Mohammed Rashad Moufti

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

It has been drawn to our attention that the simple calculation of volume from the naïve isopachs (Fig. 2) by means of the Pyleogram contains an error (a factor of pi). The actual volume thus calculated should be 0.0077 km. This error is not propagated into the remainder of the analysis, where volumes were calculated via direct numerical integration from the contours imputed from our model (Fig. 12). These are far more extensive than those in Fig. 2, particularly in the West, East and especially South directions. Hence the volume calculated for these is approximately a factor of 3 larger.

Volcanic Geotopes and Their Geosites Preserved in an Arid Climate Related to Landscape and Climate Changes Since the Neogene in Northern Saudi Arabia: Harrat Hutaymah (Hai’il Region)

Maars and tuff rings are some of the most common volcanic landforms on Earth. They are inferred to be the product of the explosive interaction between rising magma (mostly basaltic) and various groundwater sources or surface water bodies. Maar and tuff ring volcanoes are commonly associated with extensive scoria cone fields that are fed by dispersed volcanic vents, providing access to the surface for magma over a long period of time (thousands to millions of years’ timescale). The presence of maar and tuff ring volcanoes, therefore, is an important signifier of the availability of water from sub-surface and/or surface water sources. As environmental conditions change over time, the groundwater table, as well as surface water availability, can change dramatically and this is likely be reflected in the type of volcanoes formed on the surface. Such changes are the most graphic and visible in volcanic fields that are today located in arid environments, where the presence of young volcanoes formed through interactions with water demonstrates how the environment can change over geological timescales. Therefore, these areas have high geoeducational values and can contribute to our understanding of how external (water sources controlled by climatic factors) and internal (magmatic) forces can shape the style of volcanism of a volcanic field. Harrat Hutaymah is one of the excellent locations where there is great abundance of maars and tuff rings. They are located in an area dominated today by various types of deserts. Harrat Hutaymah, therefore, demonstrates the global geological changes that can affect the style of volcanism and hence the resulting volcanic landscape. The richness of the region in archaeological sites and early settlements indicates the importance of this region for the early evolution of civilizations in the Middle East, which is likely to have been enhanced and/or modified by similar environmental changes over a much smaller timescale. Harrat Hutaymah provides a firm basis to demonstrate global changes through its volcanic heritage that are easily accessible and well exposed.

Geoheritage values of one of the largest maar craters in the Arabian Peninsula: the Al Wahbah Crater and other volcanoes (Harrat Kishb, Saudi Arabia)

Al Wahbah Crater is one of the largest and deepest Quaternary maar craters in the Arabian Peninsula. It is NW-SE-elongated, ∼2.3 km wide, ∼250 m deep and surrounded by an irregular near-perpendicular crater wall cut deeply into the Proterozoic diorite basement. Very few scientific studies have been conducted on this unique site, especially in respect to understanding the associated volcanic eruption processes. Al Wahbah and adjacent large explosion craters are currently a research subject in an international project, Volcanic Risk in Saudi Arabia (VORiSA). The focus of VORiSA is to characterise the volcanic hazards and eruption mechanisms of the vast volcanic fields in Western Saudi Arabia, while also defining the unique volcanic features of this region for use in future geoconservation, geoeducation and geotourism projects. Al Wahbah is inferred to be a maar crater that formed due to an explosive interaction of magma and water. The crater is surrounded by a tephra ring that consists predominantly of base surge deposits accumulated over a pre-maar scoria cone and underlying multiple lava flow units. The tephra ring acted as an obstacle against younger lava flows that were diverted along the margin of the tephra ring creating unique lava flow surface textures that recorded inflation and deflation processes along the margin of the post-maar lava flow. Al Wahbah is a unique geological feature that is not only a dramatic landform but also a site that can promote our understanding of complex phreatomagmatic monogenetic volcanism. The complex geological features perfectly preserved at Al Wahbah makes this site as an excellent geotope and a potential centre of geoeducation programs that could lead to the establishment of a geopark in the broader area at the Kishb Volcanic Field.

Geosite of a steep lava spatter cone of the 1256 AD, Al Madinah eruption, Kingdom of Saudi Arabia

UNESCO promotes geoconservation through various programs intended to establish an inventory of geologically and geomorphologically significant features worldwide that can serve as an important database to understand the Earth’s global geoheritage. An ultimate goal of such projects globally is to establish geoparks that represent an integrated network of knowledge transfer opportunities, based on a specific array of geological and geomorphological sites able to graphically demonstrate how the Earth works to the general public. In these complex geoconservation and geoeducational programs, the identification of significant geological and geomorphological features is very important. These are commonly referred to as ‘geosites’ or ‘geomorphosites’, depending on whether the feature or processes the site demonstrates is more geological or geomorphological, respectively. The Kingdom of Saudi Arabia is an extraordinary place due to its arid climate and therefore perfect exposures of rock formations. The Kingdom is also home to extensive volcanic fields, named “harrats” in Arabic, referring particularly to the black, basaltic lava fields that dominate the desert landscape. Current efforts to increase awareness of the importance of these volcanic fields in the geological landscape of Arabia culminated in the first proposal to incorporate the superbly exposed volcanic features into an integrated geoconservation and geoeducation program that will hopefully lead to the development of a geopark named, “The Harrat Al Madinah Volcanic Geopark” [1]. Here we describe one of the extraordinary features of the proposed Harrat Al Madinah Volcanic Geopark, namely a steep lava spatter cone formed during a historical eruption in 1256 AD.

The 1256 AD Al Madinah historic eruption geosite as the youngest volcanic chain in the Kingdom of Saudi Arabia

Volcanic geosites, geomorphosites and geotops are the smallest ‘‘units’’ of intact geological features that are identifiable through their uniqueness, or because they are graphic examples of specific volcanic phenomena, or form a vital landscape representative of a specific volcanic processes. Here, we identify significant volcanic features that bear not only regional, but global, volcanic value in a confined area that could be organized and promoted as the first volcanic geopark in the Kingdom of Saudi Arabia: the Harrat Al Madinah Volcanic Geopark (HAMVG). Harrat Al Madinah (‘‘harrat’’ in Arabic means lava field) is among many intraplate basaltic volcanic fields (Camp and Roobol 1989; Camp et al. 1991, 1992) that are located in the western margin of the Arabian Peninsula forming a broad zone sub-parallel to the Red Sea Rift (Fig. 1), which has been active over the last 30 Ma. These harrat fields are relatively thin (typically \300 m) but cover vast areas, the largest of which is *60,000 km. The proposed HAMVG has many spectacular volcanic geosites including the last historically erupted volcanoes in the Kingdom of Saudi Arabia (Camp et al. 1987; Moufti et al. 2012). The 1256 AD eruption site is located near to the culturally significant Al Madinah city (*1.5 million population), which is one of the holiest places to Muslims. A major geotop tentatively named as ‘‘The 1256AD Al Madinah Historic Eruption Site’’ with distinct individual geosites/ geomorphosites has been selected to demonstrate the diversity of volcanic phenomena associated with intraplate volcanism of the Al Madinah Volcanic Field. Hawaiian to Strombolian type eruptions created lava spatter and scoria cones visible from major highways, allowing visitors to stop near the 1256 AD historic eruption site just 10 km SE of Al Madinah (Fig. 1). The historically documented eruption lasted for 52 days and formed a *2.25 km long chain of NW–SE-aligned scoria and lava spatter cones (Fig. 2), producing alkali-olivine basalt (*0.5 km) a0a and pahoehoe lava flows (Camp et al. 1987). At least seven cones have been identified. Most of them are nested lava spatter and scoria cones such the largest cone in the northern edge of the fissure shown on Fig. 2. A combination of energetic explosive eruptive episodes (violent Strombolian-style eruptions) interrupted by less explosive lava fountaining, lava flow outbreaks and corresponding volcanic cone rafting formed a moon-like

The White Mountains of Harrat Khaybar, Kingdom of Saudi Arabia

benmoreite lava flows, domes, and dome coulees (Fig. 1b, c, d). the “White Mountains” refer to a pair of comenditic volcanoes (Baker et al. 1973; Camp et al. 1991): Jabal Abyad (Fig. 1b) and Jabal Bayda (Fig. 1c, d). Both Arabic names mean “White Mountain,” with Abyad a masculine and Bayda a feminine form of white in Arabic reflecting that Jabal Bayda is a near perfect circular tuff ring with a shallow crater, while Jabal Abyad is a lava dome complex that forms a hill standing about 300 m above the surroundings. Jabal Abyad is the highest volcano of Harrat Khaybar, reaching 2,093 m above sea level, while Jabal Bayda is 1,913 m high. their age is poorly constrained, but inferred to be between 0.86 and 0.22 My (Camp et al. 1991). While felsic lava domes and tuff rings exist elsewhere (Austin-Erickson et al. 2011; Riggs and CarrascoNunez 2004), the significance of the felsic intracontinental volcanism of the Arabian Peninsula is great in terms of understanding the evolution of dispersed magma in nearsurface compositionally zoned magma chambers (Camp et al. 1991). A recently initiated Arabia Geoparks Project managed by Afaaq Consulting at King Abdulaziz University in Jeddah demonstrated the high geoeducational value of the volcanic landforms of western Arabia and how these could be utilized to understand volcanic hazards and geoconservation (Moufti and Németh 2013). the “White Mountains” of Harrat Khaybar will be flagship geotopes with numerous geosites in the provisional volcanic geopark of the region. the dominant rock types of the western Arabian Miocene to recent intracontinental volcanic fields are hawaiite, but subordinate, more felsic rock types, such as benmoreite, mugearite and trachyte, are also known, especially in the largest volcanic fields with the most complex volcanic stratigraphy, such as the Harrat Khaybar (Camp et al. 1991) (Fig. 1a). Harrat Khaybar basal volcanics formed the Jarad Basalt (5–3 Ma) that is overlain by the Murash Basalt (3–1 Ma), and it is capped by the Abyad Basalt (1 Ma—Recent) (Camp et al. 1991). Harrat Khaybar has the most prominent felsic volcanoes of the Arabian Peninsula erupted from a compositionally zoned near-surface magma chamber along an N–S fault zone in the central part of the field (Camp et al. 1991). the “White Mountains” of Harrat Khaybar are strikingly different in their appearance and their eruption history to the most landscape-dominant volcano of the field, the Jabal Qidr, which is a hawaiite stratovolcano and believed to have erupted in historic time and emitted dark lava fields (Camp et al. 1991) that are banked against the white comenditic ash and lapilli plain associated with the “White Mountains.” the “White Mountains” are composed of comenditic lavas including short, but thick obsidian lava flows and pyroclastic successions composed of intercalated small-volume block-and-ash flow, pyroclastic density current and minor air fall units that form very distinct volcanic landforms with white and beige-to-orange colors, making them stand out from the otherwise dark hawaiite, mugearite and

Geology and geochemistry of Late Quaternary volcanism in northern Harrat Rahat, Kingdom of Saudi Arabia: implications for eruption dynamics, regional stratigraphy and magma evolution

Abstract Harrat Rahat (<10 Ma) is one of the largest volcanic fields on western Arabia. In the north of the field, some of the youngest volcanic centres evolved through either point-like, complex or multiple aligned vents (i.e. along fissures), and have pyroclastic cones, lapilli fall deposits and/or lava flows associated with them. The products reflect dominantly Hawaiian eruptions, and only one centre experienced phreatomagmatism. Results from new 3He surface-exposure dating provide constraints on stratigraphy of the youngest (<0.3 Ma) products. The rocks are compositionally alkali-basalt and hawaiite, with intra-plate basalt (prevalent mantle (PREMA)) affinity. Each eruption displays a distinct whole-rock composition in an overall linear trend. We suggest that the magma source for each centre is similar, and that composition of the products is different due to different degrees of fractionation. In a single eruption, the magma that reaches the surface first is the least evolved, with the most evolved magma erupting last. We also found that the most primitive magmas erupt less explosively. We think that the degree of magma evolution might correlate with ascent times, assuming that the more evolved magma spent more time en route. We suggest that magma ascent time is likely to be longer than that of other more primitive intra-plate basalts. Supplementary material: Whole-rock chemistry results, mineral chemistry results and fractional crystallization modeling data are available at https://doi.org/10.6084/m9.figshare.c.3488988

Synthesis of the Geoheritage Values of the Volcanic Harrats of Saudi Arabia

Western Saudi Arabia is the home of extensive volcanic fields with hundreds of well-preserved volcanic landforms (Camp and Roobol 1989a; Camp et al. 1991; Camp and Roobol 1992; Camp et al. 1992; Alwelaie 1994; Bosworth et al. 2005).

Volcanic Geoheritage of Other Harrats of Kingdom of Saudi Arabia

Other than the intensive volcanological and geoheritage studies on Harrat Rahat (Moufti and Nemeth 2013; Moufti et al. 2013b; Murcia et al. 2014, 2015), only preliminary research has been done to document the volcanic geoheritage value of harrats in western Saudi Arabia.

Harrat Rahat: The Geoheritage Value of the Youngest Long-Lived Volcanic Field in the Kingdom of Saudi Arabia

Harrat Rahat is a volcanic field that consists of over 500 individual volcanoes (Fig. 3.1), many of them with multiple vents forming compound edifices (Camp and Roobol 1989; Coleman and Gregory 1983; El Difrawy et al. 2013; Moufti et al. 2013a). Harrat Rahat was formed over the past 10 million of years (Moufti et al. 2013a), and it is still considered to be an active volcanic region as it has had at least two historic eruptions (Camp et al. 1987; Moufti et al. 2013a). The volcanic field consists of extensive lava fields (Murcia et al. 2014) and various types of volcanic cones and explosion craters (Camp et al. 1991; El Difrawy et al. 2013; Moufti and Hashad 2005; Moufti et al. 2011), each of them is perfectly exposed due to the arid climate and lack of vegetation, and many of them are relatively easy to access (Fig. 3.2). The field is located nearby one of the holiest cities of Islam—Al Madinah—and also hosts the youngest volcanoes in the Kingdom of Saudi Arabia, which have historical and cultural significance (Fig. 3.1). Harrat Al Madinah is the northern part of the Harrat Rahat and the best studied in the Harrat Rahat. The distinction between Harrat Rahat and Harrat Al Madinah is loosely constrained and it has a traditional and geographic connotation rather than geological reasoning. In a similar way, different parts of Harrat Rahat have local names that refer to nearby settlements or other geographical features.