Abstract
A review of multibeam echo sounder (MBES) survey data from five locations around the United Kingdom northwest coast has led to the identification of a total of 14 separate subaqueous mass movement scars and deposits within the fjords (sea lochs) and coastal inlets of mainland Scotland, and the channels between the islands of the Inner Hebrides. In these areas, Quaternary sediment deposition was dominated by glacial and glaciomarine processes. Analysis of the morphometric parameters of each submarine mass movement has revealed that they fall into four distinct groups of subaqueous landslides; Singular Slumps, Singular Translational, Multiple Single-Type, and Complex (translational & rotational) failures. The Singular Slump Group includes discrete, individual subaqueous slumps that exhibit no evidence of modification through the merging of several scars. The Singular Translational Group comprise a single slide that displays characteristics associated with a single translational (planar) failure with no merging of multiple events. The Multiple Single-Type Group incorporates scars and deposits that displayed morphometric features consistent with the amalgamation of several failure events of the same type (e.g. debris flows or slumps). Finally, the Complex (translational & rotational) Group comprises landslides that exhibited complex styles of failures, including both translational and rotational mechanisms controlling the same slide. The submarine mass movements that comprise this dataset are then discussed in relation to global fjordic and glaciomarine nearshore settings, and slope failure trigger mechanisms associated with these environments are described with tentative links to individual submarine landslides from the database, where appropriate. It is acknowledged that additional MBES data are needed not only to expand this database, but also in order to create a more statistically robust study. However, this initial study provides the basis for a much wider investigation of subaqueous mass movements and correlations between their morphometric parameters.
Highlights
Over previous decades, seabed scars created by submarine landslides have been identified across the United Kingdom Continental Shelf (UKCS), with the vast majority having occurred along the steeper slopes of the continental margin during the Pliocene – Pleistocene (Evans et al, 2005)
In this paper we present the results of the morphometric analysis (following the methods of (Clare et al, 2018)) from five coastal inlets and sea lochs across NW Scotland (UK) where evidence of small-scale shallow submarine mass movement events has been observed on the seabed
A dataset of 14 discrete subaqueous mass movement scars and deposits was compiled from multibeam echo sounder (MBES) surveys around the United Kingdom northwest coast
Summary
Over previous decades, seabed scars created by submarine landslides have been identified across the United Kingdom Continental Shelf (UKCS), with the vast majority having occurred along the steeper slopes of the continental margin during the Pliocene – Pleistocene (Evans et al, 2005). Our lack of knowledge regarding the nature of the seabed within the fjords and inlets of Scotland is concerning given that these sea lochs have similar morphological features and settings to the global examples described above where recent slope failures have had such highly devastating results. These examples demonstrate the temporal aspect to these events, highlighting that they are caused by active modern processes and represent contemporary geohazards. Trends and correlations within the morphometrics dataset are explored, followed by the wider implications for coastal infrastructure planning across both former and contemporary glaciomarine coastlines globally
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