, ▁un con sol id ated ▁sed iment ▁aqu if ers ▁up ▁to ▁ 1 0 0 ▁meters ▁thick ▁formed ▁in ▁the ▁past ▁ 2 . 5 ▁million ▁years ▁of ▁the ▁Qu atern ary ▁in ▁w adi ▁locations ▁throughout ▁the ▁county . ▁F ract ured ▁Ple ist oc ene ▁bas alt ▁flows , ▁particularly ▁near ▁Las ▁D h ure ▁and ▁Ag ab ar ▁have ▁potential ▁as ▁aqu if ers . ▁The ▁Yes om ma ▁Sand stone ▁is ▁a ▁high ▁product ivity ▁aqu ifer . ▁ ▁Four teen ▁water ▁util ities ▁serve ▁towns ▁in ▁Som al il and ▁and ▁neighbor ing ▁P unt land , ▁although ▁at ▁least ▁ 7 5 0 , 0 0 0 ▁people ▁on ▁the ▁out sk ir ts ▁of ▁Har ge isa ▁lack ▁pip ed ▁water . ▁ ▁Natural ▁resource ▁ge ology ▁M ining ▁is ▁not ▁a ▁significant ▁part ▁of ▁the ▁economy ▁of ▁Som al il and . ▁During ▁British ▁administration ▁of ▁Som al il and , ▁ge olog ists ▁Thompson ▁and ▁Bell ▁launched ▁initial ▁hydro car bon ▁research ▁in ▁ 1 9 1 8 . ▁The ▁Ang lo - Pers ian ▁O il ▁Company ▁initi ated ▁a ▁large ▁scale ▁mapping ▁project ▁of ▁the ▁G ub an ▁Bas in ▁in ▁ 1 9 2 0 . ▁▁ ▁Com pre h ensive ▁ge olog ic ▁reports ▁were ▁made ▁available ▁in ▁ 1 9 5 4 ▁by ▁the ▁Ge ological ▁Survey ▁of ▁British ▁Som al il and ▁and ▁Som al il and ▁O il ▁Ex pl oration ▁Company . ▁Rel atively