Hellenic arc
Encyclopedia
The Hellenic arc or Aegean arc is an arcuate tectonic
feature of the eastern Mediterranean Sea
related to the subduction
of the African Plate
beneath the Aegean Sea Plate
. It consists of an oceanic trench— the Hellenic trench— on its outer side, a non-volcanic outer arc— the South Aegean Volcanic Arc
— an inner volcanic arc
and a marginal sea on its inner side.
in the west to just east of the island of Rhodes
in the east, where it links to the Cyprus arc
.
is not the surface expression of the subduction zone but is better understood as a sediment-starved part of a fore-arc basin. The Mediterranean Ridge
, which forms the southern boundary of the trench is the accretionary complex
that marks the subduction zone. The northern boundary of the Mediterranean Ridge is formed by a major backthrust. The Hellenic trench is most clearly developed in the western part of the arc, splitting into the Pliny and Strabo trenches to the east.
and Rhodes
. This zone represents an uplifted part of the fore-arc.
on the eastern coast of the Peloponnese
in the west to the island of Nisyros
off the Aegean cost of Turkey in the east. It consists of a series of dormant or active volcanic islands including Santorini
, the site of the catastrophic Minoan-era eruption.
and the 1303 Crete earthquake
.
Tectonics
Tectonics is a field of study within geology concerned generally with the structures within the lithosphere of the Earth and particularly with the forces and movements that have operated in a region to create these structures.Tectonics is concerned with the orogenies and tectonic development of...
feature of the eastern Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
related to the subduction
Subduction
In geology, subduction is the process that takes place at convergent boundaries by which one tectonic plate moves under another tectonic plate, sinking into the Earth's mantle, as the plates converge. These 3D regions of mantle downwellings are known as "Subduction Zones"...
of the African Plate
African Plate
The African Plate is a tectonic plate which includes the continent of Africa, as well as oceanic crust which lies between the continent and various surrounding ocean ridges.-Boundaries:...
beneath the Aegean Sea Plate
Aegean Sea Plate
The Aegean Sea Plate is a small tectonic plate located in the eastern Mediterranean Sea under southern Greece and far western Turkey. Its southern edge is a subduction zone south of Crete, where the African Plate is being swept under the Aegean Sea Plate...
. It consists of an oceanic trench— the Hellenic trench— on its outer side, a non-volcanic outer arc— the South Aegean Volcanic Arc
South Aegean Volcanic Arc
The South Aegean Volcanic Arc is a chain of volcanic islands in the South Aegean Sea formed by plate tectonics as a consequence of the subduction of the African tectonic plate beneath the Eurasian plate...
— an inner volcanic arc
Volcanic arc
A volcanic arc is a chain of volcanoes positioned in an arc shape as seen from above. Offshore volcanoes form islands, resulting in a volcanic island arc. Generally they result from the subduction of an oceanic tectonic plate under another tectonic plate, and often parallel an oceanic trench...
and a marginal sea on its inner side.
Geometry
The Hellenic arc extends from the Ionian islandsIonian Islands
The Ionian Islands are a group of islands in Greece. They are traditionally called the Heptanese, i.e...
in the west to just east of the island of Rhodes
Rhodes
Rhodes is an island in Greece, located in the eastern Aegean Sea. It is the largest of the Dodecanese islands in terms of both land area and population, with a population of 117,007, and also the island group's historical capital. Administratively the island forms a separate municipality within...
in the east, where it links to the Cyprus arc
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 collision between the African and Eurasian plates....
.
Hellenic trench
The Hellenic ocean trenchHellenic Trench
The Hellenic Trench is a hemispherical-scale long narrow depression in the Ionian Sea.The hadal zone of the Hellenic trench is roughly to 5,300 metres deep. The names of the three major parts of the Hellenic trench are: Matapan Deep System or Matapan–Vavilov Deep, roughly , the...
is not the surface expression of the subduction zone but is better understood as a sediment-starved part of a fore-arc basin. The Mediterranean Ridge
Mediterranean Ridge
The Mediterranean Ridge is a wide ridge in the bed of the Mediterranean Sea, running along a rough quarter circle from Calabria, south of Crete, to the southwest corner of Turkey, and from there eastwards south of Turkey, including Cyprus....
, which forms the southern boundary of the trench is the accretionary complex
Accretionary wedge
An accretionary wedge or accretionary prism is formed from sediments that are accreted onto the non-subducting tectonic plate at a convergent plate boundary...
that marks the subduction zone. The northern boundary of the Mediterranean Ridge is formed by a major backthrust. The Hellenic trench is most clearly developed in the western part of the arc, splitting into the Pliny and Strabo trenches to the east.
Non-volcanic arc
The non-volcanic arc consists of a raised topographic feature running the full length of the Hellenic arc, occasionally above sea level, forming the Ionian islands, CreteCrete
Crete is the largest and most populous of the Greek islands, the fifth largest island in the Mediterranean Sea, and one of the thirteen administrative regions of Greece. It forms a significant part of the economy and cultural heritage of Greece while retaining its own local cultural traits...
and Rhodes
Rhodes
Rhodes is an island in Greece, located in the eastern Aegean Sea. It is the largest of the Dodecanese islands in terms of both land area and population, with a population of 117,007, and also the island group's historical capital. Administratively the island forms a separate municipality within...
. This zone represents an uplifted part of the fore-arc.
Volcanic arc
The inner or volcanic arc extends for 450 km from MethanaMethana Volcano
The Methana volcano peninsula is situated approximately 50 km southeast of Athens in Greece.-Geological history:The Methana peninsula contains some 32 volcanoes, that are mostly andesitic / dacitic lava domes.The volcanic activity in the peninsula began one million years ago and continued...
on the eastern coast of the Peloponnese
Peloponnese
The Peloponnese, Peloponnesos or Peloponnesus , is a large peninsula , located in a region of southern Greece, forming the part of the country south of the Gulf of Corinth...
in the west to the island of Nisyros
Nisyros
Nisyros is a volcanic Greek island and municipality located in the Aegean Sea. It is part of the Dodecanese group of islands, situated between the islands of Kos and Tilos. Its shape is approximately round, with a diameter of about , and an area of . Several other islets are found in the direct...
off the Aegean cost of Turkey in the east. It consists of a series of dormant or active volcanic islands including Santorini
Santorini
Santorini , officially Thira , is an island located in the southern Aegean Sea, about southeast from Greece's mainland. It is the largest island of a small, circular archipelago which bears the same name and is the remnant of a volcanic caldera...
, the site of the catastrophic Minoan-era eruption.
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 earthquake365 Crete earthquake
The AD 365 Crete earthquake was an undersea earthquake that occurred at about sunrise on 21 July 365 in the Eastern Mediterranean, with an assumed epicentre near Crete. Geologists today estimate the quake to have been 8 on the Richter Scale or higher, causing widespread destruction in central and...
and the 1303 Crete earthquake
1303 Crete earthquake
The 1303 Crete earthquake occurred at about dawn on 8 August. It had an estimated magnitude of about 8 and triggered a major tsunami that caused severe damage and loss of life on Crete and at Alexandria.-Tectonic setting:...
.