Eruption Scenarios of a Monogenetic Volcanic Field Formed within a Structurally Controlled Basement Terrain: Harrat Lunayyir, Saudi Arabia

Abstract

Lunayyir Volcanic Field is one of the youngest (~600 ka to Historic) Cenozoic mafic intracontinental volcanic fields in the western margin of the Arabian Microplate. It consists of about 150 volcanic edifices that worked around 700 vents indicating strong vent alignments and potential longevity of activity to build each of its volcanoes. The volcanoes are strongly aligned following the Neoproterozoic basement structure determining the surface valley network that commonly captured lava flows. The volcanoes are typical magmatic effusive and explosive types of volcanoes ranging from minor fissure vents of spatter ramparts to complex multi-crater scoria cones. Effusive hazards are dominated by transitional lava flows with restricted pāhoehoe and ‘a‘ā lava emplacement while explosive eruptions are spatter cone formation with lava fountaining, scoria cone growth and destruction, paroxysmal sub-Plinian and/or violent Strombolian style activity, directed ballistic curtain formation and a possibility of development of passive volcanic fog (vog). According to these eruption types, effusive eruption scenarios are the most likely and long-term impactful events, while explosive eruptions are dominated by low intensity low impact scenarios. The area however shows evidence of extensive tephra blanket that explosive phases capable to reach volcanic explosivity index (VEI) 4 capable to carry ash away over 250 km.