scholarly journals Mass wasting along the NW African continental margin

2018 ◽  
Vol 477 (1) ◽  
pp. 151-167 ◽  
Author(s):  
S. Krastel ◽  
W. Li ◽  
M. Urlaub ◽  
A. Georgiopoulou ◽  
R. B. Wynn ◽  
...  
Keyword(s):  
Continental Margin ◽  
Large Scale ◽  
Current Knowledge ◽  
Special Focus ◽  
Submarine Landslides ◽  
Mass Wasting ◽  
Recurrence Rates ◽  
Volcanic Debris ◽  
Rising Sea Level ◽  
Over Time

AbstractThe NW African continental margin is well known for the occurrence of large-scale but infrequent submarine landslides. The aim of this paper is to synthesize the current knowledge on submarine mass wasting off NW Africa with a special focus on the distribution and timing of large landslides. The described area reaches from southern Senegal to the Agadir Canyon. The largest landslides from south to north are the Dakar Slide, the Mauritania Slide, the Cap Blanc Slide, the Sahara Slide and the Agadir Slide. Volumes of individual slides reach several hundreds of cubic kilometres; run-outs are up to 900 km. In addition, giant volcanic debris avalanches are widespread on the flanks of the Canary Islands. All headwall areas are complex with clear indications of multiple failures. The most prominent similarity between all investigated landsides is the existence of widespread glide planes that follow the stratigraphy, which points to weak layers as most important preconditioning factor for the failures. Landslides with volumes larger than 100 m3 are close to being evenly distributed over time, contradicting previous suggestions that landslides off NW Africa occur at periods of low or rising sea level. The risk associated with the landslides off NW Africa, however, is relatively low due to their long recurrence rates.

scholarly journals Morphological Variability of Submarine Mass Movements in the Tectonically–Controlled Calabro–Tyrrhenian Continental Margin (Southern Italy)

Geosciences ◽  
2019 ◽  
Vol 9 (1) ◽  
pp. 43 ◽  
Author(s):  
Daniele Casalbore ◽  
Alessandro Bosman ◽  
David Casas ◽  
Francesco Chiocci ◽  
Eleonora Martorelli ◽  
...  
Keyword(s):  
High Resolution ◽  
Continental Margin ◽  
Large Scale ◽  
Southern Italy ◽  
Morphological Variability ◽  
Failure Behavior ◽  
Main Role ◽  
Submarine Landslides ◽  
Large Variability ◽  
Geomorphic Features

The analysis of high resolution morpho–bathymetric data on the Calabro Tyrrhenian continental margin (Southern Italy) enabled us to identify several morphological features originated by mass–wasting processes, including shallow gullies, shelf–indenting canyons and landslides. Specifically, we focus our attention on submarine landslides occurring from the coast down to −1700 m and affecting variable areas from thousands of square meters up to few tens of square kilometers. These landslides also show a large variability of geomorphic features which seems strictly related to the physiographic/morphological domains where the landslide formed. Tectonically–controlled scarps and canyon flanks are typically characterized by several coalescent and nested landslides, with diameters ranging from hundreds to a few thousands of meters. Canyon headwalls are commonly characterized by a cauliflower shape due to an array of small (diameters of tens of meters) and coalescent scars. In all these sectors, disintegrative–like landslides dominate and are generally characterized by a marked retrogressive evolution, as demonstrated by their morphology and comparison of repeated bathymetric surveys at the canyon headwall. Only in the lower part of tectonically–controlled scarps, a few cohesive–like and isolated landslides are present, indicating the main role of slope gradients and height drop in controlling the post–failure behavior of the mobilized material. Open slopes are generally characterized by large–scale (diameters of thousands of meters) and isolated scars, with associated landslide deposits. A peculiar case is represented by the Capo Vaticano Scar Complex that affected an area of about 18 km2 and is characterized by an impressive variability of landslide morphologies, varying also at short distance. The large extent and variability of such scar complex are thought to be associated with the occurrence of a mixed contouritic–turbidite system. By integrating the high–resolution morpho–bathymetric dataset with the results of previous studies, we discuss the main factors controlling the variability in size and morphology of submarine landslides developed in a tectonically–controlled setting and provide preliminary considerations on their potential geohazard in a densely populated coastal area.

Large-Scale Mass Wasting on the Northwest African Continental Margin: Some General Implications for Mass Wasting on Passive Continental Margins

2011 ◽  
pp. 189-199 ◽  
Author(s):  
Sebastian Krastel ◽  
Russell B. Wynn ◽  
Aggeliki Georgiopoulou ◽  
Jacob Geersen ◽  
Rüdiger Henrich ◽  
...  
Keyword(s):  
Continental Margin ◽  
Large Scale ◽  
Continental Margins ◽  
Mass Wasting

scholarly journals Revisiting Key Entry Routes of Human Epidemic Arboviruses into the Mainland Americas through Large-Scale Phylogenomics

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Túlio De Lima Campos ◽  
Ricardo Durães-Carvalho ◽  
Antonio Mauro Rezende ◽  
Otávio Valério de Carvalho ◽  
Alain Kohl ◽  
...  
Keyword(s):  
Human Population ◽  
Large Scale ◽  
Evolutionary Dynamics ◽  
Special Focus ◽  
Entry Points ◽  
Socioeconomic Burden ◽  
Geographic Expansion ◽  
Similar Path ◽  
Human Population Movement ◽  
Over Time

The rapid worldwide spread of chikungunya (CHIKV), dengue (DENV), and Zika (ZIKV) viruses have raised great international concern. Knowledge about the entry routes and geographic expansion of these arboviruses to the mainland Americas remain incomplete and controversial. Epidemics caused by arboviruses continue to cause socioeconomic burden globally, particularly in countries where vector control is difficult due to climatic or infrastructure factors. Understanding how the virus circulates and moves from one country to another is of paramount importance to assist government and health officials in anticipating future epidemics, as well as to take steps to help control or mitigate the spread of the virus. Through the analyses of the sequences of arbovirus genomes collected at different locations over time, we identified patterns of accumulated mutations, being able to trace routes of dispersion of these viruses. Here, we applied robust phylogenomic methods to trace the evolutionary dynamics of these arboviruses with special focus on Brazil, the epicenter of these triple epidemics. Our results show that CHIKV, DENV-1–4, and ZIKV followed a similar path prior to their first introductions into the mainland Americas, underscoring the need for systematic arboviral surveillance at major entry points of human population movement between countries such as airports and seaports.

Large-scale mass wasting on the north Spitsbergen continental margin, Arctic Ocean

1999 ◽  
Vol 19 (1-2) ◽  
pp. 131-142 ◽  
Author(s):  
N. Z. Cherkis ◽  
M. D. Max ◽  
P. R. Vogt ◽  
K. Crane ◽  
A. Midthassel ◽  
...  
Keyword(s):  
Arctic Ocean ◽  
Continental Margin ◽  
Large Scale ◽  
Mass Wasting ◽  
The North

Mass-wasting processes along the margins of the Ulleung Basin, East Sea: insights from multichannel seismic reflection and multibeam echosounder data

2018 ◽  
Vol 477 (1) ◽  
pp. 107-119 ◽  
Author(s):  
Senay Horozal ◽  
Jang-Jun Bahk ◽  
Sang Hoon Lee ◽  
Deniz Cukur ◽  
Roger Urgeles ◽  
...  
Keyword(s):  
Large Scale ◽  
Sediment Supply ◽  
Ulleung Basin ◽  
Small Scale ◽  
Sedimentation Rates ◽  
Submarine Landslides ◽  
Slope Failures ◽  
Mass Wasting ◽  
Western Margin ◽  
Southern Margin

AbstractSubmarine landslides represent a major, previously little recognized, geological hazard to the coastal communities. This study investigates the size, depth and degree of submarine landslides along the margins of the Ulleung Basin and examines how the shelf morphology and sediment supply affect the style and occurrence of slope failures. The slopes have experienced at least 38 episodes of submarine failures, which have left clear arcuate-shaped scarps that initiate at water depths of 150–1120 m. Individual landslides comprise volumes over the range 0.1–340 km3, cover 20–800 km2 on the seafloor and have runout distances of up to 50 km from the source. The headwall scarps are observed as being in excess of 500 m high. The height of scarps in the southern margin is significantly larger than in the western margin. Moreover, the volume of mass-transport deposits in the southern margin is also much higher compared to those from the western margin. The occurrence of the broad shelf (30–150 km wide) and high sedimentation rates in the southern margin might have led to large-scale slope failures. In contrast, the narrow shelf (<20 km) and low sedimentation rates in the western margin would only have promoted small-scale mass-wasting events.

scholarly journals Submarine mass wasting and associated tsunami risk offshore western Thailand, Andaman Sea, Indian Ocean

2012 ◽  
Vol 12 (8) ◽  
pp. 2609-2630 ◽  
Author(s):  
J. M. Schwab ◽  
S. Krastel ◽  
M. Grün ◽  
F. Gross ◽  
P. Pananont ◽  
...  
Keyword(s):  
Mass Transport ◽  
Andaman Sea ◽  
Excess Pore Pressure ◽  
Western Slope ◽  
Shelf Area ◽  
Submarine Landslides ◽  
Mass Wasting ◽  
Recurrence Rates ◽  
Mass Transport Deposits ◽  
Water Depths

Abstract. 2-D seismic data from the top and the western slope of Mergui Ridge in water depths between 300 and 2200 m off the Thai west coast have been investigated in order to identify mass transport deposits (MTDs) and evaluate the tsunamigenic potential of submarine landslides in this outer shelf area. Based on our newly collected data, 17 mass transport deposits have been identified. Minimum volumes of individual MTDs range between 0.3 km3 and 14 km3. Landslide deposits have been identified in three different settings: (i) stacked MTDs within disturbed and faulted basin sediments at the transition of the East Andaman Basin to the Mergui Ridge; (ii) MTDs within a pile of drift sediments at the basin-ridge transition; and (iii) MTDs near the edge of/on top of Mergui Ridge in relatively shallow water depths (< 1000 m). Our data indicate that the Mergui Ridge slope area seems to have been generally unstable with repeated occurrence of slide events. We find that the most likely causes for slope instabilities may be the presence of unstable drift sediments, excess pore pressure, and active tectonics. Most MTDs are located in large water depths (> 1000 m) and/or comprise small volumes suggesting a small tsunami potential. Moreover, the recurrence rates of failure events seem to be low. Some MTDs with tsunami potential, however, have been identified on top of Mergui Ridge. Mass-wasting events that may occur in the future at similar locations may trigger tsunamis if they comprise sufficient volumes. Landslide tsunamis, emerging from slope failures in the working area and affecting western Thailand coastal areas therefore cannot be excluded, though the probability is very small compared to the probability of earthquake-triggered tsunamis, arising from the Sunda Trench.

scholarly journals Large-scale mass wasting on the Miocene continental margin of western India

2019 ◽  
Vol 132 (1-2) ◽  
pp. 85-112 ◽  
Author(s):  
Sarah K. Dailey ◽  
Peter D. Clift ◽  
Denise K. Kulhanek ◽  
Jerzy Blusztajn ◽  
Claire M. Routledge ◽  
...  
Keyword(s):  
Mass Transport ◽  
Continental Margin ◽  
Large Scale ◽  
High Energy ◽  
Sediment Geochemistry ◽  
Western India ◽  
Second Phase ◽  
Mass Wasting ◽  
Sediment Delivery ◽  
Transport Complex

Abstract A giant mass-transport complex was recently discovered in the eastern Arabian Sea, exceeding in volume all but one other known complex on passive margins worldwide. The complex, named the Nataraja Slide, was drilled by International Ocean Discovery Program (IODP) Expedition 355 in two locations where it is ∼300 m (Site U1456) and ∼200 m thick (Site U1457). The top of this mass-transport complex is defined by the presence of both reworked microfossil assemblages and deformation structures, such as folding and faulting. The deposit consists of two main phases of mass wasting, each consisting of smaller pulses, with generally fining-upward cycles, all emplaced just prior to 10.8 Ma based on biostratigraphy. The base of the deposit at each site is composed largely of matrix-supported carbonate breccia that is interpreted as the product of debris-flows. In the first phase, these breccias alternate with well-sorted calcarenites deposited from a high-energy current, coherent limestone blocks that are derived directly from the Indian continental margin, and a few clastic mudstone beds. In the second phase, at the top of the deposit, muddy turbidites dominate and become increasingly more siliciclastic. At Site U1456, where both phases are seen, a 20-m section of hemipelagic mudstone is present, overlain by a ∼40-m-thick section of calcarenite and slumped interbedded mud and siltstone. Bulk sediment geochemistry, heavy-mineral analysis, clay mineralogy, isotope geochemistry, and detrital zircon U-Pb ages constrain the provenance of the clastic, muddy material to being reworked, Indus-derived sediment, with input from western Indian rivers (e.g., Narmada and Tapti rivers), and some material from the Deccan Traps. The carbonate blocks found within the breccias are shallow-water limestones from the outer western Indian continental shelf, which was oversteepened from enhanced clastic sediment delivery during the mid-Miocene. The final emplacement of the material was likely related to seismicity as there are modern intraplate earthquakes close to the source of the slide. Although we hypothesize that this area is at low risk for future mass wasting events, it should be noted that other oversteepened continental margins around the world could be at risk for mass failure as large as the Nataraja Slide.

scholarly journals Analysis of 220 Years of Floodplain Population Dynamics in the US at Different Spatial Scales

Water ◽  
2021 ◽  
Vol 13 (2) ◽  
pp. 141
Author(s):  
Firoza Akhter ◽  
Maurizio Mazzoleni ◽  
Luigia Brandimarte
Keyword(s):  
Population Dynamics ◽  
Large Scale ◽  
Spatial Scales ◽  
National Level ◽  
State Level ◽  
Economic Activities ◽  
Protection Measures ◽  
Management Planning ◽  
The Us ◽  
Over Time

In this study, we explore the long-term trends of floodplain population dynamics at different spatial scales in the contiguous United States (U.S.). We exploit different types of datasets from 1790–2010—i.e., decadal spatial distribution for the population density in the US, global floodplains dataset, large-scale data of flood occurrence and damage, and structural and nonstructural flood protection measures for the US. At the national level, we found that the population initially settled down within the floodplains and then spread across its territory over time. At the state level, we observed that flood damages and national protection measures might have contributed to a learning effect, which in turn, shaped the floodplain population dynamics over time. Finally, at the county level, other socio-economic factors such as local flood insurances, economic activities, and socio-political context may predominantly influence the dynamics. Our study shows that different influencing factors affect floodplain population dynamics at different spatial scales. These facts are crucial for a reliable development and implementation of flood risk management planning.

scholarly journals Hypoxia, Acidification and Inflammation: Partners in Crime in Parkinson’s Disease Pathogenesis?

Immuno ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 78-90
Author(s):  
Johannes Burtscher ◽  
Grégoire P. Millet
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Neurodegenerative Diseases ◽  
Current Knowledge ◽  
Cell Types ◽  
Brain Cell ◽  
Special Focus ◽  
Molecular Alterations ◽  
Research Fields

Like in other neurodegenerative diseases, protein aggregation, mitochondrial dysfunction, oxidative stress and neuroinflammation are hallmarks of Parkinson’s disease (PD). Differentiating characteristics of PD include the central role of α-synuclein in the aggregation pathology, a distinct vulnerability of the striato-nigral system with the related motor symptoms, as well as specific mitochondrial deficits. Which molecular alterations cause neurodegeneration and drive PD pathogenesis is poorly understood. Here, we summarize evidence of the involvement of three interdependent factors in PD and suggest that their interplay is likely a trigger and/or aggravator of PD-related neurodegeneration: hypoxia, acidification and inflammation. We aim to integrate the existing knowledge on the well-established role of inflammation and immunity, the emerging interest in the contribution of hypoxic insults and the rather neglected effects of brain acidification in PD pathogenesis. Their tight association as an important aspect of the disease merits detailed investigation. Consequences of related injuries are discussed in the context of aging and the interaction of different brain cell types, in particular with regard to potential consequences on the vulnerability of dopaminergic neurons in the substantia nigra. A special focus is put on the identification of current knowledge gaps and we emphasize the importance of related insights from other research fields, such as cancer research and immunometabolism, for neurodegeneration research. The highlighted interplay of hypoxia, acidification and inflammation is likely also of relevance for other neurodegenerative diseases, despite disease-specific biochemical and metabolic alterations.

scholarly journals Stress-Related Dysfunction of Adult Hippocampal Neurogenesis—An Attempt for Understanding Resilience?

2021 ◽  
Vol 22 (14) ◽  
pp. 7339
Author(s):  
Julia Leschik ◽  
Beat Lutz ◽  
Antonietta Gentile
Keyword(s):  
Major Depression ◽  
Adult Neurogenesis ◽  
Current Knowledge ◽  
Functional Relation ◽  
Hippocampal Neurogenesis ◽  
Adult Hippocampal Neurogenesis ◽  
Special Focus ◽  
Extrinsic Cues ◽  
Health And Disease ◽  
Newborn Neurons

Newborn neurons in the adult hippocampus are regulated by many intrinsic and extrinsic cues. It is well accepted that elevated glucocorticoid levels lead to downregulation of adult neurogenesis, which this review discusses as one reason why psychiatric diseases, such as major depression, develop after long-term stress exposure. In reverse, adult neurogenesis has been suggested to protect against stress-induced major depression, and hence, could serve as a resilience mechanism. In this review, we will summarize current knowledge about the functional relation of adult neurogenesis and stress in health and disease. A special focus will lie on the mechanisms underlying the cascades of events from prolonged high glucocorticoid concentrations to reduced numbers of newborn neurons. In addition to neurotransmitter and neurotrophic factor dysregulation, these mechanisms include immunomodulatory pathways, as well as microbiota changes influencing the gut-brain axis. Finally, we discuss recent findings delineating the role of adult neurogenesis in stress resilience.

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