Volcanic Hazards

     Many people believe that Saudi Arabia physiographic features are only great sand seas and might not associate it with volcanic activities.

In fact, vast volcanic fields, known in Arabic as the harrat, emerged during the Cenozoic Era as a consequence of the rifting and drifting

of the Arabian plate away from the African plate which led to the formation of the Red Sea and the volcanically active passive continental

margin on western Arabia (Figure 1). Volcanic activity spanned over a large period from the Oligocene (30 Ma) to historical times.

In Saudi Arabia, the volcanic fields extend from its northern borders with the Levant to its southern borders with Yemen. There are 13

distinct volcanic fields in western Saudi Arabia that cover an approximate area of 89,670 km² with an estimated total volume of eruptive

material of about 103 to 105 km³ (Table 1). Fortunately, most of the volcanoes are extinct; very few had erupted more than 1,000 years

ago and only one erupted in AD 1256.

Table (1): Cenozoic Volcanic Fields in Western Saudi Arabia

     Harrat Khaybar is considered as one of the most spectacular volcanic fields in Saudi Arabia (Figure 2). Its landscape is dominated by

Jabal Qidr, which is a hawaiite stratovolcano believed to have erupted in historic times. The dark lava field of Jabal Qidr juxtaposes the

white comenditic ash and lapilli plains of the nearby White Mountains of Jabal Abyad and Jabal Bayda.

The significance of Harrat Rahat emerges from the fact that its northern fringes, where the historical eruption of the AD 1256 took place,

are very close to Al-Madinah Al-Munawarah (Figure 3). The eruption, which lasted for 52 days, extruded 0.5 km³ of alkali-olivine

basalt from a 2.25 km-long fissure and produced 7 scoria cones and a 23 km long lava flow that came to within 8 km from

Al-Madinah Al-Munawarah (Figure 4).

Between April and June 2009, a swarm of more than 30,000 earthquakes struck the lava field of Harrat Lunayyir in northwestern

Saudi Arabia (Figure 5). During the peak activity on May 19, 2009, nineteen earthquakes of M4.0 or greater struck the region, including

an M 5.4 event, which caused minor damages to structures in the town of Al Ays (40 km southeast of the epicenter). Concurrently,

a northwest-trending 8-km-long surface rupture with 91 cm of offset propagated across the northern part of the volcanic field (Figure 6).

     The ensuing geologic and geodetic studies suggested that the earthquake swarm resulted from a shallow magmatic intrusion of a

north-west trending dyke of about 12 km in length and a maximum thickness of 2.5 meters where two normal faults bound a

wedge-shaped graben above the arrested dyke. One of the most recent studies, however, suggests that both dyke emplacement and

normal faulting were partly triggered by a regional extensional loading. The study also inferred that the dyke tip became arrested at

a depth of only a few hundred meters concluding that the dyke, on its own, could not have generated the entire 3–7 km wide fracture

zone associated with the 2009 episode. The same study estimated the thickness of the dyke at shallow depths as being in the

range of 6–12 m with inferred strike dimension (length) of 14 km and dip dimension (or depth) in the excess of 20 km.

References:

Al Shehri, A. and Gudmundsson, A., 2018. Modelling of surface stresses and fracturing during dyke emplacement: Application to the

2009 episode at Harrat Lunayyir, Saudi Arabia. Journal of Volcanology and Geothermal Research, 356, 278–303.

Baer, G. and Hamiel, Y., 2010. Form and growth of an embryonic continental rift: InSAR observations and modelling of the 2009

western Arabia rifting episode. Geophysical Journal International, 182, 155-167.

Camp, V.E. and Roobol, M.J., 1989. The Arabian continental alkali basalt province: Part I. Evolution of Harrat Rahat, Kingdom of

Saudi Arabia. Geological Society of America Bulletin, Vol. 101, pp. 71-95.

Camp, V.E., Hooper, P.R. Roobol, M.J., and White, D.L., 1987. The Madinah eruption, Saudi Arabia: Magma mixing and

simultaneous extrusion of three basaltic chemical types. Bulletin of Volcanology, Vol. 49, pp. 489-508.

Camp, V.E., Roobol, M.J., and Hooper, P.R., 1991. The Arabian continental alkali basalt province: Part II. Evolution of Harrats Khaybar,

Ithnayn, and Kura, Kingdom of Saudi Arabia. Geological Society of America Bulletin, Vol. 103, pp. 363–391.

Coleman, R.G., Gregory, R.T., and Brown, G.F., 1983. Cenozoic volcanic rocks in Saudi Arabia. Ministry of Petroleum and

Mineral Resources, Deputy Ministry for Mineral Resources, Jeddah, Kingdom of Saudi Arabia, Open-File Report, 83-788.

Moufti, M.R. and Nemeth, K., 2014. The White Mountains of Harrat Khaybar, Kingdom of Saudi Arabia. International Journal of

Earth Sciences (Geol. Rundsch.), 103, 6, 1641–1643.

Moufti, M.R., Németh, K., Murcia, H., Lindsay, J.M., and El-Masry, N., 2013. Geosite of a steep lava spatter cone of the 1256 AD,

Al Madinah eruption, Kingdom of Saudi Arabia. Central European Journal of Geosciences, 5, 2, 189-195.

Pallister, J.S., McCausland, W.A., Jónsson, S., Lu, Z., Zharan, H.M., El Hadidy, S., Aburukbah, A., Stewart, I.C.F., Lundgren,

P.R., White, R.A., and Moufti, M.R.H., 2010. Broad accommodation of rift-related extension recorded by dyke intrusion in

Saudi Arabia. Nature Geoscience, DOI: 10.1038/NGEO966, 8 pp.

Online Sources:

1.    http://www.sgs.org.sa/English/Earthquakes/Pages/Volcanoes.aspx

2.    http://www.volcano.si.edu/volcano.cfm?vn=231040

3.    http://traversingtherazor.wordpress.com/2010/10/20/earthquakes-and-volcanoes-in-saudi-arabia/

4.    https://www.google.com/search?q=harrat+saudi+arabia&rlz=1T4GPCK_enUS344US345&tbm=isch&tbo=u&source=univ&sa=X&ei=IFyPU_nHBaLMsQT0pYD4Ag&ved=0CG0QsAQ&biw=1413&bih=730

5.    https://zoom.earth/#25.670598,39.943024,13z,sat

6.    https://zoom.earth/#24.439154,39.681185,12z,sat

7.  https://zoom.earth/#25.130341,37.845871,11z,sat