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1.
The “La Clapière” area (Tinée valley, Alpes Maritimes, France) is a typical large, complex, unstable rock slope affected by Deep Seated Gravitational Slope Deformations (DGSD) with tension cracks, scarps, and a 60 × 106 m3 rock slide at the slope foot that is currently active. The slope surface displacements since 10 ka were estimated from 10Be ages of slope gravitational features and from morpho-structural analyses. It appears that tensile cracks with a strike perpendicular to the main orientation of the slope were first triggered by the gravitational reactivation of pre-existing tectonic faults in the slope. A progressive shearing of the cracks then occurred until the failure of a large rock mass at the foot of the slope. By comparing apertures, variations and changes in direction between cracks of different ages, three phases of slope surface displacement were identified: 1) an initial slow slope deformation, spreading from the foot to the top, characterized by an average displacement rate of 4 mm yr− 1, from 10–5.6 ka BP; 2) an increase in the average displacement rate from 13 to 30 mm yr− 1 from the foot to the middle of the slope, until 3.6 ka BP; and 3) development of a large failure at the foot of the slope with fast displacement rates exceeding 80 mm yr− 1 for the last 50 years. The main finding of this study is that such a large fractured slope destabilization had a very slow displacement rate for thousands of years but was followed by a recent acceleration. The results obtained agree with several previous studies, indicating that in-situ monitoring of creep of a fractured rock slope may be useful for predicting the time and place of a rapid failure.  相似文献   

2.
Sackungs are the largest gravitational deformation observed in mountains. They are characterized by the long-term slowness of the movements, but their mechanism is still not well understood. Nowadays cosmic ray exposure (CRE) dating methods allow dating the morphologic structures involved in sackung and can contribute at the understanding of their origin. In the Alps, the 5.3 km long Arcs sackung initiated during the activity of rock glaciers. Three samples from these faulted rock glaciers provide their first CRE ages and show that at 2000 m elevation these block accumulations moved during the Younger Dryas and stopped in early Holocene. Six 10Be ages of fault scarps show that the Arcs sackung lasted only a few thousand years and stopped at about 8462 ± 432 10Be yr. They also reveal that deformation migrated upslope in agreement with a mechanism of flexural toppling of vertical layers. This unique and long gravitational event, characterized by migration of the deformation, does not support earthquake shaking as triggering mechanism for individual faults. It shows that, in the upper Isère valley, slope deformation was delayed of several thousand years after glacial debuttressing, and is not anymore active despite its fresh morphology.  相似文献   

3.
Large sector collapses are a major component of oceanic islands evolution. Here we show that voluminous events such as the Icod landslide on Tenerife (Canary Islands) cause dramatic changes on the magma feeding system and control the subsequent volcanic and geomorphologic evolution of the eruptive complex over a period of more than 150 kyr. Instantaneous unloading by the Icod landslide is marked by the development of a large phonolitic explosive eruption dated at 175 ± 3 ka and interpreted as reflecting the immediate emptying of a shallow pre-existing magma chamber. Geochronological, geomorphological and geochemical analyses, carried out on the post-landslide volcanic succession sampled in a 4.4 km-long underground water-recovery gallery, provide further evidence for an enhanced extrusion of primitive lavas starting in the 10 kyr time interval following the failure. Rapid construction (< 40 kyr) of a thick basaltic volcano in the landslide scar at high eruptive rates (up to 8 km3 kyr−1) increased the lithostatic pressure which then favored the intermittent storage of basic magma under the edifice. This resulted in more episodic construction evidenced by a significant decrease in output rates and the increasing occurrence of lavas with intermediate composition from 117 ± 7 to 52 ± 7 ka. An apparent volcanic gap is observed between 52 ± 7 and 18 ± 1 ka, after which highly differentiated lavas have been dominantly erupted. We propose that part of the gap can be explained by the individualization of a shallow magma reservoir a few kilometers below the base of the Teide volcano. During recent periods, vertical and lateral extrusions of trachytic and phonolitic viscous bodies from this storage area contributed to increase the slope of the main edifice up to 35°, overall favoring its present-day instability.  相似文献   

4.
Late Quaternary slip across the Cañada David detachment has produced an extensive array of Quaternary scarps cutting alluvial-fans along nearly the entire length (~ 60 km) of the range-bounding detachment. Eight regional alluvial-fan surfaces (Q1 [youngest] to Q8 [oldest]) are defined and mapped along the entire Sierra el Mayor range-front. Terrestrial cosmogenic nuclide 10Be concentrations from individual boulders on alluvial-fan surfaces Q4 and Q7 yield surface exposure ages of 15.5 ± 2.2 ka and 204 ± 11 ka, respectively. Formation of the fans is probably tectonic, but their evolution is strongly moderated by climate, with surfaces developing as the hydrological conditions have changed in response to climate change on Milankovitch timescales. Systematic mapping reveals that the fault scarp array along active range-bounding faults in Sierras Cucapa and El Mayor can be divided into individual rupture zones, based on cross-cutting relationships with alluvial-fans. Quantitative morphological ages of the Laguna Salada fault-scarps, derived from linear diffusive degradation modeling, are consistent with the age of the scarps based on cross-cutting relationships. The weighted means of the maximum mass diffusivity constant for all scarps with offsets < 4 m is 0.051 and 0.066 m2/ka for the infinite and finite-slope solutions of the diffusion equation, respectively. This estimate is approximately an order of magnitude smaller than the lowest diffusivity constants documented in other regions and it probably reflects the extreme aridity and other microclimatic conditions that characterize the eastern margin of Laguna Salada.  相似文献   

5.
This work proves the existence of a large deep-seated gravitational slope deformation (DGSD) in a hilly region of the southwestern Alps, whereas DGSD are usually linked with high relief energy in mountain environments. Moreover, we describe the usefulness of applying paleoseismological techniques by means of trench excavation to date and understand the deformation history and genesis of recent morphostructures, and we found evidence of causative relationships between DGSD and surface landslides. The studied DGSD of Mt. Croce della Tola–Mt. Scincina, Italy, is the largest of the western Alps: it is 7-km long and involves a minimum area of 16 km2 with a volume ≥3.5 km3 probably extending further NE beneath Lake Maggiore surface. Several parallel scarps, representing the surface expression of slip-planes, affect the upper part of the slope, whereas the lower part presents a convex profile. DGSD at Mt. Croce della Tola started in the last interglacial period (120–40 ka BP) and the following glacial phase was not able to significantly modify the general slope geometry. Post-glacial deformation also occurred, especially at Mt. Scincina, after 25 ka BP. Post-glacial and active surface landslides developed on the convex lower part of the slope, suggesting that they resulted from instability due to the new profile assumed by the slopes during the deep-seated deformation. The occurrence of Mt. Scincina DGSD with a very low topographic gradient is interpreted as an effect induced by on other large DGSD.  相似文献   

6.
Relationships between tectonic framework and gravity-driven phenomena have been investigated in an area of the Central Apennines (Italy) characterised by high relief. The north–south, half-dome shaped Maiella anticline lies in the easternmost part of the Apennine fold-and-thrust belt. Its backlimb is bordered by the Caramanico Fault, a normal fault with a maximum downthrown of about 3.5 km that separates the western slope of the Maiella Massif from the Caramanico Valley. The southwestern Maiella area is affected by deep-seated gravitational slope deformation indicated by major double crest lines, down-hill and up-hill facing scarps, a pattern of crossing trenches, bulging at the base of slopes and the presence of different types of landslide and talus slope deposits.The onset and development of deep-seated gravitational slope deformations and the location of Quaternary, massive rockslope failures have been strongly influenced by the structural framework and tectonic pattern of the anticline. Deep-seated gravitational slope deformation at Mt. Macellaro–Mt. Amaro ridge has developed along the Maiella western, reverse slope in correspondence with the anticline axial culmination; it is bordered at the rear by a NNW–SSE oriented, dextral, strike-slip fault zone and has an E–W direction of rock mass deformation. Closer to the southern plunging area of the anticline, gravity-driven phenomena show instead a N–S and NW–SE direction, influenced by bedding attitude.3D topographic models illustrate the relationship between deep-seated gravitational slope deformation and massive rockslope failures. The Campo di Giove rock avalanche, a huge Quaternary failure event, was the result of an instantaneous collapse on a mountaine slope affected by a long-term gravity-driven deformation.  相似文献   

7.
Understanding continental-slope morphological evolution is essential for predicting basin deposition. However, separating the imprints and chronology of different seafloor shaping processes is difficult. This study explores the utility of bathymetric spectral decomposition for separating and characterizing the variety of interleaved seafloor imprints of mass wasting, and clarifying their role in the morphological evolution of the southeastern Mediterranean Sea passive-margin slope. Bathymetric spectral decomposition, integrated with interpretation of seismic profiles, highlights the long-term shape of the slope and separates the observed mass transport elements into several genetic groups: (1) a series of ~25 km wide, now-buried slide scars and lobes; (2) slope-parallel bathymetric scarps representing shallow faults; (3) slope-perpendicular, open slope slide scars; (4) bathymetric roughness representing debris lobes; (5) slope-confined gullies. Our results provide a multi-scale view of the interplay between sediment transport, mass transport and shallow faulting in the evolution of the slope morphology. The base of the slope and focused disturbances are controlled by ~1 km deep salt retreat, and mimic the Messinian base of slope. The top of the open-slope is delimited by faults, accommodating internal collapse of the margin. The now-buried slides were slope-confined and presumably cohesive, and mostly nucleated along the upper-slope faults. Sediment accumulations, infilling the now-buried scars, generated more recent open-slope slides. These latter slides transported ~10 km3 of sediments, depositing a significant fraction (~3 m in average) of the sediments along the base of the studied slope during the past < 50 ka. South to north decrease in the volume of the open-slope slides highlight their role in counterbalancing the northwards diminishing sediment supply and helping to maintain a long-term steady-state bathymetric profile. The latest phase slope-confined gullies were presumably created by channelling of bottom currents into slide-scar depressions, possibly establishing incipient canyon headword erosion.  相似文献   

8.
The widely used linear diffusion model for hillslope evolution does not accurately predict the degradation of terrace scarps produced by the Late Pinedale West Spalding Bay Channelway (WSBC) near Jenny Lake in Grand Teton National Park, Wyoming USA. These scarps, cut into identical cohesionless quartzite gravel, were formed nearly simultaneously, during the brief period of time the WSBC was active. They are assumed to have had the same initial morphology as scarps currently forming along Snake River that are cut in the same material: a straight midsection sloping at 30° and a horizontal base and crest. The model best able to fit the observed morphology and the change in morphology with scarp height specifies the downslope debris flux is proportional to slope gradient raised to a power of 3.4.  相似文献   

9.
Hillslopes in central and western parts of KwaZulu-Natal, South Africa are often mantled by colluvial sediments of the Masotcheni Formation. These sediments have accreted in response to several cycles of deposition, pedogenesis and incomplete erosion. Climatic controls on these cycles are incompletely known. Results from fieldwork, micromorphology, stable carbon isotope analysis and Optically Stimulated Luminescence dating of Masotcheni Formation sediments from Okhombe valley in the Drakensberg foothills are combined. Deposition in the area had at least 11 phases, starting before 42 ka and ending before 0.17 ka. The first six deposits (from before 42 ka to after 29 ka) resulted from the interplay between slope processes and fluvial redistribution under cold conditions. Solifluction was the most important slope process. No deposits have been found from the Last Glacial Maximum, arguably because this period was too dry. The last five deposits (from about 11 ka to before 0.17 ka) resulted from fluvial redistribution of upslope material and older deposits under increasing precipitation. Current extreme gully erosion in the Masotcheni Formation indicates a lack of available upslope material, leaving downslope deposits as the only sediment source for fluvial redistribution. This model for landscape response to climate change may be able to explain how climate controlled landscape processes in other Masotcheni Formation sites in KwaZulu-Natal. In the research area and elsewhere, this proposition may be tested with numerical landscape evolution models.  相似文献   

10.
Giant landslides, which usually have volumes up to several tens of km3, tend to be related to mountainous reliefs such as fault scarps or thrust fronts. The western flank of the Precordillera in southern Peru and northern Chile is characterized by the presence of such mega-landslides. A good example is the Latagualla Landslide (19°15′S), composed of ~ 5.4 km3 of Miocene ignimbritic rock blocks located next to the Moquella Flexure, a structure resulting from the propagation of a west-vergent thrust blind fault that borders the Precordillera of the Central Depression. The landslide mass is very well preserved, allowing reconstitution of its movement and evolution in three main stages. The geomorphology of the landslide indicates that it preceded the incision of the present-day valleys during the late Miocene. Given the local geomorphological conditions 8–9 Ma ago (morphology, slopes and probably a high water table), large-magnitude earthquakes could have provided destabilization forces enough to cause the landslide. On the other hand, present seismic forces would not be sufficient to trigger such landslides; therefore the hazard related to them in the region is low.  相似文献   

11.
The Rwenzori Mountains are a high alpine mountain chain, about 40 × 80 km in size, just north of the equator in the western branch of the East African Rift System in Africa. The central part of the mountain chain is located in Uganda, and the highest peak, the Margherita Peak with 5119 m, lies on the border to the Democratic Republic of Congo. Topography is very pronounced, with steeply incised valleys and clear glacial landforms in the upper part of the mountain chain. The Rwenzori Mountains are an unusually high mountain chain located in the extensional setting of the East African Rift System, and the large elevation poses a challenging problem for geodynamists to explain.We have used the landscape evolution model ULTIMA THULE, which combines hillslope diffusion, fluvial erosion, and glacial abrasion and is driven by a climate driver, simulating the variations in temperature, precipitation, and relief over several glacial cycles. With a simulation time of 800 ka, we test the hypothesis of climate-tectonic interactions on the uplift of the Rwenzori Mountains.Our results show that a moderate cooling of around 6° causes widespread glaciation of the high mountain regions as observed during the peak glacial phases, and that morphological processes degrading the landscape allow for a tectonic uplift rate of around 0.5 mm a− 1.  相似文献   

12.
A large landslide on the urban fringe of metropolitan Phoenix, Arizona   总被引：2，自引：1，他引：2  
A granitic rock avalanche, one of the largest Quaternary landslides in Arizona outside the Grand Canyon with a volume of approximately 5.25 M m3 and a width a little under 0.5 km, ran 1 km from the eastern McDowell Mountains. With lateral levees and pressure ridges, the rock avalanche deposit displays many features found on classic sturzstroms. Failure occurred along a major joint plane paralleling the slope with a dip of 44°, when a major base level lowering event in the Salt River system would have undermined the base of the failed slope, and probably during a period of more moisture than normally available in the present-day arid climate. Failure at the subsurface weathering front highlights the importance of the dramatic permeability change between grussified regolith and relatively fresh bedrock. Rock varnish microlaminations (VMLs) dating, in concert with other geomorphic evidence, suggests that the rock avalanche deposit is slightly older than 500 ka. The rock vanish results also have important implications for sampling strategies designed to use cosmogenic nuclide to date Quaternary landslide deposits. Discovery of a large landslide in close proximity to the extending urban fringe of metropolitan Phoenix argues for a more careful analysis of landslide hazards in the region, especially where rapid development excavates bedrock at the base of steep mountain slopes and where the subsurface weathering front is near the surface.  相似文献   

13.
This paper presents a simple analytical model for estimating rock glacier age by coupling the ratio of frontal advance to total rock glacier length and the ratio of debris volume in the rock glacier to present debris flux in the talus cone–rock glacier transition zone. The model was applied to two rock glaciers at Prins Karls Forland, Svalbard. By assuming volumetric debris contents in the deforming layer of the rock glacier of between 0.3 and 0.4, we obtained age estimates for the rock glaciers of between 12 ka and 24 ka. The corresponding average rockwall retreat rates are between 0.30 and 0.62 mm a‐1. Considering the limitations of the model, we suggest a minimum age of 13 ka for the initiation of rock glacier development. Using this age, rockwall retreat rates for the seven rock glaciers investigated at Prins Karls Forland are between 0.13 and 0.64 m ka‐1 (assuming the volumetric debris content for the whole rock glacier/talus cone is 0.35). The model requires further testing on other datasets, better field estimates of the debris content and depth of the deforming layer, and could also benefit from the inclusion of an unsteady debris supply function in order to refine age estimates.  相似文献   

14.
Lukas Plan   《Geomorphology》2005,68(3-4):201-212
Carbonate dissolution rates were investigated by measuring the mass difference of carbonate tablets exposed to natural dissolution for 1 year. 70 tablets were distributed over 13 test sites on the north slope of the Hochschwab Massif in the Austrian Alps. The influences of altitude, subsoil vs. sub-aerial exposure, vegetation, karst morphology, soil humidity, sample lithology, and sample surface morphology were investigated. The observed dissolution rates varied between 13 and 40 μm/a for subcutaneous samples and about 11 μm/a for sub-aerial exposure. Outstandingly high rates of 48 μm/a were observed in a doline and nearly zero rates were measured at a site influenced by seeping spring water.A mass balance, using high-resolution hydrological data, was calculated for the Kläffer Spring, which has an average outflow of 4.8 m3/s. It indicated a loss of 21×106 kg of carbonate rock per year which gives an average dissolution rate of 95 μm/a for the catchment area of 83 km2. The dissolution rates of 10 μm/a from the sub-aerially exposed samples are comparable to values from limestone pedestals, which were protected from dissolution by glacial erratics for the past 15 ka.  相似文献   

15.
The paper analyses uphill-facing scarps and associated troughs developed in the oversteepened slopes of two neighbouring glacial valleys in the central Spanish Pyrenees. Previous studies of sackung landforms in the Pyrenees have argued for deglacial unloading as the genetic mechanism, but this causal and temporal relationship has not been proved due to the lack of chronological data. The antislope scarps in the two studied locations, Vallibierna and Estós, are developed in Palaeozoic metasedimentary rocks (parallel to the contour lines and the structural grain), occur in the intermediate sector of the hillslope, and are up to 0.5 km long and several meters high. A trench was excavated in a sackung trough fill in each of the valleys in order to gain information about their chronology and genesis. Charcoal from the lowermost unit in Vallibierna provided an age of 5.9 cal. ka for the sackung and extrapolation of the three dates obtained in Estós indicates that the trough formed ca. 7.6–7.8 cal. ka. Deglaciation of the studied sectors of the valleys occurred between 16 and 13 ka. The time lag of >5 ka suggests that glacial erosion and the subsequent debutressing of the oversteepened valley walls created slopes predisposed to sackung development, but did not initiate the movement. Seismic shaking is proposed as a probable triggering factor. This hypothesis, although supported by the sudden deformation event recorded by a failure plane exposed in Vallibierna trench, and by the seismic and neotectonic activity of the area, cannot be proved due to the lack of chronological information about paleoearthquakes.  相似文献   

16.
《Geomorphology》2007,83(1-2):1-13
Weathering and erosion processes are investigated using electrical resistivity tomography (ERT) imaging and the quantification of geomorphic patterns at the edges of a lateritic plateau overlying ultramafic rocks in the north western region of the main island of New Caledonia (Southwest Pacific). The obtained ERT images document the structure and long-term evolution of the regolith, while source area parameters such as area (A) local slope above channel head (tanθ) and longitudinal river profiles allow the characterization of contrasting geomorphic patterns around the plateau. The geo-electrical profiles show a succession of hard rock protrusions and weathering troughs, whose depth varies greatly. The area–slope relationship allows the distinction between saprolite- and ferricrete-mantled source areas. The former could result from a regolith erosion process by shallow landslides; the latter from a secondary ferruginization process of reworked lateritic debris. The deepest troughs underlie saprolite-mantled source areas above channel heads, which are characterized by a low permeability saprolite, relatively high slope gradient, and lower area/slope ratios. Such source areas generate fairly high runoff, sustaining rivers and creeks with relatively high erosion power. The ferricrete-mantled source areas are characterized by higher permeability and area/slope ratios, leading to lower runoff and less erosion but further chemical rock weathering. The ferricrete of those source areas acts as a protective hardcover against mechanical erosion of the underlying regolith. This ferricrete reworks, at least partly, allochtonous lateritic materials inherited from a previous disaggregated ferricrete that suggests past erosion processes driven by hydro-climatic condition changes.  相似文献   

17.
Kinematics of a landslide derived from archival photogrammetry and GPS data   总被引：3，自引：0，他引：3  
P. Baldi  N. Cenni  M. Fabris  A. Zanutta   《Geomorphology》2008,102(3-4):435-444
The evolution of the Patigno landslide, a deep-seated gravitational slope deformation in the Northern Apennine range (Italy), was investigated using archival photogrammetry, and GPS observations from a permanent station located inside the landslide. Historical aerial photographs of the area taken in 1975 (scale 1:13,000), 1987 (1:13,000) and 2004 (1:30,000) were co-registered into the same reference frame using an unconventional method based on the detection of homologous points in multi-temporal models. Three DTMs were produced using a Digital Photogrammetric Workstation and compared. The displacement vectors of 293 points in the landslide were determined. The average movement velocity of the GPS station since 2004 (about 3.5 cm yr− 1) agrees with the mean displacement rate obtained from photogrammetry. Furthermore, the estimated velocity varies seasonally between 3 and 6 cm yr− 1. This variability correlated with rainfall suggests that the creep of the landslide is influenced by hydrological factors.  相似文献   

18.
The Dien Bien Phu fault zone (DBP), orientated NNE to N, is one of the most seismically active zones in Indochina. In NW Vietnam, this zone is 160 km long and 6–10 km wide, cutting sedimentary and metamorphic rocks of the Late Proterozoic, Palaeozoic and Mesozoic age, as well as Palaeozoic and Late Triassic granitoids. Along the DBP relatively small, narrow pull-apart basins occur, the three largest of which (Chan Nua, Lai Chau and Dien Bien Phu) have been studied in detail. All of them are bounded by sinistral and sinistral-normal faults, responsible for offset and deflected drainage, presence of numerous shutter ridges and displaced terraces and alluvial fans. The normal component of motion is testified to by well-preserved triangular facets on fault scarps, highly elevated straths in river watergaps, overhanging tributary valleys, as well as high and uneven river-bed gradients.Our observations indicate a minimum recent sinistral offset ranging from 6–8 to 150 m for Holocene valleys to 1.2–9.75 km for middle–late Pleistocene valleys in different fault segments. The thickness of Quaternary sediments varies from 5–25 m in the Lai Chau area to some 130 m in the Dien Bien Phu Basin. In the Lai Chau Basin, the middle terrace (23 m) alluvia of Nam Na River at Muong Te bridge have been optically stimulated luminescence/single aliquot regenerative dose technique (OSL-SAR) dated at 23–40 to 13 ka. These sediments were normal-faulted by some 11 m after 13 ka, and mantled by vari-coloured slope loams, 8–12 m thick, containing colluvial wedges composed of angular debris. These wedges were probably formed due to at least three palaeoseismic events postdating 6 ka. In the Dien Bien Phu Basin, in turn, alluvium of the upper Holocene terraces has been OSL-SAR dated to 6.5–7 and 1.7–1.0 ka, whereas the younger (sub-recent) terrace sediments give ages of 0.5–0.2 ka.Displaced terraces and alluvial fans allow us to suppose that the sinistral and sinistral-normal faults bounding narrow pull-apart basins in the southern portion of the DBP fault reveal minimum rates of left-lateral strike-slip ranging from 0.6 to 2 mm/year in Holocene and 0.5–3.8 mm/year in Pleistocene times, whereas rates of Holocene uplift tend to attain 1 mm/year north of Lai Chau and 0.4–0.6 mm/year west of Dien Bien Phu. More precise estimations, however, are difficult to obtain due to poor age control of the displaced drainage. Rates of Quaternary strike-slip are comparable with those of the Red River fault; the sense of movement being, however, opposite. Taking into account the presence of two phases of Late Cenozoic strike-slip of contrasting sense of motion, as well as the geometry of the two fault zones, we hypothesize that the Red River and Dien Bien Phu faults are conjugate faults capable of generating relatively strong earthquakes in the future.  相似文献   

19.
This paper presents the results of an investigation of the prehistoric Palliser Rockslide, Rocky Mountains, Canada. Conventional aerial photograph interpretation and field mapping are complemented by terrestrial digital photogrammetry. These techniques allow quantification of the rockslide debris volume and reconstruction of the pre-slide topography. It has been estimated that the volume of rock involved in the most recent large rockslide is 8 Mm3. Terrestrial digital photogrammetry is used in the characterization of the failure surface morphology, which is subdivided into four types of step-path geometry comprising both pre-existing discontinuities and intact rock fractures. Incorporation of these data into various rock slope stability numerical modeling methods highlights a complex failure mechanism, which includes sliding along a large scale curved failure surface, intact rock bridge fracturing and lateral confinement. A preliminary quantification of the contribution of intact rock bridges to the shear strength of the failure surface is presented in terms of the apparent cohesion, apparent tensile strength and cumulative length of the intact rock segments.  相似文献   

20.
Pingos are circular to elongate ice-cored mounds that form by injection and freezing of pressurized water in near-surface permafrost. Here we use a digital surface model (DSM) derived from an airborne Interferometric Synthetic Aperture Radar (IfSAR) system to assess the distribution and morphometry of pingos within a 40,000 km2 area on the western Arctic Coastal Plain of northern Alaska. We have identified 1247 pingo forms in the study region, ranging in height from 2 to 21 m, with a mean height of 4.6 m. Pingos in this region are of hydrostatic origin, with 98% located within 995 drained lake basins, most of which are underlain by thick eolian sand deposits. The highest pingo density (0.18 km− 2) occurs where streams have reworked these deposits. Morphometric analyses indicate that most pingos are small to medium in size (< 200 m diameter), gently to moderately sloping (< 30°), circular to slightly elongate (mean circularity index of 0.88), and of relatively low height (2 to 5 m). However, 57 pingos stand higher than 10 m, 26 have a maximum slope greater than 30°, and 42 are larger than 200 m in diameter. Comparison with a legacy pingo dataset based on 1950s stereo-pair photography indicates that 66 may have partially or completely collapsed over the last half-century. However, we mapped over 400 pingos not identified in the legacy dataset, and identified only three higher than 2 m to have formed between ca. 1955 and ca. 2005, indicating that caution should be taken when comparing contemporary and legacy datasets derived by different techniques. This comprehensive database of pingo location and morphometry based on an IfSAR DSM may prove useful for land and resource managers as well as aid in the identification of pingo-like features on Mars.  相似文献   

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