6 Dr. John Ball— The Gulf of Suez. 



In his recent paper dealing with the Nile Yalley 1 my friend and 

 colleague Dr. Hume, while agreeing entirely with me in the erosive 

 origin of that valley, has mentioned two considerations which cause 

 him to hesitate about accepting a similar origin for the Gulf of Suez. 

 These are, firstly, the distribution of the Miocene beds, especially 

 their absence from the Wadi Araba, and secondly, a difficulty in 

 conceiving of erosion cutting through the dome or anticline which 

 existed across the gulf, unless aided by fracture. These difficulties 

 are easily explained. 2 As regards the distribution of the Miocene, 

 much has yet to be done before a true picture of it is obtained. 

 "Where, as usually happens, the Miocene beds overlie older limestones, 

 the limits are very difficult to trace in the field, the fossils, which are 

 often extremely scarce, being the only guide. But from Mr. Barron's 

 maps of Western Sinai it is apparent that the Miocene beds which cap 

 the hill-ranges of the Sinai coast of the gulf dip inland, and thus we 

 must infer that the deposition of the Miocene limestones antedated the 

 folding which gave rise to the dome or anticline. Now since there is 

 every reason to believe that the erosion of the Wadi Araba, like that 

 of the gulf, occurred after the folding, the absence of Miocene beds 

 from it is exactly what the erosion hypothesis requires for its support. 

 Turning next to the conception of erosion cutting through the dome 

 without fracture, I would remark that fracture at the top of the dome 

 or anticline is quite possible ; in fact, the weakening of the beds at 

 the top of the arch under tension is probably the key to why the 

 drainage-line assumed its actual position. I am not, however, now 

 concerned with the causes which determined the position of the 

 drainage-lines along which erosion went on, my point being only 

 to show that erosion, and not trough-faulting, has removed the 

 beds which formerly stretched across the gulf. And fracture is not 

 trough-faulting. The fracture at the top of an anticline is brought 

 about in an entirely different manner from a trough-fault, the one 

 heing due to tension by bending of the beds under tangential pressure, 

 the other to shearing by radial subsidence. Moreover, we cannot get 

 away from the fact that the Wadi Araba has actually cut through the 

 same dome or anticline, its drainage-line, in fact, going inwards from 

 the edge to near the centre of the dome ; and what has actually 

 happened in the case of the Wadi Araba is surely not inconceivable, 

 but rather likely, in the case of the valley which gave rise to the Gulf 

 of Suez. 



I would remark that in arguing that the Gulf of Suez is not due to 

 trough-faulting, and that the faults which bound it along the edge of 

 the North Galala plateau are merely huge landslips and not true 

 faults, I am very far from stating that no true faults are to be found 

 in the lands bordering the gulf. True faults do occur on both sides, 

 especially in Sinai, and possibly they may exist even in the gulf itself; 



1 Geol. Mag., Dec. V, Vol. VII, p. 388, 1910. 



2 I regret that owing to our separation for a long period I did not have the 

 opportunity of explaining these difficulties to Dr. Hume before he published his 

 paper. To English readers it will appear strange, but when one of two workers is in 

 Cairo and the other is in the desert, they are frequently much further apart as regards 

 time of communication than if one were in England and the other in Khartoum. 



