Architectural Geology of Segovia, Spain, Part 2: The Segovia Aqueduct (ca. early 2nd Century AD)
In contrast to the first image of this set, this shot was taken on the eastern side of the Aqueduct. It faces south.
As noted in other photo descriptions, I find myself more and more drawn into the immortality of frozen time, as embodied in the human figures captured in the frame. They may be dwarfed by the double-arcaded stone span behind them, but what they happen to be doing in this instant has a mythic significance I can't consciously explain. There's the traffic cop with his white helmet; people meeting on a crosswalk; bestockinged, book-laden girls strolling home from school; a quintet of men ascending the far steps like a skirmish line of soldiers.
But above them looms another form of eternity, or at least transmillennial longevity. The Aqueduct could have not survived this long had its ancient engineers not been experts in laying foundation in less-than-optimal substrates.
For the disposition of Segovia's underlying bedrock is a rather complicated affair. In the walk of a few blocks one goes from solid gneiss, metamorphosed from a granite protolith in the Cambrian period or earlier, to a fine-grained, Late Paleozoic granite, and then to a much softer sandstone of Upper Cretaceous age.
Here, in the plaza, where the bridge reaches its greatest overall height and mass, the Romans discovered, no doubt to their chagrin, that this is where the sandstone more or less begins. So they took special care to excavate what in the modern literature is usually called, with frustrating vagueness, "foundation pits."
Were these just holes dug down to bedrock in which the lowest courses of Guadarrama Granite blocks were set? Or did they fill the pits with rubble that would compact and form the most solid footing under the ashlar piers? Whatever the exact method they used, it probably didn't involve concrete—the production of which would've required a local source of limestone. Which there isn't.
To see the other photos and descriptions in this series, visit my Architectural Geology of Segovia album.
Architectural Geology of Segovia, Spain, Part 2: The Segovia Aqueduct (ca. early 2nd Century AD)
In contrast to the first image of this set, this shot was taken on the eastern side of the Aqueduct. It faces south.
As noted in other photo descriptions, I find myself more and more drawn into the immortality of frozen time, as embodied in the human figures captured in the frame. They may be dwarfed by the double-arcaded stone span behind them, but what they happen to be doing in this instant has a mythic significance I can't consciously explain. There's the traffic cop with his white helmet; people meeting on a crosswalk; bestockinged, book-laden girls strolling home from school; a quintet of men ascending the far steps like a skirmish line of soldiers.
But above them looms another form of eternity, or at least transmillennial longevity. The Aqueduct could have not survived this long had its ancient engineers not been experts in laying foundation in less-than-optimal substrates.
For the disposition of Segovia's underlying bedrock is a rather complicated affair. In the walk of a few blocks one goes from solid gneiss, metamorphosed from a granite protolith in the Cambrian period or earlier, to a fine-grained, Late Paleozoic granite, and then to a much softer sandstone of Upper Cretaceous age.
Here, in the plaza, where the bridge reaches its greatest overall height and mass, the Romans discovered, no doubt to their chagrin, that this is where the sandstone more or less begins. So they took special care to excavate what in the modern literature is usually called, with frustrating vagueness, "foundation pits."
Were these just holes dug down to bedrock in which the lowest courses of Guadarrama Granite blocks were set? Or did they fill the pits with rubble that would compact and form the most solid footing under the ashlar piers? Whatever the exact method they used, it probably didn't involve concrete—the production of which would've required a local source of limestone. Which there isn't.
To see the other photos and descriptions in this series, visit my Architectural Geology of Segovia album.