Reconstructing lava flow emplacement histories with rheological and morphological analyses: the Harrat Rahat volcanic field, Kingdom of Saudi Arabia

Bulletin of Volcanology
By: , and 

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Abstract

Mafic volcanic fields are widespread, but few have erupted in historic times, providing limited observations of the magnitudes, dynamics, and timescales of lava flow emplacement in these settings. To expand our knowledge of effusive mafic eruptions, we must evaluate solidified flows to discern syn-eruptive conditions. The Harrat Rahat volcanic field in western Saudi Arabia offers a good opportunity for this, with a historical eruption in 1256 CE and many well-preserved prehistoric flows. We combine historical observations and rheological and morphological analyses of the youngest flows with analytical models to reconstruct eruptive histories and lava flow emplacement conditions in Harrat Rahat. Petrologic analysis of samples for emplacement temperatures and crystallinities shows cooling trends from vent to toe of ~ 1140 to ~ 1090 °C at rates of 2–7 °C km−1, crystallinities increasing from 0.5 to 60%, and apparent viscosities increasing from 102 to 109 Pa s. High-resolution topographic data facilitates quantitative analysis of morphology and interpolation of pre-eruptive surfaces to measure flow thicknesses, channels, and levees, and enables calculation of eruptive volumes. Analytical models relating flow morphology to emplacement conditions are applied to estimate effusion rates. Within the suite of studied flows, volume estimates range from 0.07 to 0.42 km3dense rock equivalent, with effusion rates on the order of 10 to 100 s of m3 s−1 and durations from 1 to 15 weeks. These integrated analyses quantify past lava flow emplacement conditions and dynamics in Harrat Rahat, improving our understanding and observations of fundamental parameters and controls of effusive eruptions in mafic volcanic fields.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Reconstructing lava flow emplacement histories with rheological and morphological analyses: the Harrat Rahat volcanic field, Kingdom of Saudi Arabia
Series title Bulletin of Volcanology
DOI 10.1007/s00445-018-1259-4
Volume 80
Year Published 2018
Language English
Publisher Springer
Contributing office(s) Volcano Science Center
Description Article 55; 23 p.
First page 1
Last page 23
Country Saudi Arabia
Other Geospatial Harrat Rahat