In the northern part of Swedish Caledonides, north of Lake Torneträsk is a 7 km long exposure of a breccia layer. The layer thins westwards and eastwards from the central part where it is up to 27 m thick. It is called the Vakkejokk Breccia after the type section. The breccia has been described in literature since about a century, but its origin is enigmatic. The breccia layer is since the summer of 2012 investigated by three geologists specialized in impact craters, Paleozoic sediments, and the Caledonian orogeny. They put forward evidence for the breccia being formed by a hypervelocity impact during the Lower Cambrian at approximately 520 Ma (Ormö et al. 2017). At that time the target area was a shallow epicontinental sea that surrounded the mainly peneplanized continent Baltica. An impact into the sea is known to generate tsunami waves as well as resurge deposits when the water brings ejected and rip-up material back into the crater. Ormö et al. (2017) suggest the top part of the Vakkejokk Breccia to include such resurge deposits. The depositional marine environment is also known to rapidly protect an impact crater from further erosion. It is possible that only the topographic rim of the Vakkejokk crater was eroded during the millions of years it may have taken before the crater was covered by younger sediments. About 100 m.y. after the formation, it was completely covered by overthrust nappes during the Caledonian orogeny, when Baltica and Laurentia collided. The crater itself is not exposed today, merely parts of what is thought to be the ejecta layer and resurge deposits. This Bachelor of Science project aimed to investigate the putative resurge deposits to learn more about the process of formation and the provenance in the target of the clasts in the deposits. This was carried out by three short drillcores through the resurge deposit part of the Vakkejokk Breccia layer. The place to drill the boreholes was chosen at an outcrop which is proximal to the putative hidden crater. The retrieved drillcores were cut longitudinally, then polished and photographed in high resolution. Each core was then analyzed in an image analysis software with respect to clast granulometry and lithology. To the results are presented as graphs showing clast size, size sorting, clast shape, of the relative amounts of different lithologies and the matrix content. The results are discussed with respect to well-documented analogue marine-target craters

Drop impact is a canonical problem in fluid mechanics, with numerous applications in industrial as well as natural phenomena. The extremely simple initial configuration of the experiment can produce a very large variety of fast and complex dynamics. Scientific progress was made in parallel with major improvements in imaging and computational technologies. Most recently, high-speed imaging video cameras have opened the exploration of new phenomena occurring at the micro-second scale, and parallel computing allowed realistic direct numerical simulations of drop impacts. We combine these tools to bring a new understanding of two fundamental aspects of drop impacts: splashing and air entrapment. The early dynamics of a drop impacting on a liquid pool at high velocity produces an ejecta sheet, emerging horizontally in the neck between the drop and the pool. We show how the interaction of this thin liquid sheet with the air, the drop or the pool, can produce micro-droplets and bubble rings. Then we detail how the breakup of the air film stretched between the drop and the pool for lower impact velocities can produce a myriad of micro-bubbles.

Impaktite des Chicxulubkraters wurden petrographisch (Polarisationsmikroskopie, REM, KL) und chemisch (RFA, TRFA, PGE, EMS) untersucht, um das Verhalten von Ejekta während des atmosphärischen Transports zu erforschen. Die proximalen Impaktite der UNAM-7 Bohrung bestehen aus einer suevitischen Brekzie (222.2 bis 384.4 m) und einer basalen, polymikten Brekzie mit geringem Silikatschmelzanteil. Letztere beinhaltet Evaporit-Megablöcke und Karbonatschmelzpartikel; Zersetzung von Kalzit und Anhydrit ist durch Entgasungsbläschen indiziert. An der distalen Kreide-Paläogen Grenze von El Guayal (520 km SW vom Kraterzentrum) beinhaltet eine 10 m mächtige suevitische Abfolge in einer oberen Untereinheit akkretionäre Lapilli und darüber eine Toneinheit. Das Auftreten von Karbonatschmelzen mit der PGE-angereicherten Impaktorkomponente in der Toneinheit belegt den Zusammenhang der K-P Grenze mit dem Chicxulub-Impakt. Die folgenden Stadien können für die Ablagerung und Alteration der Ejekta unterschieden werden: (1) Ein Hochgeschwindigkeitsauswurf beschleunigte Zersetzungsprodukte und initiierte einen Gasstrom. (2) Karbonatschmelzen wurden mit Anhydrit-Megablöcken ausgeworfen und initiierten einen lateral ausbreitenden Ejektavorhang. Kalzitrückreaktionen erhitzte das Material während des Transports. (3) Die Ejektionswolke kollabierte teilweise, wobei der zurückfallende Suevit vom Impaktormaterial, das in die Stratosphäre verteilt wurde, fraktioniert wurde. Die Kombination von Silikatschmelze mit Kalzit initiierte einen heißen, gas-angetriebenen Strom. In einer oberen, moderat temperierten, turbulenten Aschewolke kondensierte Wasserdampf, und durch Akkretion von Asche entstanden akkretionäre Lapilli. (4) Die Impaktorkomponente wurde mit den feinsten Ejektamassen für Wochen bis Jahre abgelagert. (5) Der Transport von Ejekta in der heißen Ejektionswolke induzierte Alterationsprozesse in den Ablagerungen. Es kann geschlussfolgert werden, dass ein gewisser Anteil des CO2 zu Kalzit zurückreagierte, währenddessen SOX Gase vollständig in die Atmosphäre freigesetzt wurden. Diese Beobachtungen inklusive des Auftretens von Karbonatschmelzen unterstützen die Aussage, dass der freigesetzte Anteil von CO2 in die Atmosphäre in der Vergangenheit überbewertet wurde. / Impactites of the Chicxulub crater were studied petrographically (polarisation microscopy, SEM, CL) and chemically (XRF, TXRF, PGE, EMPA) to investigate the evolution of ejecta during transit through the atmosphere. At the proximal UNAM-7 borehole, the sequence of impactites consists of a suevitic breccia (222.2 to 348.4 m) on top of a polymict silicate melt-poor breccia. The latter is intercalated with evaporite megablocks representing an analogue to the Bunte Breccia of the Nördlinger Ries crater. It contains carbonate melt particles; calcite and anhydrite decomposition is indicated by degassing vesicles. At the distal Cretaceous-Palaeogene site of El Guayal (~520 km SW of the crater centre), a ~10 m thick suevitic succession contains at its upper subunit accretionary lapilli and on top a clay unit. Intermixing of calcite with hot silicate melt resulted in recrystallisation and decomposition of calcite. In the clay unit, the presence of carbonate melt spheroids together with the PGE-enriched impactor component links the Chicxulub impact with the K-P boundary. The following stages can be distinguished for the deposition and alteration of the ejecta: (1) Jetting accelerated decomposition products and initiated a vapour flow. (2) Carbonate melts were excavated with anhydrite megablocks and initiated a lateral extending ejecta curtain. Calcite reformations heated the material during transport. (3) The expanding ejecta plume partially collapsed separating the falling suevite from impactor material that had been lifted into the stratosphere. The combination of silicate melt with calcite initiated a hot, gas-driven, basal flow. In an upper, moderately tempered, turbulent ash cloud, steam condensed and accretion of ash-sized material formed accretionary lapilli. (4) The impactor component was deposited with the finest ejecta for weeks to years. (5) The prolonged transport of ejecta in the hot ejecta plume induced alteration processes observed in the deposits. It can be concluded that a certain amount of CO2 has back-reacted to calcite, whereas SOX gases were completely liberated. These observations including the abundant presence of carbonate melts support that the amount of CO2 released to the atmosphere during the Chicxulub impact was overestimated previously.

Fine grained sediment deposition in urban environments during natural hazard events can impact critical infrastructure and properties (urban terrain) leading to reduced social and economic function and potentially adverse public health effects. Therefore, clean-up of the sediments is required to minimise impacts and restore social and economic functionality as soon as possible. The strategies employed to manage and coordinate the clean-up significantly influence the speed, cost and quality of the clean-up operation. Additionally, the physical properties of the fine grained sediment affects the clean-up, transport, storage and future usage of the sediment. The goals of the research are to assess the resources, time and cost required for fine grained sediment clean-up in an urban environment following a disaster and to determine how the geotechnical properties of sediment will affect urban clean-up strategies. The thesis focuses on the impact of fine grained sediment (<1 mm) deposition from three liquefaction events during the Canterbury earthquake sequence (2010-2011) on residential suburbs and transport networks in Christchurch. It also presents how geotechnical properties of the material may affect clean-up strategies and methods by presenting geotechnical analysis of tephra material from the North Island of New Zealand. Finally, lessons for disaster response planning and decision making for clean-up of sediment in urban environments are presented. A series of semi-structured interviews of key stakeholders supported by relevant academic literature and media reports were used to record the clean-up operation coordination and management and to make a preliminary qualification of the Christchurch liquefaction ejecta clean-up (costs breakdown, time, volume, resources, coordination, planning and priorities). Further analysis of the costs and resources involved for better accuracy was required and so the analysis of Christchurch City Council road management database (RAMM) was done. In order to make a transition from general fine sediment clean-up to specific types of fine disaster sediment clean-up, adequate information about the material properties is required as they will define how the material will be handled, transported and stored. Laboratory analysis of young volcanic tephra from the New Zealand’s North Island was performed to identify their geotechnical properties (density, granulometry, plasticity, composition and angle of repose). The major findings of this research were that emergency planning and the use of the coordinated incident management system (CIMS) system during the emergency were important to facilitate rapid clean-up tasking, management of resources and ultimately recovery from widespread and voluminous liquefaction ejecta deposition in eastern Christchurch. A total estimated cost of approximately $NZ 40 million was calculated for the Christchurch City clean-up following the 2010-2011 Canterbury earthquake sequence with a partial cost of $NZ 12 million for the Southern part of the city, where up to 33% (418 km) of the road network was impacted by liquefaction ejecta and required clearing of the material following the 22 February 2011 earthquake. Over 500,000 tonnes of ejecta has been stockpiled at Burwood landfill for all three liquefaction inducing earthquake events. The average cost per kilometre for the event clean-up was $NZ 5,500/km (4 September 2010), $NZ 11,650/km (22 February 2011) and $NZ 11,185/km (13 June 2011). The duration of clean-up time of residential properties and the road network was approximately two to three months for each of the three liquefaction ejecta events; despite events volumes and spatial distribution of ejecta. Interviews and quantitative analysis of RAMM data revealed that the experience and knowledge gained from the Darfield earthquake (4 September 2010) clean-up increased the efficiency of the following Christchurch earthquake induced liquefaction ejecta clean-up events. Density, particle size, particle shape, clay content and moisture content, are the important geotechnical properties that need to be considered when planning for a clean-up method that incorporates collection, transport and disposal or storage. The geotechnical properties for the tephra samples were analysed to increase preparedness and reaction response of potentially affected North Island cities from possible product from the active volcanoes in their region. The geotechnical results from this study show that volcanic tephra could be used in road or construction material but the properties would have to be further investigated for a New Zealand context. Using fresh volcanic material in road, building or flood control construction requires good understanding of the material properties and precaution during design and construction to extra care, but if well planned, it can be economically beneficial.