The Hellenic arc or Aegean arc is an

arcuate ''Arcuate'' (Latin for "curved") can refer to: Anatomy * Arcuate fasciculus * Arcuate line (disambiguation) * Arcuate artery (disambiguation), several arteries * Arcuate nucleus * Arcuate nucleus (medulla) * Arcuate ligaments of the diaphragm * A ...

mountain chain of the southern

Aegean Sea The Aegean Sea ; tr, Ege Denizi (Greek: Αιγαίο Πέλαγος: "Egéo Pélagos", Turkish: "Ege Denizi" or "Adalar Denizi") is an elongated embayment of the Mediterranean Sea between Europe and Asia. It is located between the Balkans ...

located on the southern margin of the

Aegean Sea Plate The Aegean Sea Plate (also called the Hellenic Plate or Aegean Plate) is a small tectonic plate located in the eastern Mediterranean Sea under southern Greece and western Turkey. Its southern edge is the Hellenic subduction zone south of Crete, ...

. Geologically it results from the subduction of the

African Plate The African Plate is a major tectonic plate that includes much of the continent of Africa (except for its easternmost part) and the adjacent oceanic crust to the west and south. It is bounded by the North American Plate and South American Plate ...

under it along the

Hellenic subduction zone The Hellenic subduction zone (HSZ) is the convergent boundary between the African Plate and the Aegean Sea Plate, where oceanic crust of the African is being subducted north–northeastwards beneath the Aegean. The southernmost and shallowest par ...

. The

Hellenic Trench The Hellenic Trench (HT) is an oceanic trough located in the forearc of the Hellenic Arc, an arcuate archipelago on the southern margin of the Aegean Sea Plate, or Aegean Plate, also called Aegea, the basement of the Aegean Sea. The HT begin ...

trends parallel to its southern side. The Aegean Sea Plate, a microplate, is often considered part of the

Eurasian Plate The Eurasian Plate is a tectonic plate that includes most of the continent of Eurasia (a landmass consisting of the traditional continents of Europe and Asia), with the notable exceptions of the Indian subcontinent, the Arabian subcontinent and ...

from which it is in the process of diverging. The arc itself is mainly marine, the mountaintops appearing as islands in the Ionian Sea, Crete and its environs, or in the

Dodecanese The Dodecanese (, ; el, Δωδεκάνησα, ''Dodekánisa'' , ) are a group of 15 larger plus 150 smaller Greek islands in the southeastern Aegean Sea and Eastern Mediterranean, off the coast of Turkey's Anatolia, of which 26 are inhabited. ...

group. It encroaches on mainland terrain in the Peloponnesus, on Crete, on Rhodes, and on the southern coast of Anatolia, thus being encompassed by both Greece and Turkey. The direction of subduction is northward. Locations on the arc or near it on the north side are therefore called "outer" as they are at the outer margin of the plate. Locations further north are "inner." Generally the motion of subduction is from outer to inner. It so happens that, due to back-arc extension, the Hellenic Arc and Trench are moving in the reverse direction, from inner to outer, accounting for the severe arcuate form. There are in essence two layers at the subduction zone, a bottom one moving from outer to inner, and a top one moving from inner to outer. The extension of the top layer required for this excursion of the arc and the trench comes from thinning of the back-arc ("in back of the arc"), weakening the crust there. There was already a mountain chain north of the arc, a legacy from the Alpine Orogeny, called the "inner arc." Its tops are the

Cyclades The Cyclades (; el, Κυκλάδες, ) are an island group in the Aegean Sea, southeast of mainland Greece and a former administrative prefecture of Greece. They are one of the island groups which constitute the Aegean archipelago. The nam ...

. In addition, a chain of volcanos has appeared across it, due to magma breaking through the weakened crust; hence, this "inner arc" is termed the

South Aegean Volcanic Arc The South Aegean Volcanic Arc is a volcanic arc (chain of volcanoes) in the South Aegean Sea formed by plate tectonics. The prior cause was the subduction of the African plate beneath the Eurasian plate, raising the Aegean arc across what is n ...

. The two arcs are considered distinct, being from different orogenies. The term "Hellenic Arc" most often refers to the marginal, or "non-volcanic" arc, also called the Aegean forearc in the direction from outer to inner, which is consonant with the Hellenic Trench being the foredeep.

Geometry of the Hellenic arc

The Hellenic arc extends from the Ionian islands in the west to just east of the island of

Rhodes Rhodes (; el, Ρόδος , translit=Ródos ) is the largest and the historical capital of the Dodecanese islands of Greece. Administratively, the island forms a separate municipality within the Rhodes regional unit, which is part of the So ...

in the east, where it links to the

Cyprus arc The Cyprus arc is part of the plate boundary zone that accommodates the motion of the African Plate relative to the Anatolian Plate. It is an arcuate depression located in the southern reaches of Cyprus. The Cyprus arc is considered to be in col ...

Development

The current geometry of the Hellenic arc is a result of the southwards migration of the subduction zone. This has led to extension both along the line of the arc as it bulged out and extension perpendicular to the arc, which is the current tectonic state.

Seismicity

The Hellenic arc is one of the most active seismic zones in western Eurasia. It has regularly been the source for magnitude 7 earthquakes in the last hundred years of instrumental recording and the location for at least two historical events that were probably of about magnitude 8 or more, the

365 Crete earthquake The 365 Crete earthquake occurred at about sunrise on 21 July 365 in the Eastern Mediterranean, with an assumed epicentre near Crete. Geologists today estimate the undersea earthquake to have been a moment magnitude 8.5 or higher. It caused wides ...

and the 1303 Crete earthquake.

References

External links

{{commonscat-inline Megathrust earthquakes in Greece Geology of Greece

Geometry of the Hellenic arc

Development

Seismicity

See also

References

External links