The geological evidence. Author Gill has noted that much of Masada’s western spur consists of natural rock; the Romans had to add relatively little to the spur in order to reach the top of Masada. On the photo, looking north, Gill has marked the crucial evidence: Line A is a fault, dividing Masada, at right, from rock layers that used to adjoin it but which fell millions of years ago along the fault. B1 and B2 are two sections of the same rock formation (Bina), split by the fault. C1, C2 and C3 are surviving outcrops of the Menuha Formation, which sits above the Bina Formation west of the fault and which used to sit above the section of the Bina that makes up Masada; because the Menuha Formation (and the Mishash Formation that lies above it) consists of soft rock, erosion over a very long time has removed it from atop Masada and is in the process of removing it from west of Masada as well. D marks the Roman ramp.