Underrated volcanic hazard role of fissure eruptions, paired eruptions, and dynamic vent zone formation of dispersed volcanic fields of western Saudi Arabia

Dispersed volcanic fields are common in continental regions, consisting of dozens to hundreds of short-lived volcanoes that produce effusive and moderately explosive eruptions with small volumes of eruptive material. This type of volcanism is often considered monogenetic, meaning each eruption is brief and triggered by specific melting events reaching the surface. Western Arabia hosts a large volcanic province with over 13 Quaternary fields, stretching more than 2,000 km and containing more than 1,500 volcanoes, some of which erupted just a few hundred years ago. With a clear record of Pleistocene-to-Holocene eruptions in a rapidly urbanizing and developing area (e.g., AL Madinah City) that is also becoming popular for tourism, volcanic risk is rising as more people are exposed to hazards. Volcanic hazard assessment typically aims to forecast eruptions over decades or centuries, or to identify likely eruption sites using probabilistic models, which require extensive eruption data and an understanding of the spatial and temporal evolution of the volcanic fields—both of which are currently incomplete. About 5,000 post-Pliocene vents have been identified, suggesting that most volcanoes have multiple vents, leading to complex structures and eruptive products. Geological mapping of volcanoes at the volcano level is therefore crucial for understanding hazard scenarios for individual volcanoes. Recent regional mapping of Saudi Arabia’s Quaternary volcanism (at scales of 1:100,000 and beyond) has revealed frequent paired eruptions (most among the youngest events) and fissure-aligned events (tracing fissures from a few hundred meters to around 20 km), indicating eruptions along narrow fissures (in a zone less than few km wide) over limited periods (in an estimated decades-to-centuries-long eruption duration), thereby confining activity to narrow zones (few km wide) over long timescales (through millenia). The high-resolution mapping (at the volcanic edifice scale, at 1:20,000 or beyond) has also shown that eruption points and edifice growth often involve volcanic spreading, collapse, and paired sub-Plinian explosions followed by lava flows, resulting in highly complex aligned volcanic vent zones over short time spans (months to centuries). These findings highlight the importance of detailed fissure mapping to understand eruption scenarios, which is essential for volcanic hazard preparedness.