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Quick clay is found across Scandinavia and is especially prominent in south-eastern and central Norway. Quick clay is prone to failure and can cause landslides with high velocities and large run-outs. The 1978 Rissa landslide is one of the best-known quick clay landslides to have occurred in the last century, both due to its size and the fact that it was captured on film. In this article, we utilise Structure fromMotion Multi-View Stereo (SfM-MVS) photogrammetry to process historical aerial photography from 1964 to 1978 and derive the first geodetic volume of the Rissa landslide. We found that the landslide covered a total onshore area of 0.36 km2 and had a geodetic volume of 2.53 ± 0.52 × 106m3 with up to 20m of surface elevation changes. Our estimate differs profusely from previous estimates by 43–56% which can partly be accounted for our analysis not being able to measure the portion of the landslide that occurred underwater, nor account for the material deposited within the landslide area. Given the accuracy and precision of our analyses, we believe that the total volume of the Rissa landslide may have been less than originally reported. The use of modern image processing techniques such as SfM-MVS for processing historical aerial photography is recommended for understanding landscape changes related to landslides, volcanoes, glaciers, or river erosion over large spatial and temporal scales. FFG-ASAP (885370) FWFP29461- N29

This thesis investigates Holocene storminess and climate change reconstructed from lacustrine sediments from the Lofoten-Vesterålen archipelago in northern Norway (68–69°N, 12–16°E). The present thesis consists of an introduction and three individual papers in studying different perspectives of aeolian (wind) activity reconstructed from (I) glacier fluctuations, (II) coastal dunefield dynamics and (III) variations in aeolian sand influx from three different lake sediment basins. Paper I presents the first high-resolution late-Holocene glacier record from Lofoten. The study is based on glacial geomorphological mapping and analyses of sediment cores from lake Kveitvikvatnet (30.1 m a.s.l.), which currently receives meltwater from three small cirque glaciers. By combining selected sediment proxies to glacier advances of known ages, a continuous curve of the glaciers equilibrium-line altitude (ELA) over the last 1200 years has been constructed. This has further been connected to an independent proxy for summer temperature using the well-known ‘Liestøl- equation’, as well as the D/A-ratio, resulting in winter precipitation estimates throughout the recorded period. The extremely high sedimentation rates measured in the sediment cores (0.15–0.45 cm/yr) allow us to draw an analogy to instrumental data from nearby meteorological stations, which strongly supports our approach. We have identified that both the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) were periods of high glacier activity in Lofoten. It is proposed that the advancing glaciers during both periods were caused mainly by an increase in winter precipitation, in relation to an increase in the strength of the westerlies. In Paper II we investigate the aeolian activity at a coastal dunefield on Andøya in Vesterålen. The study is based on a combination of geomorphological mapping, a lacustrine sediment record from the distal lake Latjønna (14.5 m a.s.l.) and a foredune stratigraphy. The lake sediment record was analysed by high-resolution measurements of sediment properties such as X-ray fluorescence (XRF), magnetic susceptibility (MS), grain size and loss-on-ignition (LOI). Aeolian activity was calculated based on the weight of sand grains >250 μm per cm recorded in Latjønna divided by the sedimentation rate. The two investigated sites show quite contrasting chronologies, where high sedimentation rates in the lake record, associated with more aeolian influx, correspond to stability in the foredune stratigraphy reflected by the presence of palaeosols. Phases with high influx of sand to Latjønna are recorded around 4800, 4250, 3000–2000, 1850–1750, 1600–600, 450, 300 and 150 cal. yr BP. Based on the investigated sites, it is suggested that a falling sea level made sand available for deflation, and that increasing storminess was the main driver for increased aeolian activity. The influx of sand to Latjønna is concurrent with other reconstructions from the region, thus recording variations in past storminess occurring in the NE Atlantic region throughout the last 6200 years. Paper III presents a reconstruction of aeolian activity (storminess) and mass-wasting events based on analysis of lacustrine sediment cores from lake Trehynnvatnet (33 m a.s.l.), which is located in a glacially carved valley at the outmost coast of western Langøya in Vesterålen, northern Norway. Sediment cores have been examined by use of various high-resolution proxies and firmly dated with 210Pb and 14C dating to detect changes in the depositional environment. In total, 35 event layers with a recurrence interval of ~300 years have been identified throughout the Holocene. The majority of these events are characterized as discrete coarse-grained sediment layers followed by normal grading and interpreted to be deposited by turbidity currents triggered by subaerial mass-wasting events. The continuous background sediments have been systematically investigated for the content of sand grains (>250 μm), which have been linked to catchment samples from a nearby beach located c. 750 m to the southwest. Based on the current wind regime and the local setting, the influx of wind-blown sand grains to Trehynnvatnet is suggested to reflect the strength, pattern and timing of storminess. The results show that storminess increased after 2800 cal. yr BP, with maximum influx of sand grains occurring during the Little Ice Age (LIA) period. The long-term trends shown in the influx of sand grains and mass-wasting events to Trehynnvatnet are similar to other reconstructions from nearby sites and from the NE Atlantic region. Hence, this record provides further knowledge about past regional scale changes in storminess and episodic extreme events throughout the Holocene.