Identifying multiple eruption phases from a compound tephra blanket: an example of the AD1256 Al-Madinah eruption, Saudi Arabia

Kawabata, Emily; Cronin, Shane J.; Moufti, Mohammed Rashad; El-Masry, Nabil; Wang, Ting

doi:10.1007/s00445-014-0890-y

Cited by 35 publications

(29 citation statements)

References 35 publications

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“…The bulk density of the samples was measured using an envelope density analyser (Micromeritics Geopyc 1360), which measures the difference in the volume of a quasi-fluid medium with and without the sample embedded in that medium. As presented by Kawabata et al (2015) the Geopyc instrument can measure the envelope density of objects of different sizes and shapes. Prior to immersion, samples were dried in an oven for 24 hours at a temperature of 70 °C and then wrapped with thin laboratory parafilm®, to preserve external irregularities but to avoid the medium entering the porous sample.…”

Section: Chemical and Textural Analysesmentioning

confidence: 99%

Investigating physical and thermal interactions between lava and trees: the case of Kīlauea’s July 1974 flow

et al. 2019

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To examine whether there was any physical or thermal interaction between trees and lava when a lava flow inundates a forest we studied the Kīlauea's July 1974 lava flow. We mapped the location of ∼600 lava-trees and the lava type (pāhoehoe versus 'a'ā), and sampled an additional ten lava-trees for chemical and textural analysis to infer flow viscosity and dynamics. The emplacement event lasted 3.5 hours and markers on the outer surface of the lava-trees allowed us to define initial high effusion rate and velocity (∼400 m 3 /s and 5-10 m/s) that then declined to 9 m 3 /s and 4 m/s during a waning phase. We find that lava passing through the forest underwent an initial cooling rate of 4 °C/km which increased to 10 °C/km late in the eruption. This is no different to cooling rates recorded at Kīlauea for tree-free cases. There thus appears to be no effect on cooling for this case. The lava-trees did, though, form a network of vertical cylinders obstacles and evidence for local diversion of flow lines are noticed. However, this varies with lava type, as almost no lava-trees form in ʻaʻā. We find a relation between the percentage of ʻaʻā and the number of lava-trees per hectare. The pāhoehoe-ʻaʻā transition for this flow occurs at a viscosity of 10 3 Pa s and this appears to be a threshold below which lava-trees can form so as to behave as a network of obstacles, and above which they cannot.

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Section: Chemical and Textural Analysesmentioning

confidence: 99%

Investigating physical and thermal interactions between lava and trees: the case of Kīlauea’s July 1974 flow

et al. 2019

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“…Valentine and Gregg 2008), some associated with widespread pyroclastic fall deposits (e.g. Kawabata et al 2015). In addition, long and extensive lava flow fields comprise the main erupted volume of the field (e.g.…”

Section: Introductionmentioning

confidence: 99%

The Al-Du’aythah volcanic cones, Al-Madinah City: implications for volcanic hazards in northern Harrat Rahat, Kingdom of Saudi Arabia

et al. 2015

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The basaltic Al-Du'aythah volcanic cones lie in the northern part of the extensive lava field of Harrat Rahat, and only 13 km from the centre of Al-Madinah City, in the Kingdom of Saudi Arabia. Historical records indicate they may have erupted in AD 641. The four cones are formed by deposits that record a transition from phreatomagmatic to magmatic explosions followed by minor lava effusion. Three cones display elongated tuff rings at the base, and two produced late-stage lava flows. The cones themselves are symmetrical and constructed mostly by the accumulation of ballistically ejected pyroclasts. Spherical bombs and lapilli (cannonball bombs/lapilli), occasionally with country-rock fragments inside (both cored and loaded bombs/lapilli) are common within the tuff ring deposits. LiDAR data show a total volume of 1,664×10 −6 km 3 for the four cones (418×10 −6 km 3 DRE). Whole-rock chemical analyses indicate alkali-basalt compositions (SiO 2 44.7-45.9 wt%), with little compositional variation and no relationship between chemistry and eruptive styles. Small differences in composition may reflect variations in fractional crystallisation of clinopyroxene and olivine. A magnetotelluric 2D cross-section shows that the cones are located adjacent to a buried sediment-filled alluvial channel along a NNW-SSE fault dipping to the east. The AlDu'aythah eruption was related to the ascent of magma through this structure, with the first phase of the eruption triggered by the interaction of the magma with water from the northern Harrat Rahat aquifer that exists in the AlMadinah basin. This initial water source was rapidly exhausted, while the eruption progressed roughly from north to south and from west to east, the latter motion probably along the fault-controlled feeding dyke. Our work draws attention to the existence of recent explosive phreatomagmatic eruptions in the Al-Madinah basin, which, despite the hyperarid climate of the area, must be considered a potential future eruption hazard.

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“…Temperature estimates are based on the (dry) equation of Helz and Thornber (1987) recalibrated by Putirka (2008). Dissolved water content was calculated from the plagioclase hygrometer of Lange et al (2009) at 50 MPa. This pressure corresponds to the average CO 2 -H 2 O saturation pressure (recalculated with Papale et al, 2006) typically recorded in MIs from central products at PdF (e.g.…”

Section: Mineral Composition and Glass -Plagioclase Equilibriummentioning

confidence: 99%

“…Glassy outer surfaces of clasts have been interpreted as a late-stage product of fusion by Helz and Thornber (1987) modified by Putirka (2008). Water content is from the plagioclase hygrometer of Lange et al (2009). Only plagioclases in equilibrium with melts are considered, following the procedure described by Putirka (2008) for > 1050 • C melts (Kd = 0.27 ± 0.05).…”

Section: Eruptive Dynamicsmentioning

confidence: 99%

Response to Madison Myers

Gurioli¹

2017

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Identifying multiple eruption phases from a compound tephra blanket: an example of the AD1256 Al-Madinah eruption, Saudi Arabia

Cited by 35 publications

References 35 publications

Investigating physical and thermal interactions between lava and trees: the case of Kīlauea’s July 1974 flow

Investigating physical and thermal interactions between lava and trees: the case of Kīlauea’s July 1974 flow

The Al-Du’aythah volcanic cones, Al-Madinah City: implications for volcanic hazards in northern Harrat Rahat, Kingdom of Saudi Arabia

Response to Madison Myers

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