extensive deformations of rock slopes in southern coast mountains southwest british columbia canada extensive deformations of mountain slopes occur in crystalline intrusive rocks in the southern coast mountains of british columbia typical morphological evidence of slope movement includes extensive systems of tension cracks grabens and antislope scarps collectively referred to here as linears these landforms involve displacements along penetrative joints observed in surface exposures kinematic tests on rock structural data indicate that the observed patterns of linears are generally consistent with the feasible gravitational movements along the dominant discontinuities most sites indicate sliding as the most likely initial mode of movement followed by or accompanied by toppling and toppling induced sliding movements and do not support the view that linears are the traces of active faults

coastal lake records add constraints to the age and magnitude of the younger dryas ice front oscillation along the skagerrak coastline in southern norway

seven landslide dams of old seismic origin in southeastern sicily italy this paper focuses on origin morphology and evolution of seven landslide dams in southeastern sicily these landforms are part of a set of 146 landslides recently recognised in this area which was hitherto considered to have little or no slope instability southeastern sicily consists of a plateau the hyblaean mountains incised by canyons and surrounded by lower lands it is underlain mostly by subhorizontal moderately to well lithified carbonate rocks relief is low several lines of evidence justify the assumption of a seismic trigger for the landslides in this area 1 the geo climatic environment is not favourable to landsliding 2 low angle basal shear surfaces are very frequent 3 landslide distribution is consistent with the known magnitude distance relationships for earthquake induced landslides 4 historical documents testify to earthquake triggered slope instability and 5 a specific landslide can be exactly dated the phenomena illustrated here include six rock slides one with a debris flow component and one rock fall slip surfaces are mostly non circular landslide volume ranges from about 5010 3 to 3410 6 m 3 with reference to the costa and schuster geol soc am bull 100 1988 1054 classification of landslide dams five cases belong to type ii spanning the entire valley and two to type iv failures from both valley sides with frontal or side contact between failed masses with reference to crozier and pillans catena 18 1991 471 classification of landslide lakes all cases show a main valley lake while tributary valley back and supra lakes are sporadically present one damming is attributable to the 1693 earthquake with certainty another damming to the same earthquake with high probability three dams were reincised one breached or reincised one is slightly reincised and two more or less intact correspondingly five silting up deposits were reincised one is being reincised at present and two are still under formation d 2002 elsevier science b v all rights reserved

results of a magnetotelluric traverse across western oregon crustal resistivity structure and the subduction of the juan de fuca plate abstract as part of project emslab we have collected and analysed wideband magnetotelluric data along an east west transect in western oregon preliminary modelling of the data using one dimensional inversions based upon rotationally invariant earth response functions was followed by finite element two dimensional modelling the models produced indicate the presence of an electrical conductor beneath the oregon coast range dipping eastward at 12 18 from a depth of 23 32 km we believe that this conductor includes the thrust surface of the subducting juan de fuca plate and or adjacent water saturated rocks its high conductance about 200 s is thought to be due to one or more of the following mechanisms 1 sediments subducted atop and with the juan de fuca plate 2 saline fluids produced by dehydration of the former or 3 seawater contained within subducted oceanic basalts there is a distinct possibility that the high conductivity is due primarily to the presence of subducted sediments in contrast with the notion that the subduction of young buoyant lithosphere retards sediment subduction at this convergent margin the conductive layer is overlain by relatively resistive rocks presumed to be accreted oceanic lithosphere model determined resistivities for the upper part of the coast range section are in good agreement with deep well log data a strong electrical contrast appears in the determinant phase pseudosection between the coast range and the willamette valley suggesting a structural boundary between the two provinces a surficial conductor is present in the valley to depths of 1 2 km and is due to alluvial fill induction arrow data show the geomagnetic coast effect and a smaller effect by the willamette valley alluvial fill

the formation and failure of natural dams of the numerous kinds of dams that form by natural processes dams formed from landslides glacial ice and late neoglacial moraines present the greatest threat to people and property landslide dams form in a wide range of physiographic settings the most common types of mass movements that form landslide dams are rock and debris avalanches rock and soil slumps and slides and mud debris and earth flows the most common initiation mechanisms for dam forming landslides are excessive rainfall and snowmelt and earthquakes landslide dams can be classified into six categories based on their relation with the valley floor type i dams 11 of 184 landslide dams from around the world that we were able to classify do not reach from one valley side to the other type ii dams 44 span the entire valley floor in some cases depositing material high on opposite valley sides type iii dams 41 move considerable distances both upstream and downstream from the landslide failure type iv dams 1 are rare and involve the contemporaneous failure of material from both sides of a valley type v dams 1 also are rare and are created when a single landslide sends multiple tongues of debris into a valley and forms two or more landslide dams in the same reach of river type vi dams 3 involve one or more failure surfaces that extend under the stream or valley and emerge on the opposite valley side many landslide dams fail shortly after formation in our sample of 73 documented landslide dam failures 27 of the landslide dams failed less than 1 day after formation and about 50 failed within 10 days over topping is by far the most common cause of failure the timing of failure and the magnitude of the resulting floods are controlled by dam size and geometry material characteristics of the blockage rate of inflow to the impoundment size and depth of the impoundment bedrock control of flow and engineering controls such as artificial spill ways diversions tunnels and planned breaching by blasting or conventional excavation glacial ice dams can produce at least nine kinds of ice dammed lakes the most dangerous are lakes formed in main valleys dammed by tributary glaciers failure can occur by erosion of a drainage tunnel under or through the ice dam or by a channel over the ice dam cold polar ice dams generally drain supraglacially or marginally by downmelting of an outlet channel warmer temperate ice dams tend to fail by sudden englacial or subglacial breaching and drainage late neoglacial moraine dammed lakes are located in steep mountain areas affected by the advances and retreats of valley glaciers in the last several centuries these late neoglacial dams pose hazards because 1 they are sufficiently young that vegetation has not stabilized their slopes 2 many dam faces are steeper than the angle of repose 3 these dams and lakes are immediately downslope from steep crevassed glaciers and near vertical rock slopes and 4 downstream from these dams are steep canyons with easily erodible materials that can be incorporated in the flow and increase flood peaks the most common reported failure mechanism is overtopping and breaching by a wave or series of waves in the lake generated by icefalls rockfalls or snow or rock avalanches melting of ice cores or frozen ground and piping and seepage are other possible failure mechanisms natural dams may cause upstream flooding as the lake rises and downstream flooding as a result of failure of the dam although data are few for the same potential energy at the dam site ownstream flood peaks from the failure of glacier ice dams are smaller than those from landslide moraine and structed earth fill and rock fill dam failures moraine dam failures appear to produce some of the largest downstream flood peaks for potential energy at the dam site greater than 1011 1012 joules differences in flood peaks natural dam failures appear to be controlled by dam characteristics and failure mechanisms

atmosphere driven ice sheet mass loss paced by topography insights from modelling the south western scandinavian ice sheet abstract marine terminating glaciers and ice streams are important controls of ice sheet mass balance however understanding of their long term response to external forcing is limited by relatively short observational records of present day glaciers and sparse geologic evidence for paleo glaciers here we use a high resolution ice sheet model with an accurate representation of grounding line dynamics to study the deglaciation of the marine based south western norwegian sector of the scandinavian ice sheet and its sensitivity to ocean and atmosphere forcing we find that the regional response to a uniform climate change is highly dependent on the local bedrock topography consistent with ice sheet reconstructions our simulations suggest that ocean warming is able to trigger initial retreat in several fjords but is not sufficient to explain retreat everywhere widespread retreat requires additional ice thinning driven by surface melt once retreat is triggered the underlying bedrock topography and fjord width control the rate and extent of retreat while multi millennial changes over the course of deglaciation are modulated by surface melt we suggest that fjord geometry ice ocean interactions and grounding line dynamics are vital controls of decadal to centennial scale ice sheet mass loss however we postulate that atmospheric changes are the most important drivers of widespread ice sheet demise and will likely trump oceanic influence on future ice sheet mass loss and resulting sea level rise over centennial and longer time scales

geomorphic imprint of landslides on alpine river systems southwest new zealand an inventory of 846 mass movements mainly landslides in two alpine regions of southwest new zealand was created to explore the geomorphic impacts of slope failure processes on river channels and valley floors in total 213 i e 27 per cent of the slope failures descended to valley floors affecting the geomorphology of trunk channels catchment area ac 10 km2 and valley floors in recurring patterns a nominal classification system is introduced for characterizing a the physical contact nature between landslides and river channels and b the resulting geomorphic consequences for drainage although landslide area a is useful for estimating the length of channel directly impacted by debris it does not necessarily predict the direction of fluvial response or type of impact dominant persistent geomorphic imprints of bedrock landslides include channel occlusions and landslide dams in south westland and fiordland respectively differences in size distribution and geomorphic effects on river systems between the two study regions are attributed to bedrock geology tectonics and sediment flux although south westland rivers are more frequently affected by landslides disrupting long term effects such as blockage are more persistent in fiordland copyright 2005 john wiley sons ltd

transient fluvial incision in the headwaters of the yellow river northeastern tibet china 1 we utilize topographic analysis of channel profiles combined with field measurements of erosion rates to explore the distribution of channel incision in the anyemaqen shan a broad mountainous region in the northeastern tibetan plateau tributary channels to the yellow river display systematic downstream increases in channel gradient associated with convex upward longitudinal profiles steep lower reaches of channels are associated with rapid 1 m ka incision rates along the yellow river while upstream reaches are associated with relatively slow 0 05 0 1 m ka erosion of soil mantled uplands covariance between erosion rates and channel steepness indices suggest that channels are adjusted to match long wavelength differential rock uplift across the range geologic constraints indicate that rapid incision downstream of the range is associated with excavation of basin fill driven by changes in relative base level farther downstream the upstream limit of this wave of transient incision is marked by a series of knickpoints that are found at nearly the same elevation throughout the watershed consistent with knickpoint migration as a kinematic rather than diffusional wave tributary channel gradients downstream of knickpoints however display a progressive adjustment to increased incision rates that may reflect the influence of increased sediment flux comparison of observed channel profiles to a stream power model of fluvial behavior reveals that the rate of knickpoint propagation can only be explained if the erosional efficiency coefficient k increases during incision our results thus highlight the utility of channel profile analysis to reconstruct the fluvial response to both active tectonism and external changes in base level

discriminant analysis of the geomorphic characteristics and stability of landslide dams article i nfo landslides can cause the formation of dams but these dams often fail soon after lake formation thus rapidly evaluating the stability of a landslide dam is crucial for effective hazard mitigation this study utilizes discriminant analysis based on a japanese dataset consisting of 43 well documented landslide dams to determine the significant variables including log transformed peak flow or catchment area and log transformed dam height width and length in hierarchical order which affect the stability of a landslide dam the high overall prediction power 88 4 of the 43 training cases are correctly classified and the high cross validation accuracy 86 demonstrate the robustness of the proposed discriminant models phwl with variables including log transformed peak flow and log transformed dam height width and length and ahwl with variables including log transformed catchment area and log transformed dam height width and length compared to a previously proposed dbi index based graphic approach the discriminant model ahv which uses the log transformed catchment area dam height and dam volume as relevant variables shows better ability to evaluate the stability of landslide dams although these discriminant models are established using a japanese dataset only the present multivariate statistical approach can be applied for an expanded dataset without any difficulty when more completely documented worldwide landslide dam data are available

magnetic variations in the reconnaissance of sedimentary basins field procedure and generalized inversion of short period data from the rio grande rift the magnetic variation mv technique employs magnetic transients from natural sources in the magnetosphere to delineate geologic structures in the earth s interior based on their electrical properties by measuring only the magnetic field at each site and not the electric field as required for magnetotelluric mt studies a site can be set up quickly and often in places which might be quite unsuitable for mt measurements this generally allows one to execute mv surveys in culturally developed areas or in rugged and logistically difficult terrain at much closer site spacings than those used for conventional mt surveys procedures for acquiring and processing mv field data are straightforward as are methods for inverting data to obtain plausible geophysical models using a new 2 d generalized inverse algorithm which employs singular value damping of the lanczos or svd inverse we apply the mv technique to determine the basement topography beneath a sequence of 11 remote referenced mv sites from an ea

the eureka river landslide and dam peace river lowlands alberta the eureka river landslide of june 1990 at 50 mm3 is one of the largest historical landslides on the interior plains of canada it is one of seven large translational landslides to have occurred in the peace river lowlands within the last 65 years each landslide occurred in quaternary sediments deposited within a preglacial valley each landslide formed a dam the rupture surface of the eureka river landslide in preglacial lacustrine sediment 125 m below the peace river lowlands plains extended beneath the river channel causing the channel to be elevated the resulting landslide dam was over 20 m high forming a lake exceeding 8 km in length the river cut a new channel around the toe of the landslide abandoning the prelandslide channel as the new channel is free of armour incision has been rapid after 10 years the dam now stands approximately 5 m high key words landslide landslide dam peace river alberta preglacial valley geomorphology

mass movements along a rapidly uplifting river valley an example from the upper jinsha river southeast margin of the tibetan plateau because of the rapid uplift of the tibetan plateau since the middle and late pleistocene the surrounding mountainous areas of the tibetan plateau also show a rapid uplift trend the study area is located in the upper reaches of the jinsha river southeastern tibetan plateau tectonically the study area is located in the eastern segment of the jinshajiang suture zone which is the weak belt of the lithosphere affected by the rapid uplift steep slopes are formed by the rapid vertical down cutting of rivers in the studied reach under the sustained action of the gravitational field the deformation and failure of slopes readily occur to better formulate development and risk mitigation plans a mass movement inventory map at the scale of 1 50 000 was prepared for the 100 km long reach a total of 247 mass movements of different types sizes and relative ages were mapped via image interpretation and detailed field survey the statistical analysis of their spatial distributions was performed using two relative concentration indexes the correlations between the spatial distribution and six common factors were analyzed elevation slope angle slope aspect lithology active fault and river system the geomorphological survey shows that the mass movements locally play an important role in the present day landscape evolution in addition the geomorphic features indicate that the mapped giant landslides can be classified as very old landslides and they very likely occurred under a different morphoclimatic environment than that of the present

late holocene relative sea level rise and the neoglacial history of the greenland ice sheet in west greenland early and mid holocene relative sea level rsl fall was replaced by late holocene rsl rise during the neoglacial after 4 3 cal ka bp thousand calibrated years before present here we present the results of an isolation basin rsl study completed near to the coastal town of sisimiut in central west greenland rsl fell from 14 m above sea level at 5 7 cal ka bp to reach a lowstand of 4 0 m at 2 3 1 2 cal ka bp before rising by an equivalent amount to present differences in the timing and magnitude of the rsl lowstand between this and other sites in west and south greenland record the varied interplay of local and non greenland rsl processes notably the reloading of the earth s crust caused by a neoglacial expansion of the greenland ice sheet gis and the subsidence associated with the collapse of the laurentide ice sheet forebulge this means that the timing of the sea level lowstand cannot be used to infer directly when the gis advanced during the neoglacial the rise in late holocene rsl is contrary to recently reported bedrock uplift in the sisimiut area based on repeat gps surveys this indicates that a belt of peripheral subsidence around the current ice sheet margin was more extensive in the late holocene and that there has been a switch from subsidence to uplift at some point in the last thousand years or so

uphill facing antislope scarps in the coast mountains southwest british columbia uphill facing scarps are examined at affliction creek a glacierized area within the meager creek volcanic complex of southwest british columbia scarps occur directly downslope of tension cracks and are considered to have developed from a combination of 1 antithetic movement between partly toppled slices of rock defined by a master joint set dipping into the slope and 2 erosion of the upslope face of each tension crack leaving the downslope face prominent as an antislope scarp a kinematic test for toppling failure is described glacial erosion and rapid glacial downwasting are probable causes of toppling lichenometric data indicate significant scarp development since affliction glacier attained its maximum neoglacial dimensions about 140 yr ago dilatancy is cited as a possible mechanism for scarp stabilization

marine 14c reservoir ages for 19th century whales and molluscs from the north atlantic abstract in order to compare radiocarbon dates on marine and terrestrial samples the former have to be corrected for a reservoir age we present reservoir ages from dating 21 whales collected 1860 1901 and recalculating dates of 23 molluscs collected 1857 1926 most of the whales were caught along the coast of norway but one is from france and one from iceland we assume the former mainly lived in the north and equatorial atlantic and in the norwegian sea whales feed only on pelagic organisms and will provide the reservoir age for the open ocean surface water however they travel long distances and will integrate the reservoir ages of the different water masses along their way molluscs dated from norway spitsbergen and arctic canada are stationary and monitor the sea water passing their dwelling site but some also take up carbon from particulate food or sediment pore water coastal water also often contains some continental carbon we present two different views on how to analyze and interpret the data mangerud recommends to use reservoir ages based on a combination of the whale and mollusc dates i e 380 30 and 360 30 yr relative to intcal04 and british oak respectively and a r value of 20 30 for the surface water in the n atlantic and norwegian sea bondevik and gulliksen maintain that the reservoir age and r along the norwegian coast is latitude dependant with r values increasing from 3 22 in the south to 105 24 at spitsbergen whales reflecting north atlantic open ocean surface water have lower r 7 11 than most molluscs

on the timing of retreat of the loch lomond younger dryas readvance icefield in the sw scottish highlands and its wider significance abstract it has long been assumed that the last glacier expansion in the scottish highlands the loch lomond readvance llr resulted from a cold reversal that was broadly coeval with the younger dryas episode this view has recently been challenged with the suggestion that glacier ice had disappeared from rannoch moor one of the main ice accumulation centres in the sw scottish highlands by as early as 12 5 ka i e within the first half of the younger dryas here we present new radiocarbon tephrostratigraphical and pollen stratigraphical evidence from one of the key sites on rannoch moor the results of an experiment designed to test this hypothesis our results not only contradict that concept but are fully compatible with other evidence from the sw scottish highlands that suggests that the llr glaciers in this area continued to expand until towards the end of the younger dryas period and may have persisted in some places after the onset of the holocene we consider the possible reasons for this marked divergence in chronology a matter that is crucial to resolve because the precise timing of the demise of the llr glaciers has important palaeoclimatic and other implications in the wider context we also draw attention to problems with the general use of the term younger dryas and why we regard the greenland stratotype unit and term greenland stadial 1 gs 1 a more secure stratigraphic comparator

magnetotelluric soundings over a precambrian contact in australia summary the willyama complex near broken hill represents a major exposure of the precambrian terrain in australia however the eastern limits are obscured by recent cover in the murray darling basin the nature and extent of the contact with the younger basement to the east is unknown magnetotelluric data have now been obtained as an aid to regional mapping profiles are based on observations at 14 sites in a traverse east of broken hill apparent resistivities presented as pseudosections reflect the major structural units identified from surface geology continuity between sites is indicated from similarity in apparent resistivities and lateral changes east of the block are generally gradational characteristic divergences in orthogonal resistivity components are consistent with 2 d structure the foliated precambrian complex appears to form a semi vertical contact at the margin of the murray darling basin thus generating the required anisotropy at depths from 15 35 km seismic evidence indicates an equivalent structural contact possibly extending into the mantle

adv measurements around a cluster microform in a shallow mountain stream a field study was conducted to examine the turbulent properties of the flow around a naturally formed cluster bedform this was carried out on a mountain river using a 3d acoustic doppler velocimeter adv concurrent with this objective the ability of the adv to make measurements in a shallow flow over a cobble bed ho d84 1 75 was examined adv measurements in natural clear water shallow flows around obstacles are inherently difficult to obtain due to 1 signal interference between the acoustic reflections from the boundary and the adv sample volume 2 regions of high turbulent intensity such as in local detached shear layers and 3 low concentrations of suspended particles passing through the adv sampling volume these processes result in velocity time series that contain a significant amount of spikes lower than average signal to noise ratios and lower than average correlation values a filtering process that optimized the removal of bad points while retaining a sufficient number of poin

the last 18 kyr fluctuations in norwegian sea surface conditions and implications for the magnitude of climatic change evidence from the north sea a combined record of three cores spanning the last 18 kyr from the northern north sea is investigated for content of benthic and planktonic foraminifera and stable oxygen isotopes the paleoenvironmental development through this time period shows an early deglaciation 18 14 4 ka and the younger dryas 12 7 11 5 ka characterized by arctic polar conditions and increased ice rafting in the norwegian channel during the bolling allerod period warm sea surface temperature 9 c conditions similar to present conditions are inferred while bottom waters stayed cold 0 1 c with normal salinity the bolling allerod period is interrupted twice at 13 9 13 6 ka older dryas and at 13 0 12 8 ka inter allerod cooling period by reductions in sea surface temperatures and increased sea ice cover the beginning of the holocene period is marked by increases in surface and bottom water temperature superimposed on the broad climatic changes through the holocene a series of short lived oscillations in the ocean circulation are recorded the amplitude of these holocene events appears larger in the early holocene prior to 8 ka than compared with the remaining part of the holocene this amplification can possibly be attributed to a general increased freshwater budget in the north atlantic at this time during the final stages of the deglaciation of the laurentide and scandinavian ice sheets

changes in north atlantic radiocarbon reservoir ages during the allerod and younger dryas estimates of the radiocarbon age of seawater are required in correlations between marine and terrestrial records of the late quaternary climate we radiocarbon dated marine shells and terrestrial plant remains deposited in two bays on norway s west coast between 11 000 and 14 000 years ago a time of large and abrupt climatic changes that included the younger dryas yd cold episode the radiocarbon age difference between the shells and the plants showed that sea surface reservoir ages increased from 400 to 600 years in the early yd stabilized for 900 years and dropped by 300 years within a century across the yd holocene transition

quantifying variable rates of postglacial relative sea level fall from a cluster of 24 isolation basins in southern norway abstract sediment sequences obtained from 24 isolation basins located on the skagerrak coastline are used to develop new sea level index points for southern norway the basins are located near a common shoreline isobase and extend from marine limit at c 83 m asl to present sea level the abundance of bedrock isolation basins within the small study area enables a high resolution reconstruction of postglacial relative sea level change for most of the basin records 3 5 samples of terrestrial plant macrofossils were radiocarbon dated across the biostratigraphically defined isolation boundary eight of the isolation events were further constrained by bayesian modelling of the radiocarbon age results the overall reconstructed sea level history is as expected for a formerly glaciated coastline consisting of a rapid regression from marine limit followed by a slower pace of relative sea level fall from early mid holocene to present the new dataset of sea level index points however further delineates century scale oscillations in rates of sea level regression which record past changes in sea surface height and vertical land motion glacial isostatic adjustments gia results provide new constraints for future numerical models aimed at reducing uncertainty in century scale relative sea level projections for fennoscandia

velocity characteristics along a small step pool channel this paper summarizes measurements of velocity along three reaches of a small mountain channel with step pool bedforms a one dimensional electromagnetic current meter was used to record velocity fluctuations at 37 fixed measurement points during five measurement intervals spanning the peak of the annual snowmelt hydrograph measurement cross sections were located upstream from a bed step at the step lip downstream from the step and in a uniform gradient run data analyses focused on characteristics of velocity profiles and on correlations between velocity characteristics and the potential control variables bedform type reach gradient and flow depth to test the hypothesis that velocity characteristics are related to channel bedform types anova and ancova tests were performed for the average velocity and coefficient of variation of point velocity data results indicate that high frequency velocity variations correlate to some degree with both channel characteristics and discharge velocity became more variable as stage increased particularly at low gradient reaches with less variable bed roughness velocity profiles suggest that locations immediately downstream from bed steps are dominated by wake turbulence from mid profile shear layers locations immediately upstream from steps at step lips and in runs are dominated by bed generated turbulence adverse pressure gradients upstream and downstream from steps may be enhancing turbulence generation whereas favourable pressure gradients at steps are suppressing turbulence the bed generated turbulence and skin friction of runs appear to be less effective energy dissipators than the wake generated turbulence and form drag of step pool bedforms copyright 2000 john wiley sons ltd

stability of landslide dams and development of knickpoints the wenchuan earthquake triggered many landslides and numerous avalanches and created 100 odd quake lakes the quake lakes may be removed or preserved the removal strategy was applied to several large landslide dams which were dangerous because massive amounts of water pooled up in the quake lakes the dams could eventually fail under the action of dam outburst flooding potentially endangering the lives of people in the downstream reaches this paper studied the stability of landslide dams and the development of knickpoints by field investigations and experiments and analyzing satellite images the study concluded that if landslide dams were preserved they would develop into knickpoints and act as a primary control of riverbed incision and thus reduce the potential of new landslide the stability of landslide dams depends mainly on the development of the step pool system and stream power of the flood flow if a landslide dam consists of many boulders a step pool system may develop on the spillway channel of the dam which would maximize the resistance consume most of the flow energy and consequently protect the dam from incision the development degree of the step pool system is represented by a parameter s p which was measured with a specially designed instrument a preservation ratio of landslide dams is defined as the ratio of preserved height after flood scouring to the original height of the dam for streams with peak flood discharge lower than 30 m3 s the preservation ratio is linearly proportional to s p for rivers with a peak flood discharge higher than 30 m3 s 30 30 000 m3 s the minimum s p value for stable channel increases with log p in which p is the unit stream power for a landslide dam with a poorly developed step pool system s p is smaller than the minimum value and the outburst flood incises the spillway channel and causes failure of the dam for preserved landslide dams sediment deposits in the quake lakes a landslide dam may develop into a knickpoint if it is stabilized by long term action of the flow large knickpoints can totally change the fluvial processes and river morphology uplift of the qinghai tibetan plateau has caused extensive channel bed incision along almost all rivers for many rivers the incision has been partly controlled by knickpoints upstream reaches of a knickpoint have a new and unchanging base level this brings about a transition from degradation to aggradation and from vertical bed evolution to horizontal fluvial process multiple and unstable channels are prominent in the reaches upstream of the knickpoints if hundreds of landslide dams occurred simultaneously on a reach of a mountain river the potential energy of bank failure and the slope erosion would be greatly reduced and sediment yield from the watershed may be reduced to nearly zero the quake lakes may be preserved long term and become beautiful landscapes streams with long term unfilled quake lakes have good aquatic ecology

magnetotelluric regional strike a new method for determining regional strikes from the magnetotelluric impedance tensor z and tipper t is presented it involves the minimization of weighted sums of the squared magnitudes of elements of z or t over all frequencies and all stations of interest when applied to data from the mexicali valley baja california around the cerro prieto geothermal field for a particular weighting function the method yielded orientations that agree to within 2 9 degrees for three lines with a total of 16 stations the consistency of orientations can be attributed in part to the pronounced two dimensional 2 d geologic characteristics of the area but the techniques also proved stable at stations near three dimensional 3 d inhomogeneities

geomorphic hazard assessment of landslide dams in south westland new zealand fundamental problems and approaches abstract quantitative assessments of landslide hazard usually employ empirical heuristic deterministic or statistical methods to derive estimates of magnitude frequency distributions of landsliding the formation and failure of landslide dams are common geomorphic processes in mountain regions throughout the world causing a series of consequential off site hazards such as catastrophic outburst floods debris flows backwater ponding up and downstream aggradation and channel instability conceptual and methodological problems of quantifying geomorphic hazard from landslide dams result from a aspects of defining landslide dam magnitude b scaling effects i e the geomorphic long range and long term implications of river blockage and c paucity of empirical data geomorphic hazard from a landslide dam break flood on the basis of conditional probabilities is being analysed for the alpine south westland region of new zealand where formation and failure of landslide dams is frequent quantification of the annual probability of landsliding and subsequent dam formation in the area is limited by historical and only partially representative empirical data on slope instability since landslide dam stability is a major control governing the potential of catastrophic outburst flooding the ensuing hazard is best assessed on a recurring basis gis based modelling of virtual landslide dams is a simple and cost effective approach to approximate site specific landslide dam and lake dimensions reservoir infill times and scaled magnitude of potential outburst floods although crude these order of magnitude results provide information critical to natural hazard planning mitigation or emergency management decisions

geomorphometric characteristics of new zealand landslide dams abstract this study presents results from a quantitative analysis of a new inventory of n 232 landslide dam occurrences in new zealand previously published data were expanded by documentation of recent events and evidence from a regional air photo reconnaissance focused on the upland regions of southwestern south island additional geomorphometric data on landslide dams associated lakes and contributing catchment characteristics were extracted from a 25 m digital elevation model dem augmented by limited ground truthing and compiled in a gis based inventory the new zealand case examples fall into the global trend although they contain both two extremely large features in terms of landslide dam volume vd and lake volume vl analysis suggests that landslide dam height hd landslide dam volume vd lake volume vl contributing catchment area ac and local relief hr are key variables for assessing landslide dam stability independently from other catchment parameters such as lithology climate or dam sedimentology they may be provisionally used as representative characteristics of landslide dams irrespective of environmental boundary conditions such as climate geology or site specific valley geomorphometry three newly proposed dimensionless indices i e the backstow index is basin index ia and relief index ir based on landslide dam height hd allow limited yet promising preliminary assessments of landslide dam stability compared with worldwide examples they also demonstrate a much narrower conditional range for the formation of stable landslide dams in new zealand catchment parameters such as maximum elevation emax upstream relief hr contributing catchment area ac and relief ratio rr are significantly different at sites of former and existing landslide dammed lakes and may be used as independent variables in future terrain based classification schemes generally data are incomplete with underreporting of small and ephemeral landslide dams and over representation of earthquake case studies nonparametric correlation highlights the statistical interdependence between geomorphometric variables as an artefact of initial data calculation while varying accuracy poses a significant drawback for complex multivariate statistical techniques such as principal component cluster or discriminant analyses

a calendar age estimate of a very late younger dryas ice sheet maximum in western norway abstract we have established an accurate chronology in calendar years for the maximum phase of the younger dryas yd scandinavian ice sheet in western norway glaciomarine silt confidentially identified in shallow marine basins located was 1 2 km distal to a yd ice marginal delta due to the topography of this area the silt monitors faithfully the period when the ice sheet reached and remained at its maximum position in these basins the deposition of silt commenced 6 10 cm above the vedde ash bed ca 10 300 14 c yr bp or ca 12 000 cal yr bp according to calculated sedimentation rates of the deposits the deposition of silt started and thus the ice sheet reached its maximum 300 400 years after the vedde ash fall around 11 600 11 700 cal yr bp the ice sheet receded from its maximum position simultaneously with the increase of betula birch pollen at the yd holocene boundary ca 11 500 cal yr bp the duration of the yd glacial maximum of the scandinavian ice sheet in western norway was only about 100 200 years and is constrained within the 14 c plateau at 10 000 14 c yr bp the yd glacial maximum occurred extremely late in western norway later than elsewhere in scandinavia the result also demonstrates different response times for different glaciers small cirque glaciers farther north in western norway expanded to their maximum position very early in the yd whereas the ice cap at alfotbreen reached its maximum later but still before the vedde ash fall the ice sheet reached its maximum well after the vedde ash fall and only 100 200 years before the yd holocene boundary

a 10be chronology of south western scandinavian ice sheet history during the lateglacial period we present 34 new cosmogenic 10be exposure ages that constrain the lateglacial bolling preboreal history of the scandinavian ice sheet in the lysefjorden region south western norway we find that the classical lysefjorden moraines earlier thought to be entirely of younger dryas age encompass three adjacent moraines attributed to at least two ice sheet advances of distinctly different ages the 10be age of the outermost moraine 14 0 0 6 ka n 4 suggests that the first advance is of older dryas age the innermost moraine is at least 2000 years younger and was deposited near the end of the younger dryas 11 4 0 4 ka n 7 after abandonment of the innermost lysefjorden moraine the ice front receded quickly towards the head of the fjord where recession was interrupted by an advance that deposited the trollgaren moraine at 11 3 0 9 ka n 5 10be ages from the inboard side of the trollgaren moraine suggest final retreat by 10 7 0 3 ka n 7 the late culmination of the younger dryas advance contrasts with other sectors of the scandinavian ice sheet where the margin appears to have culminated earlier during the younger dryas stadial followed by retreat during the middle and late part of the younger dryas

deglaciation of fennoscandia abstract to provide a new reconstruction of the deglaciation of the fennoscandian ice sheet in the form of calendar year time slices which are particularly useful for ice sheet modelling we have compiled and synthesized published geomorphological data for eskers ice marginal formations lineations marginal meltwater channels striae ice dammed lakes and geochronological data from radiocarbon varve optically stimulated luminescence and cosmogenic nuclide dating this is summarized as a deglaciation map of the fennoscandian ice sheet with isochrons marking every 1000 years between 22 and 13 cal kyr bp and every hundred years between 11 6 and final ice decay after 9 7 cal kyr bp deglaciation patterns vary across the fennoscandian ice sheet domain reflecting differences in climatic and geomorphic settings as well as ice sheet basal thermal conditions and terrestrial versus marine margins for example the ice sheet margin in the high precipitation coastal setting of the western sector responded sensitively to climatic variations leaving a detailed record of prominent moraines and other ice marginal deposits in many fjords and coastal valleys retreat rates across the southern sector differed between slow retreat of the terrestrial margin in western and southern sweden and rapid retreat of the calving ice margin in the baltic basin our reconstruction is consistent with much of the published research however the synthesis of a large amount of existing and new data support refined reconstructions in some areas for example the lgm extent of the ice sheet in northwestern russia was located far east and it occurred at a later time than the rest of the ice sheet at around 17 15 cal kyr bp we also propose a slightly different chronology of moraine formation over southern sweden based on improved correlations of moraine segments using new lidar data and tying the timing of moraine formation to greenland ice core cold stages retreat rates vary by as much as an order of magnitude in different sectors of the ice sheet with the lowest rates on the high elevation and maritime norwegian margin retreat rates compared to the climatic information provided by the greenland ice core record show a general correspondence between retreat rate and climatic forcing although a close match between retreat rate and climate is unlikely because of other controls such as topography and marine versus terrestrial margins overall the time slice reconstructions of fennoscandian ice sheet deglaciation from 22 to 9 7 cal kyr bp provide an important dataset for understanding the contexts that underpin spatial and temporal patterns in retreat of the fennoscandian ice sheet and are an important resource for testing and refining ice sheet models

a calculation method for predicting the runout volume of dam break and non dam break debris flows in the wenchuan earthquake area abstract the factors affecting debris flow runout volume changed considerably in the wenchuan earthquake area the main characteristic parameters for calculating the debris flow runout volume namely channelized landslide dam volume are first used to establish empirical models a new empirical statistical model is established by applying a multivariate regression analysis to the runout volumes of dam break and non dam break debris flows additionally flo 2d is used to simulate the debris flow runout volumes under the non dam breaking and dam breaking scenarios when the rainfall frequency is p 1 the predicted runout volumes in the huaxi gully are 24 48 104 m3 under the non dam breaking scenario and 43 41 104 m3 under the dam breaking scenario the runout volume in the dam breaking scenario is 6 07 104 m3 more than 1 77 times that in the non dam breaking scenario the predicted runout range of the dam breaking scenario is 1 16 times that of the non dam breaking scenario the predicted alluvial fan areas and average accumulation depths in the dam breaking scenario are larger than those in the non dam breaking scenario the predicted runout volume of the dam breaking scenario is 5 58 104 m3 which is less than the actual surveyed volume 48 99 104 m3 the relative error and accuracy of the numerical simulation results are 11 39 and 88 61 for the dam breaking scenario the new runout volume model was developed in catchments with abundant loose materials in the wenchuan earthquake area and can thus be applied to debris flow gullies in meizoseismal areas with newly fractured regolith and abundant loose material to estimate runout volumes the results of this study will help authorities select safe sites for future rehabilitation and relocation projects and can also be used as an important basis for debris flow risk management

collapse of marine based outlet glaciers from the scandinavian ice sheet abstract we present a reconstruction of the timing and retreat rates of more than 2000 m thick younger dryas yd fjord glaciers in western norway using a detailed chronology of 10 be exposure ages from lateral moraines and 14 c dated end moraines a primary conclusion is that ice margins retreated up the 120 170 km long fjords at mean rates of 240 340 m yr 1 during the early holocene we further show that part of the south western sector of the scandinavian ice sheet collapsed in two distinct steps the first step occurred between 19 5 and 18 5 ka bp as break up of the norwegian channel ice stream which drained the ice sheet during the last glacial maximum lgm the second step was the rapid retreat up the fjords mentioned above dated to 11 6 11 1 ka bp during the intervening 7000 years no net retreat occurred despite oscillations of the ice margin this stepwise ice margin retreat strongly contrasts with the more monotonic decay of the ice sheet as a whole indicating that water depths set the pace for climate triggered ice margin retreat in this part of the ice sheet calving and melting of marine margins has dominated mass loss from modern ice sheets in recent decades however the mechanisms and long term 100 1000 yr rate of ice front retreat is less certain and empirical examples such as those given here may help in developing better numerical models

a major re growth of the scandinavian ice sheet in western norway during allerod younger dryas abstract distinct younger dryas yd moraines are mapped more or less continuously around the scandinavian ice sheet in most areas there is no evidence to suggest that a glacial re advance took place during the yd either because it did not happen or because older deposits have been removed by glacial erosion in contrast we here present 90 radiocarbon dates from 36 different sites that were overrun by a major ice sheet advance in the area between hardangerfjorden and sognefjorden sw norway thus this region is exceptional for examining the glacial response to the climate shifts across allerod yd the re growth of the ice sheet in this sector commenced during the allerod interstadial it expanded along 600 800 m deep fjords reaching a thickness of up to 2000 m we produce time distance diagrams for two lobes for both the outermost coast became ice free close to 15 cal ka bp i e at the onset of the bolling the hardangerfjorden lobe re advanced during the older dryas 14 cal ka bp an event that was not replicated for the herdla lobe farther north both lobes reached their most landward position before re advancing at 13 5 13 0 cal ka and obtained their maximum extent at the very end of the yd 11 5 cal ka the late culmination of the advance is accurately dated and differs from most of the scandinavian ice sheet margin where the maximum was reached during early or middle yd we also present a time distance diagram from the last glacial maximum to the ice divide showing two step retreat fast retreat occurs 21 20 and 11 5 10 cal ka bp separated by a period of almost no net retreat 20 11 5 cal ka bp which contrasts with much more even retreat in other parts of the scandinavian ice sheet

postglacial palaeoceanography in the skagerrak crucial periods of change in the latest glacial to early holocene palaeogeographic and palaeoceanographic evolution in the skagerrak region are portrayed in four time slice maps on a calibrated age scale at 14 0 kyr 11 2 kyr 10 2 kyr and 8 1 kyr the course of palaeoenvironmental events is set in a high resolution chronological framework using images core md99 2286 and a grid of chirp sonar profiles these maps visualize the complex rapid palaeogeographic and palaeoceanographic changes during the glacialinterglacial transition which is characterized by major changes in circulation sediment sources and depositional processes

fluvial response to large rock slope failures examples from the himalayas the tien shan and the southern alps in new zealand we describe remnants of large 10 7 10 10 m 3 late pleistocene to holocene rockslides and rock avalanches that block ed rivers and are preserved in the himalayas the tien shan and the new zealand southern alps despite rates of uplift and erosion of up to 10 mm year 1 these natural dams control fluvial response on 10 1 10 4 year timescales by a storing and releasing sediment during forced alluviation and fluvial re incision b relocating river channels through diversion or seepage c inhibiting river erosion into bedrock d formingpersistentlong profileknickpointsandknickslopesassociatedwithsteephigh energy n10 3 wm 2 breachand epigenetic bypass gorges and fluvial hanging valleys and e shaping valley floor morphology sediments indicate that rockslidedammed lakes may persist up to 10 4 years before being drained or infilled several short lived 10 0 10 2 year historical rockslide dams in the indian and nepal himalayas and the southern alps have had marked volumetric impacts on catchment sediment budgets shortly following failure therefore we caution against the linear extrapolation of sediment delivery from prehistoric rockslide dams through time as a response variable we find reach scale changes to channel gradient to be prominent and persistent indicators of fluvial response to large rock slope failures 2006 elsevier b v all rights reserved

remote reference magnetotellurics equipment and procedures during the past 3 years major advances in the magnetotelluric technique have improved the quality of magnetotelluric data to the point where random errors in the impedance tensor and tipper are generally smaller than the uncertainty in their interpretation the major factor in this improvement has been the introduction of the remote reference technique although the use of ultrasensitive magnetometers and minicomputers for in field data processing has also been important after a review of the remote reference technique this paper describes the equipment and procedures used for remote reference magnetotellurics by the authors magnetometers using d c superconducting quantum interference devices typically have a sensitivity of 10 14 t hz 1 2 a dynamic range of 10 7 in a 1 hz bandwidth and a slewing rate of 3 10 5 t s 1 at 10 khz the electric field measurements use conventional cu cuso 4 electrodes the remote magnetic reference signals are transmitted to the base station using fm analog telemetry the data are collected and processed by a minicomputer based on an lsi 11 microprocessor the essential results for example the apparent resistivities and the tipper components with their probable errors are available in the field practical details are given of the handling of superconducting devices low temperature cryostats and liquid helium in the field various spurious noise sources are mentioned and techniques for minimizing their effects are described

the rio grande rift new electromagnetic constraints on the socorro magma body abstract the socorro magma body in central new mexico is a prime example of an intrusive magma body associated with continental extension in one of the major active rift zones of the world the rio grande rift to study this feature further in particular its relation to large scale features delineated elsewhere beneath the rift in 1988 brown university occupied a sequence of densely spaced 5 10 km wide band 10 4000 s remote referenced three component magnetic variation sites along an east west line which transected the southern margin of the magma body our profile was deployed so as to cross precisely above the center of what has been the most seismically active portion of the structure southwest of socorro complex magnetic transfer coefficients at up to 15 periods from 21 sites along our profile have been inverted to determine two dimensional conductivity models for vertical cross sections transverse to the strike of the rift two independent generalized inverse algorithms are used an overdetermined block inversion and a mixed determined flat continuous resistivity inversion both inversions require the presence of a conducting zone beneath the rift at intermediate depths 15 20 km in the crust this feature has properties which are similar to those of the intracrustal conductor seen elsewhere along the rift in addition to this conducting zone in the deeper crust the data require a more conductive core at shallow depth 10 15 km which appears to be associated with the base of a zone of increased microseismicity described by sanford and his colleagues this latter feature might be a zone of diffuse magmatic intrusions enhanced hydrothermal circulation or a combination of both finally our two inversions suggest that the resistivity structure beneath the western end of our profile which is physiographically adjacent to the colorado plateau has properties which are similar to those reported for interior regions of the plateau

cirque glacier activity in arctic norway during the last deglaciation abstract numerous cirques of the lofoten vesteralen archipelago in northern norway have distinct moraine sequences that previously have been assigned to the allerod younger dryas 13 400 to 11 700 yr bp interval constraining the regional distribution of the equilibrium line altitude ela of cirque and valley glaciers here we present evidence from a once glacier fed lake on southern andoya that contests this view analyses of radiocarbon dated lacustrine sediments including rock magnetic parameters grain size organic matter dry bulk density and visual interpretation suggest that no glacier was present in the low lying cirque during the younger dryas allerod the initiation of the glacial retreat commenced with the onset of the bolling warming 14 700 yr bp and was completed by the onset of allerod interstade 13 400 yr bp the reconstructed glacier stages of the investigated cirque coincide with a cool and dry period from 17 500 to 14 700 yr bp and a somewhat larger last glacial maximum lgm advance possibly occurring between 21 050 and 19 100 yr bp

the influence of large landslides on river incision in a transient landscape eastern margin of the tibetan plateau sichuan china deep landscape dissection by the dadu and yalong rivers on the eastern margin of the tibetan plateau has produced high relief narrow river gorges and threshold hillslopes that frequently experience large landslides large landslides inundate river valleys and overwhelm channels with large volumes 10 5 m 3 of coarse material commonly forming stable landslide dams that trigger extensive and prolonged aggradation upstream these observations suggest that strong feedbacks among hillslope processes channel morphology and incision rate are prevalent throughout this landscape and are likely characteristic of transient landscapes experiencing large increases in local relief in general landslide effects are a by product of rapid incision initiated by regional uplift however over timescales relevant to landscape evolution 10 4 yr large landslides can also act as a primary control on channel morphology and longitudinal river profiles inhibiting incision and further preventing the complete adjustment of rivers to regional tectonic climatic and lithologic forcing we explore a probabilistic numerical model to provide a quantitative framework for evaluating how landslides influence bedrock river incision and landscape evolution the time average number of landslide dams along a river course and thus the magnitude of the landslide influence is set by two fundamental timescales the time it takes to erode landslide deposits and erase individual dams and the recurrence interval of large landslides that lead to stable dams stable gradually eroding landslide dams create mixed bedrock alluvial channels with spatial and temporal variations in incision ultimately slowing long term rates of river incision thereby reducing the total amount of incision occurring over a given length of river a stronger landslide effect implies that a higher percentage of channel length is buried by landslide related sediment leading to reduced river incision efficiency the longer it takes a river channel to incise into a landslide dam and remove all landslide related sediment the more control these events have on the evolution of the river profile and landscape evolution this can be the result of slow erosion of stable dams or a higher frequency of large events

retrieval of historical surface displacements of the baige landslide from time series sar observations for retrospective analysis of the collapse event abstract landslides and resultant barrier lakes are significant threats to human lives and infrastructures three dimensional 3d surface displacements can give vital clues to the exploration of internal structure of landslides but they are difficult to be retrieved from spaceborne synthetic aperture radar sar observations due to the intrinsic limitation of sar imaging geometry meanwhile studies on predicting slope failure based on sar measured displacements are rarely seen here we used sar pixel offset tracking to investigate the baige landslide before the collapse on 10 october 2018 3d surface displacements retrieved by combining satellite sar and optical observations revealed heterogeneous spatial patterns within the landslide complex we observed linear secondary creep and accelerating tertiary creep prior to the failure from multi sensor sar data the possibility of forecasting the failure was demonstrated by applying an inverse velocity method to the time series displacements measured by sentinel 1 during the tertiary creep which is valuable for risk evaluation and disaster early warning

timing of the younger dryas glacial maximum in western norway this study precisely constrains the timing of the younger dryas yd glacial maximum in south western norway by utilizing sediment records from lake basins two of the basins located on the distal side of the mapped herdla halsnoy moraine received meltwater directly from the ice sheet only when the ice margin reached its maximum extent during the yd in the cores the ice maximum is represented by well defined units with meltwater deposits dominantly laminated silt plant macrofossils in the sediment sequences are common and we obtained 18 radiocarbon ages from one of the cores by applying bayesian age depth modelling we obtained a precise date for this meltwater event and thereby also for the timing of the yd glacial maximum we conclude that the ice sheet advance culminated at the halsnoy moraine at 11 760 120 cal a bp and that the ice margin stayed in this position for 170 120 years the subsequent retreat started at 11 590 100 cal a bp i e close to the yd holocene boundary withdrawal was probably triggered by abrupt climatic warming at this time copyright 2011 john wiley sons ltd

timing and east west correlation of south swedish ice marginal lines during the late weichselian abstract the retreat of the late weichselian ice sheet over the southern part of sweden is marked along the southwest coast by distinct marginal moraine ridges their timing can directly and indirectly be assessed based on a number of radiocarbon dates and pollen stratigraphic investigations on lake sediment sequences adjacent to the ice marginal lines along the southeastern side of the peninsula the ice recession has been reconstructed based on a combination of clay varve chronology pollen and radiocarbon stratigraphy a morphological correlation of ice marginal lines between the west and east coast is problematic since the distinct west coast moraines cannot be followed through the central part of the peninsula towards the east coast this paper is an attempt to reconstruct an age equivalent west east extension of the ice recession lines on the basis of existing data sets for our correlation we use calibrated radiocarbon ages for ice marginal deposits on the west coast and compare these with a partly radiocarbon dated clay varve chronology on the east coast we conclude that the two oldest moraines on the west coast formed at 18 000 16 000 and 15 400 14 500 cal yr bp respectively during the following rapid deglaciation which may have coincided with the beginning of the bolling pollen zone large parts of southernmost sweden became ice free except for higher elevated areas where stagnant ice remained for another 400 500 yr a best guess is that the formation of the next younger ice marginal lines may have occurred at 14 400 14 200 14 200 and 13 400 cal yr bp and during the younger dryas cold event

from cold to cool in northernmost norway lateglacial and early holocene multi proxy environmental and climate reconstructions from jansvatnet hammerfest abstract a multi proxy palaeoecological study of the lateglacial and early holocene sediments of jansvatnet hammerfest northernmost norway 70 39 n showed that cold and arid conditions prevailed in both the lateglacial interstadial and the younger dryas terrestrial proxies are macrofossils and pollen aquatic proxies are plant and invertebrate macrofossils pollen diatoms and chironomids mean july temperatures were reconstructed using pollen and chironomid calibration functions and ecological knowledge of the fossil flora and fauna lake water ph was reconstructed using a diatom ph calibration function above sterile basal deglacial silts biotic activity was detected around 14600 years ago in the interstadial chronologically equivalent to the bolling allerod in the greenland ice core chronology catchment vegetation resembled polar desert and ultra cold stenothermic chironomids lived in the lake however diatom assemblages were diverse and dynamic in the younger dryas stadial conditions deteriorated in the early younger dryas chironomid inferred air temperatures ci tjul fell about 1 c pollen inferred temperatures pi tjul did not fall and the terrestrial vegetation hardly changed because of the extreme aridity the lake water was turbid from suspended clay which diminished aquatic life later in the younger dryas ca 12400 cal yr bp reconstructed mean july temperatures fell by a further 3 c and were close to the minimum to support life at around 3 4 c however decreased turbidity allowed moss growth on the lake bottom that provided habitats for invertebrates and diatoms in the last 200 years of the younger dryas temperatures increased by 2 3 c and terrestrial and aquatic organisms responded quickly at the start of the holocene a rapid increase of more than 3 c in pi tjul to 9 5 c initiated the replacement of sparse arctic tundra by low arctic dwarf shrub heath simultaneously a further 2 c increase in ci tjul to 10 11 c reflected a regime shift in the lake aquatic macrophytes rapidly replaced the moss carpet diatom assemblages stabilised and diatom plankton developed and cold stenotherm chironomids were replaced by cool temperate taxa productivity increased as ci tjul reached a steady maximum of around 12 c and pi tjul reached 10 5 c at about 10000 cal yr bp at this time tree birch arrived and woodland developed over the catchment birch could have immigrated from the south up the west coast or from the east along the barents sea coast acidophilous aquatic taxa increased as diatom inferred ph gradually decreased from 7 3 to 6 6 after ca 9380 cal yr bp the density and extent of birch woodland decreased and species of exposed rocky areas increased reflecting increased windiness precipitation and possibly a small decrease in july temperatures birch now formed the arctic tree line at jansvatnet the lateglacial climatic pattern at jansvatnet resembles patterns detected elsewhere in northern norway and svalbard and in marine records from the norwegian and barents seas but contrasts with patterns in southern norway

a magnetotelluric profile across the western boundary of the salton trough in northern baja california mexico abstract eighteen magnetotelluric mt stations were occupied in an east west profile across the northern part of the baja california peninsula immediately south of the international border between mexico and the u s a the profile stretches across the peninsular ranges batholith into the salton trough a region of active crustal spreading data were collected in the frequency range of 0 001 25 hz using the remote reference technique we have conducted a preliminary modeling of the data by fitting both the transverse electric and the transverse magnetic apparent resistivity curves using a two dimensional 2 d forward modeling algorithm across the batholith the geoelectric model exhibits surface resistivity 1000 m decreasing by an order of magnitude with depth however a very high conductivity has been modeled between depths of 12 and 32 km in an isolated block this anomaly may be due to a zone of entrapped water in the laguna salada basin on the western margin of the salton trough the near surface resistivities are of the order of tens of m in the center of the basin at depths the model for the mexicali valley near the center of the salton trough presents very low near surface resistivities some near 1 m in general one sees approximately a horizontal interface between more and less conductive sediments at 2 km depth this contact deepens toward the center of the valley the two layers correspond to clay rich unconsolidated sediments saturated with saline water in the upper zone and consolidated sediments with limited pore space below a systematic anisotropy present in all the soundings could be accounted for by the 3 d geometry of the salton trough which may enhance the electric field parallel to the structure

sea level fluctuations imply that the younger dryas ice sheet expansion in western norway commenced during the allerod after the first emergence following deglaciation relative sea level rose by 10 m in western norway and culminated late in the younger dryas yd the relative sea level history reconstructed by dating deposits in isolation basins shows a sea level low stand between 13 640 and 13 080 cal yr bp a 10 m sea level rise between 13 080 and 11 790 cal yr bp and a sea level high stand between 11 790 and 11 550 cal yr bp shortly after the yd holocene boundary sea level fell abruptly by 37 m the shorelines formed during the sea level low stand in the mid allerod and during the sea level high stand in the yd have almost parallel tilts with a gradient of 1 3 m km 1 indicating that hardly any isostatic movement has taken place during this period of sea level rise we conclude that the transgression was caused by the major re advance of the scandinavian ice sheet that took place in western norway during the lateglacial the extra ice load halted the isostatic uplift and elevated the geoid due to the increased gravitational attraction on the sea our results show that the crust responded to the increased load well before the yd starting 12 900 cal yr bp with a sea level low stand at 13 640 cal yr bp and the subsequent yd transgression starting at 13 080 cal yr bp thus we conclude that the so called yd ice sheet advance in western norway started during the allerod possibly more than 600 years before the allerod yd transition r 2007 elsevier ltd all rights reserved

influence of landslides on biophysical diversity a perspective from british columbia landslides have long been overlooked or underestimated as important natural disturbance agents in particular the ecological role of landslides in maintaining biological diversity has been largely ignored here we provide a western canadian british columbian perspective on the influences of landslides on biophysical diversity which is related in several ways to biological diversity we recognize several types of biophysical ecological diversity site diversity soil diversity and the derivative habitat or ecosystem including aquatic ecosystems diversity there are also a variety of landslide types depending on materials and on the rate and style of movement we discuss the roles of different landslide types on various aspects of terrestrial diversity landslides are simultaneously depositional and erosional processes that influence sites by redistributing materials and changing surface expression usually creating a complex microtopography that can include very dry ridges and hummocks and sometimes depressions with standing water landslide impacts to site also influence soil and soil development portions of landslides with exposed parent material are set back to the initial stages of soil development and ecological succession landslides can also change soil density structure porosity surface texture chemistry and microclimate by changing site and soil landslides also influence habitat landslides influence habitat diversity by engendering a mosaic of seral stages often both primary and secondary and in overwhelmingly forested landscapes often create nodes or hotspots of non forested habitat and biota in some areas like the boreal forest there is an important interplay between landslides and fire while on the coast of british columbia debris and snow avalanches can be the dominant disturbance agent low gradient and deep seated landslides are often opportunistically colonized by beaver and other water and shrub loving fauna sag ponds and impounded streams provide aquatic habitat often with standing dead trees landslide rubble and scarps provide denning nesting habitat escape terrain and cliff habitat for vertebrates

landslide induced river channel avulsions in mountain catchments of southwest new zealand pulsed or chronic supply of landslide debris to valley floors has historically caused substantial aggradation and channel instability in several alpine catchments of sw new zealand in this regional investigation of landslide impacts on river morphology three types of landslide induced channel avulsion are discerned i upstream backwater avulsions ii contact avulsions and iii downstream loading avulsions the basis for this qualitative geomorphic process response framework is the principal direction of fluvial response with respect to its position relative to the causative landslide emplacement site downstream avulsions have the highest damage potential to land use and infrastructure on unconfined mountain fringe alluvial fans in the wake of such events catastrophic aggradation may obliterate up to several km2 of mature floodplain forests by burial under several metres within a few decades estimates of mean aggradation rates are high 220 mm year 1 and exceed long term 103 year trends of fluvial degradation by an order of magnitude future potential avulsion routeways may be detected by geomorphic mapping of abandoned channels which are preferentially reactivated in the wake of landslide induced sediment waves

estimates of south greenland late glacial ice limits from a new relative sea level curve abstract marine lacustrine isolation contacts from seven basins in the nanortalik area south greenland have been analysed and dated the basins were isolated from the sea as a consequence of isostatic rebound following deglaciation the isolation contacts were identified with litho and biostratigraphical analyses especially sedimentary changes grey scale analyses and analyses of macroscopical remains of plants and animals dating was performed by analytical mass spectroscopy radiocarbon dating of macrofossils and bulk sediment samples a slow initial relative sea level fall that begins at 13 8 cal ka bp changes to a rapid relative sea level fall before the sea level fell below the present day sea level just prior to 10 cal ka bp the emergence curve goes further back in time than any previous emergence curve constructed from greenland which reflects the early deglaciation of the studied region the glacio isostatic crustal rebound following deglaciation was around 110 m the sea level history indicates that the margin of the greenland ice sheet probably extended out to the shelf margin during the last glacial maximum and that the ice thickness must have been at least 1500 m over the outer coast thus the highest coastal mountains would have been ice covered which is surprising given their alpine character in addition the major part of the recession of the ice must have occurred relatively late and quickly maybe from 14 to 12 cal ka bp the late holocene transgression may at least in part be due to increased isostatic loading as a consequence of advancing glaciers during the neoglaciation

younger dryas glaciomarine sedimentation push moraine formation and ice margin behavior in the middle swedish end moraine zone west of billingen central sweden abstract new highway exposures and drilling reveal the stratigraphy and structure of the middle swedish end moraine zone west of billingen sweden the material in the end moraines is primarily glaciomarine clay of younger dryas age that was deposited as varved clay in front of the retreating glacier and then pushed glaciotectonically to form push moraines during minor ice margin oscillations during overall retreat during the younger dryas cold event the moraines are composed of deformed and remobilized clay with some clayey diamicton and penecontemporaneously deposited and deformed sand between the moraines lie intermoraine flats composed of undeformed varved clay of younger dryas age and surface sands of younger dryas to early holocene age based on estimations of moraine volume sedimentation rate and ice margin retreat rates we calculate the overall ice margin retreat and end moraine construction to span 350 800 years within the younger dryas because the number of moraines in the middle swedish end moraine zone varies across sweden we regard the individual oscillations west of billingen to be driven by local physical and glaciologic factors rather than ice sheet wide climate drivers the study area is also the location of the early and final drainages of the baltic ice lake the final drainage of the baltic ice lake took place several decades after the youngest moraine was formed we consider it likely that the earlier allerod drainage of the baltic ice lake bil also took place at billingen despite the lack of clear local stratigraphic evidence however based on our model a retreat driven solely by climate would not have exposed the outlet at billingen and we propose a dynamic break up of the ice margin likely centered on valle harad that was driven by the head difference between the bil and the sea

geomorphic events and landform response in south eastern taranaki new zealand abstract south eastern taranaki is a tectonically rising area of hill country and marine terraces cut into plio pleistocene marine sediments in the north island of new zealand it is argued that the geomorphic development of the region is more satisfactorily explained with resort to concepts of dynamic metastable equilibrium and unsteady behaviour than by concepts of steady equilibrium behaviour the region is constantly adjusting in part or in whole to a spectrum of geomorphic events including sea level change tectonic uplift aeolian deposition large landslide triggering earthquakes deforestation and landslide triggering rainstorms the record of these events in terms of frequency and magnitude is established and the consequential landform response is discussed twelve high sea level events within the last 700 ka are recorded in the landscape each with associated phases of aeolian deposition large earthquakes with terrain forming capability occur on average once every 1000 to 10 000 years as a result of slope destabilization by recent deforestation erosion rates appear to have increased by three times their previous rate the agents involved in this process are rainstorms with a return period of about 10 years which during a single event can strip the regolith from 5 to 15 percent of hillslopes over areas of up to 100 km2

a super large landslide in tibet in 2000 background occurrence disaster and origin on april 9 2000 a super large landslide 3 x 10 8 m 3 occurred along zhamu creek southeast tibet as a result a landslide dam formed and the yigong river was blocked a channelized diversion was constructed for prevention of overtopping two months later on june 10 a catastrophic flood resulting from the failure of the landslide dam caused a serious loss of property this is the second of landslide occasion dam formation and flooding occurrence at the same site since 1900

intcal13 calibrated ages of the vedde and saksunarvatn ashes and the younger dryas boundaries from krakenes western norway from krakenes lake in western norway there exist 118 accelerator mass spectrometry 14c dates for the time interval 12 000 8000 14c a bp that we earlier calibrated using the intcal09 data set these yielded the most accurate and precise ages available for the younger dryas boundaries and the vedde and saksunarvatn ashes here we present a new calibration using the recently published intcal13 data set all differences between the two sets of calibrated ages are within the 1 error of the original intcal09 results the most significant differences are that the error for the allerod younger dryas boundary decreased that this boundary became slightly older and that the length of the younger dryas increased slightly