The Periadriatic Seam is a distinct geologic fault in Southern Europe, running S-shaped about 1000 km from the Tyrrhenian Sea through the whole Southern Alps as far as Hungary. It forms the division between the Adriatic plate and the European plate. The term Insubric line is sometimes used to address the whole Periadriatic Seam, but it is more commonly used to mean just a western part of it.

Tectonics and geology

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Within the Eastern Alps, the line marks the border between the Central Eastern Alps and the Southern Limestone Alps. In the Western Alps it forms the division between the southern Apulian foreland and the central crystalline zones of the Alps.

Continental collision is still going on, with the Apulian and European plates still converging. Movement along the Periadriatic Seam is the cause for the earthquake zone between Vienna and Friuli. Meanwhile, the central zones of the Alps are rising too, causing vertical slip along the fault. The result is the set of major faultzones collectively named Periadriatic Seam. The uplift caused violent erosion of the young orogen, which led to the formation of the Hohe Tauern window. At several regions an heavy uplift of the Central Alps by some kilometers took place, and also a shift of more than 50 km.

Geographic position and names

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From east to west, the course of the Periadriatic Seam and the names given to it regionally are as follows:

• Drau line: Southwestern Hungary - Styria - Drau valley (Jaun-, Rosental) - Klagenfurt)
• Gailtal line: Gailtal
• Pustertal line: Pustertal-Val Pusteria - Bruneck-Brunico - Meran-Merano
• Giudicárie line: Meran-Merano - Val di Sole
• Tonale or Insubric line: Tonale Pass - Val Camonica - Veltlin - Biella - Gulf of Genoa.

See also:

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• Apulian plate

Alps | Regional geology

Periadriatische Naht | Periadriatische lijn