The Avalanche Lake rock avalanche, Mackenzie Mountains, Northwest Territories, Canada: description, dating, and dynamics

1994 ◽  
Vol 31 (5) ◽  
pp. 749-768 ◽  
Author(s):  
S.G. Evans ◽  
O. Hungr ◽  
E.G. Enegren
Keyword(s):  
Dynamic Model ◽  
Rock Avalanche ◽  
The South ◽  
Valley Bottom ◽  
Alluvial Deposits ◽  
Centre Of Gravity ◽  
Valley Side ◽  
Glacier Ice ◽  
Mackenzie Mountains ◽  
Detachment Surface

At Avalanche Lake, located in the Backbone Ranges of the Mackenzie Mountains, about 200 × 106 m3 of massive Devonian carbonate rock slid down remarkably planar bedding surfaces dipping at 30° and created a spectacular runup on the opposite valley side onto a topographic feature called the Shelf. The interpretation of events at Avalanche Lake has recently been subject to controversy. It has been argued by other workers that the rock avalanche could not have run onto the Shelf without glacier ice partially filling the valley, thus reducing the magnitude of the actual runup, and implying that the rock avalanche took place at the end of the Pleistocene. Evidence is presented indicating that the rock avalanche occurred in an ice-free environment. It consists of the nature of the detachment surface, the morphology and location of the rock avalanche debris, the presence of levees in the debris and isolated patches of debris on valley-side slopes, and the entrainment of alluvial deposits and conifer fragments from the valley floor in the Shelf Lobe debris. In addition, radiocarbon ages obtained from entrained wood in the debris, converted to calendric years, indicate that the landslide took place in this millennium, with a 95% probability of it having occurred no earlier than 1440 A.D. No glacier ice then existed in the valley. Based on this evidence the behaviour of the rock avalanche is reconstructed. It is characterized by dramatic mobility in which the rock avalanche split into two parts. The west part smashed into the opposite valley side and about 5 × 106 m3 rode up onto the Shelf. The remainder (155 × 106 m3) fell back into the valley, partially running back up the detachment surface to an elevation 360 m above the valley, and then, reversing direction again, ran back into the valley bottom where it was deposited. The east part, the South Lobe (40 × 106 m3), ran down a valley reentrant opposite the detachment surface. The maximum vertical drop in the path is 1220 m, and the maximum runup is 640 m. The fahrböschung is 8° for the Shelf Lobe and 10° for the South Lobe. An analysis of the movement of the centre of gravity using a version of Koerner's dynamic model simulates the runup onto the Shelf, indicating that the presence of glacier ice is not necessary to account for the runup magnitude. Estimated maximum velocities during the movement reached 80 m/s. The runup is the highest recorded and on an empirical runup plot is highly anomalous in relation to the height of the descent slope. The case history illustrates the limitation of a dynamic model applied to a rock avalanche when it is assumed that the centre of gravity of the mass is displaced from the highest point on the detachment surface to the farthest tip of the debris. It also demonstrates that massive detachments have taken place in the Mackenzie Mountains in the comparatively recent past. Key words : rock avalanche, runup, Avalanche Lake, dynamics, radiocarbon dating, Mackenzie Mountains.

A reassessment of transport mechanisms of some rock avalanches in the Mackenzie Mountains, Yukon and Northwest Territories, Canada

1990 ◽  
Vol 27 (1) ◽  
pp. 129-144 ◽  
Author(s):  
P. K. Kaiser ◽  
J. V. Simmons
Keyword(s):  
Debris Flow ◽  
Northwest Territories ◽  
Valley Bottom ◽  
Flow Simulations ◽  
Rock Avalanches ◽  
Field Evidence ◽  
Debris Transport ◽  
Glacier Ice ◽  
Mackenzie Mountains ◽  
New Hypothesis

The transport mechanism of some rock avalanches of the Mackenzie Mountains in the Yukon and Northwest Territories of Canada is reassessed on the basis of evidence collected during fieldwork and by comparison with results from numerical simulations of the debris flow mechanism. A new hypothesis of glaciation-related transport is advanced as an alternate explanation of apparently very mobile rock avalanches with anomalous travel distances. By the example of the Avalanche Lake slide, it is demonstrated that the debris was most likely not deposited on the current topography but on valley glacier ice at an elevation of about 400–500 m above the valley bottom. This conclusion is supported by field evidence, an empirical runup relationship, and the results from numerical flow simulations. A qualitative interpretation of other debris deposits suggests that several events in the Mackenzie Mountains can be interpreted in the same manner. Key words: rock avalanches, rock slides, debris transport, debris flow modelling, Mackenzie Mountains, Northwest Territories.

scholarly journals Back-calculation of the 2017 Piz Cengalo-Bondo landslide cascade with r.avaflow

2019 ◽  
Author(s):  
Martin Mergili ◽  
Michel Jaboyedoff ◽  
José Pullarello ◽  
Shiva P. Pudasaini
Keyword(s):  
Debris Flow ◽  
Flow Model ◽  
Rock Avalanche ◽  
Simulation Software ◽  
Process Models ◽  
Rock Fall ◽  
Model Parameters ◽  
Rock Slide ◽  
Glacier Ice ◽  
Initial Rock

Abstract. In the morning of 23 August 2017, around 3 million m3 of granitoid rock broke off from the east face of Piz Cengalo, SE Switzerland. The initial rock slide-rock fall entrained 0.6 million m3 of a glacier and continued as a rock(-ice) avalanche, before evolving into a channelized debris flow that reached the village of Bondo at a distance of 6.5 km after a couple of minutes. Subsequent debris flow surges followed in the next hours and days. The event resulted in eight fatalities along its path and severely damaged Bondo. The most likely candidates for the water causing the transformation of the rock avalanche into a long-runout debris flow are the entrained glacier ice and water originating from the debris beneath the rock avalanche. In the present work we try to reconstruct conceptually and numerically the cascade from the initial rock slide-rock fall to the first debris flow surge and thereby consider two scenarios in terms of qualitative conceptual process models: (i) entrainment of most of the glacier ice by the frontal part of the initial rock slide-rock fall and/or injection of water from the basal sediments due to sudden rise in pore pressure, leading to a frontal debris flow, with the rear part largely remaining dry and depositing mid-valley; and (ii) most of the entrained glacier ice remaining beneath/behind the frontal rock avalanche, and developing into an avalanching flow of ice and water, part of which overtops and partially entrains the rock avalanche deposit, resulting in a debris flow. Both scenarios can be numerically reproduced with the two-phase mass flow model implemented with the simulation software r.avaflow, based on plausible assumptions of the model parameters. However, these simulation results do not allow to conclude on which of the two scenarios is the more likely one. Future work will be directed towards the application of a three-phase flow model (rock, ice, fluid) including phase transitions, in order to better represent the melting of glacier ice, and a more appropriate consideration of deposition of debris flow material along the channel.

scholarly journals III. A General View of the Phenomena displayed in the neighbourhood of Edinburgh by the Igneous Rocks, in their relations with the Secondary Strata; with reference to a more particular description of the Section which has been exposed to view on the south side of the Castle Hill

1835 ◽  
Vol 13 (1) ◽  
pp. 39-45
Author(s):  
Greenock
Keyword(s):  
Large Volume ◽  
Igneous Rocks ◽  
General View ◽  
The South ◽  
Alluvial Deposits ◽  
True Nature ◽  
South Side ◽  
The Earth ◽  
Igneous Origin ◽  
Great Pressure

The country in which Edinburgh is situated has no great elevation above the level of the sea, presenting a gently undulating surface, except where hills of igneous origin, in groups, or perfectly insulated, rise abruptly through the strata, which consist of the sandstones and shales of the coal-formation, with occasional beds of limestone, which they overlie, and this country is more or less covered by old and new alluvial deposits.The views suggested by these hills to the penetrating genius of Hutton, who may be justly considered the founder of modern geology, first led to the knowledge of the true nature and origin of the trap-rocks. Their analogy to those produced by existing volcanoes, and the phenomena observed in their relations with the secondary strata, leave no doubt as to their having been poured out from the interior of the earth in a fluid or viscid state, through fissures in the strata occasioned by subterranean convulsions—not, however, in the open air, like currents of lava from recent craters, but in sheets or masses at the bottom of the sea, their cooling and consolidation having evidently been slow and gradual, under great pressure, such as might be produced by a large volume of superincumbent water, as was ably illus trated by the experiments of the late Sir James Hall; or by their having been originally formed as dykes, at considerable depths, either below or among the strata.

New Neolithic Sites in Dorset and Bedfordshire, with a Note on the Distribution of Neolithic Storage-Pits in Britain

1964 ◽  
Vol 30 ◽  
pp. 352-381 ◽  
Author(s):  
N. H. Field ◽  
C. L. Matthews ◽  
I. F. Smith ◽  
Jane M. Ewbank
Keyword(s):  
Flood Plain ◽  
County Council ◽  
The South ◽  
The West ◽  
Valley Bottom ◽  
Gentle Slope ◽  
North East ◽  
The North ◽  
Trunk Road

This discovery was made as a result of rescue excavation in advance of road improvements by the Dorset County Council in the autumn of 1962. The site (NGR SY/99789918) now lies in the north verge of the A31 trunk road, 500 feet towards Wimborne Minster from the new Lake junction to Corfe Mullen, but in 1962 it was still included in field No. 7924, belonging to Lake Farm. Here the land, which forms part of the flood-plain of the Stour, is crossed by a spur of slightly more elevated ground extending north from Willetts Lane. There is a gentle slope westwards from the site towards the Chillwater Stream, which flows north to the Stour after descending from higher ground. The lowlying terrain to the west of this low spur used to be marshland until its reclamation, accounting for the name ‘lake’ given to the locality. The subsoil of the valley-bottom is composed variously of gravel, shingly stones and brown alluvial loam. The original vegetational cover would have been woodland of deciduous type, extending from the floor of the valley up the slope to the south and thinning out to scrub and heath on the gravel plateau 150 feet above the Stour. Today, pasture dominates the scene, with oak prominent only in hedgerow or isolated clumps.The pit to be described below lay just over half a mile to the north-east of the site of one similar in shape and contents that was discovered in a quarry in Corfe Mullen parish some twenty-five years ago.

A Bronze Cauldron from Sompting, Sussex

1948 ◽  
Vol 28 (3-4) ◽  
pp. 157-163 ◽  
Author(s):  
E. Cecil Curwen
Keyword(s):  
The South ◽  
Valley Bottom ◽  
Modern Times ◽  
North East ◽  
South West

During the autumn of 1946 a hoard of bronzes was discovered during excavation for foundations in the bottom of a down-land valley in the parish of Sompting, near Worthing. The site is a point approximately 300 ft. north-east of Hill Barn and 1,500 ft. south-west of the south-west edge of Lancing Ring, and is on property belonging to Hill Barn Nurseries. The bronzes were unearthed by a mechanical excavator at a depth of about 5 ft. in a valley-bottom accumulation of brown clayey mould. How much of this material is natural hill-wash and how much the result of cultivation of the valley in ancient and modern times it would be difficult to say. The depth at which the bronzes were found suggests that some of the soil may have been ploughed down into the valley bottom at a later period.

scholarly journals The Identification of Land Subsidance by Levelling Measurement and GPR Data at Tanjung Emas Harbour, Semarang

2017 ◽  
Vol 32 (1) ◽  
Author(s):  
Purnomo Raharjo ◽  
Mira Yosi
Keyword(s):  
Marine Sediments ◽  
Land Subsidence ◽  
Ground Penetrating Radar ◽  
Volcanic Rocks ◽  
Geological Condition ◽  
The South ◽  
Alluvial Deposits ◽  
Alluvial Deposit ◽  
Ground Penetrating ◽  
Harbour Area

Recently, the main problem in Semarang City is flood. This area has low relief that consists of coastal alluvial deposits, swamp and marine sediments. The coastline is characterized by muddy, sandy, and rocky coasts, and mangrove coast. Ground Penetrating Radar (GPR) records, show that subsurface geological condition of northern part of Semarang is coastal alluvial deposit and in the south is volcanic rocks. The aims of this this research is to determine land subsidence by levelling measurement in 2005 in Tanjung Emas Harbour area built on 1995. During ten years, there are various land subsidance in this area: in Coaster Street (21 – 41 cm), container wharf (62 – 94 cm), north breakwater (64 – 79 cm), west breakwater (74 – 140 cm), east groin (76 – 89 cm), and stacking area ( 77 – 109 cm). According to this research, it is concluded that one reason causes of flooding in this area is land subsidence.Keywords : flood, land subsidence, levelling, Tanjung Emas Harbour, Semarang Permasalahan yang berkembang di Kota Semarang saat ini adalah terjadinya banjir. Kawasan ini berelief rendah yang disusun oleh endapan aluvial pantai, rawa dan sedimen laut. Karakteristik garis pantai dicirikan oleh pantai berlumpur, berpasir dan berbatuan, serta pantai berbakau. Rekaman Ground Penetrating Radar (GPR) menunjukkan kondisi geologi bawah permukaan utara kota Semarang merupakan endapan aluvial pantai dan bagian selatan disusun oleh batuan vulkanik. Tujuan penelitian ini adalah untuk mengetahui kondisi penurunan tanah melalui pengukuran sifatdatar yang dilakukan pada tahun 2005, di kawasan Pelabuhan Tanjung Emas yang dibangun pada tahun 1995. Dalam kurun waktu 10 tahun, diketahui bahwa terdapat variasi penurunan tanah di kawasan ini: ruas jalan Coaster (21-41 cm), di kawasan dermaga peti kemas (62-94 cm), pemecah gelombang sebelah utara (64-79 cm), pemecah gelombang sebelah barat (74-140 cm), penahan gelombang sebelah timur (76-89 cm), dan pelataran peti kemas (77-109 cm). Berdasarkan penelitian ini, maka dapat disimpulkan bahwa salahsatu penyebab banjir di kawasan ini adalah akibat penurunan tanah.Kata Kunci : banjir, penurunan tanah, sipatdatar, Pelabuhan Tanjung Emas, Semarang

scholarly journals Back calculation of the 2017 Piz Cengalo–Bondo landslide cascade with r.avaflow: what we can do and what we can learn

2020 ◽  
Vol 20 (2) ◽  
pp. 505-520 ◽  
Author(s):  
Martin Mergili ◽  
Michel Jaboyedoff ◽  
José Pullarello ◽  
Shiva P. Pudasaini
Keyword(s):  
Debris Flow ◽  
Flow Model ◽  
Rock Avalanche ◽  
Simulation Software ◽  
Process Models ◽  
Model Parameters ◽  
Two Phase ◽  
Three Phase Flow ◽  
Glacier Ice ◽  
Future Work

Abstract. In the morning of 23 August 2017, around 3×106 m3 of granitoid rock broke off from the eastern face of Piz Cengalo, southeastern Switzerland. The initial rockslide–rockfall entrained 6×105m3 of a glacier and continued as a rock (or rock–ice) avalanche before evolving into a channelized debris flow that reached the village of Bondo at a distance of 6.5 km after a couple of minutes. Subsequent debris flow surges followed in the next hours and days. The event resulted in eight fatalities along its path and severely damaged Bondo. The most likely candidates for the water causing the transformation of the rock avalanche into a long-runout debris flow are the entrained glacier ice and water originating from the debris beneath the rock avalanche. In the present work we try to reconstruct conceptually and numerically the cascade from the initial rockslide–rockfall to the first debris flow surge and thereby consider two scenarios in terms of qualitative conceptual process models: (i) entrainment of most of the glacier ice by the frontal part of the initial rockslide–rockfall and/or injection of water from the basal sediments due to sudden rise in pore pressure, leading to a frontal debris flow, with the rear part largely remaining dry and depositing mid-valley, and (ii) most of the entrained glacier ice remaining beneath or behind the frontal rock avalanche and developing into an avalanching flow of ice and water, part of which overtops and partially entrains the rock avalanche deposit, resulting in a debris flow. Both scenarios can – with some limitations – be numerically reproduced with an enhanced version of the two-phase mass flow model (Pudasaini, 2012) implemented with the simulation software r.avaflow, based on plausible assumptions of the model parameters. However, these simulation results do not allow us to conclude on which of the two scenarios is the more likely one. Future work will be directed towards the application of a three-phase flow model (rock, ice, and fluid) including phase transitions in order to better represent the melting of glacier ice and a more appropriate consideration of deposition of debris flow material along the channel.

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