Moraines

A simple filter is developed which transforms VLF-EM real magnetic field transfer functions into apparent resistivities. It is based on the relationship between the horizontal derivative of the surface electric field and the vertical magnetic field at the surface of a two-dimensional earth model. The performance of this simple autoregressive filter is tested for modelled and real survey data. The technique yields profiles of apparent resistivity very similar, both in magnitude and in wavelength, to those which would have been obtained using VLF-EM resistivity measurements or d.c. resistivity profiling. This low-pass filter has the advantage of reducing high-wavenumber noise in the data; therefore only the major features of the VLF-EM profile are displayed.

Este documento hace una evaluación de depósitos morrénicos ubicados en diferentes lugares de la cadena occidental de los Andes del Perú, con la finalidad de identificar material morrénico de baja permeabilidad para su uso como cantera. La evaluación, realizada en base a investigaciones geotécnicas in situ y resultados de ensayos de laboratorio, es comparada con las características litológicas y genéticas de los depósitos, con la finalidad de establecer patrones geotécnicos para los depósitos de un determinado origen litológico, así como para explicar diferencias existentes entre los materiales morrénicos evaluados.

The instability of moraine-dammed proglacial lakes creates the potential for catastrophic glacial lake outburst floods (GLOFs) in high-mountain regions. In this research, we use a unique combination of numerical dam-breach and two-dimensional hydrodynamic modelling, employed within a generalised likelihood uncertainty estimation (GLUE) framework, to quantify predictive uncertainty in model outputs associated with a reconstruction of the Dig Tsho failure in Nepal. Monte Carlo analysis was used to sample the model parameter space, and morphological descriptors of the moraine breach were used to evaluate model performance. Multiple breach scenarios were produced by differing parameter ensembles associated with a range of breach initiation mechanisms, including overtopping waves and mechanical failure of the dam face. The material roughness coefficient was found to exert a dominant influence over model performance. The downstream routing of scenario-specific breach hydrographs revealed ...

High-resolution topographic surveying is traditionally associated with high capital and logistical costs, so that data acquisition is often passed on to specialist third party organizations. The high costs of data collection are, for many applications in the earth sciences, exacerbated by the remoteness and inaccessibility of many field sites, rendering cheaper, more portable surveying platforms (i.e. terrestrial laser scanning or GPS) impractical.

This paper outlines a revolutionary, low-cost, user-friendly photogrammetric technique for obtaining high-resolution datasets at a range of scales, termed ‘Structure-from-Motion’ (SfM). Traditional softcopy photogrammetric methods require the 3-D location and pose of the camera(s), or the 3-D location of ground control points to be known to facilitate scene triangulation and reconstruction. In contrast, the SfM method solves the camera pose and scene geometry simultaneously and automatically, using a highly redundant bundle adjustment based on matching features in multiple overlapping, offset images.

A comprehensive introduction to the technique is presented, followed by an outline of the methods used to create high-resolution Digital Elevation Models (DEMs) from extensive photosets obtained using a consumer-grade digital camera. As an initial appraisal of the technique, an SfM-derived DEM is compared directly with a similar model obtained using Terrestrial Laser Scanning. This intercomparison reveals that decimetre-scale vertical accuracy can be achieved using SfM even for sites with complex topography and a range of land-covers. Example applications of SfM are presented for three contrasting landforms across a range of scales including; an exposed rocky coastal cliff; a breached moraine-dam complex; and a glacially-sculpted bedrock ridge.

The SfM technique represents a major advancement in the field of photogrammetry for geoscience applications. Our results and experiences indicate SfM is an inexpensive, effective, and flexible approach to capturing complex topography.

The instability of moraine-dammed proglacial lakes creates the potential for catastrophic glacial lake outburst floods (GLOFs) in high-mountain regions. In this research, we use a unique combination of numerical dam-breach and two-dimensional hydrodynamic modelling, employed within a generalised likelihood uncertainty estimation (GLUE) framework, to quantify predictive uncertainty in model outputs associated with a reconstruction of the Dig Tsho failure in Nepal. Monte Carlo analysis was used to sample the model parameter space, and morphological descriptors of the moraine breach were used to evaluate model performance. Multiple breach scenarios were produced by differing parameter ensembles associated with a range of breach initiation mechanisms, including overtopping waves and mechanical failure of the dam face. The material roughness coefficient was found to exert a dominant influence over model performance. The downstream routing of scenario-specific breach hydrographs revealed significant differences in the timing and extent of inundation. A GLUE-based methodology for constructing probabilistic maps of inundation extent, flow depth, and hazard is presented and provides a useful tool for communicating uncertainty in GLOF hazard assessment.

The Pleistocene glaciolacustrine basin of La Massana has been studied by some authors since LLOBET (1947). An important advance in the knowledge of that basin has been carried out in the 80’s by PRAT (1980) and VILAPLANA (1985). In the 90’s an intense construction activity in La Massana village has given me the opportunity to study some outcrops of glacial deposits that shows the relationship of a synsedimentary deformation of gravels and silts from Proglacial outwash waters.

Les fluctuations glaciaires dans le bassin versant du Drac Blanc (Massif des Écrins, Alpes françaises) n’ont jusqu’à aujourd´hui pas fait l’objet d’une étude. Ce travail vise à établir une chronologie relative des stades de moraines dans le vallon de Rougnoux. Deuxièmement, l’étude s’intéresse à l’estimation de l’âge des différents stades de moraines. Troisièmement, un modèle numérique de terrain a rendu possible un calcul approximatif du volume du glacier. Ce travail permet d’identifier quatre stades et un sous-stade de moraines dans le vallon de Rougnoux. Les moraines des stades I-III peuvent probablement être attribuées au stade d’Egesen (Dryas récent). Le stade de moraines IV date vraisemblablement de la fin du Petit Age Glaciaire. Pour résumer, cette étude a permis d’identifier, pour la première fois, des dépôts morainiques qui démontrent une avancée glaciaire à la transition entre le Dryas récent et l’Holocène dans le bassin versant du Drac Blanc. Ce travail contribue donc à une meilleure connaissance des fluctuations glaciaires dans la partie Sud du massif des Écrins.

In this paper, we discuss the advantages and drawbacks of the most classical approaches used in lichenometry. In particular, we perform a detailed comparison among methods based on the statistical analysis of either the largest lichen diameters recorded on geomorphic features or the frequency of all lichens. To assess the performance of each method, a careful comparison design with well-defined criteria is proposed and applied to two distinct data sets. First, we study 350 tombstones. This represents an ideal test bed because tombstone dates are known and, therefore, the quality of the estimated lichen growth curve can be easily tested for the different techniques. Secondly, 37 moraines from two tropical glaciers are investigated. This analysis corresponds to our real case study. For both data sets, we apply our list of criteria that reflects precision, error measurements and their theoretical foundations when proposing estimated ages and their associated confidence intervals. From this comparison, it clearly appears that two methods, the mean of the n largest lichen diameters and the recent Bayesian method based on extreme value theory, offer the most reliable estimates of moraine and tombstones dates. Concerning the spread of the error, the latter approach provides the smallest uncertainty and it is the only one that takes advantage of the statistical nature of the observations by fitting an extreme value distribution to the largest diameters.

"Horcones Inferior glacier’s moraines extend for about 20 km, and we can distinguish five different areas, beginning with the most recent ones: 1) The current moraines, which correspond to lateral moraines and one frontal moraine. 2) The Confluência moraines, which form a rather complex structure, and which appear to include a medial moraine, a hummock moraine and several moraines coming from neighboring valleys. 3) The Horcones moraines, which appear to constitute two distinct sets. 4) The Penitentes moraines, between Puente del Inca and Punta de Vacas. 5) The Punta de Vacas moraine, which runs downstream Punta de Vacas, in the proglacial area, and may result from the glacier’s progress, coming from Horcones and meeting other Andean glaciers, probably being the biggest and oldest glacier’s
advance in the valley. In this paper, we will study the first three of the mentioned areas.
Keywords: Argentinean Andes, Moraines, Glacial Geomorphology, Geoheritage, Geomorphologic hazards"

Alice M. Doughty, Joerg M. Schaefer, Aaron E. Putnam, George H. Denton, Michael R. Kaplan, David J.A.
Barrell, Bjørn G. Andersen, Samuel E. Kelley, Robert C. Finkel, and Roseanne Schwartz

Here we address a long-standing puzzle of ice-age climate called
the “fly in the ointment of the Milankovitch theory.” Using geomorphic mapping and 10Be surface-exposure dating, we show that five moraine belts were formed during maxima of the last ice age by the Pukaki glacier in New Zealand’s Southern Alps. They afford ages of 41.76 ± 1.09 ka, 35.50 ± 1.26 ka, 27.17 ± 0.68 ka, 20.27 ± 0.60 ka, and 18.29 ± 0.49 ka. These five maxima spanned an entire precessional cycle in summer insolation intensity at the latitude of the Southern Alps. A similar mismatch between summer insolation and glacier extent also characterized the Chilean Lake District in the mid-latitudes of South America. Thus, in apparent contrast to northern ice sheets linked by Milankovitch to summer insolation at 65°N latitude, the behavior of southern mid-latitude glaciers was not tied to local summer insolation intensity. Instead, glacier extent between 41.76 ka and 18.29 ka, as well as during the last termination, was aligned with Southern Ocean surface temperature and with atmospheric carbon dioxide.

Barr and Clark published a series of maps depicting the distribution of end moraines across Far NE Russia. These moraines outlined the former distribution and dimensions of glaciers, and were identified through the analysis of Landsat ETM+ satellite images (15- and 30-m resolution). Now, a number of freely available digital elevation model (DEM) datasets are available, which cover the entire 4 million km2 of Far NE Russia. These include the 30-m resolution ASTER GDEM and the 90-m resolution Viewfinder Panorama DEM. Here we use these datasets, in conjunction with Landsat ETM+ images, to complete the process of systematically and comprehensively mapping end moraines. With the aid of the DEMs described above, here we present a total dataset of 8414 moraines, which almost quadruples the inventory of Barr and Clark. This increase in the number of moraines is considered to reflect the utility of the DEMs for mapping glacial landforms. In terms of moraine distribution, the Barr and Clark map and the one presented here are comparable, with moraines found to cluster in highland regions and upon adjacent lowlands, attesting to the former occupation of the region by mountain-centred ice masses. This record is considered to reflect palaeoclimatic and topographic controls upon the extent and dynamics of palaeoglaciers, as well as spatial variability in moraine preservation.

Comprehensive glacial Quaternary studies involving geochronological methods, modelling of ice topography with the support of field geomorphological and geological data in the Balkan Peninsula are relatively scarce, although there is evidence of past glaciations in several mountain ranges. Here, we present research on the extent and timing of past glaciations on the northern Velebit Mt. in coastal Croatia and inferences of the climate during that time. Based on geomorphological and sedimentological evidence and using cosmogenic 36 Cl surface exposure dating of moraine boulders, we provide an empirical reconstruction of past glaciers and compare this with the Parallel Ice Sheet Model (PISM) simulations under different palaeoclimate forcings. The dating results show that the northern Velebit glaciers reached their maximum extent during the last glacial cycle before the global Last Glacial Maximum (LGM). Maximum ice extent likely correlates with Marine Isotope Stage 5-4, although the exact timing cannot be determined at this point due to poorly known site-and time-specific denudation rates. Empirical reconstruction of the maximum extent suggests that the area covered by glaciers was 116 km 2. The-best fit PISM simulation indicates that the most likely palaeoclimate scenario for the glaciers of this size to form is a cooling of~8°C and a 10% reduction in precipitation from present-day levels. However, the best-fit simulation does not correctly model all mapped ice margins when changes in climatological parameters are applied uniformly across the model domain, potentially reflecting a different palaeoprecipitation pattern to today.

The internal sedimentology of the Armoy moraine, which marks a late Devensian (Weichselian) incursion of Scottish ice into the north of Ireland, is described from a temporary exposure near Armoy village. The exposure (up to 30 m long, 10 m high) comprises folded gravel beds, massive clay grading up to pebbly diamicton, massive gravel, overfolded and deformed sand, and a gravel and massive diamicton cover. These sediments overlie glacially smoothed basalt bedrock. The sediment succession records the interaction of near-touching Scottish and Irish ice margins, and the formation, infilling and drainage of an ice-supported proglacial lake. Scottish ice likely advanced into the north of Ireland by a short-lived glacier surge during the Killard Point Stadial (coeval with Heinrich Event 1 at 14.5 14C ka BP), forming the Armoy moraine at its maximum extent. The presence of rafted sediment blocks within the moraine suggests ice-marginal thrusting and deformation of proglacial sands, and syntectonic resedimentation into low points on the sediment surface. Asynchroneity between Scottish and Irish ice-marginal fluctuations may reflect differing responses to climate forcing during the Killard Point Stadial, or the effects of local factors such as substrate type and basal ice thermal regime.

As cristas morénicas laterais, centrais e de fundo são indicadores geomorfológicos de origem glaciar que permitem compreender a extensão máxima de glaciares de montanha, particularmente, em áreas que os tiveram no passado. Na prática, a interpretação geomorfológica da posição das moreias permite aferir a altitude da deposição lateral e frontal de sedimentos transportados pelo glaciar e o correspondente alcance máximo das línguas glaciárias. Este trabalho teve como objetivo o mapeamento detalhado de moreias na Serra do Soajo (PN Peneda-Gerês). Assim, a sua interpretação e distribuição permitirá estimar a máxima extensão e recuos das línguas glaciárias plistocénicas. A identificação e confirmação das moreias baseou-se nos seguintes dados: 1) bibliografia existente (Coudé, 1983; Pereira et al. 2009, 2020; Santos et al., 2015); 2) dados altimétricos LiDAR com 70 cm de resolução espacial (MDT, MDS e Ortofotomapa); 3) Cartas Militares (1/25.000) e Cartas Geológicas (1/50.000); 4) Ortofotomapas com 50 cm de resolução (Google Maps); 5) reconhecimentos de campo. Os resultados do reconhecimento de campo e da análise de gabinete, evidenciam a presença das moreias assinaladas na bibliografia. Porém, foi possível refinar a sua expressão em termos de forma e extensão, salientando-se o caso mais expressivo do Lombo de Gorbelas (1006 m). Todavia, no sector do Alto Vez identificaram-se novas cristas morénicas laterais: na base da elevação do Maranho (entre 1210 m e 1240 m), no vale imediatamente a sul da Pedrada (1416 m), e lateralmente no vale do Ramiscal. Durante o trabalho de campo também foi possível georreferenciar outros elementos que confirmam a passagem de gelo e as direções que tomou, como é caso de superfícies rochosas polidas, estrias, blocos erráticos e rochas aborregadas. Estes novos dados permitem um ensaio preliminar de reconstituição dos limites máximos altitudinais das línguas glaciares a partir da altitude máxima das moreias laterais (MELM) e da extensão máxima (área) da Glaciação Plistocénica. Por fim, espera-se que os dados georreferenciados numa base cartográfica de pormenor e as novas interpretações possam contribuir para a discussão sobre a extensão da Glaciação Plistocénica na Serra do Soajo, assim como, para a identificação e compreensão das heranças glaciárias nas montanhas do NW de Portugal e Galiza.