Bulletin of the Geological Society of Malaysia, Volume 71, May 2021, pp. 71 - 78 DOI: https://doi.org/10.7186/bgsm71202106 0126-6187; 2637-109X / © 2021 Geological Society of Malaysia. All rights reserved. Overview of slope stability, earthquakes, fash foods and expansive soil hazards in the Republic of Yemen Hussein Ahmed Hasan Zaid * , T.A. Jamaluddin, Mohd Hariri Arifin Geology Programme, Faculty of Science and Technology, National University of Malaysia (UKM), 43600 Selangor, Malaysia * Corresponding author email address: hussenhassan2012@gmail.com Abstract: Yemen has harsh natural conditions that increase certain geological processes more than other regions, leading to a variety of geological hazards. Yemen’s typical topography is distinguished by coastal plains of the Red Sea and clif foothillls, followed by mountains of the Arabian Shield. These types of geological hazards can be classifed into slope stability, earthquakes, fash foods and expansive soils. The current literature review presents a description backed with examples of the certain geological hazards in Yemen. The obtained results indicate that further consideration and thought are highly required for semi-arid regions. National and foreign organizations have to collaborate together with other individuals to maintain the adjusted environmental system and reduce the potential geological hazards. Therefore, mitigation measures should be implemented to avoid and minimize these geological hazards. Keywords: Hazards, Yemen, fash foods, slope stability, expansive soils, earthquakes INTRODUCTION Geological hazards often occur where severe and extreme weather changes, climate events, earthquakes, volcanic eruptions and mountain-building movements occur naturally in many parts of the world and determine the topographic and geomorphological characteristics of the earth. These hazards are caused, controlled or associated with the geological factors that may cause loss of life or property damages (Dhakal, 2013). Rockfall hazards are a frequent phenomenon in mountainous regions. The lack of awareness of the magnitude and frequency of the rockfall undoubtedly endangers people’s lives and causes devastating damage to the infrastructure. There are several examples to prove the plausibility of infrastructures damaged or people killed by rockfalls (e.g., Mignelli et al., 2012; Mackey & Quigley, 2014; Ferrari et al., 2016). By defnition, the rockfall is considered a moderately small landslide limited to the particular removal of rocks from a clif face (Selby, 1982). When the rockfall exists in a large-scale mass movement, it is defned as rockslides or rock avalanches (Abele, 1994; Cruden & Varnes, 1996). Mitigation measures against rockfalls can be taken by constructing barrier fences, retaining walls and restraining nets (Hearn et al., 1992; Spang & Sonser, 1995; Peila et al., 1998). The tectonic movement and divergence of African plate and Arabian plate, comprising rifts of the Red Sea and Aden Gulf, are the main reason of earthquakes in Yemen, located in the south part of the Arabian Peninsula (Figure 1), which are common from historical sources over the last millennia (Mohindra et al., 2012). Earthquakes that strike Yemen are primarily related to rifts of the Red Sea and the Aden Gulf (Adams & Barazangi, 1984). Flash food is also one form of geological hazards, it killed many inhabitants in the south and north of Yemen and caused devastating infrastructure damages. Lastly, in this literature, expansive soil is addressed as a potential natural hazard, which can cause huge damage to infrastructures if it is not properly managed. The present work focuses on evaluating the geological hazards in Yemen. The paper presents a review of the causes and impacts of these hazards, which are classifed into slope stability, earthquakes, fash foods and expansive soils. However, a discussion of issues such as subsidence, fssures, karst and sand accumulations are beyond the scope of this paper. GEOLOGICAL HAZARDS Slope stability hazards Transport structures, like roads and highways, are vulnerable to rockfalls and rockslides where they cross mountains, hills, edges and the similar topographic characteristics (Bunce et al., 1997; Hungr et al., 1999; Youssef & Maerz, 2013). Rockfall starts at the separation of rock from bedrock slopes. All bedrock slopes are afected by varying weathering degrees, which may trigger joints and fractures, thus they contribute to advancement of the rockfalls. The triggering degree is dependent on the environmental factors that lead to weathering, and on bedrock types (Day, 1997; Dorren, 2003; Pradhan & Fanos, 2017). Furthermore, earthquake activities and high groundwater pressure (after heavy rainstorms) will cause high slope failure risks (Youssef & Maerz, 2013; Islam et al., 2019). In this literature, various mechanics that initiated rockfall in Yemen have already been demonstrated.