by cloud to ground lightning several different morphologies of fulgurites have been reported in previous studies including sand fulgurites rock fulgurites and clay fulgurites herein we examine sand clay and caliche fulgurites and demonstrate that these differ systematically in their morphology we further use morphological features to constrain properties of fulgurite forming lightning strikes we classify fulgurites into four types of morphologies with an additional minor type type i fulgurites are sand fulgurites consisting of thin glass walls type ii fulgurites are clay fulgurites consisting of thick melt rich walls type iii fulgurites are caliche fulgurites consisting of thick glass poor walls and type iv fulgurites are rock fulgurites consisting of glasses with walls consisting of surrounding unmelted rock fulgurite morphology shows that the energy of fulgurite forming strikes is between 1 and 30 mj m of fulgurite formed suggests heating rates in the order of 1 000 k s and lightning channel thicknesses of about 1 mm diameter lightning generates mixtures of at least two components in most fulgurites an sio2 glass identified as lechatelierite and a groundmass of more varied composition in addition to these four primary types a fifth type droplet fulgurites is morphologically dissimilar from the other types but is compositionally related to the type ii or iv fulgurites additionally two fulgurites both from york county pennsylvania usa showed the reduction of iron to iron metal with an assortment of fe ti and si p compounds with stoichiometry that ranges from nearly pure fe metal to fesi these metal silicides include stoichiometric fe3si fe2si and fe5si3 and possibly fe8si3 and fe7si3 and provide a terrestrial source for these phases which are typically associated with extraterrestrial material

active tectonics and geomorphology of the gaenserndorf terrace in the central vienna basin austria abstract in the central vienna basin the area north of the river danube is dominated by large river terraces consisting mainly of coarse sandy gravels and sand deposited by the danube and the morava river irsl dating for the terrace body yielded minimum ages from about 200 to 300 ka the terrace deposits are locally covered with loess and aeolian sand of the last glacial period revealing osl irsl ages of about 15 ka the terraces are dissected by a system of normal faults one of these faults the aderklaa bockfliess fault was investigated in 2014 by paleoseismological trenching eventually the exact fault location and its vertical offset of 10 m were defined by combining electrical resistivity measurements and the analysis of remote sensing data in addition at the northern part of this so called gaenserndorf terrace high resolution digital terrain models based on lidar measurements show landforms comparable with relief features resulting from permafrost degradation large elongated and clam shaped depressions are interpreted as basins of former thermokarst lakes current dry valleys are interpreted as the pleistocene drainages of the terrace surface the cryogenic morphology is preserved only in the elevated parts of the terrace and therefore in the footwall of the bounding normal faults in contrast quaternary basins of the hanging wall are filled with up to 40 m thick pleistocene and holocene growth strata therefore most characteristics of the recent geomorphology can be interpreted as a result of overlapping neotectonic processes and permafrost degeneration during the pleistocene

unusual features caused by lightning impact in west greenland two lightning impacts are described from an area near the inland ice in west greenland the first lightning blasted an outcrop of metacherts it subsequently split into two branches which traversed rock outcrops and boulders leaving behind two white almost straight lines 30 m and 14 m long respectively where all lichens and plants were burned away on the white lines the upper few millimetres of the traversed boulders were melted to a glass which subsequently peeled off by thermal expansion to leave a rough surface magnetic investigation of an amphibolite boulder found on the white line showed that a strong electric current indeed traversed the boulder a few years later a second lightning impacted on a mountaintop close to the first impact the second lightning left a trail on the rock surface covered by a thin layer of glass the glass displays spectacular colours ranging from metallic blue to red yellow and green

compositionally diverse magmas erupted close together in space and time within a karoo flood basalt crater complex geochemical data and mapping from a karoo flood basalt crater complex reveals new information about the ascent and eruption of magma batches during the earliest phases of flood basalt volcanism flood basalt eruptions at sterkspruit south africa began with emplacement of thin lava flows before abruptly switching to explosive phreatomagmatic and magmatic activity that formed a nest of craters spatter and tuff rings and cones that collectively comprise a crater complex 40 km2 filled by 9 18 km3 of volcaniclastic debris rising magma flux rates combined with reduced access of magma to external water led to effusion of thick karoo flood basalts burying the crater complex beneath the 1 5 km thick lesotho lava pile geochemical data is consistent with flood basalt effusion from local dikes and some lava flows likely shared or re occupied vent sites active during explosive eruptions at sterkspruit flood basalt magmas involved in sterkspruit eruptions were chemically heterogenous this study documents the rapid perhaps simultaneous eruption of three chemically distinct basaltic magmas which cannot be simply related to one another from one vent site within the sterkspruit crater complex stratigraphic and map relationships indicate that eruption of the same three magma types took place from closely spaced vents over a short time during formation of the bulk of the crater complex two magma types recognized there have not been recognized in the karoo province before the variable composition of flood basalts at sterkspruit argues that magma batches in flood basalt fields may be small 0 5 1 km3 and not simply related to one another this implies in turn that heterogeneities in the magma source region may be close to each other in time and space and that eruptions of chemically distinct magmas may take place over short intervals of space and time without significant hybridisation in flood basalt fields

lightning as a geomorphic agent on mountain summits evidence from southern africa abstract the presence of angular bedrock derived debris on mountain summits worldwide has usually been associated with present or past periglacial frost shattering thermal fracturing and other climatically mediated weathering processes climatic inferences are commonly made based on such geomorphological evidence even if frost shattering and other processes are unlikely under present climatic conditions this paper questions this assumed genetic link between present past climate and production of angular bedrock derived debris by describing the geomorphological impacts of lightning strikes on exposed mountain summits using examples from the high drakensberg of eastern lesotho southern africa the impacts of lightning strikes are described which include the generation of angular fractured bedrock derived debris these impacts are identified in the field based on clear and unambiguous criteria that can be used to distinguish between lightning induced weathering processes and those processes associated with more typical alpine weathering this paper argues that lightning strikes are an important geomorphic agent of in particular low latitude mountain summits and that to make uncritical climatic inferences based on the presence of frost shattered debris on mountain summits is wholly erroneous

periglacial evolution of slopes rock control versus climate factors cracow upland s poland abstract this paper concerns the periglacial morphogenesis of slopes occurring on typical relief forms of the cracow upland namely 1 valleys with asymmetric slopes 2 undulating plateau with monadnocks and 3 the edge of the tectonic graben the research aims to reconstruct denudation processes and slope relief development based on the analysis of slope deposit distribution the analysis was carried out in the context of climate change during the last glacial cycle the upper vistulian evolution of slopes in the investigated area is mainly conditioned by the geological setting i e facies of jurassic limestones tectonics and presence of karstic forms on the other hand climate intensified and stimulated the type of denudation processes intensive denudation occurred in conditions of cold and wet climate in the phases of increasing and decaying permafrost during extremely frosty and dry climate in the phases of continuous permafrost denudation processes declined and loess deposition predominated in places the presence of soft deposits protected the substratum against weathering the following types of slope evolution dominated lateral recession development of convex concave slopes slope flattening and elongation and development of convex slope shapes steep slopes were laterally retreated gentle slopes were a lowered and elongated especially on the substratum made up of inclined bedded limestones and b transformed into convex concave slopes on substratum made up of different facies of limestones a convex profile in the lower part of gentle deluvial valley slopes originated as a result of cutting down by river erosion

controls on basalt terrace formation in the eastern lesotho highlands abstract the objective of this study is to ascertain the relative importance of lithological controls and geomorphological processes in the development of drakensberg basalt terraces various hypotheses for terrace formation are considered including geological controls macroscale geomorphology and climatic geomorphological controls the variations in strength and relative age differences for scarp surface exposures on two slopes of varying aspect are determined so that a comparison can be made between various scarp outcrops and relative rates of weathering scarp outcrops were measured for their rock mass strength rock surface roughness and percentage lichen cover the ethylene glycol test was performed on prepared rock samples to determine susceptibility to tensional breakup a satellite image depicting the distribution of late lying contemporary snow was used to assist in the construction of topo climatic linkages with scarp terrace localities findings show that terraces are most common on southeast facing aspects and coincide with the major joint strike direction lithological factors are thus considered the primary control to such terrace development it is suggested that a different set of geomorphological processes operates on various slope altitudinal and slope orientational positions at any given time

rock control on microweathering of bedrock surfaces in a periglacial environment abstract microweathering of ice smoothed bedrock surfaces was investigated in the roldal area of hardanger plateau 60 southern norway postglacial rates of weathering were determined from surface lowering using quartz veins as reference surfaces weathering processes are inferred from assessment of weathering rind formation surface hardness and the preservation of small scale glacial erosional features surface lowering rates for a range of metamorphic rocks vary from 0 05 to 2 20 mm ka 1 and are broadly comparable with those obtained from crystalline rocks in other periglacial environments the mean rate of surface lowering at 0 55 mm ka 1 is low and demonstrates the relatively small impact of microweathering on postglacial landscape evolution variations in bedrock microweathering can be explained by lithological variation amphibolite and mica rich bedrock surfaces experience greater denudation and weakening least weathering rind formation and abundant preservation of glacial striae despite greater surface lowering conversely quartz rich bedrock surfaces are most resistant to denudation and weakening but have greater weathering rind formation and fewer preserved striae postglacial microweathering is achieved primarily through granular disintegration involving detachment and removal of mineral grains and weakening from increased porosity granular decomposition is manifest in the formation of weathering rinds analysis of interactions between weathering indices indicates that rind accumulation is limited by microerosion a conceptual model is proposed that illustrates the temporal interrelationships between in situ and erosional facets of microweathering in two contrasting mineral assemblages the model proposes that cyclic processes of in situ disintegration decomposition and erosion are at work the relative balance between these processes varies with lithology so that in more resistant quartz rich rocks the net effect is minimal surface lowering and accumulation of weathering rind in weaker amphibolitic and micaceous rocks the net effect is greater surface lowering and minimal accumulation of weathering rind the results of the research demonstrate the important influence of rock properties notably mineral composition in postglacial microweathering of crystalline bedrock in a periglacial environment

new insights into rock weathering from high frequency rock temperature data an antarctic study of weathering by thermal stress a major limitation of many weathering studies has been the acquisition of rock temperature data at insufficiently frequent intervals for the meaningful determination of the rate of change of temperature t t equipment and or logistical constraints frequently facilitate temperature measurement at only hourly intervals or at best every 10 min such data are not adequate for the determination of t t required for the evaluation of the freeze thaw mechanism or thermal stress fatigue recent undertakings at different sites in antarctica and at other cold region locations provide rock temperature measurements at 1 min intervals which indicate that the perception of the weathering regime would be very different from that generally assumed from longer interval geomorphological data these data clearly show that thermal stress fatigue and thermal shock may be more active components of the antarctic weathering regime than have generally been recognised the aridity of the study area limits the role of freeze thaw weathering values of t t of 2 c min 1 that suggest thermal stress fatigue shock is operative were recorded observations of rock flaking are thought to reflect the impact of thermal stress further the data show that contrary to general perceptions the southern aspect can in summer experience higher rock surface temperatures than the north facing exposure an examination of rock fracture patterns found in the field shows great similarity to fracture patterns developed in the laboratory as a direct result of thermal shock the argument is made that greater cognizance should be given to thermal effects

the last ice sheet in north west scotland reconstruction and implications recent models of the last scottish ice sheet suggest that nunataks remained above the ice surface in areas peripheral to the main centres of accumulation this proposition has been investigated on 140 mountains over an area of 10 000 km2 in nw scotland outside the limits of the later loch lomond readvance in this area there is evidence for a single high level weathering limit that separates glacially eroded terrain from higher areas of in situ frost debris this limit occurs at altitudes ranging from 425 to 450 m in the outer hebrides to 950 m on the mainland and is best developed on lithologies that resisted breakdown after ice sheet downwastage interpretation of this weathering limit as a periglacial trimline cut by the last ice sheet at its maximum thickness is supported by 1 joint depth and schmidt hammer measurements that indicate significantly more advanced rock breakdown above the weathering limit 2 a much greater representation of gibbsite a pre late devensian weathering product in the clay fraction of soils above the limit 3 cosmogenic isotope dating of the exposure ages of rock outcrops above and below the limit 4 the sharpness of the limit at some sites and its regular decline along former ice flowlines and 5 shear stress calculations based on the inferred altitude and gradient of the former ice surface reconstruction of the ice surface based on trimline evidence indicates that the mainland ice shed lay near or slightly east of the present watershed and descended northwards from 900 m to ca 550 m at the north coast independent dispersion centres fed broad ice streams that occupied major troughs on skye an ice dome 800 m deflected the northwestwards movement of mainland ice but the mountains of rum were over ridden by mainland ice up to an altitude of ca 700 m the outer hebrides supported an independent ice cap that was confluent with mainland ice in the minches extrapolation of the trimline evidence indicates that most reconstructions of ice extent are too conservative and suggests that low gradient ice streams extended across the hebridean shelf offshore wider implications of this research are 1 that blockfields and other periglacial weathering covers are not all of the same age or significance depending on the resistance of different lithologies to frost weathering 2 that the contrasting degree of glacial modification in the western and eastern highlands of scotland may reflect a former cover of predominantly warm based ice in the former and predominantly cold based ice in the latter and 3 that the approach and techniques developed in this study have potential application for constraining ice sheet models not only in areas peripheral to the main centres of ice accumulation in britain and ireland but also in other mountain areas where nunataks protruded through warm based late pleistocene ice masses

felsenmeer persistence under non erosive ice in the torngat and kaumajet mountains quebec and labrador as determined by soil weathering and cosmogenic nuclide exposure dating soil analyses and terrestrial cosmogenic nuclide exposure dating are combined and a conceptual model proposed to explain altitudinal weathering contrasts in high latitude highlands we show that summits in the torngat and kaumajet mountains were covered by ice during the last glacial maximum and that their felsenmeer cover probably survived multiple glaciation events for similar lithologies soils on felsenmeer covered summits are signigicantly more weathered than those below the felsenmeer limit displaying higher concentrations of crystalline iron amorphous aluminium and silicium extracted with oxalate secondary minerals such as gibbsite and kaolinite occur in felsenmeer soils whereas those formed in till lacked these secondary minerals 10be and 26al exposure ages for nine of ten samples from high elevation tors and autochthonous felsenmeer blocks range from 73 6 to 157 15 ka by contrast ages of 11 4 1 0 and 11 7 1 0 ka are measured for bedrock in the much lower saglek zone indicating extensive 3 m glacial erosion of this zone during late wisconsinan glaciation 26al 10be ratios demonstrate that exposure of the high elevation surfaces was interrupted during at least one cosmic ray shielding event by either ice or till cover in either case late wisconsinan glaciers could not have extensively eroded these surfaces five erratics dated above the saglek zone including one in the felsenmeer zone have exposure ages ranging from 11 6 1 0 to 13 6 0 7 ka this indicates that valley and high elevation ice persisted through the younger dryas chron and provides further evidence that the highlands were not nunataks during the late wisconsinan period

direct observation of frost wedging in alpine bedrock width and temperature of rock joints were automatically monitored in the japanese alps three years of monitoring on a sandstone rock face shows two seasonal peaks of joint widening in autumn and spring the autumn events are associated with short term freeze thaw cycles and the magnitude of widening reflects the freezing intensity and water availability the short term freezing can produce wedging to a depth of at least 20 cm the spring events follow a rise in the rock surface temperature to 0 c beneath the seasonal snowcover and likely originate from refreezing of meltwater entering the joint some of these events contribute to permanent enlargement of the joint two other joints on nearby rock faces experience only sporadic widening accompanying freeze thaw cycles and insignificant permanent enlargement observations indicate that no single thermal criterion can explain frost weathering the temperature range at which wedging occurs varies with the bedrock conditions water availability and duration of freezing copyright 2001 john wiley sons ltd

alluvial cover dynamics in response to floods of various magnitudes the effect of the release of glaciogenic material in a swiss alpine catchment abstract fluvial incision into formerly glaciated landscapes is commonly affected by the release of glaciogenic sediments from the hillslopes via landsliding hillslope failure and debris flow activity these deposits typically comprise abundant block size clasts here we determine the ability of the fluvial processes to evacuate glacially derived sediments in an alpine hanging valley blanketed by 100 m thick glacial till we assess along stream profiles of basal shear stress during annual decadal and centennial floods by means of the hydrological model hec ras we use bed surface grain size data to i evaluate the shields stress profiles for these floods ii determine at which timescale the bed undergoes significant changes and to iii predict transport capacity patterns for each flood in addition we present digital photogrammetry based estimates of bed elevation changes over two selected time intervals that experienced low and high magnitude floods respectively the results indicate that floods with return periods of 10 years are capable of mobilizing the coarse fraction of the bed material thereby substantially altering the channel geometry the predicted near critical shields stress values for these floods in the area where the glacial deposits are thickest suggest a strong hillslope channel coupling which may have resulted in the formation of the knickzone observed in this sector however decadal to centennial floods are required to transport the material over long distances and scour the bed in the upper part of the inner gorge in addition the observed downstream trend from bed scouring to deposition in the inner gorge for these floods and the opposite trend for low magnitude floods suggest that these patterns are not directly controlled by downstream variations of transport capacity we propose that the supply of sediment through hillslope failure and bank collapse significantly contributes to the sediment flux for high magnitude floods we conclude that the morphology and the timescale of sediment transport in this glacially conditioned landscape have been substantially controlled by the hillslope derived supply of coarse grained material

chemical weathering and boulder mantles karkevagge swedish lapland abstract a deposit of giant boulders covers much of the floor of karkevagge an alpine valley in the swedish arctic these mica schist and garnet mica schist boulders apparently have been there since the waning stages of glaciation in the valley about 13 000 to 9000 years ago according to cosmogenic dating boulder elevations range from 665 to 825 m asl with the higher and possibly younger boulders situated farther up the valley we used total chemical analyses of rock and incipient soils forming on the boulders to determine relative weathering intensity on the tops of 20 boulders arrayed across lower middle and upper valley positions an additional three boulders from a deposit of giant boulders damming lake rissajaure at the valley head were also analyzed the dam may be a later deposit as indicated by preliminary cosmogenic dates or may be part of the larger valley deposit as other interpretations surmise total chemistry was not significantly different between the mica schist and garnet mica schist boulders however total chemistry did vary by position boulders at the lowest positions were chemically more similar to those at the dam than to the other positions this difference was removed when calculating the overall weathering indices by taking the ratio of weathering indices of the c horizon to exposed rock a clear trend in the weathering was revealed by the analyses lower valley boulders show significantly more weathering than the upper group and the middle group is intermediate this indicates that weathering rates differ because of elevation or age of the boulders strewn down the valley however boulders on the lake rissajaure dam complicate those simple interpretations because they show as much weathering evidence as the lower boulders all of the weathering indices exhibited this same trend elevated levels of fe in the two more weathered positions indicate influence of pyrite a known weathering accelerant and undoubtedly the factor controlling boulder weathering in karkevagge

zooming in on frozen bed patches scale dependent controls on fennoscandian ice sheet basal thermal zonation in this paper we explore geomorphological evidence allowing a first order reconstruction of the extent and pattern of frozen bed conditions under the last fennoscandian ice sheet we mapped relict landscapes i e glacial landforms and subaerially developed ground surfaces predating the last ice sheet and marking sustained frozen bed conditions at four different spatial scales at the ice sheet scale relict landscapes are most abundant between the last glacial maximum ice divide and the elevation axis of the scandinavian mountain range the location of frozen bed zones was mainly a function of dispersal centre location low surface temperatures and small strain heating and small ice thickness over the eastern flank of the mountain range at the mesoscale 260 360 km map area the pattern of relict surfaces is governed by inward cutting ice stream erosion topographical control was weak but relation to flow pattern was strong with the major frozen bed zone located where ice flow was strongly divergent at the regional scale 40 65 km map area in hilly terrain topographical control was strong with relict surfaces only appearing above a plane dipping in the up ice direction at the local scale 12 14 km map area control by topography was likewise strong but the detailed boundary pattern was irregular with specific landforms occurring both up and down ice of frozen patches

glacial survival of blockfields on the varanger peninsula northern norway for more than hundred years it has been debated whether blockfields in mountain summit areas can be used to delimit the vertical extent of pleistocene ice sheets in this study the relationship between blockfields developed in quartzites and sandstones on the varanger peninsula northern norway and glacially derived features have been evaluated erratics and circular ablation moraines are superimposed on the blockfields and lateral meltwater channels are eroded into them glacial striations and other signs of glacial sculpturing are restricted to low lying areas with channelled ice flow relative ages of the blockfields and the features in them are inferred and the first measurements of in situ produced cosmogenic nuclides from the varanger peninsula are reported we conclude that the blockfields have survived underneath at least one thick cold based ice sheet thus these blockfields cannot be used as indicators of ice free conditions as previously suggested for southern norway our results have implications for the potential for land surface preservation beneath ice sheets and for glacial reconstructions in northern fennoscandia

blockfields old or new evidence and implications from some plateaus in northern norway evidence is presented from investigations on plateau top blockfields in still glaciated regions of north norway pits dug into these blockfields typically show profile depths 0 5 m and sometimes in excess of 1 m analysis of fines shows enrichment in the silt and clay sized fraction suggestive of prolonged chemical weathering chemical alteration of parent material is supported by xrd analysis which identifies a number of clay minerals present in blockfield samples a chemical weathering origin suggests that these plateau top blockfields are features which have considerable longevity in the landscape and have been forming since perhaps tertiary times the original weathering profiles have been destroyed by frost heaving mechanisms protection of the blockfield by cold based ice occurred during periods of glacial coverage

colluvial sediment dynamics in mountain drainage basins abstract colluvial sediment dynamics are examined using a 70 year landslide inventory in formerly glaciated mountain drainage basins of coastal british columbia canada landslide sediment transfer is documented by identifying landslide types and by characterizing preferential sites of landslide initiation delivery and storage across spatial scales data analysis reveals that open slope landslides delivering material to seasonal or perennial channels and fluvial terraces are the dominant mechanisms of sediment transfer this finding suggests high instability of the low order channel network and its ongoing re organization degradation after generalized sediment recharge occurred in the last glacial maximum in the study period landslide activity across the landscape has generated net degradation on planar slopes and first order colluvial channels whereas unchannelled valleys higher order colluvial channels and alluvial channels have accumulated material the scaling relation of the landslide sediment yield appears to be controlled by the spatial arrangement of the relict glacial macro forms landslide yield is highest in unchannelled topography decreases at the scale of channel initiation ad 0 002 km2 and remains constant for drainage areas where length scales of cirque valley walls and hanging valley floors overlap 0 002

spatial variations of soil weathering processes in a tropical mountain environment the baturite massif and its piedmont ceara ne brazil abstract strong spatial variations in soil weathering processes were identified in the uplands and piedmont zones of the baturite massif ceara ne brazil a medium elevation tropical mountain characterized by a steep ecocline between humid climate of the summit zone and semi arid conditions of the erosional piedmont with the combined help of field surveys and laboratory analyses involving micromorphological observations as well as geochemical and mineralogical investigations this study demonstrates a close spatial correlation between soil weathering processes and present day water balance wbi variations i in the humid massif wbi 500 mm y 1 monosiallitization is exclusive in soil and upper saprolite horizons and leads to the neoformation of 1 1 clay minerals well crystallized kaolinite with minor amounts of gibbsite ii in the subhumid peripheral area of the massif 50 1 monosiallitization coexists with bisiallitization in the soil profiles producing a mixture of 1 1 kaolinite and 2 1 illite clay minerals along with lower weathering intensity iii in the semiarid piedmont 0 1 bisiallitization becomes the dominant weathering pathway conducive to grus formation and fersiallitic pedogenesis with the most vulnerable primary minerals weathered into high charge 2 1 clay minerals smectite and illite given that soils and weathering mantles are integrators of average bioclimatic conditions that prevail at timescales of 1 to 10 myr the distribution of soil weathering signatures in the study area is probably reflective of inevitable long term quaternary to neogene climatic fluctuations around median values close to the present ones paleoclimatic legacies inherited from the paleogene lateritization event are rare because of the denudation pulse occurring in the late tertiary and favoring soil stripping to the paleoweathering front on the erosional piedmont

weathering characteristics of arctic islands in northern norway the arctic islands of the lofoten vesteralen archipelago in northern norway have a wide distribution of weathered land surfaces commonly located above 250 m with several apparent similarities in order to investigate the characteristics of deep weathering in this region northern langoya and hadseloya were chosen for in depth analyses eight weathering profiles were excavated from various surfaces and the stratigraphies were logged in detail material was collected throughout the weathering horizons and all samples were subsequently analysed for clay mineralogy 40 000 years of subaerial conditions considering the steady surface erosion this figure should be viewed as an absolute minimum age estimate mapping of the superficial sediments and geomorphological features of the study areas has revealed several common morphological features which indicate dominance of glacial and periglacial processes in the areas lying below the lower boundary of blockfields c 250 m the weathering mantles are not a periglacial end product but rather a relict tertiary landform that were modulated by permafrost processes as well as biological processes at later stages the regolith cover constrain the vertical extension of warmbased quaternary ice sheets challenging the notion of a parabolic ice mass consuming every mountain top of lofoten and vesteralen

on the persistence of weathering abstract the term weathering has been in use for a very long time but it has come to mean different things to different people and hence as scientific short hand it no longer functions here we question the tenets underpinning the most common usage of the term and note that the climate process linkage implicit to the term is often missing and amounts to misdirection rather than climate as the primary driver behind specific weathering processes it is argued that rock properties constitute the dominant control further a case is made for reconsideration of our present bipartite mechanical chemical division of weathering processes and of the weathering processes currently deemed to be those that occur as process studies become evermore reductionist in nature so the functionality of the term comes more and more into question the linkage between process and landform the scaling up attribute is seen as a current weakness and one that will become more confusing as reductionist approaches continue as a way forward it is suggested that weathering stripped of specific preconceived notions of specific processes be envisaged as a function of energy transfer and be investigated in that light identification of new processes as well as restructuring of known processes particularly when considering weathering on other planets is a potential outcome of such an approach with a process foundation rooted in energy transfer rock decay provides a better umbrella term and liberates researchers from the inescapable conceptual baggage implicit to the term weathering

weathering patterns in high latitude regolith 1 large areas distributed on the earth s surface are covered by regolith an unconsolidated heterogeneous material overlying bedrock in high latitude areas most of the land surface has been reworked and eroded by both glacial and fluvial processes leaving only remnants of formerly extensive regolith covers in an effort to further the understanding of weathering patterns and processes in old regolith covers a comprehensive study of localities spread across norway was carried out on the basis of the distribution of minerals and elements within regolith as well as its internal structure and geomorphologic setting we ascertained that it was formed in situ and originated in pre quaternary times there are similarities between the study sites with respect to regolith thickness zonation and composition the chemical index of alteration cia and the weathering index of parker wip suggests that the degree of chemical weathering in the regolith is advanced compared to the parental bedrock with a maximum change of over 80 which indicates a substantial increase in the proportion of secondary versus primary minerals mineral analysis identified kaolinite and gibbsite which are considered indicative of advanced weathering and therefore support this observation on the basis of statistical relationships between different grain size fractions 125 m we observed a consistent pattern which revealed that physical weathering becomes progressively less important in the production of grains smaller than 32 m on the basis of this finding we infer that chemical weathering progressively dominates the production of fine silt very fine silt and clay whereas physical weathering primarily controls the production of grain size fractions larger than 32 m this particular pattern is suggested to be an intrinsic feature in the formation of weathered high latitude regolith

reconstruction of palaeo ice sheets the use of geomorphological data the article discusses the nature of the glacial inversion problem which is defined as the extraction of time slice ice sheet flow patterns from the patchy and partly overprinted landform record present in former ice sheet areas a coherent inversion model for derivation of flow patterns and interior ice sheet configuration from geomorphological data is presented glacial landscapes are classified according to the three criteria of internal age gradients presence or absence of meltwater traces aligned to flow traces and basal condition frozen bed thawed bed inferred from morphology the inversion model uses landscapes classified accordingly spatially delineated into fans as input data relative chronologies at fan intersections are used to sort fans in a relative age stack that can be linked to stratigraphic dating information

estimating peak currents at ground lightning impacts using remanent magnetization 1 the impact of lightning is permanently recorded in struck material by a secondary magnetization called lightning induced remanent magnetization lirm we introduce an original rock magnetic method based on alternating field demagnetization to define both the geometry and the intensity of the peak lightning magnetic field it also provides positive evidence than a material has effectively been struck on a schoolyard tree struck by lightning we were able to locate the impact to within a few centimeters to prove that it was a vertical negative current and to estimate a peak current intensity of 99 7 ka this value is 14 ka higher than the one provided by meteorage lightning detection network and offers an independent calibration

is climate change responsible for changing landslide activity in high mountains climate change manifested by an increase in mean minimum and maximum temperatures and by more intense rainstorms is becoming more evident in many regions an important consequence of these changes may be an increase in landslides in high mountains more research however is necessary to detect changes in landslide magnitude and frequency related to contemporary climate particularly in alpine regions hosting glaciers permafrost and snow these regions not only are sensitive to changes in both temperature and precipitation but are also areas in which landslides are ubiquitous even under a stable climate we analyze a series of catastrophic slope failures that occurred in the mountains of europe the americas and the caucasus since the end of the 1990s we distinguish between rock and ice avalanches debris flows from de glaciated areas and landslides that involve dynamic interactions with glacial and river processes analysis of these events indicates several important controls on slope stability in high mountains including the non linear response of firn and ice to warming three dimensional warming of subsurface bedrock and its relation to site geology de glaciation accompanied by exposure of new sediment and combined short term effects of precipitation and temperature based on several case studies we propose that the following mechanisms can significantly alter landslide magnitude and frequency and thus hazard under warming conditions 1 positive feedbacks acting on mass movement processes that after an initial climatic stimulus may evolve independently of climate change 2 threshold behavior and tipping points in geomorphic systems 3 storage of sediment and ice involving important lag time effects

do periglacial landscapes evolve under periglacial conditions polar and alpine periglacial areas are traditionally regarded as necessarily submitted to very efficient frost driven processes that control the holocene and ongoing geomorphic activity during the last decade the validity of this academic view has been increasingly questioned among the international scientific community the search for the real past and present processes responsible for landform evolution in cold nonglaciated areas is based mainly on more and more refined monitoring protocols relying upon sophisticated equipment to assess the representativeness and significance of monitoring data collected in restricted sites it appears necessary however to widen the perspective by adopting a twofold multiscale approach as proposed in the present paper 1 in space by integrating various scales from the general slope system to the bioclimatic nanoenvironment and 2 in time by taking into account the landscape history from tertiary inherited features to recent process changes induced by the contemporary warming reintegrating the historical approach should help both to place the ongoing processes within a succession and or combination of interoperating processes and to avoid misinterpretations of features considered wrongly as emblematic of frost action overall both the historical and monitoring approaches tend to reduce the geomorphic efficiency of frost derived processes instead the role of noncold related processes such as chemical thermal biogenic and rainfall induced ones is being emphasized of special interest would be an interdisciplinary discussion between geomorphologists and various disciplines of biological sciences including biochemistry and ecology studying processes of primary successions

surface climate attributes at injisuthi outpost drakensberg and possible ramifications for weathering aerial and sub aerial climatic data were collected from a station at 1920 m a s l in the injisuthi region of the south african drakensberg sensors monitored air temperature soil surface and rock surface temperature for two rock types over the summer and winter of 2001 2002 rainfall was measured from the summer of 2001 to january 2004 these are the first rock and soil surface climate data to be collected for an exposed site at this altitude in the area rainfall over the two calendar years 2002 and 2003 was found to be below estimates for the region but patterns imply numerous rock wetting and drying cycles in summer at the site air rock and soil temperatures differ considerably on a diurnal basis with respect to both absolute temperature and daily ranges mean rock daily ranges as conducive to possible thermal fatigue are found to be similar in the summer and winter periods of the two rock types monitored the darker coloured basalt attained higher maximum and marginally lower minimum temperatures than the sandstone soil frost did not occur at 2 5 cm depth but rock did reach below 6 c in winter both rock types maintain relatively high rock temperatures in winter exceeding 25 c thus chemical weathering is probably only moisture restricted during this dry period findings highlight the importance of directly monitoring rock temperature when attempting to discern the rock weathering environment copyright 2006 john wiley sons ltd

a relict landscape in the centre of fennoscandian glaciation cosmogenic radionuclide evidence of tors preserved through multiple glacial cycles the presence of well developed tors boulder fields and weathering mantles in the parkajoki area of northeastern sweden near the centre of fennoscandian glaciation has been used to suggest that these landscapes were preserved during all glacial cycles since ice sheet initiation in the late cainozoic this implies that all successive large scale glaciations must have had frozen bed conditions across this area to allow for subglacial landscape preservation cosmogenic 10be and 26al data from three tors and a meltwater channel in the parkajoki area were used to test this hypothesis of landscape preservation through multiple glacial cycles apparent exposure ages of tor summit bedrock surfaces ranging between 79 and 37 ka in an area deglaciated at 11 ka are consistent with the interpretation of these features as relict landforms that have survived glaciation with little or no erosion single nuclide minimum exposure age data require that the tors have survived at least two complete glacial cycles this estimate is based on i the approximate duration of periods of ice sheet cover versus ice free conditions as deduced from the dsdp 607 marine benthic foraminifer oxygen isotope record in conjunction with ii a record of fennoscandian ice sheet flow traces and hence ice sheet extent and iii noting that cosmogenic nuclides are accumulated only during ice free periods in addition mean cosmogenic 26al 10be concentration ratios from two of the sites indicate a minimum model total history of 605 ka and a maximum erosion rate of 1 6 m ma 1 thus the numerical ages confirm the overall qualitative interpretation of landscape preservation through multiple glacial cycles

the historical legacy of spatial scales in freeze thaw weathering misrepresentation and resulting misdirection discussion of weathering in cold regions has historically been dominated by widespread acceptance of the significance of the freeze thaw concept among periglacial geomorphologists and an essentially universal acceptance by those geomorphologists not directly involved in researching the topic debris produced by freeze thaw is frequently deemed to be angular in form and the observation of such debris has been used to identify the former or present operation of this weathering mechanism large debris blocks and small debris grains or flakes have been recognised as the outcome of the two scales of freeze thaw weathering macrogelivation and microgelivation respectively however the fusion of climatic geomorphology and process geomorphology in the ongoing development of the freeze thaw concept has resulted in the confusion of product with process whereby microgelivation producing small products and macrogelivation producing large products are seen due to the product dichotomy as distinctly different processes despite the recent highly sophisticated laboratory experimentation on freeze thaw weathering this historical process scale dichotomy still pervades thinking and experimental evaluation here we consider the historical development of microgelivation macrogelivation and outline what are thought to be fundamental flaws with the concepts and their underpinnings built within the two notions are elements of rock properties hard and soft and scale issues regarding rock attributes solid rock and existing weaknesses in rock that serve only to confuse the process and scale issues even more the whole notion of frost weathered debris having a specific form is also highly spurious there being no shape attribute that is uniquely diagnostic of frost action and this in turn leads to the further problem of process synergy or other processes entirely being the cause of rock failure in cold regions ultimately we argue that while there may be a range of product sizes and shapes resulting from frost weathering per se the widely invoked scale concepts are fraught with problems and are best dropped as too are any process shape connotations

the use of the schmidt hammer and equotip for rock hardness assessment in geomorphology and heritage science a comparative analysis rapid field based measurements of rock hardness are of use in investigating many geomorphological and heritage science problems several different methods are now available for taking such measurements but little work has been done to assess their comparability and strengths and weaknesses we review here the capabilities of two types of schmidt hammer classic n type and silver schmidt bl type alongside two types of equotip standard type d and piccolo for investigating rock hardness in relation to rock weathering on various types of sandstone and limestone as well as basalt and dolerite whilst the two schmidt hammers and the two equotips show comparable results when tested at 15 individual sites interesting differences are found between the equotip and schmidt hammer values which may reveal information about the nature of weathering on different surfaces operator variance is shown to be an issue in particular for the equotip devices which also exhibit higher variability in measurements and necessitate larger sample sizes carborundum pre treatment also has varying effects on the data collected depending on the nature of the surface studied the equotip devices are shown to be particularly useful on smaller blocks and in situations where edge effects may affect schmidt hammer readings we conclude that whilst each device contributes to geomorphological research they do not necessarily produce comparable information indeed using schmidt hammer and equotip in combination and looking at any differences in results may provide invaluable insights into the structure of the near surface zones and the nature of weathering processes copyright 2010 john wiley sons ltd

deciphering a non glacial glacial landscape mosaic in the northern swedish mountains relict surfaces contain information on past surface processes and long term landscape evolution a detailed investigation of relict non glacial surfaces in a formerly glaciated mountain landscape of northern sweden was completed based on interpretation of colour infrared aerial photographs analysis in a gis and fieldwork working backwards from landscape to process surfaces were classified according to large and small scale morphologies that result from the operation of non glacial processes the degree of weathering regolith characteristics and the style of glacial modification surfaces were also compared in the gis according to elevation slope angle and bedrock lithology the study revealed five types of relict non glacial surfaces but also two types of extensively weathered glacial surfaces that were transitional to relict non glacial surfaces illustrating spatially variable processes and rates of non glacial and glacial landscape evolution rather than being static preglacial remnants relict non glacial surfaces are dynamic features that have continued to evolve during the quaternary the classification provides hypotheses for landscape evolution that can be field tested through for example terrestrial cosmogenic nuclide studies and geochemical analyses of fine matrix materials the classification may be applicable to relict non glacial surfaces in other formerly glaciated landscapes

does lightning destroy rocks results from a laboratory lightning experiment using an impulse high current generator abstract to understand the destruction of rocks and changes to landforms by lightning strikes laboratory experiments of lightning strikes were performed using three kinds of rock samples as targets artificial lightning with known electric current was simulated by an impulse high current generator in the laboratory the artificial lightning is different to natural lightning the high current generator can generate up to 20 ka of electric current equal to 50 of the value of natural lightning but up to 50 kv of electric voltage which is a tenth to hundredth that of natural lightning experimental results showed that the rock samples with low mechanical resistance tuff and rhyolite were destroyed while the rock sample with high mechanical resistance i e granite was not broken by lightning strikes these results indicate that natural lightning causes rocks and bedrock to break these imply that lightning might change landforms for example gnammas and fractures on tors and mountain peaks where lightning tends to strike