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26-416: Syrtis Major may refer to: Syrtis Major Planum , ancient volcanic area on Mars Gulf of Sidra , body of water on the coast of Libya Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with the title Syrtis Major . If an internal link led you here, you may wish to change the link to point directly to

52-520: A large slope from its western edge at Aeria , dropping 4 km (2.5 mi) to its eastern edge at Isidis Planitia . Most of Syrtis Major has slopes of less than 1°, a much lower inclination than the slopes of the Tharsis shield volcanoes. It has a 350 km × 150 km north–south elongated central depression containing the calderas Nili Patera and Meroe Patera, which are about 2 km deep. The roughly 2,300-meter high peak of Syrtis Major

78-583: A new rock type to separate calc-alkaline rocks with oligoclase phenocrysts (dacites) from rocks with orthoclase phenocrysts (rhyolites). 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 transitions to

104-455: A positive gravity anomaly centered on the caldera complex, suggesting the presence of a 600 km × 300 km north–south elongated extinct magma chamber below, containing dense minerals (probably mainly pyroxene , with olivine also possible) that precipitated out of magma before eruptions. Crater counts date Syrtis Major to the early Hesperian epoch ; it postdates formation of the adjacent Isidis impact basin . The name Syrtis Major

130-537: A province of the Roman Empire which lay between the Danube River and Carpathian Mountains (now modern Romania and Moldova ) where the rock was first described. The term dacite was used for the first time in the scientific literature in the book Geologie Siebenbürgens ( The Geology of Transylvania ) by Austrian geologists Franz Ritter von Hauer and Guido Stache. Dacite was originally defined as

156-401: A thick felsic continental plate. Oceanic crust is hydrothermally altered causing addition of quartz and sodium. As the young, hot oceanic plate is subducted under continental crust, the subducted slab partially melts and interacts with the upper mantle through convection and dehydration reactions. The process of subduction creates metamorphism in the subducting slab. When this slab reaches

182-615: Is a massive shield volcano in the eastern hemisphere of Mars . A "dark spot" (an albedo feature ), Syrtis Major Planum is located in the boundary between the northern lowlands and southern highlands of Mars just west of the impact basin Isidis in the Syrtis Major quadrangle . It was formerly believed to be a plain , and was therefore described as a planitia . Later data from the Mars Global Surveyor revealed that it

208-484: Is actually a broad topographic rise. The dark color of Syrtis Major Planum comes from the basaltic volcanic rock of the region and the relative lack of dust. The selected landing site for the Mars 2020 mission that includes the rover Perseverance and the helicopter drone Ingenuity was Jezero crater , at 18°51′18″N 77°31′08″E  /  18.855°N 77.519°E  / 18.855; 77.519 within

234-467: Is derived from the classical Roman name Syrtis maior for the Gulf of Sidra on the coast of Libya (classical Cyrenaica ). Syrtis Major was the first documented surface feature of another planet . It was discovered by Christiaan Huygens , who included it in a drawing of Mars in 1659. He used repeated observations of the feature to estimate the length of day on Mars. The feature was originally known as

260-866: Is impractical. The rock must then be classified chemically based on its content of silica and alkali metal oxides ( K 2 O plus Na 2 O ). The TAS classification puts dacite in the O3 sector. In hand specimen, many of the hornblende and biotite dacites are grey or pale brown and yellow rocks with white feldspars, and black crystals of biotite and hornblende. Other dacites, especially pyroxene-bearing dacites, are darker colored. In thin section, dacites may have an aphanitic to porphyritic texture. Porphyritic dacites contain blocky highly zoned plagioclase phenocrysts and/or rounded corroded quartz phenocrysts. Subhedral hornblende and elongated biotite grains are present. Sanidine phenocrysts and augite (or enstatite ) are found in some samples. The groundmass of these rocks

286-562: Is located northwest of Nili Patera. The floors of the calderas are unique among large Martian volcanoes as they are not elevated relative to the terrain surrounding Syrtis Major. This may account for the high degree of magmatic evolution and hydrothermal activity seen in Nili Patera. The floor of Nili Patera is the less cratered, and therefore the younger, of the two. While most of the rock is basaltic, dacite has also been detected in Nili Patera. Satellite gravity field measurements show

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312-425: Is often aphanitic microcrystalline , with a web of minute feldspars mixed with interstitial grains of quartz or tridymite; but in many dacites it is largely vitreous, while in others it is felsitic or cryptocrystalline. Dacite usually forms as an intrusive rock such as a dike or sill . Examples of this type of dacite outcrop are found in northwestern Montana and northeastern Bulgaria . Nevertheless, because of

338-722: The Hourglass Sea but has been given different names by different cartographers . In 1850s, Angelo Secchi called the feature Atlantic Canale . Later he called it Scorpion and Cook Sea or Cook Canal . . In Richard Proctor 's 1867 map it is called the Kaiser Sea , after Frederik Kaiser of the Leiden Observatory . In 1876, Camille Flammarion called it the Mer du Sablier (French for "Hourglass Sea") when he revised Proctor's nomenclature. The name "Syrtis Major"

364-457: The history of the magma. The formation of dacite provides a great deal of information about the connection between oceanic crust and continental crust. It provides a model for the generation of felsic, buoyant, perennial rock from a mafic, dense, short-lived one. The process by which dacite forms has been used to explain the generation of continental crust during the Archean eon . At that time,

390-399: The intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=Syrtis_Major&oldid=933149828 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Syrtis Major Planum Syrtis Major Planum (formerly Syrtis Major Planitia )

416-428: The mantle and initiates the dehydration reactions, minerals such as talc , serpentine , mica and amphiboles break down generating a more sodic melt. The magma then continues to migrate upwards causing differentiation and becomes even more sodic and silicic as it rises. Once at the cold surface, the sodium rich magma crystallizes plagioclase, quartz and hornblende. Accessory minerals like pyroxenes provide insight to

442-478: The moderately high silica content, dacitic magma is quite viscous and therefore prone to explosive eruption. A notorious example of this is Mount St. Helens in which dacite domes formed from previous eruptions. Pyroclastic flows may also be of dacitic composition as is the case with the Fish Canyon Tuff of La Garita Caldera . Dacitic magma is formed by the subduction of young oceanic crust under

468-507: The production of dacitic magma was more ubiquitous, due to the availability of young, hot oceanic crust. Today, the colder oceanic crust that subducts under most plates is not able to melt prior to the dehydration reactions, thus inhibiting the process. Dacitic magma was encountered in a drillhole during geothermal exploration on Kīlauea in 2005. At a depth of 2488 m, the magma flowed up the wellbore. This produced several kilograms of clear, colorless vitric (glassy, non-crystalline) cuttings at

494-422: The region. The northeastern region of Syrtis Major Planum was also considered a potential landing site. Syrtis Major is centered near at 8°24′N 69°30′E  /  8.4°N 69.5°E  / 8.4; 69.5 . It extends some 1,500 km (930 mi) north from the planet's equator, and spans 1,000 km (620 mi) from west to east. It is in the Syrtis Major quadrangle . It encompasses

520-571: The rhyolites. The relative proportions of feldspars and quartz in dacite, and in many other volcanic rocks, are illustrated in the QAPF diagram . This defines dacite as having a content of 20% to 60% quartz, with plagioclase making up 65% or more of its feldspar content. However, while the IUGS recommends classifying volcanic rocks on the basis of their mineral composition whenever possible, dacites are often so fine-grained that mineral identification

546-473: The south are the primary named calderas within a nested caldera complex developed by multiple eruption and collapse events. In the Northeast quadrant of Nili Patera is a 630 m tall volcanic cone named Nili Tholus, on and around this cone is a light-tone lava flow of chemically evolved lava with multiple occurrences of relict silica sinter deposits created by a formerly active hot spring system. Nili Patera

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572-866: The surface. The dacite magma is a residual melt of the typical basalt magma of Kīlauea. Dacite is relatively common and occurs in various tectonic and magmatic contexts: The type locality of dacite is Gizella quarry near Poieni, Cluj in Romania . Other occurrences of dacite in Europe are Germany ( Weiselberg ), Greece ( Nisyros and Thera ), Italy (in Bozen quartz porphyry, and Sardinia ), Austria (Styrian Volcano Arc), Scotland ( Argyll ), Slovakia , Spain (El Hoyazo near Almería ), France ( Massif de l'Esterel ) and Hungary (Csódi Hill). Sites outside Europe include Iran , Morocco , New Zealand (volcanic region of Taupo ), Turkey , USA and Zambia . Dacite

598-545: The variations were caused by wind blowing dust and sand across the area. It has many windblown deposits that include light-colored halos or plumose streaks that form downwind of craters . These streaks are accumulations of dust resulting from disruption of the wind by the elevated rims of the craters ('wind shadows'). Nili Patera is a 50 km diameter caldera at the center of the Syrtis Major Volcanic Complex. It and Meroe Patera located to

624-494: The weaker Mars gravity. The lee fronts of the dunes in this region move on average 0.5 meters per year. The selection may be biased here as they only measured dunes with clear lee edges to measure. The ripples move on average 0.1 meters per year. Dacite Dacite is relatively common, occurring in many tectonic settings. It is associated with andesite and rhyolite as part of the subalkaline tholeiitic and calc-alkaline magma series . The word dacite comes from Dacia ,

650-495: Was chosen by Giovanni Schiaparelli when he created a map based on observations made during Mars' close approach to Earth in 1877. Syrtis Major was the object of much observation due to its seasonal and long-term variations. This led to theories that it was a shallow sea and later that its variability was due to seasonal vegetation. In the 1960s and 1970s, the Mariner and Viking planetary probes led scientists to conclude that

676-544: Was the subject of a 2010 study into moving sand dunes and wind ripples. The study showed that dunes are active and that sand ripples are actively migrating on the surface of Mars. A following study also showed that the sand dunes move at about the same flux (volume per time) as dunes in Antarctica. This was unexpected because of the thin air and the winds which are weaker than Earth winds. It may be due to " saltation " - ballistic movement of sand grains which travel further in

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