Area 51 old photos mystery runway

Older photos of Area 51:

September 8, 2005

Area 51 in 1958

Ten years later, in 1968. The runway had been extended.

Focusing on the upper-left section, the details are unclear.

In A, the runway appears "blocked off." In B, it extends into a "ravined" area. In C, the shading suggests this extension—remember, the runway is 30 meters wide—lies within a depressed section. It's hard to see how a 30-meter-wide runway, or aircraft using it, could function properly in such a setting. But then, what purpose would this section serve? Could it be a horizontal extension of the runway, intended to be covered later? We can compare this with a more recent view (Google Earth):

End of the 8.2 km runway, more recent. Date unknown

If there was a runway extension in a ravine, it might have been covered later, since a road now runs over it. Mystery...