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Online communication and adolescent health. Exploring adolescent mental and physical health and online communication in the early 21st century: Longitudinal and cross-sectional perspectives
(University of Iceland, School of Education, Faculty of Health Promotion, Sport and Leisure Studies, 2025-09) Birgisson, Ottar; Erlingur Jóhannsson, G. Sunna Gestsdóttir; Deild heilsueflingar, íþrótta og tómstunda (HÍ); Faculty of Health Promotion, Sport & Leisure Studies (UI); Menntavísindasvið (HÍ); School of Education (UI)
In this thesis, I investigate the evolving relationship between online communication and adolescent mental and physical health, focusing on changes over time. The main aim was to assess how online communication relates to mental health outcomes (depression, anxiety, self-esteem, and body image) and physical health, measured as cardiorespiratory fitness (CRF). Additionally, how these relationships have changed in the early 21st century, during a period of significant transformations in online communication, was explored. Three datasets collected from Icelandic adolescents were used. 1) A cohort born in 1988 assessed in 2003 at age 15 (n = 385), 2) a cohort born in 1999 assessed in 2015 at age 15 (n = 302), and 3) the cohort born in 1999 followed up in 2017 at age 17 (n = 236). Measurements included self-reported online communication frequency, validated questionnaires assessing mental health, and objective CRF measurements using a maximal cycle ergometer test. Socioeconomic status (SES) was estimated based on parental education and living arrangements. Statistical analyses included descriptive statistics, multiple regression, analysis of variance, structural equation modeling, and mixed-effects models. Results showed that depressive symptoms increased among adolescent females between 2003 and 2015 while remaining stable for males. Anxiety levels and self- esteem did not change significantly for either sex. Body image improved slightly for males but was stable for females. By 2015, a significant relationship was found between online communication and an increase in depressive and anxiety symptoms in females but not in males. CRF declined from 2003 to 2015, and a negative association between CRF and mental health outcomes was observed. Lastly, online communication had a negative association with mental health and CRF at the age of 15, and that this relationship persisted until the age of 17, regardless of sex and SES. The findings highlight the complex dynamics of online communication and its impact on adolescent mental and physical health. Increased online communication appears to be linked to poorer mental health outcomes particularly for females, possibly mediated by social comparison. Declining CRF underscores the importance of promoting physical fitness alongside mental health interventions. To address these challenges, interventions should integrate both digital literacy and physical activity strategies. This study contributes to a deeper understanding of adolescent well-being in the digital age and provides a foundation for targeted interventions.
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Tourist safety on adventure trips: Guide competencies and risk management strategies in the Arctic
(University of Iceland, School of Engineering and Natural Sciences, Faculty of Life and Environmental Sciences, 2025-09) Hild, Barbara Olga; Gunnar Þór Jóhannesson; Líf- og umhverfisvísindadeild (HÍ); Faculty of Life and Environmental Sciences (UI); Verkfræði- og náttúruvísindasvið (HÍ); School of Engineering and Natural Science (UI)
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Improving modelling of crustal deformation in relation to magmatic and geothermal processes
(University of Iceland, School of Engineering and Natural Sciences, Faculty of Earth Sciences, 2025-09) Lanzi, Chiara; Freysteinn Sigmundsson; Jarðvísindadeild (HÍ); Faculty of Earth Sciences (UI); Verkfræði- og náttúruvísindi (HÍ); School of Engineering and Natural Sciences (UI)
Understanding small crustal deformation signals is important for improving volcano monitoring and hazard mitigation. Spatial and temporal ground displacement patterns were mapped with Global Navigation Satellite System (GNSS) geodesy and Interferometric analysis of Synthetic Aperture Radar (InSAR) images, allowing detection of millimeter- to centimeter-scale deformation. Geodetic modelling, through inversion or forward modelling, was used to infer deformation source parameters and increase understanding of volcanic, geothermal and tectonic processes. In summer 2018, a change in the pattern of ground deformation at the Krafla caldera coincided with increased pressure in a monitoring well. This occurred at a similar time as re-injection of water, in relation to geothermal utilization, was modified. The difference between GNSS and InSAR velocity fields from 2015–2018 and 2018–2020 reveals an inflation pattern with horizontal motion up to 8–10 mm/yr. Geodetic inversion shows that the difference velocity field can be fit with a 2.1–2.5 km deep point-source, near the magma-hydrothermal interface. The observations are broadly explained by local variations in intra-caldera crustal elasticity and pressure increase at ~2.2 km depth, consistent with the well data. The study also examined how local elastic and viscoelastic crustal and mantle properties at volcanoes located at divergent plate boundaries influence deformation by regional processes like plate spreading, using a Finite Element Method model to simulate local rheological anomalies beneath calderas and rifts. This approach helps explaining the observed decades-long subsidence at Krafla (1989–2018) and Askja (1985–2021). The results show that extensional forces and rheological anomalies can drive volcanic subsidence. At Krafla, this account for much of observed 2015-2018 subsidence, but only 20–30% at Askja. Finally, the ~40-60 mm subsidence during the 2021 Fagradalsfjall eruption was analyzed and evaluated how changes in deformation relate to changes in eruption rate, geochemistry of eruptive products, and eruptive style. Surface lava loading within 1-2 km significantly contributed to the subsidence. After removing this effect, geodetic inversion locates a 12–14 km deep sill source with volume contraction of 2127 Mm3. This research highlights the need to consider complex geological settings when interpreting small ground deformation signals, as multiple interacting processes may produce observed deformation.
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Basalt lava degassing: mechanism and characterisation
(University of Iceland, School of Engineering and Natural Sciences, Faculty of Earth Sciences, 2025-05) Levillayer, Nicolas; Olgeir Sigmarsson; Jarðvísindadeild (HÍ); Faculty of Earth Sciences (UI); Verkfræði- og náttúruvísindasvið (HÍ); School of Engineering and Natural Sciences (UI)
The volcanic gas composition emitted during basaltic eruptions is relatively well understood, but the emissions from cooling lava fields have been less studied, along with their environmental impacts. The study investigated the gas emission from crystallising lava, as well as the internal structure of lava and associated segregation veins. Gas samples were collected from the eruptive crater, cooling vents, and solidifying lava in Fagradalsfjall. The gas emissions were found rich in sulphur and sulphide-forming elements at the eruptive crater, while post-eruptive gas is richer in halogens, especially chlorine at the crystallising lava and fluorine at the cooling vent. Estimates of emissions from crystallising lava show significant release of metals that form chlorides. The relationship between emission and fractional crystallisation, along with segregation melt formation during lava solidification, was examined. The first minerals to from are anhydrous, forming a fully crystallised framework after 40-50% crystallisation. In the residual melt, volatile elements saturate and form a volume-rich gas phase. The gas presses the melt through the crystal framework, forming segregation veins. Chemical analyses of these veins reveal whether the gas phase escaped into the atmosphere or solidified with the melt. The similar compositions of segregation veins and gas from solidifying lava indicate a relationship between the internal lava evolution and lava degassing. Overall, the results show that gas emissions from lava are distinct from emissions at the vent but correlate well with the fractional emission of basalt melt, both in terms of origin and nature. The environmental impacts of heavy metal gas emissions from basalt lava are a worthy subject for future research.
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Ágripabók: 25. ráðstefna Þjóðarspegilsins
(University of Iceland, School of Social Sciences, Social Science Research Institute, 2024-11) Háskóli Íslands, Félagsvísindastofnun; Félagsvísindastofnun (HÍ); Social Science Research Institute (UI); Félagsvísindasvið (HÍ); School of Social Sciences (UI)