ALBERT

All Library Books, journals and Electronic Records Telegrafenberg

X
feed icon rss

Your email was sent successfully. Check your inbox.

An error occurred while sending the email. Please try again.

Proceed reservation?

Export
  • 1
    facet.materialart.
    Unknown
    Transient numerical model of magma ascent dynamics: application to the explosive eruptions at the Soufrière Hills Volcano (2018)
    Elsevier
    Details
    Publication Date: 2021-06-30
    Description: Volcanic activity exhibits a wide range of eruption styles, from relatively slow effusive eruptions that produce lava flows and lava domes, to explosive eruptions that can inject large volumes of fragmented magma and volcanic gases high into the atmosphere. Although controls on eruption style and scale are not fully understood, previous research suggests that the dynamics of magma ascent in the shallow subsurface (〈 10 km depth) may in part control the transition from effusive to explosive eruption and variations in eruption style and scale. Here we investigate the initial stages of explosive eruptions using a 1D transient model for magma ascent through a conduit based on the theory of the thermodynamically compatible systems. The model is novel in that it implements finite rates of volatile exsolution and velocity and pressure relaxation between the phases. We validate the model against a simple two-phase Riemann problem, the Air-Water Shock Tube problem, which contains strong shock and rarefaction waves. We then use the model to explore the role of the aforementioned finite rates in controlling eruption style and duration, within the context of two types of eruptions at the Soufrière Hills Volcano, Montserrat: Vulcanian and sub-Plinian eruptions. Exsolution, pressure, and velocity relaxation rates all appear to exert important controls on eruption duration. More significantly, however, a single finite exsolution rate characteristic of the Soufrière Hills magma composition is able to produce both end-member eruption durations observed in nature. The duration therefore appears to be largely controlled by the timescales available for exsolution, which depend on dynamic processes such as ascent rate and fragmentation wave speed.
    Description: Published
    Description: 110-139
    Description: 5V. Dinamica dei processi eruttivi e post-eruttivi
    Description: JCR Journal
    Keywords: Magma ascent ; Conduit dynamics ; Soufrière Hills Volcano ; Finite-rate exsolution ; Pressure relaxation ; Velocity relaxation ; 04.08. Volcanology ; Numerical modeling
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 2
    facet.materialart.
    Unknown
    Effects of conduit geometry on magma ascent dynamics in dome-forming eruptions (2008)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: We develop a steady-state, two-phase flow model of magma ascent through an axisymmetric conduit of variable radius R and length L in order to quantify relationships between conduit geometry and magma ascent dynamics. Holding boundary conditions and chamber magma properties constant, we vary conduit geometry systematically and independently, such that the upper conduit radius increases or decreases by a factor of Rt /Rb (radius ratio; 0.4 ≤ Rt /Rb ≤ 2.5), above a change initiation height H (0.1 ≤ H /L ≤ 0.7), and over length Le (Le /L = 0.2), where Rt and Rb are conduit radius above (t) and below (b) the radius change and H is the height above the top of the magma chamber. Conduit widening causes a drop in overpressure and corresponding increase in gas volume fraction and magma acceleration over the whole length of the conduit, with all changes increasing in magnitude with increasing radius ratio. Magma ascent rate increases roughly as R2 and volumetric flow rate subsequently increases as R4 when Rt = Rb = R. Both increasing Rt for a fixed Rb (increasing radius ratio) and increasing Rb for a fixed Rt (decreasing radius ratio), increase volume flow and magma ascent rates. Compared to changes in geometry, small changes in chamber pressure (〈 5%) have a weak effect on flow rate. Many model runs produce a magma plug at the top of the conduit, largely due to permeable gas loss through conduit walls. In general, large radii and low radius ratios (i.e., nearly cylindrical conduits) favor thin, low-density plugs, which may facilitate sudden destruction of a plug, and thus enhance the likelihood of explosive over extrusive eruptions. These findings suggest that changes in conduit geometry, such as those caused by conduit erosion during explosive eruptions or by accretion of magma along conduit walls, are strongly coupled to magma ascent dynamics and should not be ignored when interpreting changes in eruptive behavior.
    Description: Published
    Description: 567-578
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: conduit dynamics ; conduit geometry ; magma ascent ; effusion rate ; computational model ; 05. General::05.01. Computational geophysics::05.01.99. General or miscellaneous
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 3
    facet.materialart.
    Unknown
    Transient effects of magma ascent dynamics along a geometrically variable dome-feeding conduit (2011)
    Elsevier
    Details
    Publication Date: 2017-04-04
    Description: The transient dynamics of magma ascent during dome-forming eruptions were investigated and the effects of magma chamber pressure perturbations on eruption rate are illustrated. The numerical model DOMEFLOW, developed by the authors for this work, is applied to the problem. DOMEFLOW is a transient 1.5D isothermal two-phase flow model of magma ascent through an axisymmetric conduit of variable radius, which accounts for gas exsolution, bubble growth, crystallization induced by degassing, permeable gas loss through overlying magma and through conduit walls, as well as viscosity changes due to crystallization and degassing. For runs in which chamber pressure increases, the time required to reach the new steady state (transition time) is a complex function of the pressure perturbation, while for decreasing chamber pressure, transition time is a monotonic function of the magnitude of the pressure perturbation. The transition to the new steady state is mainly controlled by magma compressibility, travel time (time required for one parcel of magma to travel from chamber to surface), and the time over which the pressure perturbation occurs. Results of many runs (〉 300) were analyzed using dimensional analysis to reveal a general relationship which predicts the temporal evolution of magma effusion rate for a given sudden increase in chamber pressure; the product of the change in steady-state extrusion rate and the time required to reach the new steady state is linearly proportional to the normalized change in chamber pressure, the volume of the conduit, and the ratio of top and bottom conduit radii, and inversely proportional to the cubic root of volatile fraction. This relationship is used to interpret observed variations in two ongoing dome-building eruptions, the Soufrière Hills volcano, Montserrat, and Merapi volcano, Indonesia.
    Description: Published
    Description: 541-553
    Description: 3.6. Fisica del vulcanismo
    Description: JCR Journal
    Description: reserved
    Keywords: conduit dynamics ; conduit geometry ; magma ascent ; effusion rate ; computational model ; dome-building ; 04. Solid Earth::04.08. Volcanology::04.08.03. Magmas ; 05. General::05.01. Computational geophysics::05.01.05. Algorithms and implementation
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
    Type: article
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    PAPER (OA)
  • 4
    facet.materialart.
    Unknown
    Evidence for a Noachian-Aged Ephemeral Lake in Gusev Crater, Mars (2014)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: Gusev crater was selected as the landing site for the Spirit rover because of the likelihood that it contained an ancient lake. Although outcrops rich in Mg-Fe carbonate dubbed Comanche were discovered in the Noachian-aged Columbia Hills, they were inferred to result from volcanic hydrothermal activity. Spirit encountered other mineral and chemical indicators of aqueous activity, but none was recognized as definitive evidence for a former lake in part because none was associated with obvious lacustrine sedimentary deposits. However, water discharge into Martian crater basins like Gusev may have been episodic, producing only small amounts of sediment and shallow ephemeral lakes. Evaporative precipitation from such water bodies has been suggested as a way of producing the Mg- and Fe-rich carbonates found in ALH84001 and carbonates and salts in some nakhlites a hypothesis we examine for the Comanche carbonate.
    Keywords: Lunar and Planetary Science and Exploration
    Type: JSC-CN-30542 , Lunar and Planetary Science Conference; Mar 17, 2014 - Mar 21, 2014; The Woodlands, TX; United States
    Format: application/pdf
    Location Call Number Expected Availability
    BibTip Others were also interested in ...
    NASA TECHNICAL REPORTS
Close ⊗
This website uses cookies and the analysis tool Matomo. More information can be found here...