scholarly journals Emplacing a Cooling-Limited Rhyolite Lava Flow: Similarities with Basaltic Lava Flows

2017 ◽  
Vol 5 ◽  
Author(s):  
Nathan Magnall ◽  
Mike R. James ◽  
Hugh Tuffen ◽  
Charlotte Vye-Brown
Keyword(s):  
Lava Flow ◽  
Lava Flows ◽  
Basaltic Lava ◽  
Rhyolite Lava

Magnetic fabric and flow directions in magmatic rocks of the Franz Josef Land, Arctic Ocean

2020 ◽  
Author(s):  
Anna Chernova ◽  
Viktor Abashev ◽  
Dmitry Metelkin ◽  
Valery Vernikovsky ◽  
Nikolay Mikhaltsov
Keyword(s):  
Lava Flow ◽  
Complex Analysis ◽  
Flow Direction ◽  
Lava Flows ◽  
Magnetic Fabric ◽  
Basaltic Lava ◽  
Magma Flow ◽  
Franz Josef Land ◽  
Degree Of Anisotropy ◽  
Flow Directions

<p>Here, we present the results of a study of the anisotropy of magnetic susceptibility (AMS) completed in the Early Cretaceous magmatic complexes from the Franz Josef Land (FJL). AMS was measured in the framework of paleomagnetic research as a leading indicator of the rock magnetic fabric to help in understanding the lava flow directions and forming mechanisms. The three types of magmatic bodies were available in these studies: dolerite sills, dykes and basaltic lava flows from several islands (Alexandra, Hall, Ziegler, Jackson and Heiss Islands) among FJL. During the experiments the different parameters of AMS ellipsoids were obtained which have a good correlation with the igneous body shapes and also could illustrate lava flows direction parameters. The degree of anisotropy P is 1.01-1.06 for most sites that is typical for the primary igneous magnetic fabric. The form factor T characterizing the shape of the AMS ellipsoids demonstrates both planar and linear magnetic fabric in studied magmatic bodies. What is remarkable the part of the dykes is characterized strictly oblate magnetic fabric and another dykes have the prolate AMS ellipsoids. The linear magnetic structure is also more typical for lava flows with the maximum axes K1 lying in the flow plane that is obviously could point to the flow direction. The part of the igneous bodies are characterized by the inverse type of magnetic fabric, when the principal axis K1 of the ellipsoid is oriented perpendicularly to the plane of the flow or the sill, that was likely caused by the effect of secondary processes. The previous studies (Abashev et al., 2019) demonstrated that the primary orientation of the AMS ellipsoid could be recovered after temperature demagnetization. Noticeable changes were revealed at heating up to ~450 deg C, which generally corresponds to deblocking temperatures of titanomagnetites identified in the rocks by rock-magnetic methods. The degree of anisotropy was decreased after heating in 2-3 times. The heating also resulted to the redistribution of magnetic axes and in several cases the axes becomes more grouped. Analysis of the AMS results from the basaltic lava flows of the Aleksandra Island defined the magma flow direction to be NW-SE. Similar behavior of the AMS ellipsoids and lava flow orientation is typical for Ziegler Island. Generally our results show that complex analysis of AMS data in basaltic rocks is promising for identifying magma flow direction and it can give more detailed information about forming mechanisms of the different magmatic bodies.</p><p>This work was supported by the RSF (project no. 19-17-00091) and the RFBR (project nos. 18-35-00273, 18-05-70035).</p>

scholarly journals Rheological and morphological evolution of basaltic lava flows

2018 ◽  
Author(s):  
◽  
Arianna Soldati
Keyword(s):  
Lava Flow ◽  
Flow Structure ◽  
Flow System ◽  
Morphological Evolution ◽  
Human Life ◽  
Active Volcano ◽  
Flow Dynamics ◽  
Lava Flows ◽  
System Structure ◽  
Basaltic Lava

Over 500 million people live in proximity of an active volcano globally. Although lava flows rarely endanger human life, they often destroy critical infrastructure. Advancing our understanding of lava flow dynamics is therefore critical to developing accurate hazard assessment, with key socio-economic impacts for many communities. This work focuses on basaltic lava rheology, which exerts a first-order control on flow dynamics and is reflected in lava morphology. In particular, I address the following research questions: (1) How does the rheology of active flows evolve during emplacement; and (2) How can we use flow morphology to infer the rheology of inactive flows? ... At Piton de La Fournaise (La R�union, FR DOM), I addressed the longstanding question of how pre-existing topography controls lava flow system structure in volume-limited flows (Soldati et al., accepted). I concluded that a steep slope results in a single, stable channel, whereas a gentle slope results in an unstable, braided channel. The findings of this study allow us to interpret and explain the observed flow structure on the basis of pre-existing volcano topography, and to forecast future flow structure. This allowed me to determine that rheology neither affects nor is affected by flow system configuration.

OCCURRENCE OF NATIVE COPPER, SILVER AND GOLD IN BASALTIC LAVA FLOWS

2017 ◽  
Author(s):  
Peishu Li ◽  
◽  
Alan E. Boudreau ◽  
Alan E. Boudreau
Keyword(s):  
Lava Flows ◽  
Basaltic Lava ◽  
Native Copper

scholarly journals Anatomy of a Paroxysmal Lava Fountain at Etna Volcano: The Case of the 12 March 2021, Episode

2021 ◽  
Vol 13 (15) ◽  
pp. 3052
Author(s):  
Sonia Calvari ◽  
Alessandro Bonaccorso ◽  
Gaetana Ganci
Keyword(s):  
Lava Flow ◽  
Ground Deformation ◽  
Monitoring Network ◽  
Lava Flows ◽  
Etna Volcano ◽  
Lava Fountain ◽  
Eruptive Episode ◽  
Lava Fountains ◽  
Borehole Strainmeter ◽  
Ash Plume

On 13 December 2020, Etna volcano entered a new eruptive phase, giving rise to a number of paroxysmal episodes involving increased Strombolian activity from the summit craters, lava fountains feeding several-km high eruptive columns and ash plumes, as well as lava flows. As of 2 August 2021, 57 such episodes have occurred in 2021, all of them from the New Southeast Crater (NSEC). Each paroxysmal episode lasted a few hours and was sometimes preceded (but more often followed) by lava flow output from the crater rim lasting a few hours. In this paper, we use remote sensing data from the ground and satellite, integrated with ground deformation data recorded by a high precision borehole strainmeter to characterize the 12 March 2021 eruptive episode, which was one of the most powerful (and best recorded) among that occurred since 13 December 2020. We describe the formation and growth of the lava fountains, and the way they feed the eruptive column and the ash plume, using data gathered from the INGV visible and thermal camera monitoring network, compared with satellite images. We show the growth of the lava flow field associated with the explosive phase obtained from a fixed thermal monitoring camera. We estimate the erupted volume of pyroclasts from the heights of the lava fountains measured by the cameras, and the erupted lava flow volume from the satellite-derived radiant heat flux. We compare all erupted volumes (pyroclasts plus lava flows) with the total erupted volume inferred from the volcano deflation recorded by the borehole strainmeter, obtaining a total erupted volume of ~3 × 106 m3 of magma constrained by the strainmeter. This volume comprises ~1.6 × 106 m3 of pyroclasts erupted during the lava fountain and 2.4 × 106 m3 of lava flow, with ~30% of the erupted pyroclasts being remobilized as rootless lava to feed the lava flows. The episode lasted 130 min and resulted in an eruption rate of ~385 m3 s−1 and caused the formation of an ash plume rising from the margins of the lava fountain that rose up to 12.6 km a.s.l. in ~1 h. The maximum elevation of the ash plume was well constrained by an empirical formula that can be used for prompt hazard assessment.

The effect of bubbles on the rheology of basaltic lava flows: Insights from large-scale two-phase experiments

2020 ◽  
Vol 548 ◽  
pp. 116504
Author(s):  
A. Soldati ◽  
J.A. Farrell ◽  
C. Sant ◽  
R. Wysocki ◽  
J.A. Karson
Keyword(s):  
Large Scale ◽  
Lava Flows ◽  
Basaltic Lava ◽  
Two Phase

scholarly journals Some physical requirements for the emplacement of long basaltic lava flows

1998 ◽  
Vol 103 (B11) ◽  
pp. 27447-27464 ◽  
Author(s):  
L. Keszthelyi ◽  
S. Self
Keyword(s):  
Lava Flows ◽  
Basaltic Lava

On Composite Lava Flows.

1931 ◽  
Vol 68 (4) ◽  
pp. 166-181 ◽  
Author(s):  
W. Q. Kennedy
Keyword(s):  
Lava Flow ◽  
Lava Flows ◽  
The Other ◽  
Geological Survey ◽  
Main Subject ◽  
Lower Carboniferous ◽  
Fluid State ◽  
Mutual Contact ◽  
The World ◽  
Probable Effect

For many years composite minor intrusions, both sills and dykes, have been known from various parts of the world and most petrologists must have speculated as to the probable effect produced in the event of such composite intrusions having reached the surface in the form of an effusion. For obvious reasons it has not been found possible to trace a composite dyke upwards into a lava flow. However, during the revision of 1 inch Sheet 30 (Renfrewshire) for the Geological Survey, the author encountered, in the neighbourhood of Inverkip, a small village on the Firth of Clyde south of Greenock, certain peculiar lava flows which are believed to represent the effusive equivalents of composite minor intrusions. These “composite lavas”, which form the main subject of the present paper, are of Lower Carboniferous age (Calciferous Sandstone Series) and occur interbedded among the more normal flows towards the base of the volcanic group. Two distinct rock varieties, one highly porphyritic, with large phenocrysts (up to 1·5 cms. long) of basic plagioclase, and the other non-porphyritic, are associated within the same flow. The porphyritic type always forms the upper part of the flow and overlies the non-porphyritic; the junction shows unmistakable evidence that both were in a fluid state along their mutual contact at the time of emplacement.

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