To see the other types of publications on this topic, follow the link: Lava flows.
Dissertations / Theses on the topic 'Lava flows'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Lava flows.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Chevrel, Magdalena Oryaelle. "Rheology of Martian lava flows." Diss., Ludwig-Maximilians-Universität München, 2013. http://nbn-resolving.de/urn:nbn:de:bvb:19-157836.
Full textAbstract:
In recent years, high-resolution topographic images from Mars’ surface as well as mineralogical and chemical data, have rapidly become more accessible. Martian volcanic landforms are characterized by giant low slope shield volcanoes, abundant lava flood plains and long lava flows. In-situ rock analysis and remote sensing spectroscopy reveal mainly basaltic compositions with particularly high iron concentrations, distinct from terrestrial basalts. As yet, very little is known about the rheological properties of such iron-rich Martian magmas that are essential to understand magmatic processes. Understanding the chemical and physical contributions to lava rheology is fundamental to provide constraints on magma ascent and lava flow emplacement that shaped the volcanic landforms on Mars. This study provides an experimental investigation of the rheological properties of Martian lavas and discusses the diversity of compositions in terms of lava viscosity / flow morphology relationship. The effect of iron, and its redox state on silicate melt viscosity is experimentally investigated and the viscosities of five synthetic silicate liquids having compositions representative of the diversity of Martian volcanic rocks were measured under controlled ambient oxygen fugacity. The results highlight the low viscosity of the iron-rich Martian melts that is consistent with viscosity values derived from morphological observations. A solidified lava flow on Earth was studied by combining analyses of remote sensing images (as commonly done on Mars), as well as experimental investigations of the rheological properties of the sampled rocks, in order to describe the viscous behavior of lava as emplacement, cooling, and crystallization occur. We show that a cooling-limited basaltic flow seemingly stop flowing when it reaches a critical viscosity value that is function of crystals content and shapes. As a result, the lava apparent viscosity appears to be largely influenced by the details of the crystallization sequence and is not uniquely and simply related to the bulk chemical composition of the erupted material. Variation of the chemical evolution of Martian primary mantle melts through the volcanic history is not large to produce an significant shift of the viscosity range that could be observed them from their morphologies. Low apparent viscosities inferred from lava flow morphology on Mars may in turn be attributed to lavas with primary mantle melt composition crystallizing high proportion of olivine and possibly forming spinifex textures. Higher viscosity values derived from the morphology are compatible with mildly alkaline or trachybasalts and do not necessarily imply the occurrence of silica-rich lavas.Über die letzten Jahre sind hochauflösende topographische Bilder der Oberfläche des Mars, sowie chemische und mineralogische Daten der Marsgesteine zunehmend verfüg- bar geworden. Die vulkanischen Formationen des Mars beinhalten gigantische Schild- vulkane flacher Ausprägung, grosse Flutbasaltebenen und weitfliessende Lavaströme. In- situ Analysen der Mars Gesteine und “Remote Sensing Spectroscopy“ zeigen grösstenteils basaltische Zusammensetzungen, jedoch mit besonders hohem Eisengehalt, der Mars- gesteine von terrestrischen Proben unterscheidet. Bis dato sind die rheologischen Eigen- schaften dieser eisen-reichen Mars Magmen wenig erforscht. Das Verständnis der physiko- chemischen Parameter, die die Lava Rheologie beeinflussen, ist jedoch fundamental, um Magmaaufstieg und die Ablagerung von Lavaströmen auf dem Mars zu verstehen. In dieser Studie wurden die rheologischen Eigenschaften marsianischer Laven experi- mentell untersucht und die Variabilität der natürlich vorkommenden Zusammensetzungen in Beziehung zu Lava-Viskosität und Lava-Morphologie gesetzt. Der Effekt von Eisen und seines Redox Zustandes auf die Viskosität von Silikatschmelzen wurde experimentell untersucht. Unter kontrollierten Sauerstofffugazitäten wurden die Viskositäten von fünf synthetischen Silikatschmelzen untersucht, deren Zusammensetzun- gen repräsentativ für die Spannbreite der Zusammensetzungen der vulkanischen Gesteine des Mars ist. Die niedrige Viskosität der eisenreichen, marsähnlichen Schmelzen ist kon- sistent mit den Viskositätswerten, die durch morphologische Analysen bestimmt wurden. Als terrestrisches Analog wurde ein erkalteter Lavastrom mit Hilfe von fernerkundlichen Bildern, die in der gleichen Weise für Mars angewendet werden, sowie Messungen der Rheologie an Gesteinsproben dieser Lava untersucht, um Änderungen in der Viskosität während der Ablagerung, des Abkühlens und der Kristallisation zu charakterisieren. Laut unserer Ergebnisse wird ein durch Abkühlen limitierter basaltischer Lavastrom aufgrund von erhöhtem Kristallgehalt und als Funktion von Kristallhabitus gestoppt. Die appar- ente Viskosität scheint daher grösstenteils von der Kinetik der Kristallisatiosnsequenz beeinflusst und weniger von der Gesamtzusammensetzung des eruptierten Materials. Als Folge hätte die Variabilität in der Zusammensetzung der primären, marsianischen Man- telschmelzen über die vulkanische Historie keinen signifikanten Effekt auf die apparente Viskosität, die durch Lava-Morphologie-Analysen bestimmt wird. Niedrige apparente Viskositäten aus diesen Morphologie-Analysen erklären sich dadurch hauptsächlich als Folge von primären Mantelschmelzen, die einen hohen Anteil von Olivin kristallisieren und möglicherweise Spinifex Texturen ausbilden. Wenn Morphologieanalysen höhere Viskositäten ausgeben ist dies kompatibel mit schwach alkalinen Basalten oder Trachy- basalten, bedeutet jedoch nicht notwendigerweise das Vorkommen felsischer Laven.
Ces dernières années, des nouvelles données satellites de la surface de Mars de haute résolution (topographiques ainsi que minéralogiques et chimiques), sont devenues accessi- bles à la communauté scientifique. Sur Mars, les paysages volcaniques sont caractérisés par des volcans boucliers géants à pentes faibles, des plaines de lave et des longues coulées de lave. L’analyse des roches in situ et par spectroscopie orbitale révèlent que la composition des roches est essentiellement basaltique contenant une quantité de Fer particulièrement élevée, clairement distincte des basaltes terrestres. À ce jour, les propriétés rhéologiques des magmas martiens riches en Fer, qui sont essentielles pour comprendre les processus magmatiques, n’ont pas été étudiées en détails. Définir comment la teneur en Fer con- trôle la rhéologie des laves est fondamental pour comprendre l’ascension des magmas et interpréter la mise en place des coulées de lave qui façonnent les paysages volcaniques sur Mars. Cette thèse fournit une étude expérimentale des propriétés rhéologiques des laves martiennes et discute de la diversité des compositions en termes de relation entre viscosité et morphologie des coulées. L’effet du Fer et son état d’oxydo-réduction sur la viscosité des liquides silicatés sont étudiés expérimentalement et les viscosités de cinq laves ayant des compositions représen- tatives de la diversité des roches volcaniques martiennes ont été mesurées en fonction de la température. Les résultats mettent en évidence la faible viscosité de ces liquides martiens riches en fer, ce qui est compatible avec la viscosité déduite des observations morphologiques. Afin de décrire le comportement visqueux d’une coulée de lave pendant sa mise en place (refroidissement et cristallisation), une coulée terrestre a été étudiée, en combinant l’analyse des images de télédétection (comme on le fait sur Mars) et l’étude expérimentale des propriétés rhéologiques des roches échantillonnées. Nous montrons que la forme des coulées basaltiques qui ont cessé d’avancer à cause de leur refroidissement, atteignent une limite rhéologique qui dépend des détails de la séquence de cristallisation et de la forme des cristaux. Leur viscosité apparente n’est pas uniquement et simplement liée à la composition chimique de la lave. Ainsi, l’évolution chimique des liquides pri- maires issus de la fonte partielle du manteau martien à travers l’histoire volcanique de Mars n’a pas d’effet significatif sur la viscosité apparente déterminée par la morphologie des coulées. Les faibles viscosités apparentes déduites de la morphologie des laves sur Mars peuvent être attribuées à des compositions de liquides primaires qui cristallisent des olivines en forte proportion et pouvant former une texture spinifex. Les viscosité plus élevées dérivées de la morphologie sont elles compatibles avec des basaltes légèrement alcalins ou trachytique et n’impliquent pas nécessairement la présence de laves riches en silice de type andésitique.
2
Castruccio, Angelo. "Rheology and dynamics of lava flows." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.556978.
Full textAbstract:
This thesis presents the results of laboratory experiments, theoretical analysis, field work and petrological analysis conducted to study the rheology and dynamics of lava flows. The rheology of suspensions of cubic crystals in viscous liquids was investigated with a series of experiments, consisting of the release of a fixed volume of fluid inside a horizontal channel. A Herschel-Bulkley rheology was assumed and the consistency K and the shear rate exponent n of this constitutive equation were calculated using the evolution of the flow front; the yield strength was calculated using the final shape of the flow. Results show an increase in K when crystal content increases. The mixtures start to show a shear thinning behaviour at 4>-0.3 with n values going from approximately 1 (Newtonian behaviour) to 0.5 at 4>=0.6. Yield strength was detected at the same 4> as the beginning of shear thinning behaviour and increases with a power-law relationship with crystal content. Suspensions with bimodal crystal sizes show a dramatic decrease of the apparent viscosity compared to unimodal suspensions, especially at the higher total crystal concentrations. Further experiments, with the same types of fluids (with approximately Herschel- Bulkley rheology) in a sloping channel with a constant flux rate were approximated with a simplified 2-D model. The results show an excellent agreement between the theory and the experiments. Additionally, experiments with two fluids, where a low viscosity fluid (syrup) is injected in a fixed volume of more viscous material (syrup plus crystals) suggest that the front advance and height is controlled mainly by the rheology of the fixed volume fluid. The simplified 2-D theory was applied to real lava flows. Three dynamical regimes were considered: A Newtonian viscous regime, a yield strength-dominated regime, and a crust-dominated regime. The resulting equations were applied to published data from eruptions of 10 lava flows with a range of compositions and conditions. Comparisons of the fits of the models to the data reveal that short-lived, high effusion rate eruptions typical of Hawaiian lava flows, are dominated by the internal viscosity of the lava, whereas low effusion rate or long lived eruptions are dominated by the yield strength in the growing crust. Finally, eruptions with very high initial crystal contents are dominated by the internal yield strength. The developed rheological model and 2-D theory were applied to the 2002 lava flow deposits at the NE flank of Etna volcano to reconstruct the variations in flow rate and advance of the flow front. Analyses of samples were used to estimate crystal content and liquid viscosity variations with distance. Yield strength variations were estimated from levee width measurements. The modelled flow rate and advance of the flow front compare well with the measured data, with a mean flow rate of 19.5 m3/s. The method developed in this thesis provides the prospect of using measurements of flow dimensions together with analysis of samples from the deposits to estimate the rheology of the flow and reconstruct variations of eruption parameters.
3
Calvari, Sonia. "Hazard assessment on Etna volcano, Italy." Thesis, Lancaster University, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.301816.
Full text
4
Bond, A. J. "The simulation of lava flows with small scale models." Thesis, Lancaster University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.236289.
Full text
5
Demchuk, Robert W. "Detailed Mapping of Lava Flows in Syrtis Major Planum, Mars." Ohio University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1617806602421614.
Full text
6
Soule, Samuel Adam. "Basaltic lava flow surface morphology : genesis, evolution, and impact on flow dynamics /." view abstract or download file of text, 2003. http://wwwlib.umi.com/cr/uoregon/fullcit?p3102190.
Full textAbstract:
Thesis (Ph. D.)--University of Oregon, 2003.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 271-279). Also available for download via the World Wide Web; free to University of Oregon users.
7
Jones, Alun Christopher. "Remote sensing and thermal modelling of active lava flows, Kilauea volcano, Hawai'i." Thesis, Lancaster University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.358927.
Full text
8
Deligne, Natalia, and Natalia Deligne. "After the Flow: Landscape Response to the Emplacement of Holocene Lava Flows, Central Oregon Cascades, USA." Thesis, University of Oregon, 2012. http://hdl.handle.net/1794/12515.
Full textAbstract:
Effusive volcanic eruptions repave landscapes rapidly with lava flows, resetting the underlying landscape and ecosystem. The unique physical properties of lava pose interesting challenges for recovery, as lava flows can be highly permeable while lava itself is dense, sterile, and generally inhospitable towards life. This dissertation examines two aspects of landscape recovery following lava flow emplacement: (1) hydrologic adaptation of surface and groundwater to recent volcanism and (2) plant colonization of young lava flows. I examine two sites in the central Oregon Cascades: the c. 3 ka Sand Mountain volcanic field (SMVF), located in the headwaters of the McKenzie River, a critical water resource for the state of Oregon, and the c. 1.5 ka Collier Cone lava flow, originating on the north flanks of North Sister volcano.
My investigation of the SMVF and upper McKenzie River watershed reveals a complex volcanic history with profound impacts on the configuration and short-term discharge of the McKenzie River: lava flows from the SMVF and other Holocene vents have buried, dammed, and altered the path of the McKenzie River. Moreover, given the large groundwater contribution from the SMVF to the McKenzie River, I estimate that SMVF activity caused McKenzie River discharge in present-day Eugene, Oregon to decrease by up to 20% for days to months at a time; future regional mafic volcanic activity could have a similar impact.
The SMVF and the Collier Cone lava flow are notable for the juxtaposition of barren exposed lava and mature forests on the same or similarly aged lava flows. I use a combination of LiDAR analysis, field observations, and soil characterization to examine soil and vegetation at these two sites and find that the presence of an external soil source greatly facilitates plant establishment, growth, and survival. Here, external soil sources are syn- or post-eruptive tephra (SMVF) or flood-borne deposits (Collier Cone lava flow). External soil appears to provide a substrate for plants to grow in along with key nutrients and sufficient moisture; overall, external soil sources are key for the initial recovery following an effusive volcanic disturbance.
This dissertation includes co-authored material submitted for publication.
9
Fornaciai, Alessandro <1974>. "Morphometric Analysis of Mount Etna Lava Flows Using High Resolution Digital Elevation Models." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amsdottorato.unibo.it/7847/1/Alessandro_Fornaciai_Tesi.pdf.
Full textAbstract:
Morphometric analysis of lava flows provides crucial information for a better understanding of the processes of lava flow dynamics and emplacement. In this thesis, high-resolution DEMs obtained by the airborne LiDAR system and the UAV-SfM system are used for an extensive morphometric analysis of the Mount Etna (Italy) lava flow. A digital comparison of pre- and post-eruptive LiDAR DEMs of Etna was made to quantify the lava volumes emitted in the 2004-2005, 2005-2006 and 2007-2010 intervals. The erupted volume of 2004-2005 is ~63.3 × 106 m3 entirely emitted by the 2004-05 eruption. The erupted volume of 2005-2007 is ~ 42.0 × 106 m3, of which ~33.5 × 106 m3 emitted by the September-December 2006 eruption. The erupted volume of 2007-2010 is >86 × 106m3, most of which (~74 × 106m3) is formed by the lava flows of the 2008-2009 flank eruption. Lava flow morphometric analysis was performed over LiDAR DEM for eleven channel-fed lava flows through a semi-automatic procedure and using SVF and openness down parameters to better detect and delimit surface-specific elements, i.e. lava levees, base and channel-bed. The results show an inverse relation between slope and channel width, a certain coherence between average slope of levees and pre-emplacing slope, and the same trend between the channel width and channel-bed width. Finally, in order to investigate less costly methods for producing DEMs, we created a high-resolution DEM of the 1974 lava flow using the UAV-SfM system and then we compared it with the LiDAR-derived DEM. The UAV-SfM system can be effectively used to produce topographic data for large areas with an accuracy and resolution that are even higher than those of the LiDAR system. Therefore, the UAV-SfM system can be effectively used to update the topography of active volcanic areas with reasonable costs and short time of deployment.
10
Montierth, Charlene. "Geothermometry, crystallization, and the pahoehoe/àà transition in Mauna Loa lavas /." view abstract or download file of text, 1999. http://wwwlib.umi.com/cr/uoregon/fullcit?p9948026.
Full textAbstract:
Thesis (Ph. D.)--University of Oregon, 1999.Typescript. Includes vita and abstract. Includes bibliographical references (leaves 129-135). Also available for download via the World Wide Web; free to University of Oregon users. Address: http://wwwlib.umi.com/cr/uoregon/fullcit?p9948026.
11
Dietterich, Hannah. "Remote Sensing, Morphologic Analysis, and Analogue Modeling of Lava Channel Networks in Hawai`i." Thesis, University of Oregon, 2014. http://hdl.handle.net/1794/18335.
Full textAbstract:
Lava flows are common at volcanoes around the world and on other terrestrial planets, but their behavior is not fully understood. In Hawai`i, advances in remote sensing are offering new insights into lava flow emplacement. In this dissertation, I develop new techniques using satellite-based synthetic aperature radar, aerial photographs, and airborne lidar to produce three-dimensional high-resolution maps of lava flows from data collected before, during, and after emplacement. These new datasets highlight complex lava channel networks within these flows, which are not incorporated into current predictive or probabilistic lava flow models yet may affect flow behavior. I investigate the origin and influence of these channel networks through morphologic analysis of underlying topography, network topology, and flow morphology and volume. Channel network geometries range from distributary systems dominated by flow branching around local obstacles to tributary systems constricted by topography. I find that flow branching occurs where the flow thins over steeper slopes and that the degree of flow branching, network connectivity, and longevity of flow segments all influence the final flow morphology. Furthermore, because channel networks govern the distribution of lava supply within a flow, changes in the channel topology can dramatically alter the effective volumetric flux in any one branch, which affects both flow length and advance rate. Specifically, branching will slow and shorten flows, while merging can accelerate and lengthen them. To test these observations from historic eruptions and morphologic analysis, I use analogue experiments to simulate the interaction of a lava flow with a topographic obstacle and determine the conditions under which the flow branches and the effects of the bifurcation on flow advance rate. These experiments support the earlier results but also demonstrate the importance of flow dynamics and obstacle morphology on governing when flows may overtop obstacles. Consideration of channel networks is thus important for predicting lava flow behavior and mitigating flow hazards with diversion barriers.
One video of Kilauea lava flow activity from 2003-2010 accompanies this dissertation as a supplemental file.
This dissertation includes both previously published and unpublished co-authored material.
12
Chevrel, Magdalena Oryaelle [Verfasser], and Donald Bruce [Akademischer Betreuer] Dingwell. "Rheology of Martian lava flows : an experimental approach / Magdalena Oryaelle Chevrel. Betreuer: Donald Bruce Dingwell." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2013. http://d-nb.info/1036101118/34.
Full text
13
Ball, Matthew Dominic. "The validation and use of thermal imaging cameras for quantitative temperature measurements of lava flows." Thesis, Lancaster University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.441110.
Full text
14
Harburger, Aleeza. "Probabilistic Modeling of Lava Flows: A Hazard Assessment for the San Francisco Volcanic Field, Arizona." Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5033.
Full textAbstract:
This study serves as a first step towards a comprehensive hazard assessment for the San Francisco volcanic field in northern Arizona, which can be applied to local response plans and educational initiatives. The primary goal of this thesis is to resolve the conditional probability that, given a lava flow effusing from a new vent in the San Francisco volcanic field, it will inundate the city limits of Flagstaff. The spatial distribution of vents within the San Francisco volcanic field was analyzed in order to execute a lava flow simulation to determine the inundation hazard to Flagstaff. The Gaussian kernel function for estimating spatial density showed that there is a 99% chance that a future vent will be located within a 3.6 x 109 m2 area about 20 kilometers north of Flagstaff. This area contains the location of the most recent eruption at Sunset Crater, suggesting that the model is a good predictor of future vent locations. A Monte Carlo analysis of potential vent locations (N = 7,769) showed that 3.5% of simulated vents generated lava flows that inundated Flagstaff, and 1.1% of simulated vents were located within the city limits. Based on the average recurrence rate of vents formed during the Brunhes chronozone, the aggregate probability of lava flow inundation in Flagstaff is 1.1 x 10-5 per year. This suggests that there is a need for the city to plan for lava flows and associated hazards, especially forest fires. Even though it is unlikely that the city will ever have to utilize such a plan, it is imperative that thorough mitigation and response plans are established now-- before the onset of renewed volcanic activity.
15
Proietti, Cristina <1978>. "Multitemporal geometrical analysis and numerical simulation of lava flows: the case of the 2001 Etna eruption." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/358/1/Proietti_C_XIXciclo.pdf.
Full text
16
Proietti, Cristina <1978>. "Multitemporal geometrical analysis and numerical simulation of lava flows: the case of the 2001 Etna eruption." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2007. http://amsdottorato.unibo.it/358/.
Full text
17
Mejia, Victoria. "Geomagnetic field for the past 5 myr recorded in lava flows from British Columbia, Patagonia, and Mexico." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010071.
Full text
18
Reiners, Peter William. "Reactive melt transport in the mantle and petrogenesis of Hawaiian post-erosional magmas /." Thesis, Connect to this title online; UW restricted, 1997. http://hdl.handle.net/1773/6714.
Full text
19
Robinson, Danielle D. Sandvol Eric Alan. "Seismic anisotropy beneath the southern Puna Plateau." Diss., Columbia, Mo. : University of Missouri--Columbia, 2009. http://hdl.handle.net/10355/5362.
Full textAbstract:
The entire thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file; a non-technical public abstract appears in the public.pdf file. Title from PDF of title page (University of Missouri--Columbia, viewed on December 30, 2009). Thesis advisor: Dr. Eric Sandvol. Includes bibliographical references.
20
BIAGIOLI, ELISA. "Depth-averaged and 3D Finite Volume numerical models for viscous fluids, with application to the simulation of lava flows." Doctoral thesis, Università degli studi di Genova, 2021. http://hdl.handle.net/11567/1057651.
Full textAbstract:
This Ph.D. project was initially born from the motivation to contribute to the depth-averaged and 3D modeling of lava flows. Still, we can frame the work done in a broader and more generalist vision. We developed two models that may be used for generic viscous fluids, and we applied efficient numerical schemes for both cases, as explained in the following.
The new solvers simulate free-surface viscous fluids whose temperature changes are due to radiative, convective, and conductive heat exchanges. A temperature-dependent viscoplastic model is used for the final application to lava flows. Both the models behind the solvers were derived from mass, momentum, and energy conservation laws. Still, one was obtained by following the depth-averaged model approach and the other by the 3D model approach. The numerical schemes adopted in both our models belong to the family of finite volume methods, based on the integral form of the conservation laws. This choice of methods family is fundamental because it allows the creation and propagation of discontinuities in the solutions and enforces the conservation properties of the equations.
We propose a depth-averaged model for a viscous fluid in an incompressible and laminar regime with an additional transport equation for a scalar quantity varying horizontally and a variable density that depends on such transported quantity. Viscosity and non-constant vertical profiles for the velocity and the transported quantity are assumed, overtaking the classic shallow-water formulation. The classic formulation bases on several assumptions, such as the fact that the vertical pressure distribution is hydrostatic, that the vertical component of the velocity can be neglected, and that the horizontal velocity field can be considered constant with depth because the classic formulation accounts for non-viscous fluids. When the vertical shear is essential, the last assumption is too restrictive, so it must relax, producing a modified momentum equation in which a coefficient, known as the Boussinesq factor, appears in the advective term. The spatial discretization method we employed is a modified version of the central-upwind scheme introduced by Kurganov and Petrova in 2007 for the classical shallow water equations. This method is based on a semi-discretization of the computational domain, is stable, and, being a high-order method, has a low numerical diffusion. For the temporal discretization, we used an implicit-explicit Runge-Kutta technique discussed by Russo in 2005 that permits an implicit treatment of the stiff terms. The whole scheme is proved to preserve the positivity of flow thickness and the stationary steady-states. Several numerical experiments validate the proposed method, show the incidence on the numerical solutions of shape coefficients introduced in the model and present the effects of the viscosity-related parameters on the final emplacement of a lava flow.
Our 3D model describes the dynamics of two incompressible, viscous, and immiscible fluids, possibly belonging to different phases. Being interested in the final application of lava flows, we also have an equation for energy that models the thermal exchanges between the fluid and the environment. We implemented this model in OpenFOAM, which employs a segregated strategy and the Finite Volume Methods to solve the equations. The Volume of Fluid (VoF) technique introduced by Hirt and Nichols in 1981 is used to deal with the multiphase dynamics (based on the Interphase Capturing strategy), and hence a new transport equation for the volume fraction of one phase is added. The challenging effort of maintaining an accurate description of the interphase between fluids is solved by using the Multidimensional Universal Limiter for Explicit Solution (MULES) method (described by Marquez Damian in 2013) that implements the Flux-Corrected Transport (FCT) technique introduced by Boris and Book in 1973, proposing a mix of high and low order schemes. The choice of the framework to use for any new numerical code is crucial.
Our contribution consists of creating a new solver called interThermalRadConvFoam in the OpenFOAM framework by modifying the already existing solver interFoam (described by Deshpande et al. in 2012). Finally, we compared the results of our simulations with some benchmarks to evaluate the performances of our model.
21
Samasiri, Peeradon. "Mixing in axisymmetric gravity currents and volcanic conduits." Thesis, University of Cambridge, 2018. https://www.repository.cam.ac.uk/handle/1810/280120.
Full textAbstract:
The first part of this thesis investigates the mixing of ambient fluid into axisymmetric high Reynolds number gravity currents. A series of laboratory experiments were conducted in which small scale gravity currents travelled along a wedge shaped channel with an increasing width in the downstream direction. The channel was filled with fresh water and the current was generated using saline solution introduced either by a rapid release of a known finite volume from behind a lock gate or by pumping at a constant rate into the apex of the channel. The distribution and evolution of the density of the flow with distance downstream was measured using a light attenuation technique. Additional experiments were performed by injecting parcels of dye in different regions of the flow in order to visualise the motion of fluid in and surrounding the gravity current. Unlike currents introduced by the release of a finite volume of fluid, where most mixing occurs in the head of the flow, currents produced from a steady source develop a steady tail region behind the front which is also found to entrain a significant amount of ambient fluid. In both types of current, we estimate the fraction of displaced ambient fluid that is entrained into the flow. We then derive a new class of self-similar solutions for gravity currents produced from a finite volume release of fluid. The second part of this thesis develops the experimental method of measuring mixing using light attenuation to investigate the mixing of liquid in a vertical conduit which results from a continuous stream of high Reynolds number gas bubbles. The experiments identify that the mixing in the wake of the bubbles leads to a net dispersive transport along the conduit. The process provides an explanation for the heat transfer within a volcanic conduit in the case of a gas-slug flow regime as occurs in the near surface region of volcanic conduits connected to surface lava lakes. We derive a theoretical model to estimate the heat flux associated with such a system using the empirical law for the dispersive mixing. The predicted heat flux associated with the bubbles is found to be comparable to the heat loss at the surface of lava lakes associated with radiative and convective heat loss. Given values for the gas flux, the lake area and the temperature at the surface of the lake, the model enables new predictions for the size of the volcanic conduit.
22
Morris, Aisha R. "Emplacement of deep submarine lava flows on the North Hawaiian Arch: a study of thermal and rheological evolution using a numerical model." Thesis, University of Hawaii at Manoa, 2003. http://hdl.handle.net/10125/6982.
Full text
23
Hrysiewicz, Alexis. "Caractérisation des déplacements liés aux coulées de lave au Piton de la Fournaise à partir de données InSAR." Thesis, Université Clermont Auvergne (2017-2020), 2019. http://www.theses.fr/2019CLFAC062.
Full textAbstract:
Depuis 2003, le service d’observation OI2 (Observatoire InSAR de l’Océan Indien), composante du Service National des Observations en Volcanologie (SNOV) analyse les déplacements du sol causés par l’activité volcanique du Piton de la Fournaise en utilisant des données InSAR (Interférométrie Radar à Synthèse d’Ouverture). Un des résultats majeurs est l’identification lors de l’éruption de 2007 d’un déplacement horizontal de plus de 1.4 m de l’ensemble du Flanc Est du Piton de la Fournaise vers la mer. Des résultats plus récents ont montré que ce glissement continuait entre 2009 et 2014 avec une décroissance de la vitesse des déplacements. Il a aussi été montré qu’à ce déplacement de grande longueur d’onde se superposent des déplacements plus localisés dus à la contraction thermo-mécanique des coulées de lave et à la flexion du substratum sous le poids de ces coulées. Il est donc difficile de caractériser précisément et indépendamment ces deux composantes des déplacements affectant le Flanc Est du Piton de la Fournaise. Le principal objectif de cette thèse est de caractériser les déplacements associés aux coulées de lave pour supprimer la contribution des coulées des observations et isoler les signaux qui sont seulement liés à des signaux de grande longueur d’onde. Afin d’atteindre cet objectif, nous avons dû développer des algorithmes permettant de contourner précisément les coulées, d’estimer leur surface et leur volume avec les incertitudes associées. Ces algorithmes exploitent les données de cohérence interférométrique dans une approche probabiliste itérative. Ils sont maintenant utilisés en routine dans le cadre du service OI2 pour fournir aussi rapidement que possible à l’Observatoire Volcanologique du Piton de la Fournaise, des cartes des coulées. L’étude des coulées de lave mises en place entre 2014 et 2018 montre que la contraction thermo-mécanique de la coulée et la flexion du substratum dépendent à la fois de la durée écoulée depuis la mise en place, de l’épaisseur de la coulée, de la pente locale et éventuellement de la structure interne de la coulée (présence de tunnels de lave). Un an après la mise en place, les déplacements verticaux et horizontaux peuvent atteindre plusieurs dizaines de centimètres par an. Ces déplacements diminuent ensuite de façon exponentielle avec le temps. Nous avons cherché à modéliser les déplacements verticaux en fonction de l’épaisseur des coulées. Nos résultats montrent que ces déplacements pourraient contribuer jusqu’à 80% des déplacements mesurés sur le Flanc Est du Piton de la Fournaise. Les déplacements du substratum observés sur le pourtour des coulées apportent des contraintes sur la rhéologie de la partie la plus superficielle de ce substratum. Cette rhéologie apparaît fortement variable au sein de l’Enclos Fouqué révélant une forte dépendance à l’histoire des dépôts successifs accumulés en chaque endroit. Un substratum se comportant de façon poroélastique dans sa partie la plus superficielle (∼ 100 m) permet néanmoins d’expliquer de façon relativement satisfaisante les observationsSince 2003, the observation national service for the volcanology (SNOV) OI2 have been analyzing the ground surface displacements due to the volcanic eruptions at Piton de la Fournaise using the Interferometry by Synthetic Aperture Radar (InSAR). One of major results is the observation of Eastern seaward flank sliding during the 2007 eruption (around 1.4 m of horizontal displacements). More recent results demonstrated that this sliding continued between 2009 and 2014 with a decreasing of displacement rates. However, this signal is combined with the displacements caused by the lava flows, (thermo-mechanical compaction, substratum flexure under the lava-flow weight), and the signal deconvolution is complex. Consequently, the thesis objective is to characterize these displacements to remove the contribution of lava flows from our observations. Therefore, we should only observe the signals related to the internal volcanic processes. To characterize the lava flows, we have to estimate their displacements, their locations, their surface areas and thicknesses. From the InSAR coherence data, the developped algorithms enable us to extract the lava-flow outlines and estimate the surface area value of the lava flow with the associated uncertainties. They use an iterative and probabilistical approach. These algorithms are now used during effusive crisis at Piton de la Fournaise and are become a product within OI2. The vertical-displacements evolutions of the October 2010 lava flow spanning from mid-2011 to mid-2015 follow an exponential decreasing form with rates of 10’s milimetre per year. Over the same period, the horizontal displacements are negligeable. The results about the displacement rates for lava flows emplaced between 2014 and 2018 show that these displacements are caused by the thermo-mechanical compaction, the substratum flexure, the slope and the lava field structures (as lava tunnels). One year after the emplacement of the lava flow, the vertical displacement rates can reach some 10’s centimetre per year and these values are similar for the horizontal displacements. Modelling of vertical displacements has been made using the lava thicknesses as input parameter. The preliminar results show that the flank sliding amplitude must be reduced of around 80%, (10 mm.yr-1 ) and its location is different from that of the post-2007 period. Finally, the displacements outside lava flows allow a characterization of the substratum rheology. This last one appears variable. Our models estimate that the poroelasticity, with a rheological constrast, (about 100 m-deep), is a possibility to represent the rheology of susbtratum. Ultimately, the precise substratum characterization from the co-eruptive displacements will enable us to better constrain the geometry of magmatic intrusion
24
Rossetti, Lucas de Magalhães May. "Arcabouço estratigráfico da Formação Serra Geral no Vale Principal da Sinclinal de Torres." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/88617.
Full textAbstract:
A Província Basáltica Continental do Paraná-Etendeka registra o intenso vulcanismo do Cretáceo inferior que precedeu a fragmentação do supercontinente Gondwana. Tradicionalmente investigações sobre estas rochas priorizaram a aquisição de dados geoquímicos e isotópicos, considerando a pilha vulcânica como uma monótona sucessão de derrames tabulares e espessos. O presente trabalho propõe a análise das características físicas deste vulcanismo aplicando conceitos de arquitetura de fácies vulcânicas, integrados a estudos petrográficos e geoquímicos. A Sinclinal de Torres é uma estrutura tectônica localizada na porção sul do Brasil onde ocorrem preservadas as sequencias vulcânicas do magmatismo Paraná-Etendeka. Na área de estudo As rochas vulcânicas básicas podem ser divididas em duas unidades: derrames e campos de derrames pahoehoe (Unidade I) e derrames rubbly simples (Unidade II). Geoquimicamente as duas unidades pertencem a serie de baixo- TiO2 e ao magma tipo Gramado. As primeiras lavas pahoehoe são olivina basaltos, mais primitivos. A unidade I é composta por inúmeros derrames pahoehoe que ocorrem sobre os arenitos eólicos da Formação Botucatu. Essa lavas ocorrem como sheet pahoehoe, compound lavas, e lavas do tipo ponded nos vales interduna. O emplacement dessas lavas esta relacionado a baixas taxas de erupção sustentadas por longos intervalos de tempo. A unidade II é formada por espessas lavas simples do tipo rubbly, estas são caracterizadas por núcleos maciços e topos fragmentados (rubbly tops). Essas lavas são formadas por altas taxas de erupção e durante a fase principal do vulcanismo na área. O vale principal da Sinclinal de Torres tem uma evolução formada por derames compostos na porção basal e derrames simples nas porções superiores, siilar a de outras Províncias Basálticas Continentais.The Parana-Etendeka Volcanic Province records the volcanism of the Earlier Cretaceous that precedes the fragmentation of the Gondwana supercontinent. Traditionally, investigations of these rocks prioritized the acquisition of geochemical and isotopic data, considering the volcanic stack as a monotonous succession of tabular flows. This work provides a detailed analysis of the physical conditions of the emplacement of these volcanic rocks, applying the facies architecture integrated to petrographic and geochemical data. Torres Syncline is a tectonic structure located in southern Brazil and where the Parana- Etendeka basalts are well preserved. The basaltic lava flows in the area can be divided in pahoehoe flow fields (Unit I) and simple rubbly flows (Unit II). Geochemically both units are low TiO2 and Gramado magma type. The first pahoehoe lavas are more primitive and are olivine basalts with higher contents of MgO. The fist unit is build up by innumerous pahoehoe lava flows and flow fields that cover the sandstones of Botucatu Fm. These flows occur like sheet pahoehoe, compound pahoehoe, and ponded lavas in the interdune settings. The emplacement of pahoehoe flow fields is related to sustain low eruptive rates. The unit two is formed by thick simple rubbly lavas, characterized by a massive core and a rubbly top. These flows are associated to high effusion rates and were formed during the main phase of volcanism in the area. The Torres Syncline main valley has a similar evolution when compared with other lips with compound flows at the base and simple flows in the upper portions.
25
Curti, Daiane Katya. "Tipologia e origem das fraturas sub-horizontais em basaltos da Formação Serra Geral, Brasil." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/44/44141/tde-16082011-164931/.
Full textAbstract:
Nos derrames basálticos da Formação Serra Geral são reconhecidas numerosas ocorrências de fraturas sub-horizontais de grande continuidade lateral. Tais fraturas, de até centenas de metros de extensão, foram consideradas estruturas típicas em derrames e constituem importantes descontinuidades na estabilidade de obras de engenharia e como rotas de percolação de fluídos. Descritas inicialmente no final da década de 60, as fraturas sub-horizontais em derrames basálticos foram intensamente estudadas até o início da década de 90, por ocasião da construção de grandes barragens sobre os derrames basálticos da Formação Serra Geral. No presente trabalho, a reunião das informações disponíveis sobre as fraturas sub-horizontais em basaltos permitiu estabelecer as relações entre suas formas de ocorrência e seus processos geradores, bem como a análise crítica dos modelos apresentados na literatura no que diz respeito a movimentações sobre fraturas sub-horizontais. As fraturas sub-horizontais possuem uma ampla variação de características, atribuída a diferentes processos genéticos e atuação de agentes secundários. Tais estruturas podem ocorrer como simples juntas sub-horizontais bastante contínuas, de abertura milimétrica, ou constituírem horizontes fraturados com espessura decimétrica a métrica (até 2 metros), apresentando fortes ondulações. Esses horizontes são caracterizados por fraturas pouco persistentes, que delimitam blocos tabulares com terminações em cunha e em forma de lentes. As fraturas sub-horizontais ocorrem em porções específicas dos derrames: abaixo da zona vesiculo-amigdaloidal do topo; em meio ao basalto maciço, normalmente no limite entre diferentes níveis de disjunções colunares; ou próximo à base do derrame. Os diferentes tipos de fraturas sub-horizontais foram classificados dentro do quadro de eventos sin-, tardi- e pós-magmáticos. As fraturas sub-horizontais sin-magmáticas correspondem a feições de fluxo formadas devido a esforços cisalhantes gerados pela diferença de velocidade de fluxo da lava. As fraturas sub-horizontais tardi-magmáticas correspondem a juntas de resfriamento geradas pelo avanço das frentes de resfriamento que se deslocam das periferias para o centro do derrame. As fraturas sub-horizontais pós-magmáticas correspondem a dois principais tipos de estruturas: juntas de alívio e fraturas de cisalhamento. Tais estruturas podem ser neoformadas, ocorrendo em qualquer porção do derrame, ou se desenvolverem sobre fraturas sub-horizontais preexistentes. Na literatura, as fraturas sub-horizontais foram denominadas como juntasfalhas, devido a variedade de estruturas que apresentavam correlações com feições primárias do derrame e sinais de movimentações como estrias de atrito e deslocamentos de diques e fraturas verticais. Os deslocamentos observados nas fraturas sub-horizontais podem estar associados ao processo de alívio de tensões laterais em taludes, pelo entalhamento de vales fluviais, bem como a movimentações decorrentes de esforços tectônicos regionais. Estrias de fricção ao longo de fraturas sub-horizontais preexistentes têm indicado que tais deslocamentos são compatíveis com movimentações transcorrentes na bacia. Fraturas no fundo dos vales apresentam um padrão conjugado com fraturas sub-horizontais podendo apresentar feições de cisalhamento.In the basaltic lava flows of Serra Geral Formation, numerous occurrences of subhorizontal fractures of extensive continuity are recognized. Such fractures, of up to hundreds of meters long, were considered typical structures in lava flows and are relevant discontinuities in the stability of engineering works and as fluid percolation routes. Described initially in the late 60s, the subhorizontal fractures in basaltic lava flows were intensely studied until the early 90s, when large dams were built over the rocks of Serra Geral Formation. In this work, a reunion of available information on subhorizontal fractures in basalts allowed to establish the relations between the ways they take place and their genetic processes, as well as the critical analysis of the models presented in the literature with respect to movements on such subhorizontal fractures. Subhorizontal fractures have a wide variety of characteristics, due to different genetic processes and action of secondary agents. Such structures may occur as quite continuous simple subhorizontal joints, of millimetric opening, or fractured undulate horizons with decimetric to metric (up to 2 meters) thickness. Such horizons are characterized by low lateral continuity, limiting tabular blocks with wedge and lensshaped endings. The subhorizontal fractures occur in specific portions of the flows: below the upper crust zone; in the massive basalt, usually at the boundaries between different levels of columnar joints; or near the base of the flow. The different types of subhorizontal fractures were classified within the syn-, late- and post-magmatic events. The synmagmatic subhorizontal fractures correspond to features of flow formed due to shear stress generated by lava flow speed difference. The late magmatic subhorizontal fractures correspond to cooling joints generated by moving forward of those cooling fronts displacing from the peripheral areas to the middle of the flow. The postmagmatic subhorizontal fractures correspond to two different types of structures: release joints and shear fractures. Such structures may be neoformed, and occur in any portion of the flow, or being developed over the preexisting subhorizontal fractures. In the literature, the subhorizontal fractures were named as joint-faults, due to the variety of structures that presented correlations with the flow primary features and signs of movements such as friction striae and displacement of vertical dikes and fractures. The displacements observed in the subhorizontal fractures may be associated with the process of lateral stress release in slopes, by erosion in river valleys, as well as regional tectonic movements. Friction striae along preexisting subhorizontal fractures have shown that displacements are compatible with transcurrent movements in the basin. Fractures in the valley bottoms present a pattern of conjugate subhorizontal fractures and it may also present shear features.
26
Van, Vlack Kathleen, Richard W. Stoffle, and Katherine Brooks. "Photographs of Little Springs Lava Flow." Bureau of Applied Research in Anthropology, Unversity of Arizona, 2013. http://hdl.handle.net/10150/305045.
Full textAbstract:
This presentation contains photographs taken during the Little Springs Ethnographic Investigation. These photographs are meant to supplement the information presented in the report entitled: Unav~Nuquaint: Little Springs Lava Flow Ethnographic Investigation (Van Vlack et al. 2013).
27
Gallant, Elisabeth. "Modeling and Assessing Lava Flow Hazards." Scholar Commons, 2019. https://scholarcommons.usf.edu/etd/7792.
Full textAbstract:
Lava flow hazards are one of the few constant themes across the wide spectrum of volcanic research in the solar system. These dynamic hazards are controlled by the location of the eruption, the topography and material properties of the land upon which the flow spreads, and the properties of the lava (e.g., volume, temperature, and rheology). Understanding the influences on eruption location and how lava flows modify the landscape are important steps to accurately forecast volcanic hazards. Three studies are presented in this dissertation that address di˙erent aspects of modeling and assessing vent opening and lava flow hazards.
The first study uses hierarchical clustering to explore the distribution of activity at Craters of the Moon (COM) lava field on the eastern Snake River Plain (ESRP). Volcanism at COM is characterized by 53 mapped eruptive vents and 60+ lava flows over the last 15 ka. Temporal, spatial, and spatio-temporal clustering methods that examine different aspects of the distribution of volcanic vents are introduced. The sensitivity of temporal clustering to different criteria that capture the age range of magma generation and ascent is examined Spatial clustering is dictated by structures on the ESRP that attempt to capture the footprint of an emplacing dike. A combined spatio-temporal is the best approach to understanding the distribution of linked eruptive centers and can also provide insight into the evolution of volcanism for the region. Spatial density estimation is used to visualize the differences between these models. The goal of this work is to improve vent opening forecasting tools for use in assessing lava flow hazards.
The second study presents a new probabilistic lava flow hazard assessment for the U.S. Department of Energy’s Idaho National Laboratory (INL) nuclear facility that (1) explores the way eruptions are defined and modeled, (2) stochastically samples lava flow parameters from observed values for use in MOLASSES, a lava flow simulator, (3) calculates the likelihood of a new vent opening within the boundaries of INL, (4) determines probabilities of lava flow inundation for INL through Monte Carlo simulation, and (5) couples inundation probabilities with recurrence rates to determine the annual likelihood of lava flow inundation for INL. Results show a 30% probability of partial inundation of the INL given an e˙usive eruption on the ESRP, with an annual inundation probability of 8.4×10^−5 to 1.8×10^−4. An annual probability of 6.2×10^−5 to 1.2×10^−4 is estimated for the opening of a new eruptive center within INL boundaries.
The third study models thermo-mechanical erosion of a pyroclastic substrate by flow-ing lava on Volcán Momotombo, Nicaragua. It describes the unique morphology of a lava flow channel using TanDEM-X/TerraSAR-X and terrestrial radar digital elevation models. New methods for modeling paleotopography on steep-sided cones are introduced to mea-sure incision depths and document cross-channel profiles. The channel is incised ~35 m into the edifice at the summit and transitions into a constructional feature halfway down the ~1,300 m high cone. An eroded volume of ~4×10^5 m3 was calculated. It is likely that a lava flow eroded into the cone as it emplaced during an eruption in 1905. There is not suÿcient energy to thermally erode this volume, given the observed morphology of the flow. Models are tested that explore the relationship of shearing and material properties of the lava and substrate against measured erosion depths and find that thermo-mechanical erosion is the most likely mode of channel formation. Additionally, it is likely that all forms of erosion via lava flow are impacted by thermal conditions due to the relationship between temperature and substrate hardness. The evolution of these structures (their creation and subsequent infilling) plays an important role in the growth of young volcanoes and also controls future lava flows hazards, as seen by the routing of the 2015 flow into the 1905 channel.
28
Guilbaud, Marie-Noëlle. "The origin of basaltic lava flow textures." Thesis, Open University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.429548.
Full text
29
Rizo, Steven R. "Quantifying the Effect of Topographic Slope on Lava Flow Thickness: A First Step to Improve Lava Flow Volume Estimation Methods." Scholar Commons, 2018. http://scholarcommons.usf.edu/etd/7222.
Full textAbstract:
The volume of lava flows provide important information on the magnitude of volcanic eruptions, and accurate volumes are necessary to produce reliable models of lava flow emplacement or constrain the internal structure of volcanoes. The most accurate lava flow volumes are obtainable when the topography before and after an eruption are both known, but information for the topography before lava flow emplacement is absent in non-historic lava flows. To calculate the volume of non-historic lava flows, this pre-emplacement topography needs to be reconstructed. Common methods for this include using inverse distance-weighted averages or global polynomial interpolation methods, but these can still underestimate the volume of the flow, and the surface of the flow itself is not considered in these interpolations. A new calculation method seems necessary to better constrain the volume of lava flows, and including the lava flow surface in the volume calculation, given that it is generally excluded during interpolation of pre-emplacement topography, may be the solution to improving lava flow volume calculation for flows where the base surface is unknown. The 2012-2013 Tolbachik lava flow is used to look at potential relationships due to the availability of elevation data before and after the eruption. A quantitative analysis on the relationships between the slope of topography before and after lava flow emplacement and on the relationship between the slope and thickness of lava flows is performed. In addition to this, the slope of the topography calculated over local and regional scales is used as a new interpolation method, and the calculated thickness from the interpolated surface is compared to the known thickness for the lava flow.
30
Van, Vlack Kathleen, Richard W. Stoffle, Evelyn Pickering, Katherine Brooks, and Jennie Delfs. "Unav-Nuquaint: Little Springs Lava Flow Ethnographic Investigation." Bureau of Applied Research in Anthropology, University of Arizona, 2013. http://hdl.handle.net/10150/302850.
Full textAbstract:
This is a study about a very unusual place and the innovative American Indian ceremonial response to an event that uniquely occurred at this place. The place, defined here as the Uinkaret Volcanic Field, was always culturally important to Indian people for ceremony. The place is so covered with evidence of past volcanic activity that one can think of it as a place to go to talk with and experience volcanoes. This seems according to Indian testimony to have been its primary purpose for thousands of years before the event.
31
Cappello, Annalisa. "Probabilistic modelling of lava flow hazard at Mount Etna." Doctoral thesis, Università di Catania, 2013. http://hdl.handle.net/10761/1367.
Full textAbstract:
This thesis aims at presenting a groundbreaking methodology for lava flow hazard assessment that represents a challenging topic in modern volcanology. Specifically, the methodology is based on three main steps: (i) the construction of a spatiotemporal probability map for the future opening of new eruptive vents; (ii) the estimation of occurrence probabilities associated to classes of expected eruptions; and (iii) the overlapping of a large number of lava flows simulated using the MAGFLOW model. The results from these steps are processed in order to obtain a hazard map showing, for a given area, the probability of being affected by at least one lava flow inundation during the time interval considered. The preferred scenario for this study has been Mount Etna being one of the most intensively monitored volcanoes in the world, thereby offering large amounts of input data for the application of the proposed methodology.
32
Nolan, Marie. "Levee stability and the evolution of 'A'a lava flow-fields." Thesis, University of Portsmouth, 2014. https://researchportal.port.ac.uk/portal/en/theses/levee-stability-and-the-evolution-of-a-a-lava-flowfields(d2bf4697-8120-4645-97fa-a2cc1f05b8bb).html.
Full textAbstract:
The capability to predict the final dimensions of an ‘a’a flow-field and the timeline for emplacement is key to effective lava hazard management. Levee breaching and the subsequent generation of secondary flows has been recognised as an intrinsic process in flow-field development. However, the conditions, locations and mechanisms for levee failure are not fully understood and so a multidisciplinary approach was taken utilising field studies of extant flow-fields on Mount Etna and Tenerife, analogue modelling and uniaxial compression tests to investigate levee failure. The experimental results were used to define three stages of flow-field development – lengthening, widening and thickening, a modification of the classification of Kilburn and Lopes (1991). Levee breaching was identified to be a key process by which flow-fields widen during stage two of emplacement. Four mechanisms for breaching are identified, providing a classification system for levee failure. Secondary flows originating from breaching consistently formed at an angle of 30 – 50o to the original channel, significantly contributing to overall flow-field width. Uniaxial compression tests were performed to quantify the mechanical properties of levees. Levee strength was shown to change with direction according to the size, orientation and distribution of vesicles. Samples with vesicle alignment orientated obliquely to the angle of principal stress were consistently weaker. A set of conditions, relating to the mechanical properties of the levee, is therefore identified under which levees are more susceptible to failure. The results of the study have been combined to produce a set of guidelines to the locations and conditions under which levee breaching is more likely to occur, aiding decision making for lava hazard management.
33
Norman, Louise May. "Fluid dynamics and thermodynamics of lava flow emplacement on Mars." Thesis, Lancaster University, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428657.
Full text
34
Heslop, S. E. "Aspects of volcanic fluid dynamics." Thesis, Lancaster University, 1987. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.383570.
Full text
35
Stevens, Nicola Frances. "Lava flow volume and morphology from ERS synthetic aperture radar interferometry." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266817.
Full text
36
Kent, Russell Malcolm. "Modelling fluid flow and heat transfer in some volcanic systems." Thesis, Lancaster University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.306912.
Full text
37
Vera, Vidal Camila Constanza. "Analysis of cooling effects and non-Newtonian rheology on lava flow dynamics." Tesis, Universidad de Chile, 2018. http://repositorio.uchile.cl/handle/2250/169867.
Full textAbstract:
Tesis para optar al grado de Doctor en Ciencias, Mención GeologíaMemoria para optar al título de Geóloga
La actividad volcanica representa una gran amenaza para la propiedad privada, comunidades y habitantes ubicados en las cercanias de centros volcanicos. La volcanologia y mecanica de fluidos se utilizan en conjunto con el fin de estudiar la evolucion de los flujos de lava. Nos enfocamos en el estudio de flujos de lava simples y viscosos, de composiciones andesitica hasta riolitica, para determinar la relevancia de la evolucion reologica del flujo en tiempos de emplazamiento, distancias, y proporciones finales. Los experimentos analogos han sido una herramienta util en previos estudios de flujos de lava. Para este trabajo se caracterizo el manjar, un derivado de la leche, para utilizarlo como material analogo de lava viscosa con una reologia dependiente de la temperatura. Los experimentos simularon un flujo no confinado simple sobre una superficie inclinada, en el Laboratorio de Volcanologia Experimental del Laboratoire de Magmas et Volcans, Clermont-Ferrand, Francia. Un total de 33 experimentos de extrusiones puntuales sobre una superficie inclinada, con caudales desde 1 $ (cc/s) $ a 25 $ (cc/s) $, con inclinaciones entre 10$^\circ$ - 15$^\circ$, y diferentes temperaturas iniciales desde ambiente hasta 71\textcelsius{}. Cada experimento fue grabado con camara visual y camara termica, con los cuales se pudo obtener la evolucion termica y las distancias en el tiempo a las que avanzaba cada flujo. Se utilizo python para obtener la base de datos de temperatura, y bibliotecas especificas para manejar, procesar y visualizar datos, tales com matplotlib, scipy y pandas. Los resultados indican que la formacion de una pseudo corteza en los flujos de manjar que estan sujetos a enfriamiento, controlan las distintas dimensiones y tiempos de emplazamiento obtenidos para los flujos estudiados, mientras que los cambios de pendiente tambien juegan un rol importante en estos resultados. La existencia de esta pseudo corteza esta basada en la perdida de agua presente en el manjar, asi como tambien en la buena correlacion existente que muestra el numero de Graetz con las diferentes dimensiones obtenidas, que dependen de la tasa efusiva, la escala de tiempo de extrusion, y por ende el desarrollo de esta corteza obtenida segun estimaciones basadas en la difusividad termica del material. Mayores caudales presentan flujos mas anchos con menores espesores, mientras que menores caudales se desarrollan de manera vertical, teniendo menor expansion areal y mayores espesores. Mayores pendientes resultan en flujos que se desarrollan principalmente pendiente abajo, con distancias de $ X_{min} $ e $ Y_{max} $ menores. Por otro lado, la comparacion entre flujos sujetos a enfriamiento versus flujos en condiciones isotermales, tambien apoyan la teoria de existencia de una pseudo corteza que controla la dinamica de flujo. Los modelos DEM realizados presentan caracteristicas similares a las presentes en flujos de lava, con zonas de menor espesor cerca del punto extrusivo, seguido por un posible canal central entre estructuras tipo levee que culminan en un frente de flujo de gran espesor, presentando la mayor potencia del flujo. Este frente de flujo inflado, consideramos que es evidencia de que existe una pseudo corteza que contiene material con mayor movilidad en su interior. Los perfiles de temperatura de termocuplas y FLIR, tambien muestran como existe un perfil termal vertical en los flujos, con altas temperaturas en porciones internas luego de que todo el material ya ha sido extruido, mientras la superficie del flujo presenta menores temperaturas.
38
Ashwell, Paul. "Controls on rhyolite lava dome eruptions in the Taupo Volcanic Zone." Thesis, University of Canterbury. Geological Sciences, 2014. http://hdl.handle.net/10092/8965.
Full textAbstract:
The evolution of rhyolitic lava from effusion to cessation of activity is poorly understood. Recent lava dome eruptions at Unzen, Colima, Chaiten and Soufrière Hills have vastly increased our knowledge on the changes in behaviour of active domes. However, in ancient domes, little knowledge of the evolution of individual extrusion events exists. Instead, internal structures and facies variations can be used to assess the mechanisms of eruption.
Rhyolitic magma rising in a conduit vesiculates and undergoes shear, such that lava erupting at the surface will be a mix of glass and sheared vesicles that form a permeable network, and with or without phenocryst or microlites. This foam will undergo compression from overburden in the shallow conduit and lava dome, forcing the vesicles to close and affecting the permeable network. High temperature, uniaxial compression experiments on crystal-rich and crystal-poor lavas have quantified the evolution of porosity and permeability in such environments. The deformation mechanisms involved in uniaxial deformation are viscous deformation and cracking. Crack production is controlled by strain rate and crystallinity, as strain is localised in crystals in crystal rich lavas. In crystal poor lavas, high strain rates result in long cracks that drastically increase permeability at low strain. Numerous and small cracks in crystal rich lavas allow the permeable network to remain open (although at a lower permeability than undeformed samples) while the porosity decreases.
Flow bands result from shear movement within the conduit. Upon extrusion, these bands will become modified from movement of lava, and can therefore be used to reconstruct styles of eruption. Both Ngongotaha and Ruawahia domes, from Rotorua caldera and Okataina caldera complex (OCC) respectively, show complex flow banding that can be traced to elongated or aligned vents. The northernmost lobe at Ngongotaha exhibits a fan-like distribution of flow bands that are interpreted as resulting from an initial lava flow from a N – S trending fissure. This flow then transitioned into intrusion of obsidian sheets directly above the conduit, bound by wide breccia zones which show vertical movement of the sheets. Progressive intrusions then forced the sheets laterally, forming a sequence of sheets and breccia zones. At Ruawahia, the flow bands show two types of eruption; long flow lobes with ramp structures, and smaller spiny lobes which show vertical movement and possible spine extrusion. The difference is likely due to palaeotopography, as a large pyroclastic cone would have confined the small domes, while the flow lobes were unconfined and able to flow down slope. The vents at Ruawahia are aligned in a NE – SW orientation. Both domes are suggested to have formed from the intrusion of a dyke.
The orientations of the alignment or elongation of vents at Ngongotaha and Ruawahia can be attributed to the overall regional structure of the Taupo Volcanic Zone (TVZ). At Ngongotaha, the N – S trending elongated vent is suggested to be controlled by a N – S trending caldera collapse structure at Rotorua caldera. The rest of the lobes at Ngongotaha, as well as other domes at Rotorua caldera, are controlled by the NE – SW trending extensional regional structure or a NW – SE trending basement structure. The collapse of Rotorua caldera, and geometry of the deformation margin, are related to the interplay of these structures. At Ruawahia, the NE – SW trending vent zone is parallel to the regional extension across the OCC, as shown by the orientation of intrusion of the 1886AD dyke through the Tarawera dome complex.
The NE – SW trending regional structures observed at both Rotorua caldera and Okataina caldera complex are very similar to each other, but differ from extension within the Taupo rift to the south. Lava domes, such as Ngongotaha, that are controlled by this structure show that the ‘kink’ in the extension across Okataina caldera complex was active across Rotorua caldera during the collapse at 240 ka, and possibly earlier.
This study shows the evolution of dyke-fed lava domes during eruption, and the control of regional structures in the location and timing of eruption. These findings improve our knowledge of the evolution of porosity and permeability in a compacting lava dome, as well as of the structures of Rotorua caldera, the longevity of volcanic activity at dormant calderas and the hazard potential of dyke-fed lava domes.
39
Kolisnik, Angela M. E. "Petrology of the McCartys lava flow sequence, Zuni-Bandera volcanic field, New Mexico." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1998. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq31043.pdf.
Full text
40
Carter, Catherine S. "Communication of Lava Flow Hazards at the San Francisco Volcanic Field, Flagstaff, Arizona." Thesis, University of South Florida, 2015. http://pqdtopen.proquest.com/#viewpdf?dispub=1595006.
Full textAbstract:
This thesis examines different methods of communicating volcanic hazards to the population of Flagstaff, Arizona using the results of a recent lava flow hazard assessment of the nearby San Francisco Volcanic Field (SFVF). Harburger (2014) determined that given a lava flow originating in the SFVF, there is a statistical probability that it will inundate the city of Flagstaff or even originate from a vent within the city limits. Based on the recurrence rates for the most recent eruptions (3 x 10-4/year), the probability of lava flow inundation in Flagstaff is 1.1 x 10-5 per year.
This study considers the effects of three different communication methods on participants’ perceived risk. The methods were administered through a questionnaire and included a statement of probability of lava flow inundation per year, a statement of probability over a 100 year period, and an interactive lava flow map derived from the results of the lava flow hazard assessment. Each method was followed by questions gauging level of concern. Questionnaires were administered to 213 Flagstaff residents over a two week period in February 2015.
Results showed that levels of concern, rated from 1 (not concerned) to 5 (very concerned), varied based on each method of communication. The method with the greatest effect on perceived risk was the simulated lava flow map, while the first method with a one year odds resulted in a statistically lower mean rating of concern. It is suggested that the best way to change levels of perceived risk when communicating lava flow hazards includes a combination of comprehensible odds and visual aids. Further studies could also include visualization of the entire eruption scenario, including time scales and other volcanic hazards, which may have more effect on concern than a simplified visualization of lava flows.
41
Carter, Catherine St John. "Communication of Lava Flow Hazards at the San Francisco Volcanic Field, Flagstaff, Arizona." Scholar Commons, 2015. http://scholarcommons.usf.edu/etd/5655.
Full textAbstract:
This thesis examines different methods of communicating volcanic hazards to the population of Flagstaff, Arizona using the results of a recent lava flow hazard assessment of the nearby San Francisco Volcanic Field (SFVF). Harburger (2014) determined that given a lava flow originating in the SFVF, there is a statistical probability that it will inundate the city of Flagstaff or even originate from a vent within the city limits. Based on the recurrence rates for the most recent eruptions (3 x 10-4/year), the probability of lava flow inundation in Flagstaff is 1.1 x 10-5 per year.
This study considers the effects of three different communication methods on participants’ perceived risk. The methods were administered through a questionnaire and included a statement of probability of lava flow inundation per year, a statement of probability over a 100 year period, and an interactive lava flow map derived from the results of the lava flow hazard assessment. Each method was followed by questions gauging level of concern. Questionnaires were administered to 213 Flagstaff residents over a two week period in February 2015.
Results showed that levels of concern, rated from 1 (not concerned) to 5 (very concerned), varied based on each method of communication. The method with the greatest effect on perceived risk was the simulated lava flow map, while the first method with a one year odds resulted in a statistically lower mean rating of concern. It is suggested that the best way to change levels of perceived risk when communicating lava flow hazards includes a combination of comprehensible odds and visual aids. Further studies could also include visualization of the entire eruption scenario, including time scales and other volcanic hazards, which may have more effect on concern than a simplified visualization of lava flows.
42
Vardhan, Gadepalli Venkata Vishnu. "Numerical simulation of gas flows in a De-Laval micro nozzle." FIU Digital Commons, 2005. http://digitalcommons.fiu.edu/etd/3619.
Full textAbstract:
A numerical study has been conducted to understand the gas flows in a De-Laval micronozzles using 2D continuum axisymmetric model, which solves the governing equations by control volume method. The numerical model was validated with existing experimental data employing slip and no-slip boundary conditions at the wall. The numerical results showed good agreement with experimental data on exit thrust values except at low Reynolds number. Parametric studies included the effect of geometric scaling via scaling down of throat diameter for various throat Reynolds numbers and the effect of chemical propellants on the integrated performance of the nozzle. On the effect of geometric scaling, the nozzle throat diameter was scaled from 10 mm to 0.1 mm and the throat Reynolds number was varied from 5 to 100. A correlation was developed and presented to predict the specific Impulse for any given throat diameter and throat Reynolds number. To understand the effect of chemical propellants on nozzle performance, propellants like helium, nitrogen, argon and carbon dioxide were selected and simulations were conducted for throat diameter equal to 0.1, 1 and 10 mm respectively for Rethroat varying from 5 to 2000.
43
Gadepalli, Venkata Vishnu Vardhan. "Numerical simulation of gas flows in a De-Laval micro nozzle." FIU Digital Commons, 2005. http://digitalcommons.fiu.edu/etd/3637.
Full textAbstract:
A numerical study has been conducted to understand the gas flows in a De-Laval micronozzles using 2D continuum axisymmetric model, which solves the governing equations by control volume method. The numerical model was validated with existing experimental data employing slip and no-slip boundary conditions at the wall. The numerical results showed good agreement with experimental data on exit thrust values except at low Reynolds number. Parametric studies included the effect of geometric scaling via scaling down of throat diameter for various throat Reynolds numbers and the effect of chemical propellants on the integrated performance of the nozzle. On the effect of geometric scaling, the nozzle throat diameter was scaled from 10 mm to 0.1 mm and the throat Reynolds number was varied from 5 to 100. A correlation was developed and presented to predict the specific Impulse for any given throat diameter and throat Reynolds number. To understand the effect of chemical propellants on nozzle performance, propellants like helium, nitrogen, argon and carbon dioxide were selected and simulations were conducted for throat diameter equal to 0.1, 1 and 10 mm respectively for Rethroat varying from 5 to 2000.
44
Atluri, Lava Kumar. "Design Automation Flow using Library Adaptation for Variation Aware Logic Synthesis." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1397466797.
Full text
45
Jouval, Florian. "Successions écologiques et potentiel de récupération des communautés coralliennes : structure, démographie et recrutement dans le sud-ouest de l'océan Indien." Thesis, La Réunion, 2019. http://www.theses.fr/2019LARE0019.
Full textAbstract:
Les récifs coralliens subviennent aux besoins de millions de personnes à travers le monde. Toutefois, les effets du changement climatique et l’accentuation de la fréquence et de l’intensité des perturbations mènent à une accélération de leur dégradation et au déclin des communautés de coraux scléractiniaires. Les préoccupations actuelles portent sur les capacités de résilience de ces écosystèmes vulnérables. Dans ce contexte, il apparait essentiel d’améliorer la compréhension des mécanismes de maintien des communautés coralliennes dans l’optique d’aider à la conservation et à la gestion des récifs. Ce travail de thèse vise à analyser les processus démographiques, y compris le recrutement, et la structure des assemblages coralliens à plusieurs échelles dans différents milieux insulaires de la zone sud-ouest de l’océan Indien. Ces descripteurs ont été abordés au travers de la succession écologique sur les récifs et coulées de lave sous-marines de La Réunion et par l’évaluation du potentiel de récupération des récifs de cinq systèmes insulaires de la zone. Les résultats montrent que le recrutement corallien est faible dans les Mascareignes (La Réunion et Rodrigues) et très variable à toutes les échelles spatiales étudiées, de quelques centimètres à plusieurs centaines de kilomètres. Cette variabilité spatiale est également observée entre sites en termes de recouvrement benthique, de densité, de structure de taille, de mortalité ou encore de potentiel de récupération des communautés coralliennes. Cette variabilité spatiale n’est cependant pas clairement liée aux niveaux de protection des sites ni aux patrons théoriques de la succession écologique (étudiés à La Réunion). Un patron de succession est toutefois mis en évidence, au cours duquel la taille des coraux et la richesse spécifique augmentent avec le temps jusqu'à ce que les interactions interspécifiques (e.g. la compétition pour l'espace) conduisent à leur diminution. De plus, une forte dominance du genre Pocillopora est observée sur tous les sites de coulées de lave, confirmant sa nature pionnière et compétitive. L’indice de récupération (RI) développé suggère que le potentiel de récupération des récifs du canal du Mozambique est supérieur (notamment pour Europa) à celui des récifs des Mascareignes, soumis de manière plus générale aux pressions anthropiques directes. Ces résultats sont cohérents avec les observations passées de la récupération des récifs étudiés suite à des perturbations diverses. L’ajout des taux de recrutement au calcul des RI pour La Réunion et Rodrigues modifie nettement le potentiel de récupération des sites de ces îles : les sites ayant les taux de recrutement les plus forts sont également ceux dont le RI est le plus élevé. Ce projet apporte ainsi des informations essentielles sur les communautés récifales de l’océan Indien qui permettront d’améliorer les plans de gestion pour la conservation des récifs coralliensCoral reefs support millions of people’s livelihood around the world. However, the effects of climate change and the increase in frequency and intensity of disturbances are leading to their accelerated degradation and to the decline of scleractinian coral communities. Current concerns relate to the resilience of these vulnerable ecosystems. In this context, it is essential to improve our understanding of the mechanisms underlying maintenance of coral communities, which may also improve conservation and management efforts that are urgently needed for these ecosystems. This PhD work aims to analyze demographic processes, including recruitment, and the structure of coral assemblages at several scales in different island environments of the southwestern Indian Ocean region. These descriptors were addressed through ecological succession on reefs and underwater lava flows of Reunion Island, and through the assessment of the reef recovery potential of five island systems in the area. Results show that coral recruitment in the Mascarene Islands (Reunion and Rodrigues) is low and highly variable at all spatial scales, from a few centimeters to several hundreds of kilometers. This spatial variability is also observed between sites in terms of benthic cover, density, size structure, mortality and recovery potential of coral communities. However, this spatial variability is not clearly linked to the protection levels of the sites, nor to the theoretical patterns of ecological succession (studied in Reunion Island). A succession pattern is yet highlighted through the increase in coral size and species richness over time until interspecific interactions (e.g. competition for space) lead to their decline. In addition, a strong dominance of the Pocillopora genus is recorded at all lava flow sites, confirming its pioneering and competitive nature. The recovery index (RI) that we developed suggests that the recovery potential of the reefs of the Mozambique Channel is higher (especially for Europa) than that of the reefs of the Mascarene Islands, which are more subject to direct anthropogenic pressures. These results are consistent with past observations of recovery trajectories of the studied reefs following various disturbances. The addition of recruitment rates to the calculation of RI for Reunion and Rodrigues islands clearly modifies the recovery potential of these islands sites: the sites with the highest recruitment rates are also those with the highest RI. This project thus provides essential information on Indian Ocean reef communities that may improve management strategies for coral reef conservation
46
Gallant, Elisabeth. "Lava Flow Hazard Assessment for the Idaho National Laboratory, Idaho Falls, and Pocatello, Idaho, U.S.A." Scholar Commons, 2016. http://scholarcommons.usf.edu/etd/6502.
Full textAbstract:
This study presents a probabilistic lava flow hazard assessment for the Idaho National Laboratory (INL) and the cities of Idaho Falls and Pocatello, Idaho. The impetus of this work is to estimate the conditional probability that a lava flow on the eastern Snake River Plain (ESRP) will impact the areas of interest given the formation of a new volcanic vent in the region. A list of 288 eruptive events, derived from a previously published inventory of 506 surface and 32 buried vents, was created to reduce the biasing of spatial density maps towards eruptions with multiple dependent vents. Conditional probabilities of new vents and events occurring on the ESRP were modeled using the the Sum of Asymptotic Mean Squared Error (SAMSE) optimal pilot bandwidth estimator with a bivariate Gaussian kernel function. Monte Carlo analyses of potential eruption scenarios were performed using MOLASSES, a cellular automata fluid flow simulator. Results show that Idaho Falls is impacted <1% of the time for both the vent and event simulations; Pocatello is not impacted by any simulated flows. 25.45% of vent flows and 33.74% of event flows breach the boundaries of INL. 18.27%of vent and 25.85% of event simulations initiate on the INL property. Annual inundation probabilities of 1.06 x 10-4 for vent-based flows and 7.12 x 10-5 for event-based flows are reported for INL; annual probabilities of an eruptive center initiating on INL property are 7.60 x 10-5 for vents and 5.45 x 10-5 for events. All of these values exceed the International Atomic Energy Agency’s acceptable risk probability of 10-7 by several orders of magnitude.
47
Moore, Jillian Nicole. "Molecular Variation in the Agouti Gene in Pocket Mice from the Carrizozo Malpaís Lava Flow." Thesis, The University of Arizona, 2012. http://hdl.handle.net/10150/244481.
Full textAbstract:
Color variation in pocket mice, Chaetodipus intermedius, presents a unique opportunity to study genes contributing to convergent adaptation. While pocket mice generally have light coats matching sand-colored rocks on which they live, dark mice are found on basalt lava flows in the desert southwest. Because the mice match their habitat, they are less likely to be recognized by visual hunters. In one lava flow population, the genetic basis of melanism was identified in the melanocortin-1 receptor (Mc1r). However, it is known that the underlying locus is different in a lava flow population in Carrizozo, NM. In a backcross, it was demonstrated that melanism in Carrizozo is recessive and associated with a marker in agouti, a locus encoding an MC1R antagonist. However, because of the low level of recombination in this cross, genes linked to this marker could underlie color variation. Here, I sequenced regions of agouti previously uncharacterized in pocket mice. I genotyped Carrizozo mice in these regions and identified a SNP significantly associated with coat color likely linked to a causative mutation within agouti. These data support the hypothesis that melanism has arisen at least twice in pocket mice due to changes in different pigmentation genes, Mc1r and agouti.
48
Zago, Vito. "Smoothed Particle Hydrodynamics method and flow dynamics: the case of lava numerical modeling and simulation." Doctoral thesis, Università di Catania, 2019. http://hdl.handle.net/10761/4145.
Full textAbstract:
Lo Smoothed Particle Hydrodynamics è un metodo Lagrangiano mesh-free che sta riscuotendo interesse nel campo della fluidodinamica computazionale. Grazie alla sua natura, il metodo SPH è in grado di gestire fluidi complessi caratterizzati da reolgie non-Newtoniane, superfici libere, dipendenze dalla temperatura, transizioni di fase, grandi deformazioni, e così via. Il metodo SPH è caratterizzato da una natura intrinsecamente parallela, che ne rende possibile l'esecuzione su hardware per il calcolo parallelo ad alte prestazioni, come ad esempio le moderne schede grafiche (GPU), ottenendo così tempi di simulazione vantaggiosi. In questa tesi lavoreremo su GPUSPH, un'implementazione su GPU del metodo SPH. Studieremo la simulazione di un fluido molto complesso: la lava. La combinazione di superficie libera, topografia naturale, transizioni di fase e la formazione di strutture come argini e tunnel, rende la modellazione e la simulazione della lava un aspetto di interesse nel campo della fluidodinamica computazionale, con un notevole impatto in numerosi campi dell'Ingegneria e della ricerca scientifica. Vedremo l'introduzione in GPUSPH di modelli e strategie che permetteranno di trattare le diverse caratteristiche delle colate laviche, includendo lo sviluppo di uno schema di integrazione semi-implicito, che permetterà la simulazione di fluidi altamente viscosi, assicurando robustezza e riducendo i tempi di simulazione.
La nuova implementazione sarà testata per verificarne la correttezza e studiarne i livelli accuratezza e performance raggiunti.
49
Bondre, Ninad R. "FIELD AND GEOCHEMICAL INVESTIGATION OF BASALTIC MAGMATISM IN THE WESTERN UNITED STATES AND WESTERN INDIA." Miami University / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=miami1164916380.
Full text
50
Brown, Sarah Krystyna. "The distribution and development of eruptive centres and lava flow-field characteristics at Somma-Vesuvius, Italy." Thesis, University of Portsmouth, 2013. https://researchportal.port.ac.uk/portal/en/theses/the-distribution-and-development-of-eruptive-centres-and-lava-flowfield-characteristics-at-sommavesuvius-italy(5ce1bfb2-dc28-4513-b1a4-62d4eaedcff3).html.
Full textAbstract:
Vesuvius in Southern Italy is among the most densely populated active volcanoes on Earth. Although famous for its Plinian eruption that destroyed Pompeii and Herculaneum in AD 79, its recent activity, between 1631 and 1944, was primarily effusive. Data from field studies, analogue modelling and historical accounts are here combined to investigate Vesuvius’ activity during this latest eruptive phase and to identify behavioural trends of value for enhancing emergency responses during future unrest. The focus of this study is on the activity of 1631-1944, and data have been compiled for 183 eruptions during this period. Further data regarding earlier flank eruptions have been incorporated permitting a more comprehensive examination of these infrequent events. Such flank vents have been concentrated on the southern flanks at about 300m above sea level and a mean distance of 4.2 km from the summit. A submarine pit crater, newly correlated here with the 1861 eruption, highlights the potential for vents to form at almost twice the mean distance from the summit and further than previously considered. Analogue studies of magma injection, using a gelatine model, have shown that the vent distribution is consistent with a regional stress field modified by gravitational stresses due to the size and shape of the volcanic edifice. The study of the 1631 to 1944 lava flow-fields shows that lavas from flank vents reached similar lengths to summit and lateral vent flow-fields, all with mean lengths around 4km. Over half of all lava flow-fields extended to beyond 4km from the crater, and so threatened the principal settlements around the foot of the volcano. The flow-fields had typical surface areas of less than 5 km², and approximately a third reached their maximum length within a week. Flank eruptions normally occurred when the summit crater was full of lava and were commonly preceded by three days of elevated seismicity. Such events can thus potentially be forecast with at least a 24-hour warning and, even after an eruption has begun, several days may be available before a settlement is threatened. The design of an effective emergency response to future effusions is thus a feasible objective.