Limestone is a carbonate sedimentary rock, composed of the skeletal fragments of marine organisms such as coral and molluscs. Its major materials are the minerals calcite and aragonite, which are different crystal forms of calcium carbonate. A related rock is dolostone, which contains a high percentage of the mineral dolomite, CaMg2. In fact, in old USGS publications, dolostone was referred to as magnesian limestone, a term now reserved for magnesium-deficient dolostones or magnesium-rich limestones. About 10% of sedimentary rocks are limestones; the solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years. Most cave systems are through limestone bedrock. Limestone has numerous uses: as a building material, an essential component of concrete, as aggregate for the base of roads, as white pigment or filler in products such as toothpaste or paints, as a chemical feedstock for the production of lime, as a soil conditioner, or as a popular decorative addition to rock gardens.
Like most other sedimentary rocks, most limestone is composed of grains. Most grains in limestone are skeletal fragments of marine organisms such as foraminifera; these organisms secrete shells made of aragonite or calcite, leave these shells behind when they die. Other carbonate grains composing limestones are ooids, peloids and extraclasts. Limestone contains variable amounts of silica in the form of chert or siliceous skeletal fragment, varying amounts of clay and sand carried in by rivers; some limestones do not consist of grains, are formed by the chemical precipitation of calcite or aragonite, i.e. travertine. Secondary calcite may be deposited by supersaturated meteoric waters; this produces speleothems, such as stalactites. Another form taken by calcite is oolitic limestone, which can be recognized by its granular appearance; the primary source of the calcite in limestone is most marine organisms. Some of these organisms can construct mounds of rock building upon past generations. Below about 3,000 meters, water pressure and temperature conditions cause the dissolution of calcite to increase nonlinearly, so limestone does not form in deeper waters.
Limestones may form in lacustrine and evaporite depositional environments. Calcite can be dissolved or precipitated by groundwater, depending on several factors, including the water temperature, pH, dissolved ion concentrations. Calcite exhibits an unusual characteristic called retrograde solubility, in which it becomes less soluble in water as the temperature increases. Impurities will cause limestones to exhibit different colors with weathered surfaces. Limestone may be crystalline, granular, or massive, depending on the method of formation. Crystals of calcite, dolomite or barite may line small cavities in the rock; when conditions are right for precipitation, calcite forms mineral coatings that cement the existing rock grains together, or it can fill fractures. Travertine is a banded, compact variety of limestone formed along streams where there are waterfalls and around hot or cold springs. Calcium carbonate is deposited where evaporation of the water leaves a solution supersaturated with the chemical constituents of calcite.
Tufa, a porous or cellular variety of travertine, is found near waterfalls. Coquina is a poorly consolidated limestone composed of pieces of coral or shells. During regional metamorphism that occurs during the mountain building process, limestone recrystallizes into marble. Limestone is a parent material of Mollisol soil group. Two major classification schemes, the Folk and the Dunham, are used for identifying the types of carbonate rocks collectively known as limestone. Robert L. Folk developed a classification system that places primary emphasis on the detailed composition of grains and interstitial material in carbonate rocks. Based on composition, there are three main components: allochems and cement; the Folk system uses two-part names. It is helpful to have a petrographic microscope when using the Folk scheme, because it is easier to determine the components present in each sample; the Dunham scheme focuses on depositional textures. Each name is based upon the texture of the grains. Robert J. Dunham published his system for limestone in 1962.
Dunham divides the rocks into four main groups based on relative proportions of coarser clastic particles. Dunham names are for rock families, his efforts deal with the question of whether or not the grains were in mutual contact, therefore self-supporting, or whether the rock is characterized by the presence of frame builders and algal mats. Unlike the Folk scheme, Dunham deals with the original porosity of the rock; the Dunham scheme is more useful for hand samples because it is based on texture, not the grains in the sample. A revised classification was proposed by Wright, it adds some diagenetic patterns and can be summarized as follows: See: Carbonate platform About 10% of all sedimentary rocks are limestones. Limestone is soluble in acid, therefore forms many erosional landforms; these include limestone pavements, pot holes, cenotes and gorges. Such erosion landscapes are known
Nemrut is a dormant volcano in Eastern Turkey, close to Lake Van. The volcano is named after King Nimrod, said to have ruled this area in about 2100 BC; the most powerful eruptions of Nemrut occurred in the Pleistocene. Many small eruptions occurred during the Holocene, the last one in 1692; the top of the volcano is a large caldera. Nemrut is a polygenic stratovolcano located in the collision zone of the Arabian and Eurasian tectonic plates, which determines the seismic and volcanic activity in the region; the collision of these plates began in the Middle Eocene and closed the stretch of water, which in the Mesozoic formed the Tethys Ocean. Nemrut, along with three other extinct volcanoes of eastern Turkey: Ararat, Tendürek and Süphan, is located in the area of a complex fault, which runs along the boundary of the Arabian and Eurasian plates in the territory of the Armenian Highland, it is the westernmost of these volcanoes, the only one that remains active, the only volcano in Anatolia, which erupted in the historical period.
Nemrut is located 10 km north in the north-western shore of Lake Van. Nemrut was formed in the early Quaternary Period, about 1 million years ago, it showed the greatest activity in the Pleistocene, with regular eruptions occurring in the Holocene. In the middle Pleistocene, about 250,000 years ago, a major eruption formed a lava flow over 60 km long, which blocked the water discharge from the Van basin and formed Lake Van, the world's largest alkali endorheic lake. In the same period, the conical top of the volcano collapsed inward; the freshwater Lake Nemrut formed inside the caldera, becoming the world's second largest caldera lake. Subsequent eruptions separated a small lake Ilı from Lake Nemrut. Nemrut volcano has an elliptical shape, its size at the base is 27×18 km, its center contains 377.5 km3 of volcanic materials. The caldera of Nemrut is the largest in Turkey, the fourth largest in Europe and sixteenth largest in the world. Locals link the name of the volcano with the legendary ruler Nimrod, credited with the construction of the Tower of Babel.
Turkish chronicles of the 16th century reproduce a local legend as follows: Native believe that Nemruz used to spend the winters around and the summers on this mountain. For this purpose, he had a palace built on the summit, he used to spend lots of time there. He got caught; the god let this mountain, the height of, not less than 2000 zira collapse and sink 1500 zira. This sinking created a lake of 5000 zira wide. Eruptions of Nemrut are mentioned in Armenian sources of the 15th century and Kurdish sources of the 16th century; these records allowed to confirm the activity of the volcano during the Holocene and to establish the dates of some eruptions. In 1441 a great sign took place, for the mountain called Nemrud, which lies between Kelath and Bitlis began to rumble like heavy thunder; this set the whole land into terror and consternation, for one saw that the mountain was rent asunder to the breadth of a city. Red-hod stones glowed in the terrible flames, boulders of enormous size were hurled aloft with peals of thunder.
In other provinces men saw all this distinctly. A more recent eruption is mentioned in Turkish records: In the northern part of this location there is a canal through which flows a dark water, it resembles the dark water which flows off the blacksmith's bellows and its weight is heavier than iron. It spouts upward and flows down to the gorge. According to me, each year this water decreases, it spreads around longer than 100 zira. And there it spouts out from several points. Whoever has the intention to separate part of this water will face great difficulties; the Armenian name of the volcano might reflect the regular activity of the volcano in the historical period. The first systematic studies of the volcano began in the mid-19th century, taking advantage of the British influence in the region, it was visited by several European explorers, they described and mapped the area, some, including the British archaeologist Austen Henry Layard, explored the remains of Urartu fortresses around Lake Van.
In this period it was suggested that the unusual structure of the watersheds in the region, the formation of Lake Van, is related to a large volcanic eruption and the blocking of the water discharge to Murat River by the lava flow. The most detailed work on the subject was the doctoral thesis of the English scientist Felix Oswald, "A Treatise on the Geology of Armenia", which devotes a large part to Nemrut. Oswald documented many measurements and observations, he suggested possible ways of the evolution of Nemrut, most of which were confirmed later. In the 20th century, the scientific study of the volcano was interrupted by the political instability in the region. In the first half of the 20th century Nemrut was wrongly classified as an extinct volcano. Only in the 1980s, with the resumption of the studies, its status was changed to dormant. Nemrut is studied by Turkish volcanologists; the volcano is still poorly understood, there is no consensus on the interpretation of stratigraphic data. Analysis of the sediments of Lake Van, near the volcano, allowed clarification of the chronology and activity of recent eruptions.
Iconoclasm is the social belief in the importance of the destruction of icons and other images or monuments, most for religious or political reasons. People who engage in or support iconoclasm are called iconoclasts, a term that has come to be applied figuratively to any individual who challenges "cherished beliefs or venerated institutions on the grounds that they are erroneous or pernicious". Conversely, one who reveres or venerates religious images is called an iconolater; the term does not encompass the specific destruction of images of a ruler after his death or overthrow. Iconoclasm may be carried out by people of a different religion, but is the result of sectarian disputes between factions of the same religion. Within Christianity, iconoclasm has been motivated by those who adopt a strict interpretation of the Ten Commandments, which forbid the making and worshipping of "graven images or any likeness of anything"; the Church Fathers identified Jews, fundamental iconoclasts, with heresy and saw deviations from orthodox Christianity and opposition to the veneration of images as heresies that were "Jewish in spirit".
The degree of iconoclasm among Christian branches varies. Islam, in general, tends to be more iconoclastic than Christianity, with Sunni Islam being more iconoclastic than Shia Islam. In the Bronze Age, the most significant episode of iconoclasm occurred in Egypt during the Amarna Period, when Akhenaten, based in his new capital of Akhetaten, instituted a significant shift in Egyptian artistic styles alongside a campaign of intolerance towards the traditional gods and a new emphasis on a state monolatristic tradition focused on the god Aten, the Sun disk— many temples and monuments were destroyed as a result: In rebellion against the old religion and the powerful priests of Amun, Akhenaten ordered the eradication of all of Egypt's traditional gods, he sent royal officials to chisel out and destroy every reference to Amun and the names of other deities on tombs, temple walls, cartouches to instill in the people that the Aten was the one true god. Public references to Akhenaten were destroyed soon after his death.
Comparing the ancient Egyptians with the Israelites, Jan Assmann writes: For Egypt, the greatest horror was the destruction or abduction of the cult images. In the eyes of the Israelites, the erection of images meant the destruction of divine presence. In Egypt, iconoclasm was the most terrible religious crime. In this respect Osarseph alias Akhenaten, the iconoclast, the Golden Calf, the paragon of idolatry, correspond to each other inversely, it is strange that Aaron could so avoid the role of the religious criminal, it is more than probable. In this respect and Akhenaten became, after all related. Although widespread use of Christian iconography only began as Christianity spread among gentiles after the legalization of Christianity by Roman Emperor Constantine, scattered expressions of opposition to the use of images were reported; the period after the reign of Byzantine Emperor Justinian evidently saw a huge increase in the use of images, both in volume and quality, a gathering aniconic reaction.
In the Eastern Roman Empire, government-led iconoclasm began with Byzantine Emperor Leo III, following what seems to have been a long period of rising opposition to the use or misuse of images. The religious conflict created economic divisions in Byzantine society, it was supported by the Eastern, non-Greek peoples of the Empire who had to deal with raids from the new Muslim Empire. On the other hand, the wealthier Greeks of Constantinople, the peoples of the Balkan and Italian provinces opposed iconoclasm. Within the Byzantine Empire the government had been adopting Christian images more frequently. One notable change came in 695, when Justinian II's government added a full-face image of Christ on the obverse of imperial gold coins; the change caused the Caliph Abd al-Malik to stop his earlier adoption of Byzantine coin types. He started a purely Islamic coinage with lettering only. A letter by the Patriarch Germanus written before 726 to two Iconoclast bishops says that "now whole towns and multitudes of people are in considerable agitation over this matter" but there is little written evidence of the debate.
The first iconoclastic wave happened in Wittenberg in the early 1520s under reformers Thomas Müntzer and Andreas Karlstadt. It prompted Martin Luther concealing as Junker Jörg, to intervene. In contrast to the Lutherans who favoured sacred art in their churches and homes, the Reformed leaders, in particular Andreas Karlstadt, Huldrych Zwingli and John Calvin, encouraged the removal of religious images by invoking the Decalogue's prohibition of idolatry and the manufacture of graven images of God; as a result, individuals attacked images. However, in most cases, civil authorities removed images in an orderly manner in the newly Reformed Protestant cities and territories of Europe. Calvinist Iconoclasm during the Reformation Significant iconoclastic riots took place in Basel, Copenhagen, Münster, Augsburg, Scotland and Saintes and La Rochelle. Calvinist iconoclasm in Europe "provoked reactive riots by Lutheran mobs" in Germany and "antagonized the neighbouring Eastern Orth
In architecture the frieze is the wide central section part of an entablature and may be plain in the Ionic or Doric order, or decorated with bas-reliefs. When neither columns nor pilasters are expressed, on an astylar wall it lies upon the architrave and is capped by the moldings of the cornice. A frieze can be found on many Greek and Roman buildings, the Parthenon Frieze being the most famous, the most elaborate; this style is typical for the Persians. In interiors, the frieze of a room is the section of wall above the picture rail and under the crown moldings or cornice. By extension, a frieze is a long stretch of painted, sculpted or calligraphic decoration in such a position above eye-level. Frieze decorations may depict scenes in a sequence of discrete panels; the material of which the frieze is made of may be plasterwork, carved wood or other decorative medium. In an example of an architectural frieze on the façade of a building, the octagonal Tower of the Winds in the Roman agora at Athens bears relief sculptures of the eight winds on its frieze.
A pulvinated frieze is convex in section. Such friezes were features of 17th-century Northern Mannerism in subsidiary friezes, much employed in interior architecture and in furniture; the concept of a frieze has been generalized in the mathematical construction of frieze patterns. Media related to Friezes at Wikimedia Commons "Frieze". Encyclopædia Britannica. 1911
Mercury is the smallest and innermost planet in the Solar System. Its orbital period around the Sun of 87.97 days is the shortest of all the planets in the Solar System. It is named after the messenger of the gods. Like Venus, Mercury orbits the Sun within Earth's orbit as an inferior planet, never exceeds 28° away from the Sun when viewed from Earth; this proximity to the Sun means the planet can only be seen near the western or eastern horizon during the early evening or early morning. At this time it may appear as a bright star-like object, but is far more difficult to observe than Venus; the planet telescopically displays the complete range of phases, similar to Venus and the Moon, as it moves in its inner orbit relative to Earth, which reoccurs over the so-called synodic period every 116 days. Mercury is tidally locked with the Sun in a 3:2 spin-orbit resonance, rotates in a way, unique in the Solar System; as seen relative to the fixed stars, it rotates on its axis three times for every two revolutions it makes around the Sun.
As seen from the Sun, in a frame of reference that rotates with the orbital motion, it appears to rotate only once every two Mercurian years. An observer on Mercury would therefore see only one day every two Mercurian years. Mercury's axis has the smallest tilt of any of the Solar System's planets, its orbital eccentricity is the largest of all known planets in the Solar System. Mercury's surface appears cratered and is similar in appearance to the Moon's, indicating that it has been geologically inactive for billions of years. Having no atmosphere to retain heat, it has surface temperatures that vary diurnally more than on any other planet in the Solar System, ranging from 100 K at night to 700 K during the day across the equatorial regions; the polar regions are below 180 K. The planet has no known natural satellites. Two spacecraft have visited Mercury: Mariner 10 flew by in 1974 and 1975; the BepiColombo spacecraft is planned to arrive at Mercury in 2025. Mercury appears to have a solid silicate crust and mantle overlying a solid, iron sulfide outer core layer, a deeper liquid core layer, a solid inner core.
Mercury is one of four terrestrial planets in the Solar System, is a rocky body like Earth. It is the smallest planet in the Solar System, with an equatorial radius of 2,439.7 kilometres. Mercury is smaller—albeit more massive—than the largest natural satellites in the Solar System and Titan. Mercury consists of 70% metallic and 30% silicate material. Mercury's density is the second highest in the Solar System at 5.427 g/cm3, only less than Earth's density of 5.515 g/cm3. If the effect of gravitational compression were to be factored out from both planets, the materials of which Mercury is made would be denser than those of Earth, with an uncompressed density of 5.3 g/cm3 versus Earth's 4.4 g/cm3. Mercury's density can be used to infer details of its inner structure. Although Earth's high density results appreciably from gravitational compression at the core, Mercury is much smaller and its inner regions are not as compressed. Therefore, for it to have such a high density, its core must be rich in iron.
Geologists estimate. Research published in 2007 suggests. Surrounding the core is a 500–700 km mantle consisting of silicates. Based on data from the Mariner 10 mission and Earth-based observation, Mercury's crust is estimated to be 35 km thick.. One distinctive feature of Mercury's surface is the presence of numerous narrow ridges, extending up to several hundred kilometers in length, it is thought that these were formed as Mercury's core and mantle cooled and contracted at a time when the crust had solidified. Mercury's core has a higher iron content than that of any other major planet in the Solar System, several theories have been proposed to explain this; the most accepted theory is that Mercury had a metal–silicate ratio similar to common chondrite meteorites, thought to be typical of the Solar System's rocky matter, a mass 2.25 times its current mass. Early in the Solar System's history, Mercury may have been struck by a planetesimal of 1/6 that mass and several thousand kilometers across.
The impact would have stripped away much of the original crust and mantle, leaving the core behind as a major component. A similar process, known as the giant impact hypothesis, has been proposed to explain the formation of the Moon. Alternatively, Mercury may have formed from the solar nebula before the Sun's energy output had stabilized, it would have had twice its present mass, but as the protosun contracted, temperatures near Mercury could have been between 2,500 and 3,500 K and even as high as 10,000 K. Much of Mercury's surface rock could have been vaporized at such temperatures, forming an atmosphere of "rock vapor" that could have been carried away by the solar wind. A third hypothesis proposes that the solar nebula caused drag on the particles from which Mercury was accreting, which meant that lighter particles were lost from the accreting material and not gathered by Mercury; each hypothesis predicts a different surface composition, there are two space missions set to make observations.
A tumulus is a mound of earth and stones raised over a grave or graves. Tumuli are known as barrows, burial mounds or kurgans, may be found throughout much of the world. A cairn, a mound of stones built for various purposes, may originally have been a tumulus. Tumuli are categorised according to their external apparent shape. In this respect, a long barrow is a long tumulus constructed on top of several burials, such as passage graves. A round barrow is a round tumulus commonly constructed on top of burials; the internal structure and architecture of both long and round barrows has a broad range, the categorization only refers to the external apparent shape. The method of inhumation may involve a dolmen, a cist, a mortuary enclosure, a mortuary house, or a chamber tomb. Examples of barrows include Duggleby Maeshowe; the word tumulus is Latin for'mound' or'small hill', derived from the Proto-Indo-European root *teuh2- with extended zero grade *tum-,'to bulge, swell' found in tumor, thumb and thousand.
The funeral of Patroclus is described in book 23 of the Iliad. Patroclus is burned on a pyre, his bones are collected into a golden urn in two layers of fat; the barrow is built on the location of the pyre. Achilles sponsors funeral games, consisting of a chariot race, wrestling, running, a duel between two champions to the first blood, discus throwing and spear throwing. Beowulf's body is taken to Hronesness. During cremation, the Geats lament the death of their lord, a widow's lament being mentioned in particular, singing dirges as they circumambulate the barrow. Afterwards, a mound is built on top of a hill, overlooking the sea, filled with treasure. A band of twelve of the best warriors ride around the barrow, singing dirges in praise of their lord. Parallels have been drawn to the account of Attila's burial in Jordanes' Getica. Jordanes tells that as Attila's body was lying in state, the best horsemen of the Huns circled it, as in circus games. An Old Irish Life of Columcille reports that every funeral procession "halted at a mound called Eala, whereupon the corpse was laid, the mourners marched thrice solemnly round the spot."
Archaeologists classify tumuli according to their location and date of construction. Some British types are listed below: Bank barrow Bell barrow Bowl barrow D-shaped barrow – round barrow with a purposely flat edge at one side defined by stone slabs. Disc barrow Fancy barrow – generic term for any Bronze Age barrows more elaborate than a simple hemispherical shape. Long barrow Oval barrow – a Neolithic long barrow consisting of an elliptical, rather than rectangular or trapezoidal mound. Platform barrow – The least common of the recognised types of round barrow, consisting of a flat, wide circular mound that may be surrounded by a ditch, they occur across southern England with a marked concentration in East and West Sussex. Pond barrow – a barrow consisting of a shallow circular depression, surrounded by a bank running around the rim of the depression, from the Bronze Age. Ring barrow – a bank that encircles a number of burials. Round barrow – a circular feature created by the Bronze Age peoples of Britain and the Romans and Saxons.
Divided into subclasses such as saucer and bell barrow—the Six Hills are a rare Roman example. Saucer barrow – a circular Bronze Age barrow that features a low, wide mound surrounded by a ditch that may have an external bank. Square barrow – burial site of Iron Age date, consisting of a small, ditched enclosure surrounding a central burial, which may have been covered by a mound. In 2015, the first long barrow in thousands of years, inspired by those built in the Neolithic Period, was built near All Cannings in England; the project was steward of Stonehenge. The barrow was designed to have a large number of private niches within the stone and earth structure to receive cremation urns; the structure received significant media attention, with national press writing extensively about the revival of the structures, various episodes of filming, for example by BBC Countryfile as it was being built. It was subscribed within eighteen months; this was followed soon after by a new barrow near St Neots. Further plans to revive barrows are at Soulton in Shropshire.
The word kurgan is of Turkic origin, derives from Proto-Turkic *Kur-. In Ukraine and Russia, there are royal kurgans of Varangian chieftains, such as the Black Grave in Ukrainian Chernihiv, Oleg's Grave in Russian Staraya Ladoga, vast, intricate Rurik's Hill near Russian Novgorod. Other important kurgans are found in Ukraine and South Russia and are associated with much more ancient steppe peoples, notably the Scythians and early Indo-Europeans The steppe cultures found in Ukraine and South Russia continue into Central Asia, in particular Kazakhstan. Salweyn in northern Somalia contains a large field of cairns, which stretches for a distance of around 8 km. An excavation of one of these tumuli by Georges Révoil in 1881 uncovered a tomb, beside which were artefacts pointing to an ancient, advanced civilization; the interred objects included pottery shards from Samos, some well-crafted enamels, a mask of Ancient Greek design. Tumuli are one of the most prominent types of prehistoric monuments spread throughout northern and southern Albania.
Some well-known local tumuli are: Kamenica Tumulus Lofkënd Tumulus Pazhok Tumulus More than 50 burial mounds were found in Kupres. Man from Kupres- the skeleton found
Ahura Mazda is the creator and sole God of Zoroastrianism. Ahura Mazda is the highest spirit of worship in Zoroastrianism, along with being the first and most invoked spirit in the Yasna; the literal meaning of the word Ahura is "lord", that of Mazda is "wisdom". Ahura Mazda first appeared in the Achaemenid period under Darius I's Behistun Inscription; until Artaxerxes II of Persia, Ahura Mazda was invoked alone. With Artaxerxes II, Ahura Mazda was invoked with Mithra and Anahita. In the Achaemenid period, there are no representations of Ahura Mazda other than the custom for every emperor to have an empty chariot drawn by white horses, to invite Ahura Mazda to accompany the Persian army on battles. Images of Ahura Mazda began in the Parthian period, but were stopped and replaced with stone carved figures in the Sassanid period. "Mazda", or rather the Avestan stem-form Mazdā-, nominative Mazdå, reflects Proto-Iranian *mazdáH. It is taken to be the proper name of the spirit, like its Vedic cognate medhā́, means "intelligence" or "wisdom".
Both the Avestan and Sanskrit words reflect Proto-Indo-Iranian *mazdʰáH, from Proto-Indo-European *mn̥sdʰh₁éh₂ meaning "placing one's mind", hence "wise". The name was rendered as Ahuramazda during the Achaemenid era, Hormazd during the Parthian era, Ohrmazd was used during the Sassanian era; the name may be attested on cuneiform tablets of Assyrian Assurbanipal, in the form Assara Mazaš, though this interpretation is controversial. Though Ahura Mazda was a spirit in the Old Iranian religion, he had not yet been given the title of "uncreated spirit"; this title was given by Zoroaster, who proclaimed Ahura Mazda as the uncreated spirit, wholly wise and good, as well as the creator and upholder of Asha. At the age of 30, Zoroaster received a revelation: while fetching water at dawn for a sacred ritual, he saw the shining figure of the yazata, Vohu Manah, who led Zoroaster to the presence of Ahura Mazda, where he was taught the cardinal principles of the "Good Religion" known as Zoroastrianism.
As a result of this vision, Zoroaster preach the religion. He stated, he further stated that Ahura Mazda created spirits known as yazatas to aid him, who merited devotion. Zoroaster deserved no worship; these "bad" spirits were created by the hostile and evil spirit. The existence of Angra Mainyu was the source of all misery in the universe. Zoroaster claimed that Ahura Mazda was not an omnipotent God, but used the aid of humans in the cosmic struggle against Angra Mainyu. Nonetheless, Ahura Mazda is Angra Mainyu's superior, not his equal. Angra Mainyu and his daevas, which attempt to attract humans away from the path of truth and righteousness, would be destroyed. Whether the Achaemenids were Zoroastrians is a matter of much debate. However, it is known; the representation and invocation of Ahura Mazda can be seen on royal inscriptions written by Achaemenid kings. The most notable of all the inscriptions is the Behistun Inscription written by Darius I which contains many references to Ahura Mazda.
An inscription written in Greek was found in a late Achaemenid temple at Persepolis which invoked Ahura Mazda and two other spirits, most Mithra and Anahita. On the Elamite Persepolis Fortification Tablet 377, Ahura Mazda is invoked along with Mithra and Voruna. Artaxerxes III makes this invocation to the three spirits again in his reign; the early Achaemenid period contained no representation of Ahura Mazda. The winged symbol with a male figure, regarded by European scholars as Ahura Mazda has been shown to represent the royal xvarənah, the personification of royal power and glory. However, it was customary for every emperor from Cyrus until Darius III to have an empty chariot drawn by white horses as a place for Ahura Mazda to accompany the Persian army on battles; the use of images of Ahura Mazda began in the western satraps of the Achaemenid Empire in the late 5th century BCE. Under Artaxerxes II, the first literary reference as well as a statue of Ahura Mazda was built by a Persian governor of Lydia in 365 BCE.
It is known that the reverence for Ahura Mazda, as well as Anahita and Mithra continued with the same traditions during this period. The worship of Ahura Mazda with symbolic images is noticed, but it stopped with the beginning of the Sassanid period. Zoroastrian iconoclasm, which can be traced to the end of the Parthian period and the beginning of the Sassanid put an end to the use of all images of Ahura Mazda in worship. However, Ahura Mazda remained symbolized by a dignified male figure, standing or on horseback, found in Sassanian investiture. During the Sassanid Empire, a heretical form of Zoroastrianism, termed Zurvanism, emerged, it gained adherents throughout the Sassanid Empire, most notably the royal lineage of Sassanian emperors. Under the reign of Shapur I, Zurvanism became a widespread cult. Zurvanism revokes Zoroaster's original message of Ahura Mazda as the uncreated spirit, the "uncreated creator" of all, reduces him to a created spirit, one of two twin sons of Zurvan, their father and the primary spirit.
Zurvanism makes Ahura Mazda and Angra Mainyu of equal strength and only contrasting spirits. Other than Zurvanism, the Sassanian kings demonstrated their devotion to Ahura Mazda i