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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 part of the zone is obscured beneath the deformed thick sedimentary sequence that forms the Mediterranean Ridge accretionary complex. It has a well-defined Wadati–Benioff zone of seismicity, which demonstrates the relatively shallow dip of its southern part, which increases markedly to the north of the non-volcanic part of the Hellenic arc. The descending slab has been imaged using seismic tomography down to the top of the mantle transition zone at 410 km depth. Surface expression When the subduction zone was originally identified in the 1970s, it was thought that the Hellenic trench was the surface expression of the HSZ. Once the Mediterranean Ridge was recognised as an accretionary complex, the majority of geoscientists regarded the Hell ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Hellenic Arc
The Hellenic arc or Aegean arc is an arcuate mountain chain of the southern Aegean Sea located on the southern margin of the Aegean Sea Plate. Geologically it results from the subduction of the African Plate under it along the Hellenic subduction zone. The Hellenic Trench trends parallel to its southern side. The Aegean Sea Plate, a microplate, is often considered part of the Eurasian Plate 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 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 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Forearc
Forearc is a plate tectonic term referring to a region between an oceanic trench, also known as a subduction zone, and the associated volcanic arc. Forearc regions are present along a convergent margins and eponymously form 'in front of' the volcanic arcs that are characteristic of convergent plate margins. A back-arc region is the companion region behind the volcanic arc. Many forearcs have an accretionary wedge which may form a topographic ridge known as an outer arc ridge that parallels the volcanic arc. Between the accretionary wedge and the volcanic arc a forearc basin, sometimes referred to as an outer arc trough, may be present and can accumulate thick deposits of sediment. Due to tectonic stresses as one tectonic plate rides over another, forearc regions are sources for great thrust earthquakes. Formation During subduction, an oceanic plate is thrust below another tectonic plate, which may be oceanic or continental. Water and other volatiles in the down-going plat ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Saronic Gulf
The Saronic Gulf (Greek: Σαρωνικός κόλπος, ''Saronikós kólpos'') or Gulf of Aegina in Greece is formed between the peninsulas of Attica and Argolis and forms part of the Aegean Sea. It defines the eastern side of the isthmus of Corinth, being the eastern terminus of the Corinth Canal, which cuts across the isthmus. The Saronic Islands in the gulf have played a pivotal role in the history of Greece, with the largest, Salamis, naming a significant naval battle in the Greco-Persian wars. The Megara Gulf makes up the northern end of the Saronic Gulf. The capital of Greece, Athens, lies on the north coast of the Saronic Gulf. Etymology The origin of the gulf's name comes from the mythological king Saron who drowned at the Psifaei lake (modern Psifta). The Saronic Gulf was a string of six entrances to the Underworld, each guarded by a chthonic enemy in the shape of a thief or bandit. History The Battle of Salamis, just to the west of modern-day Piraeus, took ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Dacite
Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. It is composed predominantly of plagioclase feldspar and quartz. Dacite is relatively common, occurring in many tectonic settings. It is associated with andesite and rhyolite as part of the subalkaline volcanic rock, subalkaline tholeiite, tholeiitic and calc-alkaline magma series. Composition Dacite consists mostly of plagioclase feldspar and quartz with biotite, hornblende, and pyroxene (augite or enstatite). The quartz appears as rounded, corroded phenocrysts, or as an element of the ground-mass. The plagioclase in dacite ranges from oligoclase to andesine and labradorite. Sanidine occurs, although in small proportions, in some dacites, and when abundant gives rise to rocks that form rhyodacite, transitions to the rhyolites. The rel ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Andesite
Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predominantly of sodium-rich plagioclase plus pyroxene or hornblende. Andesite is the extrusive equivalent of plutonic diorite. Characteristic of subduction zones, andesite represents the dominant rock type in island arcs. The average composition of the continental crust is andesitic. Along with basalts, andesites are a component of the Martian crust. The name ''andesite'' is derived from the Andes mountain range, where this rock type is found in abundance. It was first applied by Christian Leopold von Buch in 1826. Description Andesite is an aphanitic (fine-grained) igneous rock that is intermediate in its content of silica and low in alkali metals. It has less than 20% quartz and 10% feldspathoid by volume, with at least 65% of the fe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pliocene
The Pliocene ( ; also Pleiocene) is the epoch in the geologic time scale that extends from 5.333 million to 2.58See the 2014 version of the ICS geologic time scale million years ago. It is the second and most recent epoch of the Neogene Period in the . The Pliocene follows the Epoch and is followed by the Epoch. Prior to the 2009 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 now the north Aegean Sea. It was not yet the sea, nor an arc, or at least not the one it is today, nor was there a chain of volcanoes. In the Holocene the process of back-arc extension began, probably stimulated by pressure from the Arabian Plate compressing the region behind the arc. The extension deformed the region into its current configuration. First, the arc moved to the south and assumed its arcuate configuration. Second, the Aegean Sea opened behind the arc because the crust was thinned and weakened there. Third, magma broke through the thinned crust to form a second arc composed of a volcanic chain. And finally, the Aegean Sea Plate broke away from Eurasia in the new fault zone to the north. The extension is still ongoing. The curren ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Volcanic Arc
A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc located further from the subducting plate than the trench. The oceanic plate is saturated with water, mostly in the form of hydrous minerals such as micas, amphiboles, and serpentine minerals. As the oceanic plate is subducted, it is subjected to increasing pressure and temperature with increasing depth. The heat and pressure break down the hydrous minerals in the plate, releasing water into the overlying mantle. Volatiles such as water drastically lower the melting point of the mantle, causing some of the mantle to melt and form magma at depth under the overriding plate. The magma ascends to form an arc of volcanoes parallel to the subduction zone. Volcanic arcs are distinct from volcanic chains formed over hotspots in the middle of a te ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Slab Tear
Slab or SLAB may refer to: Physical materials * Concrete slab, a flat concrete plate used in construction * Stone slab, a flat stone used in construction * Slab (casting), a length of metal * Slab (geology), that portion of a tectonic plate that is subducting ** Slab pull force, the tectonic plate force due to subduction ** Slab suction, one of the major plate tectonic driving forces ** Slab window, a gap that forms in a subducted oceanic plate ** Slab (fossil) and counter slab, the two counterparts of a fossil impression * Slab hut, a kind of dwelling made from slabs of split or sawn timber * Slab of beer, a flat package containing a large number of cans of beer Places * Slab Point, a rocky point in the South Shetland Islands, Antarctica United States * Slab, West Virginia, an unincorporated community in Ritchie County, West Virginia * Slab City, California, a locality in the Colorado Desert * Slab City, Wisconsin, an unincorporated community in Shawano County, Wisconsin * ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Crete
Crete ( el, Κρήτη, translit=, Modern: , Ancient: ) is the largest and most populous of the Greek islands, the 88th largest island in the world and the fifth largest island in the Mediterranean Sea, after Sicily, Sardinia, Cyprus, and Corsica. Crete rests about south of the Greek mainland, and about southwest of Anatolia. Crete has an area of and a coastline of 1,046 km (650 mi). It bounds the southern border of the Aegean Sea, with the Sea of Crete (or North Cretan Sea) to the north and the Libyan Sea (or South Cretan Sea) to the south. Crete and a number of islands and islets that surround it constitute the Region of Crete ( el, Περιφέρεια Κρήτης, links=no), which is the southernmost of the 13 top-level administrative units of Greece, and the fifth most populous of Greece's regions. Its capital and largest city is Heraklion, on the north shore of the island. , the region had a population of 636,504. The Dodecanese are located to the no ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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 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 ...s. References Geology of Cyprus {{tectonics-stub ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
