Geology (Architectural & Otherwise) of the Earth's Center, Part 30: A Town with a Major Fault | Arachova, Boeotia, Greece
Taken from Route 48 just east of the tourist destination of Arachova.
Uh-oh. This guy is about to relate geology to the built environment again. All good professional geologists, the kind with higher reductionist degrees who want to keep their sacred subject pure and untainted by nonscientific aspects of human culture, should stop reading and exit this post now.
Here’s a softball question. What do the ancient site of Delphi, the modern town of Delphi, and Arachova all have in common?
Well, one answer, easily ascertained on Google Earth, is that they all lie along Greece’s National Road 48. And another is that they all sit on the southern flank of the Parnassus Massif. And yet another is that they’re all perched on the edge of the vertiginous Pleistos River Gorge.
Actually, the last two answers lead to still one more. The reason they’re on the boundary of massif and gorge is that they lie along what has been described as a “major active fault” (see the Piccardi et al. reference, below). That fault has been one of the mechanisms allowing the southern section of the crust to drop down relative to the northern.
In fact, the fault is one of many local manifestations of the extensional tectonics that have dominated the region since the Miocene epoch (23-5 Ma ago). While Parnassus itself is a nappe that was pushed over preexisting crust during the compressional phase that existed before the Miocene, the Pleistos Gorge and its bordering faults are part of the larger extensional rifting that includes the much larger Corinth Gulf nearby.
The Arachova-Delphi-Amphissa Fault, the one I’ve been talking about, is a normal fault that has already produced some notable earthquakes—which is one reason a lot of the Delphi archaeological complex looks like a collection of giant children’s building blocks spilled out on the ground
But then the Mediterranean Basin is undoubtedly one of the best places on Earth to perceive that Homo sapiens has never shied away from building towns and even supersized cities like Istanbul on or dangerously near very nasty fault zones. (Of course, another place to see this is San Francisco.)
Still, one has to realize that the settlement of these very populated places began long before geologists were on hand to map and understand the structural makeup of the rock beneath. And even highly visible geologic hazards like volcanoes weren’t really understood to be "fire mountains” until pyroclastic surges erupting from them turned the locals into Roman candles. (Here I’m thinking especially of AD 79 in the Gulf of Naples.)
As usual, our species, manifestly quite insapiens, just puts down its stakes wherever it damn well wants to, and then, decades or centuries later, it realizes how potentially disastrous Home Sweet Home really is. And then it rationalizes away the danger until the Dies Irae finally arrives.
Not that I’m predicting doom for Arachova, necessarily. It’s a very pretty town and I encourage you to visit it and sample its famous Formaella cheese and its black Mavroudi wine.
And, if you are geologically inclined, you can marvel at the striking, ocher-colored Parnassus Flysch visible in this photo at lower right. It dates to the Paleocene and Eocene epochs, whereas the Parnassus carbonate units higher up—look for the heavily jointed gray rock up above the town—dates to the Mesozoic.
So that means I am once again writing in a Greek context about older rock sitting on top of younger rock. This interesting inversion of the natural, layer-cake order is remindful of Athens’s Acropolis klippe. But in this case a whole nappe has flipped over on itself, rather than just pushing up over another, more ancient piece of real estate.
.
Sources Consulted for This Essay
- de Vals, Marilou, Renaldo Gastineau, Amélie Perrier4, Romain Rubi, and Isabelle Moretti. “The Stones of the Sanctuary of Delphi – Northern Shore of the Corinth Gulf – Greece.” BSGF Earth Sciences Bulletin 191:11 (2020).
- Nirta, Giuseppe, Giovanna Moratti, Luigi Piccardi, Domenico Montanari, Nicolaos Carras, Rita Catanzariti, Marco Chiari, and Marta Marcucci. “From Obduction to Continental Collision: New Data from Central Greece.” Geological Magazine 155:2 (2018), 377–421.
- Piccardi, Luigi, Cassandra Monti, Orlando Vaselli, Franco Tassi, Kalliopi Gaki-Papanastassiou, and Dimitris Papanastassiou. “Scent of a Myth: Tectonics, Geochemistry and Geomythology at Delphi (Greece). Journal of the Geological Society, London 165 (2008) 5–18.
To see the other photos and descriptions in this series, visit my Geology (Architectural & Otherwise) of the Earth's Center album.
Geology (Architectural & Otherwise) of the Earth's Center, Part 30: A Town with a Major Fault | Arachova, Boeotia, Greece
Taken from Route 48 just east of the tourist destination of Arachova.
Uh-oh. This guy is about to relate geology to the built environment again. All good professional geologists, the kind with higher reductionist degrees who want to keep their sacred subject pure and untainted by nonscientific aspects of human culture, should stop reading and exit this post now.
Here’s a softball question. What do the ancient site of Delphi, the modern town of Delphi, and Arachova all have in common?
Well, one answer, easily ascertained on Google Earth, is that they all lie along Greece’s National Road 48. And another is that they all sit on the southern flank of the Parnassus Massif. And yet another is that they’re all perched on the edge of the vertiginous Pleistos River Gorge.
Actually, the last two answers lead to still one more. The reason they’re on the boundary of massif and gorge is that they lie along what has been described as a “major active fault” (see the Piccardi et al. reference, below). That fault has been one of the mechanisms allowing the southern section of the crust to drop down relative to the northern.
In fact, the fault is one of many local manifestations of the extensional tectonics that have dominated the region since the Miocene epoch (23-5 Ma ago). While Parnassus itself is a nappe that was pushed over preexisting crust during the compressional phase that existed before the Miocene, the Pleistos Gorge and its bordering faults are part of the larger extensional rifting that includes the much larger Corinth Gulf nearby.
The Arachova-Delphi-Amphissa Fault, the one I’ve been talking about, is a normal fault that has already produced some notable earthquakes—which is one reason a lot of the Delphi archaeological complex looks like a collection of giant children’s building blocks spilled out on the ground
But then the Mediterranean Basin is undoubtedly one of the best places on Earth to perceive that Homo sapiens has never shied away from building towns and even supersized cities like Istanbul on or dangerously near very nasty fault zones. (Of course, another place to see this is San Francisco.)
Still, one has to realize that the settlement of these very populated places began long before geologists were on hand to map and understand the structural makeup of the rock beneath. And even highly visible geologic hazards like volcanoes weren’t really understood to be "fire mountains” until pyroclastic surges erupting from them turned the locals into Roman candles. (Here I’m thinking especially of AD 79 in the Gulf of Naples.)
As usual, our species, manifestly quite insapiens, just puts down its stakes wherever it damn well wants to, and then, decades or centuries later, it realizes how potentially disastrous Home Sweet Home really is. And then it rationalizes away the danger until the Dies Irae finally arrives.
Not that I’m predicting doom for Arachova, necessarily. It’s a very pretty town and I encourage you to visit it and sample its famous Formaella cheese and its black Mavroudi wine.
And, if you are geologically inclined, you can marvel at the striking, ocher-colored Parnassus Flysch visible in this photo at lower right. It dates to the Paleocene and Eocene epochs, whereas the Parnassus carbonate units higher up—look for the heavily jointed gray rock up above the town—dates to the Mesozoic.
So that means I am once again writing in a Greek context about older rock sitting on top of younger rock. This interesting inversion of the natural, layer-cake order is remindful of Athens’s Acropolis klippe. But in this case a whole nappe has flipped over on itself, rather than just pushing up over another, more ancient piece of real estate.
.
Sources Consulted for This Essay
- de Vals, Marilou, Renaldo Gastineau, Amélie Perrier4, Romain Rubi, and Isabelle Moretti. “The Stones of the Sanctuary of Delphi – Northern Shore of the Corinth Gulf – Greece.” BSGF Earth Sciences Bulletin 191:11 (2020).
- Nirta, Giuseppe, Giovanna Moratti, Luigi Piccardi, Domenico Montanari, Nicolaos Carras, Rita Catanzariti, Marco Chiari, and Marta Marcucci. “From Obduction to Continental Collision: New Data from Central Greece.” Geological Magazine 155:2 (2018), 377–421.
- Piccardi, Luigi, Cassandra Monti, Orlando Vaselli, Franco Tassi, Kalliopi Gaki-Papanastassiou, and Dimitris Papanastassiou. “Scent of a Myth: Tectonics, Geochemistry and Geomythology at Delphi (Greece). Journal of the Geological Society, London 165 (2008) 5–18.
To see the other photos and descriptions in this series, visit my Geology (Architectural & Otherwise) of the Earth's Center album.