Study and modelling of rapid shoreline displacement due to coseismic subsidence along the Kamchatka subduction zone

The first studies of geological evidences of coastal coseismic subsidence (associated with subduction-zone earthquakes) were carried out in Russia at the Institute of Volcanology and Seismology, in Kamchatka. We developed a special method based on tephrostratigraphy and tephrochronology, descriptions and dating of the soil-pyroclastic sequence (SPS) overlying the coastal wave-build beach ridges. Three seismic events accompanied by coastal coseismic subsidence were detected in the northern part of Avachinsky Bay during the past ~5 thousand years. We found subsidence from one of the greatest historical tsunamigenic earthquake (1952 AD) south of Petropavlovsk-Kamchatsky. We identified, that 5 events of coastal coseismic subsidence had occurred during the past ~6 thousand years at the coast of Kronotsky Bay and Shipunsky Peninsula. Amplitudes of subsidence were estimated by geological data using three different methods. Erosion of the active beach and marine accumulative terrace becomes active after coastal subsidence. We calculated the shoreline retreat process and the amount of horizontal erosion by numerical simulation using Bruun rule. In some areas, shoreline retreat was about 300 m according to the model results.

Assessing the Impacts of Rising Sea Level on Coastal Morpho-Dynamics with Automated High-Frequency Shoreline Mapping Using Multi-Sensor Optical Satellites

Rising sea level is generally assumed and widely reported to be the significant driver of coastal erosion of most low-lying sandy beaches globally. However, there is limited data-driven evidence of this relationship due to the challenges in quantifying shoreline dynamics at the same temporal scale as sea-level records. Using a Google Earth Engine (GEE)-enabled Python toolkit, this study conducted shoreline dynamic analysis using high-frequency data sampling to analyze the impact of sea-level rise on the Malaysian coastline between 1993 and 2019. Instantaneous shorelines were extracted from a test site on Teluk Nipah Island and 21 tide gauge sites from the combined Landsat 5–8 and Sentinel 2 images using an automated shoreline-detection method, which was based on supervised image classification and sub-pixel border segmentation. The results indicated that rising sea level is contributing to shoreline erosion in the study area, but is not the only driver of shoreline displacement. The impacts of high population density, anthropogenic activities, and longshore sediment transportation on shoreline displacement were observed in some of the beaches. The conclusions of this study highlight that the synergistic use of multi-sensor remote-sensing data improves temporal resolution of shoreline detection, removes short-term variability, and reduces uncertainties in satellite-derived shoreline analysis compared to the low-frequency sampling approach.

Análise da Evolução da Linha de Costa da Região Metropolitana Sul da Cidade do Recife – PE, Brasil

O processo de erosão costeira vem afetando de forma contínua as praias do município do Jaboatão dos Guararapes, município da Região Metropolitana do Recife – PE. A ocupação desordenada ao longo dos últimos 42 anos tem agravado o processo erosivo nas praias deste município. A prefeitura em parceria com o governo do estado implantou a técnica de engenharia costeira conhecida como transpasse de sedimentos, engorda da praia, para contenção da erosão, mas que vem apresentando retirada de sedimentos, mesmo após a engorda. Por esta razão este trabalho teve o objetivo de analisar a variabilidade multitemporal da linha de costa do município de Jaboatão dos Guararapes. O ano de 1974 foi utilizado como referência para a realização do cálculo da taxa de deslocamento da linha de costa para os anos de 1981, 1997, 2010, 2013 e 2016, realizado no programa Arcgis 10.1. A área de estudo foi dividida em 4 (quatro) setores de sul para o norte. Foi observada uma relevante retrogradação para o Setor 1 (praia de Barra de Jangada) entre 1974 e 1981, apresentando estabilização entre 1981 e 1997. Já no Setor 2 (praia de Candeias), houve progradação no período de 1974 a 2010. Em 2013 ocorreu uma grande progradação da linha de costa, devido a execução da técnica de transpasse de sedimentos, sendo o Setor 1 o que obteve maior deslocamento da linha em relação aos anos anteriores. Para o ano de 2015 ocorreu o processo inverso, ou seja, uma grande retrogradação em toda extensão do litoral de Jaboatão, principalmente na praia de Barra de Jangada (Setor 1). A linha de costa do ano 2016 apresentou um grande recuo, apresentando semelhança em diferentes trechos nos 4 setores em relação a linha do ano de 1997. Analysis of the Evolution of the Coastline of the Metropolitan Region Aouth of the City of Recife – PE, Brasil A B S T R A C TThe process of coastal erosion has been continuously affecting the Jaboatão dos Guararapes’s beaches, city of the Metropolitan Region of Recife - PE. The disorderly occupation over the last 42 years has aggravated the erosive process in the beaches of this city. The city government in partnership with the state government implemented the coastal engineering technique known as sediment transfer, fattening the beach to contain erosion, but which has been showing sediment removal, even after fattening. For this reason, this work aimed to analyze the multitemporal variability of the coastline of the city of Jaboatão dos Guararapes. The year 1974 was used as a reference for the calculation of the shoreline displacement rate for the years 1981, 1997, 2010, 2013 and 2016, performed in the program Arcgis 10.1. The study area was divided into 4 (four) sectors from south to north. A large retrogradation was observed for Sector 1 (Barra de Jangada beach) between 1974 and 1981, showing stabilization between 1981 and 1997. In Sector 2 (Candeias beach), there was progression from 1974 to 2010. In 2013 there was a great progradation of the shoreline, due to the execution of the sediment transfer technique, being Sector 1 the one that had the largest displacement of the line in relation to previous years. For 2015, the opposite process occurred, that is, a major retrogradation in the entire length of the Jaboatão coast, especially in Barra de Jangada beach (Sector 1). The shoreline of the year 2016 showed a large setback, showing similarity in different stretches in the 4 sectors compared to the 1997 line.Key words. Sediment transfer, shoreline, erosion, fattening.

Lake and mire isolation data set for the estimation of post-glacial land uplift in Fennoscandia

Postglacial land uplift is a complex process related to the continental ice retreat that took place about 10 000 years ago and thus started the viscoelastic response of the Earth's crust to rebound back to its equilibrium state. To empirically model the land uplift process based on past behaviour of shoreline displacement, data points of known spatial location, elevation and dating are needed. Such data can be obtained by studying the isolation of lakes and mires from the sea. Archaeological data on human settlements (i.e. human remains, fireplaces etc.) are also very useful as the settlements were indeed situated on dry land and were often located close to the coast. This information can be used to validate and update the postglacial land uplift model. In this paper, a collection of data underlying empirical land uplift modelling in Fennoscandia is presented. The data set is available at https://doi.org/10.1594/PANGAEA.905352 (Pohjola et al., 2019).

Mistet på sjøen? En nyoppdaget fiskekrok fra steinalderen i Søgne, Vest-Agder.

The starting point for the present paper is a recent discovery of a well-preserved bone or antler fishhook, which turned up in a test pit during an underwater survey outside Tømmervigodden in Søgne, southernmost Norway. The hook is the third archaeological bone find from submarine context in Søgne. Tømmervigodden is located two kilometers away from Hummervikholmen, a submarine site known for revealing the oldest human remains from Norway, dated to the Middle Mesolithic (c. 8300-6300 cal. BC). Furthermore, a harpoon has been found in Lundeelva, approx. eight kilometers inland to the northeast. These finds demonstrate the extraordinary conditions for preservation of organic remains in the area. This article present the artefact and we discuss the issue of dating and deposition based on typology, context, and shoreline displacement curves. How old is the fishhook? How did it end up in the sea, and why is it so well preserved? The site is located in one of three areas along the Norwegian coast with potential for transgressed Mesolithic sites. The sea levels has fluctuated in Vest-Agder since the end of the Ice Age, and the sea has periodically been both higher and lower than today.The location close to Hummervikholmen and another Mesolithic site located on dry land at Tømmervigodden, initially suggested a Mesolithic date. However, the form of the fishhook, with a barb and elongated knob for attachment of the line, differs considerably from well-dated Mesolithic fishhooks in the region. The newly discovered fishhook has a distinct barb, an attribute previously considered a Neolithic trait. A precise dating would be crucial, but the closest typological parallels are undated stray-finds and C14-analysis would have destroyed the small object. Hence, dating of the hook requires a new assessment of the typology and chronology of the Stone Age fishhooks. Based on chronological and regional comparisons, we argue for a Middle Neolithic date of the fishhook from Søgne. Based on current knowledge of the local shoreline displacement curve and the formation processes influencing the seabed, we further suggest that the fishhook was lost at sea during fishing, when the sea level was at least five meters above present.

Shoreline Displacement, Coastal Environments and Human Subsistence in the Hanö Bay Region during The Mesolithic

Southern Scandinavia experienced significant environmental changes during the early Holocene. Shoreline displacement reconstructions and results from several zooarchaeological studies were used to describe the environmental changes and the associated human subsistence and settlement development in the Hanö Bay region of southern Sweden during the Mesolithic. GIS-based palaeogeographic reconstructions building on shoreline displacement records from eastern Skåne and western Blekinge together with a sediment sequence from an infilled coastal lake were used to describe the environmental changes during five key periods. The results show a rapid transformation of the coastal landscape during the Mesolithic. During this time, the investigated coastal settlements indicate a shift towards a more sedentary lifestyle and a subsistence focused on large-scale freshwater fishing. The development of permanent settlements coincided with an extended period of coastline stability and the development of rich coastal environments in a more closed forest vegetation. This study provides a regional synthesis of the shoreline displacement, coastal landscape dynamics and settlement development during the Mesolithic. It also demonstrates a new way of combining zooarchaeological and palaeoecological approaches, which can produce multi-faceted and highly resolved palaeoenvironmental reconstructions in a wide range of settings.

Shoreline displacement and human resource utilization in the southern Baltic Basin coastal zone during the early Holocene: New insights from a submerged Mesolithic landscape in south-eastern Sweden

Along parts of the Hanö Bay coast in south-eastern Sweden, remains of a submerged landscape can be found down to depths of almost 25 m b.s.l. The coastal landscape was formed during two periods of lowered water levels in the Baltic Basin: the Yoldia Sea and the Initial Littorina Sea stages. In order to reconstruct the local environment and shoreline displacement during the Yoldia Sea and Ancylus Lake stages, sediment sequences were obtained at 4.5, 17.5 and 18.7 m b.s.l. Detailed bathymetric mapping was based on multi-beam echo-sounding while surveillance and sampling of tree remains and archaeological findings were performed through diving. The Yoldia Sea low-stand reached its minimum level at 24–25 m b.s.l. just before 10,800 cal. BP. During the subsequent Ancylus transgression, a slow-flowing river passed through the area, accumulating thick deposits of fine-grained organic sediments in lagoonal basins. The river was surrounded by open woodland dominated by pine. Based on successive flooding of rooted tree stumps, the transgression rate was estimated at 4 cm·yr−1, until the Ancylus high-stand was reached at 5 m b.s.l. at 10,400–10,300 cal. BP. Findings of worked aurochs and beaver bones provide evidence of human presence in the landscape and show the importance of terrestrial resources for their subsistence. These integrated palaeoecological and archaeological investigations demonstrate the importance of submerged landscapes with well-preserved sediment, wood and bone material for our understanding of southern Baltic coastal landscapes and their inhabitants during the Early Mesolithic.