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117-517: The Toroweap Formation is a darker unit of gypsum and shale ; also sandstone . In photos the cliff-forming Kaibab and Coconino units, show the more erodable Toroweap Formation slope-forming accumulations upon the underlying Coconino Sandstone; likewise below the Coconino, the softer Hermit Formation is shown forming slopes, above the slope forming 'redbeds' of the Supai Group . Close-up views of

234-633: A devastating war with Persia exhausted the empire's resources; the early Muslim conquests that followed saw the loss of the empire's richest provinces— Egypt and Syria —to the Rashidun Caliphate . In 698, Africa was lost to the Umayyad Caliphate , but the empire subsequently stabilised under the Isaurian dynasty. The empire was able to expand once more under the Macedonian dynasty , experiencing

351-577: A recommended exposure limit (REL) of TWA 10 mg/m for total exposure and TWA 5 mg/m for respiratory exposure over an eight-hour workday. Gypsum is used in a wide variety of applications: Byzantine Empire The Byzantine Empire , also referred to as the Eastern Roman Empire , was the continuation of the Roman Empire centred in Constantinople during late antiquity and

468-456: A sensational victory against Bulgaria and the Kievan Rus' in 971. John in particular was an astute administrator who reformed military structures and implemented effective fiscal policies. After John's death, Constantine VII's grandsons Basil II and Constantine VIII ruled jointly for half a century, although the latter exercised no real power before Basil's death in 1025. Their early reign

585-463: A combination of external threats and internal instabilities caused the Roman state to splinter as regional armies acclaimed their generals as "soldier-emperors". One of these, Diocletian ( r.  284–305 ), seeing that the state was too big to be ruled by one man, attempted to fix the problem by instituting a Tetrarchy , or rule of four, and dividing the empire into eastern and western halves. Although

702-626: A considerable increase in the size of urban settlements, together with a notable upsurge in new towns. Trade was also flourishing; the Venetians, the Genoese and others opened up the ports of the Aegean to commerce, shipping goods from the Crusader states and Fatimid Egypt to the west and trading with the empire via Constantinople. Manuel's death on 24 September 1180 left his 11-year-old son Alexios II Komnenos on

819-512: A fertilizer. Gypsum may act as a source of sulfur for plant growth, and in the early 19th century, it was regarded as an almost miraculous fertilizer. American farmers were so anxious to acquire it that a lively smuggling trade with Nova Scotia evolved, resulting in the so-called "Plaster War" of 1820. Gypsum is moderately water-soluble (~2.0–2.5 g/L at 25 °C) and, in contrast to most other salts, it exhibits retrograde solubility, becoming less soluble at higher temperatures. When gypsum

936-577: A large number in Venice. According to chronicler Niketas Choniates , a prostitute was even set up on the patriarchal throne. When order had been restored, the crusaders and the Venetians proceeded to implement their agreement; Baldwin of Flanders was elected emperor of a new Latin Empire , and the Venetian Thomas Morosini was chosen as patriarch. The lands divided up among the leaders included most of

1053-504: A lengthy conflict against Sasanid Persia and ended in 363 with the death of his son-in-law Julian . The short Valentinianic dynasty , occupied with wars against barbarians , religious debates, and anti-corruption campaigns, ended in the East with the death of Valens at the Battle of Adrianople in 378. Valens's successor, Theodosius I ( r.  379–395 ), restored political stability in

1170-632: A line through the Adriatic Sea and south to Cyrene, Libya . This encompassed most of the Balkans , all of modern Greece, Turkey, Syria , Palestine ; North Africa, primarily with modern Egypt and Libya ; the Aegean islands along with Crete , Cyprus and Sicily , and a small settlement in Crimea . The landscape of the Empire was defined by the fertile fields of Anatolia , long mountain ranges and rivers such as

1287-474: A range of industrial processes. Flue gas desulfurization gypsum (FGDG) is recovered at some coal-fired power plants. The main contaminants are Mg, K, Cl, F, B, Al, Fe, Si, and Se. They come both from the limestone used in desulfurization and from the coal burned. This product is pure enough to replace natural gypsum in a wide variety of fields including drywalls, water treatment, and cement set retarder. Improvements in flue gas desulfurization have greatly reduced

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1404-413: A result, waste gypsum is stored in stacks indefinitely, with significant risk of leaching their contaminants into water and soil. To reduce the accumulation and ultimately clear out these stacks, research is underway to find more applications for such waste products. People can be exposed to gypsum in the workplace by breathing it in, skin contact, and eye contact. Calcium sulfate per se is nontoxic and

1521-450: A small fleet of 100 ships to defend the capital, but other than that he was indifferent to the populace. He was finally overthrown when Isaac II Angelos , surviving an imperial assassination attempt, seized power with the aid of the people and had Andronikos killed. The reign of Isaac II, and more so that of his brother Alexios III , saw the collapse of what remained of the centralised machinery of Byzantine government and defence. Although

1638-417: A speedy and marked improvement. Gradually, however, Andronikos's reign deteriorated. The aristocrats were infuriated against him, and to make matters worse, Andronikos seemed to have become increasingly unbalanced; executions and violence became increasingly common, and his reign turned into a reign of terror. Andronikos seemed almost to seek the extermination of the aristocracy as a whole. The struggle against

1755-593: A two-century-long renaissance . This came to an end in 1071, with the defeat by the Seljuk Turks at the Battle of Manzikert . Thereafter, periods of civil war and Seljuk incursion resulted in the loss of most of Asia Minor . The empire recovered during the Komnenian restoration , and Constantinople would remain the largest and wealthiest city in Europe until the 13th century. The empire was largely dismantled in 1204, following

1872-510: A two-month siege on 29 May 1453. The final Byzantine emperor, Constantine XI Palaiologos , was last seen casting off his imperial regalia and throwing himself into hand-to-hand combat after the walls of the city were taken. The Empire was centred in what is now Greece and Turkey with Constantinople as its capital. In the 5th century, it controlled the eastern basis of the Mediterranean running east from Singidunum (modern Belgrade ) in

1989-529: A wide range of colors to local deposits. Because gypsum dissolves over time in water, gypsum is rarely found in the form of sand. However, the unique conditions of the White Sands National Park in the US state of New Mexico have created a 710 km (270 sq mi) expanse of white gypsum sand, enough to supply the US construction industry with drywall for 1,000 years. Commercial exploitation of

2106-510: Is contaminated by impurities found in the rock, namely fluoride , silica , radioactive elements such as radium , and heavy metal elements such as cadmium . Similarly, production of titanium dioxide produces titanium gypsum (TG) due to neutralization of excess acid with lime . The product is contaminated with silica, fluorides, organic matters, and alkalis. Impurities in refinery gypsum waste have, in many cases, prevented them from being used as normal gypsum in fields such as construction. As

2223-448: Is even approved as a food additive, but as powdered gypsum, it can irritate skin and mucous membranes. The Occupational Safety and Health Administration (OSHA) has set the legal limit ( permissible exposure limit ) for gypsum exposure in the workplace as TWA 15 mg/m for total exposure and TWA 5 mg/m for respiratory exposure over an eight-hour workday. The National Institute for Occupational Safety and Health (NIOSH) has set

2340-531: Is evidence that some Komnenian heirs had set up a semi-independent state in Trebizond before 1204. According to the historian Alexander Vasiliev , "the dynasty of the Angeloi, Greek in its origin, ... accelerated the ruin of the Empire, already weakened without and disunited within." In 1198, Pope Innocent III broached the subject of a new crusade through legates and encyclical letters. The stated intent of

2457-593: Is heated in air it loses water and converts first to calcium sulfate hemihydrate ( bassanite , often simply called "plaster") and, if heated further, to anhydrous calcium sulfate ( anhydrite ). As with anhydrite , the solubility of gypsum in saline solutions and in brines is also strongly dependent on sodium chloride (common table salt) concentration. The structure of gypsum consists of layers of calcium (Ca ) and sulfate ( SO 2− 4 ) ions tightly bound together. These layers are bonded by sheets of anion water molecules via weaker hydrogen bonding , which gives

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2574-532: Is impossible to precisely date the foundation of the Byzantine Empire. In a series of conflicts between the third and first centuries   BC, the Roman Republic gradually established hegemony over the eastern Mediterranean , while its government ultimately transformed into the one-person rule of an emperor . The Roman Empire enjoyed a period of relative stability until the third century AD , when

2691-585: Is just upstream, with the Toroweap Fault forming its west flank). The Toroweap Overlook was visited in the 1800s by original photographers of the Grand Canyon. The Permian geologic sequence common in the Grand Canyon: Gypsum Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate , with the chemical formula CaSO 4 ·2H 2 O . It is widely mined and

2808-462: Is prized for ornamental work of various sorts. In arid areas, gypsum can occur in a flower-like form, typically opaque, with embedded sand grains called desert rose . It also forms some of the largest crystals found in nature, up to 12 m (39 ft) long, in the form of selenite. Gypsum is a common mineral, with thick and extensive evaporite beds in association with sedimentary rocks . Deposits are known to occur in strata from as far back as

2925-575: Is used as a fertilizer and as the main constituent in many forms of plaster , drywall and blackboard or sidewalk chalk . Gypsum also crystallizes as translucent crystals of selenite . It forms as an evaporite mineral and as a hydration product of anhydrite . The Mohs scale of mineral hardness defines gypsum as hardness value 2 based on scratch hardness comparison . Fine-grained white or lightly tinted forms of gypsum known as alabaster have been used for sculpture by many cultures including Ancient Egypt , Mesopotamia , Ancient Rome ,

3042-692: The Tactica , a military treatise; and the Book of the Eparch , which codified Constantinople's trading regulations. In non-literary contexts Leo was less successful: the empire lost in Sicily and against the Bulgarians , while he provoked theological scandal by marrying four times in an attempt to father a legitimate heir. The early reign of that heir, Constantine VII , was tumultuous, as his mother Zoe , his uncle Alexander ,

3159-493: The Archaean eon . Gypsum is deposited from lake and sea water, as well as in hot springs , from volcanic vapors, and sulfate solutions in veins . Hydrothermal anhydrite in veins is commonly hydrated to gypsum by groundwater in near-surface exposures. It is often associated with the minerals halite and sulfur . Gypsum is the most common sulfate mineral. Pure gypsum is white, but other substances found as impurities may give

3276-693: The Byzantine Empire , and the Nottingham alabasters of Medieval England . The word gypsum is derived from the Greek word γύψος ( gypsos ), "plaster". Because the quarries of the Montmartre district of Paris have long furnished burnt gypsum ( calcined gypsum) used for various purposes, this dehydrated gypsum became known as plaster of Paris . Upon adding water, after a few dozen minutes, plaster of Paris becomes regular gypsum (dihydrate) again, causing

3393-524: The Catalan Company ravaging the countryside and increasing resentment towards Constantinople. The situation became worse for Byzantium during the civil wars after Andronikos III died. A six-year-long civil war devastated the empire, allowing the Serbian ruler Stefan Dušan to overrun most of the empire's remaining territory and establish a Serbian Empire . In 1354, an earthquake at Gallipoli devastated

3510-681: The Council of Clermont and urged all those present to take up arms under the sign of the Cross and launch an armed pilgrimage to recover Jerusalem and the East from the Muslims. The response in Western Europe was overwhelming. Alexios was able to recover a number of important cities, islands and much of western Asia Minor. The Crusaders agreed to become Alexios' vassals under the Treaty of Devol in 1108, which marked

3627-655: The Council of Piacenza in 1095, envoys from Alexios spoke to Pope Urban II about the suffering of the Christians of the East and underscored that without help from the West, they would continue to suffer under Muslim rule. Urban saw Alexios' request as a dual opportunity to cement Western Europe and reunite the Eastern Orthodox Church with the Roman Catholic Church under his rule. On 27 November 1095, Urban called

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3744-471: The Danube , he pushed his troops too far in 602—they mutinied, proclaimed an officer named Phocas as emperor, and executed Maurice. The Sasanians seized their moment and reopened hostilities ; Phocas was unable to cope and soon faced a major rebellion led by Heraclius . Phocas lost Constantinople in 610 and was soon executed, but the destructive civil war accelerated the empire's decline. Under Khosrow II ,

3861-717: The Danube . In the north and west were the Balkans, the corridors between the mountain ranges of Pindos , the Dinaric Alps , the Rhodopes and the Balkans . In the south and east were Anatolia, the Pontic Mountains and the Taurus - Anti-Taurus range, which served as passages for armies, while the Caucasus mountains lay between the Empire and its eastern neighbours. Roman roads connected

3978-617: The Empire of Trebizond , was created after Alexios I of Trebizond , commanding the Georgian expedition in Chaldia a few weeks before the sack of Constantinople, found himself de facto emperor and established himself in Trebizond. Of the three successor states, Epirus and Nicaea stood the best chance of reclaiming Constantinople. The Nicaean Empire struggled to survive the next few decades, however, and by

4095-756: The Mars Reconnaissance Orbiter (MRO) have indicated the existence of gypsum dunes in the northern polar region of Mars, which were later confirmed at ground level by the Mars Exploration Rover (MER) Opportunity . Commercial quantities of gypsum are found in the cities of Araripina and Grajaú in Brazil; in Pakistan, Jamaica, Iran (world's second largest producer), Thailand, Spain (the main producer in Europe), Germany, Italy, England, Ireland, Canada and

4212-582: The Middle Ages . The eastern half of the Empire survived the conditions that caused the fall of the West in the 5th century AD, and continued to exist until the fall of Constantinople to the Ottoman Empire in 1453. During most of its existence, the empire remained the most powerful economic, cultural, and military force in the Mediterranean world . The term "Byzantine Empire" was only coined following

4329-663: The Normans who arrived in Italy at the beginning of the 11th century. During a period of strife between Constantinople and Rome culminating in the East-West Schism of 1054 , the Normans advanced gradually into Byzantine Italy . Reggio , the capital of the tagma of Calabria, was captured in 1060 by Robert Guiscard , followed by Otranto in 1068. Bari , the main Byzantine stronghold in Apulia ,

4446-565: The Pechenegs , who were caught by surprise and annihilated at the Battle of Levounion on 28 April 1091. Having achieved stability in the West, Alexios could turn his attention to the severe economic difficulties and the disintegration of the empire's traditional defences. However, he still did not have enough manpower to recover the lost territories in Asia Minor and to the advance by the Seljuks. At

4563-454: The Roman papacy . In 780, Empress Irene assumed power on behalf of her son Constantine VI . Although she was a capable administrator who temporarily resolved the iconoclasm controversy, the empire was destabilized by her feud with her son. The Bulgars and Abbasids meanwhile inflicted numerous defeats on the Byzantine armies, and the papacy crowned Charlemagne as Roman emperor in 800. In 802,

4680-599: The Sack of Constantinople by Latin armies at the end of the Fourth Crusade ; its former territories were then divided into competing Greek rump states and Latin realms . Despite the eventual recovery of Constantinople in 1261, the reconstituted empire would wield only regional power during its final two centuries of existence. Its remaining territories were progressively annexed by the Ottomans in perennial wars fought throughout

4797-508: The sea walls of Constantinople , overhaul provincial governance, and wage inconclusive campaigns against the Abbasids. After his death, his empress Theodora , ruling on behalf of her son Michael III , permanently extinguished the iconoclastic movement; the empire prospered under their sometimes-fraught rule. However, Michael was posthumously vilified by historians loyal to the dynasty of his successor Basil I , who assassinated him in 867 and who

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4914-453: The state religion , and other religious practices were proscribed . Greek gradually replaced Latin for official use as Latin fell into disuse. The empire experienced several cycles of decline and recovery throughout its history, reaching its greatest extent after the fall of the west during the reign of Justinian I ( r. 527–565 ), who briefly reconquered much of Italy and the western Mediterranean coast . The appearance of plague and

5031-514: The "land of the Romans" ( Bilād al-Rūm ), but the people of medieval Western Europe preferred to call them "Greeks" ( Graeci ), due to having a contested legacy to Roman identity and to associate negative connotations from ancient Latin literature. The adjective "Byzantine", which derived from Byzantion (Latinised as Byzantium ), the name of the Greek settlement Constantinople was established on,

5148-655: The 14th and 15th centuries. The fall of Constantinople to the Ottomans in 1453 ultimately brought the empire to an end. Many refugees who had fled the city after its capture settled in Italy and throughout Europe, helping to ignite the Renaissance . The fall of Constantinople is sometimes used to mark the dividing line between the Middle Ages and the early modern period . The inhabitants of the empire, now generally termed Byzantines, thought of themselves as Romans ( Romaioi ). Their Islamic neighbours similarly called their empire

5265-464: The 15th-century historian Laonikos Chalkokondyles , whose works were widely propagated, including by Hieronymus Wolf . "Byzantine" was used adjectivally alongside terms such as "Empire of the Greeks" until the 19th century. It is now the primary term, used to refer to all aspects of the empire; some modern historians believe that, as an originally prejudicial and inaccurate term, it should not be used. As

5382-626: The 532 Nika revolt he rebuilt much of Constantinople, including the original Hagia Sophia . Justinian took advantage of political instability in Italy to attempt the reconquest of lost western territories. The Vandal Kingdom in North Africa was subjugated in 534 by the general Belisarius , who then invaded Italy ; the Ostrogothic Kingdom was destroyed in 554. In the 540s, however, Justinian began to suffer reversals on multiple fronts. Taking advantage of Constantinople's preoccupation with

5499-504: The Arab efforts to capture Constantinople in the 670s , but suffered a reversal against the Bulgars , who soon established an empire in the northern Balkans . Nevertheless, he and Constans had done enough to secure the empire's position, especially as the Umayyad Caliphate was undergoing another civil war . Justinian II sought to build on the stability secured by his father Constantine but

5616-408: The Byzantine administration's policy of heavy taxation and abolishing of the levy. The weakening of Georgia and Armenia played a significant role in the Byzantine defeat at Manzikert in 1071. Basil II is considered among the most capable Byzantine emperors and his reign as the apex of the empire in the Middle Ages . By 1025, the date of Basil II's death, the Byzantine Empire stretched from Armenia in

5733-572: The Empire by land, with the Via Egnatia running from Constantinople to the Albanian coast through Macedonia and the Via Traiana to Adrianople (modern Edirne ), Serdica (modern Sofia ) and Singidunum. By water, Crete, Cyprus and Sicily were key naval points and the main ports connecting Constantinople were Alexandria, Gaza, Caesarea and Antioch. The Aegean sea was considered an internal lake within

5850-432: The Empire. The emperor was the centre of the whole administration of the Empire, who the legal historian Kaius Tuori has said was "above the law, within the law, and the law itself"; with a power that is difficult to define and which does not align with our modern understanding of the separation of powers. The proclamations of the crowds of Constantinople, and the inaugurations of the patriarch from 457, would legitimise

5967-411: The Mongol invasion also gave Nicaea a temporary respite from Seljuk attacks, allowing it to concentrate on the Latin Empire to its north. The Empire of Nicaea, founded by the Laskarid dynasty , managed to recapture Constantinople in 1261 and defeat Epirus . This led to a short-lived revival of Byzantine fortunes under Michael VIII Palaiologos , but the war-ravaged empire was ill-equipped to deal with

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6084-405: The Normans were driven out of Greece, in 1186 the Vlachs and Bulgars began a rebellion that led to the formation of the Second Bulgarian Empire . The internal policy of the Angeloi was characterised by the squandering of the public treasure and fiscal maladministration. Imperial authority was severely weakened, and the growing power vacuum at the centre of the empire encouraged fragmentation. There

6201-401: The Sassanids occupied the Levant and Egypt and pushed into Asia Minor, while Byzantine control of Italy slipped and the Avars and Slavs ran riot in the Balkans. Although Heraclius repelled a siege of Constantinople in 626 and defeated the Sassanids in 627, this was a pyrrhic victory . The early Muslim conquests soon saw the conquest of the Levant , Egypt , and the Sassanid Empire by

6318-413: The Tetrarchy system quickly failed, the division of the empire proved an enduring concept. Constantine I ( r.  306–337 ) secured sole power in 324. Over the following six years, he rebuilt the city of Byzantium as a capital city , which was renamed Constantinople . Rome , the previous capital, was further from the important eastern provinces and in a less strategically important location; it

6435-587: The Toroweap will show the resistant sandstone sub-units as erosion resistant sections. Cliffs of the Toroweap Formation can be found in Walnut Canyon National Monument , about 70 mi southeast of the Grand Canyon, and east of Flagstaff, Arizona . Marine transgression , and continental wind-blown sand, laid down the three units of Kaibab, Toroweap, and Coconino. The oceanic sea came from the west, and receded and re-transgressed. The Coconino Sandstone being made of sand dunes, continental, means that near-shore Toroweap deposits, and off-shore Kaibab Limestone, can all have

6552-426: The Turkish invaders at the Battle of Hyelion and Leimocheir , brought troops from the capital and was able to gather an army along the way, a sign that the Byzantine army remained strong and that the defensive program of western Asia Minor was still successful. John and Manuel pursued active military policies, and both deployed considerable resources on sieges and city defences; aggressive fortification policies were at

6669-570: The United States. Large open pit quarries are located in many places including Fort Dodge, Iowa , which sits on one of the largest deposits of gypsum in the world, and Plaster City, California , United States, and East Kutai , Kalimantan , Indonesia. Several small mines also exist in places such as Kalannie in Western Australia , where gypsum is sold to private buyers for additions of calcium and sulfur as well as reduction of aluminum toxicities on soil for agricultural purposes. Crystals of gypsum up to 11 m (36 ft) long have been found in

6786-402: The West Grand Canyon section. It is the site of the Toroweap Fault . Nine miles to the west is the roughly parallel Hurricane Fault (of Hurricane Cliffs , of Arizona/Utah), the west fault, of the Uinkaret Mountains ( Mount Trumbull Wilderness ). An eastern fault section separates here, and goes north into Utah, passing the west side of the Kanab Plateau . The Toroweap Overlook lies above

6903-486: The West, Khosrow I of the Sasanian Empire invaded Byzantine territory and sacked Antioch in 540. Meanwhile, the emperor's internal reforms and policies began to falter, not helped by a devastating plague that killed a large proportion of the population and severely weakened the empire's social and financial stability. The most difficult period of the Ostrogothic war, against their king Totila , came during this decade, while divisions among Justinian's advisors undercut

7020-401: The West. Zeno ( r.  474–491 ) convinced the problematic Ostrogoth king Theodoric to take control of Italy from Odoacer, which he did; dying with the empire at peace, Zeno was succeeded by Anastasius I ( r.  491–518 ). Although his Monophysitism brought occasional issues, Anastasius was a capable administrator and instituted several successful financial reforms including

7137-429: The Western provinces to achieve an economic revival that continued until the close of the century. It has been argued that Byzantium under the Komnenian rule was more prosperous than at any time since the Persian invasions of the 7th century. During the 12th century, population levels rose and extensive tracts of new agricultural land were brought into production. Archaeological evidence from both Europe and Asia Minor shows

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7254-522: The abolition of the chrysargyron tax . He was the first emperor to die with no serious problems affecting his empire since Diocletian. The reign of Justinian I was a watershed in Byzantine history. Following his accession in 527, the law-code was rewritten as the influential Corpus Juris Civilis and Justinian produced extensive legislation on provincial administration; he reasserted imperial control over religion and morality through purges of non-Christians and "deviants"; and having ruthlessly subdued

7371-401: The administration's response. He also did not fully heal the divisions in Chalcedonian Christianity , as the Second Council of Constantinople failed to make a real difference. Justinian died in 565; his reign saw more success than that of any other Byzantine emperor, yet he left his empire under massive strain. Financially and territorially overextended, Justin II ( r.  565–578 )

7488-495: The amount of toxic elements present. Gypsum precipitates onto brackish water membranes , a phenomenon known as mineral salt scaling , such as during brackish water desalination of water with high concentrations of calcium and sulfate . Scaling decreases membrane life and productivity. This is one of the main obstacles in brackish water membrane desalination processes, such as reverse osmosis or nanofiltration . Other forms of scaling, such as calcite scaling, depending on

7605-418: The area, strongly opposed by area residents, was permanently prevented in 1933 when President Herbert Hoover declared the gypsum dunes a protected national monument . Gypsum is also formed as a by-product of sulfide oxidation , amongst others by pyrite oxidation , when the sulfuric acid generated reacts with calcium carbonate . Its presence indicates oxidizing conditions. Under reducing conditions,

7722-568: The aristocracy turned into wholesale slaughter, while the emperor resorted to ever more ruthless measures to shore up his regime. Despite his military background, Andronikos failed to deal with Isaac Komnenos of Cyprus, Béla III of Hungary who reincorporated Croatian territories into Hungary, and Stephen Nemanja of Serbia who declared his independence from the Byzantine Empire. Yet, none of these troubles compared to William II of Sicily 's invasion force of 300 ships and 80,000 men, arriving in 1185 and sacking Thessalonica . Andronikos mobilised

7839-432: The capital, and Alexios Angelos was elevated to the throne as Alexios IV along with his blind father Isaac. Alexios IV and Isaac II were unable to keep their promises and were deposed by Alexios V . The crusaders again took the city on 13 April 1204 , and Constantinople was subjected to pillage and massacre by the rank and file for three days. Many priceless icons, relics and other objects later turned up in Western Europe ,

7956-431: The caves of the Naica Mine of Chihuahua , Mexico. The crystals thrived in the cave's extremely rare and stable natural environment. Temperatures stayed at 58 °C (136 °F), and the cave was filled with mineral-rich water that drove the crystals' growth. The largest of those crystals weighs 55 tonnes (61 short tons) and is around 500,000 years old. Synthetic gypsum is produced as a waste product or by-product in

8073-413: The city had collapsed so severely that it was now little more than a cluster of villages separated by fields. On 2 April 1453, Sultan Mehmed 's army of 80,000 men and large numbers of irregulars laid siege to the city. Despite a desperate last-ditch defence of the city by the massively outnumbered Christian forces (c. 7,000 men, 2,000 of whom were foreign), Constantinople finally fell to the Ottomans after

8190-439: The crusade was to conquer Egypt , the centre of Muslim power in the Levant. The Crusader army arrived at Venice in the summer of 1202 and hired the Venetian fleet to transport them to Egypt. As a payment to the Venetians, they captured the (Christian) port of Zara in Dalmatia , which was a vassal city of Venice, it had rebelled and placed itself under Hungary's protection in 1186. Shortly afterward, Alexios IV Angelos , son of

8307-622: The crystal perfect cleavage along the sheets (in the {010} plane). Gypsum occurs in nature as flattened and often twinned crystals , and transparent, cleavable masses called selenite . Selenite contains no significant selenium ; rather, both substances were named for the ancient Greek word for the Moon . Selenite may also occur in a silky, fibrous form, in which case it is commonly called "satin spar". Finally, it may also be granular or quite compact. In hand-sized samples, it can be anywhere from transparent to opaque. A very fine-grained white or lightly tinted variety of gypsum, called alabaster ,

8424-499: The deposed and blinded Emperor Isaac II, made contact with the Crusaders. Alexios offered to reunite the Byzantine church with Rome, pay the Crusaders 200,000 silver marks, join the crusade, and provide all the supplies they needed to reach Egypt. The crusaders arrived at Constantinople in the summer of 1203 and quickly attacked , starting a major fire that damaged large parts of the city, and briefly seized control. Alexios III fled from

8541-471: The east by allowing the Goths to settle in Roman territory; he also twice intervened in the western half, defeating the usurpers Magnus Maximus and Eugenius in 388 and 394 respectively. He actively condemned paganism , confirmed the primacy of Nicene Christianity over Arianism , and established Christianity as the Roman state religion . He was the last emperor to rule both the western and eastern halves of

8658-433: The east to Calabria in southern Italy in the west. Many successes had been achieved, ranging from the conquest of Bulgaria to the annexation of parts of Georgia and Armenia, and the reconquests of Crete , Cyprus , and the important city of Antioch . These were not temporary tactical gains but long-term reconquests. At the same time, Byzantium was faced with new enemies. Its provinces in southern Italy were threatened by

8775-527: The emperor's role as the leader of the Christian world, John marched into the Holy Land at the head of the combined forces of the empire and the Crusader states; yet despite his efforts in leading the campaign, his hopes were disappointed by the treachery of his Crusader allies. In 1142, John returned to press his claims to Antioch, but he died in the spring of 1143 following a hunting accident. John's chosen heir

8892-418: The empire's demise; its citizens referred to the polity as the "Roman Empire" and to themselves as "Romans". Due to the imperial seat's move from Rome to Byzantium , the adoption of state Christianity , and the predominance of Greek instead of Latin , modern historians continue to make a distinction between the earlier Roman Empire and the later Byzantine Empire . During the earlier Pax Romana period,

9009-523: The empire's eastern defences. The emergency lent weight to the military aristocracy in Anatolia, who in 1068 secured the election of one of their own, Romanos Diogenes , as emperor. In the summer of 1071, Romanos undertook a massive eastern campaign to draw the Seljuks into a general engagement with the Byzantine army. At the Battle of Manzikert , Romanos suffered a surprise defeat against Sultan Alp Arslan and

9126-544: The empire, gaining only short-term success. To avoid another sacking of the capital by the Latins, he forced the Church to submit to Rome, again a temporary solution for which the peasantry hated Michael and Constantinople. The efforts of Andronikos II and later his grandson Andronikos III marked Byzantium's last genuine attempts to restoring the glory of the empire. However, the use of mercenaries by Andronikos II often backfired, with

9243-460: The empire; after his death, the West would be destabilised by a succession of "soldier-emperors", unlike the East, where administrators would continue to hold power. Theodosius II ( r.  408–450 ) largely left the rule of the east to officials such as Anthemius , who constructed the Theodosian Walls to defend Constantinople, now firmly entrenched as Rome's capital. Theodosius' reign

9360-514: The end of the Norman threat during Alexios' reign. Alexios's son John II Komnenos succeeded him in 1118 and ruled until 1143. John was a pious and dedicated emperor who was determined to undo the damage to the empire suffered at the Battle of Manzikert half a century earlier. Famed for his piety and his remarkably mild and just reign, John was an exceptional example of a moral ruler at a time when cruelty

9477-606: The enemies that surrounded it. To maintain his campaigns against the Latins, Michael pulled troops from Asia Minor and levied crippling taxes on the peasantry, causing much resentment. Massive construction projects were completed in Constantinople to repair the damage of the Fourth Crusade, but none of these initiatives were of any comfort to the farmers in Asia Minor suffering raids from Muslim ghazis. Rather than holding on to his possessions in Asia Minor, Michael chose to expand

9594-504: The erosion resistant Tapeats Sandstone , near its west terminus in Grand Canyon . Southeast, across the river The Esplanade -(a regional section) is created, upon the erosion resistant Esplanade Sandstone , a resistant member of the Supai Group , (a unit above the Tapeats, but occurs on both the downside block, and upside block in the south side of the canyon, Colorado River); (The Esplanade

9711-569: The former Byzantine possessions. Although Venice was more interested in commerce than conquering territory, it took key areas of Constantinople, and the Doge took the title of " Lord of a Quarter and Half a Quarter of the Roman Empire ". After the sack of Constantinople in 1204 by Latin crusaders, two Byzantine successor states were established: the Empire of Nicaea and the Despotate of Epirus . A third,

9828-544: The fort, allowing the Ottomans (who were hired as mercenaries during the civil war by John VI Kantakouzenos ) to establish themselves in Europe. By the time the Byzantine civil wars had ended, the Ottomans had defeated the Serbians and subjugated them as vassals. Following the Battle of Kosovo , much of the Balkans became dominated by the Ottomans. Constantinople by this stage was underpopulated and dilapidated. The population of

9945-483: The heart of their imperial military policies. Despite the defeat at Myriokephalon, the policies of Alexios, John and Manuel resulted in vast territorial gains, increased frontier stability in Asia Minor, and secured the stabilisation of the empire's European frontiers. From c.  1081 to c.  1180 , the Komnenian army assured the empire's security, enabling Byzantine civilisation to flourish. This allowed

10062-583: The historiographical periodizations of " Roman history ", " late antiquity ", and "Byzantine history" significantly overlap, there is no consensus on a "foundation date" for the Byzantine Empire, if there was one at all. The growth of the study of "late antiquity" has led to some historians setting a start date in the seventh or eighth centuries. Others believe a "new empire" began during changes in c.  300   AD. Still others hold that these starting points are too early or too late, and instead begin c.  500 . Geoffrey Greatrex believes that it

10179-708: The later part of his reign, John focused his activities on the East, personally leading numerous campaigns against the Turks in Asia Minor. His campaigns fundamentally altered the balance of power in the East, forcing the Turks onto the defensive, while retaking many towns, fortresses, and cities across the peninsula for the Byzantines. He defeated the Danishmend Emirate of Melitene and reconquered all of Cilicia , while forcing Raymond of Poitiers , Prince of Antioch, to recognise Byzantine suzerainty. In an effort to demonstrate

10296-576: The material to harden or "set" in ways that are useful for casting and construction. Gypsum was known in Old English as spærstān , "spear stone", referring to its crystalline projections. Thus, the word spar in mineralogy, by comparison to gypsum, refers to any non- ore mineral or crystal that forms in spearlike projections. In the mid-18th century, the German clergyman and agriculturalist Johann Friderich Mayer investigated and publicized gypsum's use as

10413-418: The measures he took to reform the government of the empire have been praised by historians. According to the historian George Ostrogorsky , Andronikos was determined to root out corruption: under his rule, the sale of offices ceased; selection was based on merit, rather than favouritism; and officials were paid an adequate salary to reduce the temptation of bribery. In the provinces, Andronikos's reforms produced

10530-579: The mid-13th century it had lost much of southern Anatolia. The weakening of the Sultanate of Rûm following the Mongol invasion in 1242–1243 allowed many beyliks and ghazis to set up their own principalities in Anatolia, weakening the Byzantine hold on Asia Minor. Two centuries later, one of the Beys of these beyliks, Osman I , would establish the Ottoman Empire that would eventually conquer Constantinople. However,

10647-542: The most capable Byzantine emperors, withstood continued Arab attacks, civil unrest, and natural disasters, and reestablished the state as a major regional power. Leo's reign produced the Ecloga , a new code of law to succeed that of Justinian II, and continued to reform the "theme system" in order to lead offensive campaigns against the Muslims, culminating in a decisive victory in 740 . Constantine overcame an early civil war against his brother-in-law Artabasdos , made peace with

10764-567: The new Abbasid Caliphate , campaigned successfully against the Bulgars, and continued to make administrative and military reforms. However, due to both emperors' support for the Byzantine Iconoclasm , which opposed the use of religious icons , they were later vilified by Byzantine historians; Constantine's reign also saw the loss of Ravenna to the Lombards , and the beginning of a split with

10881-466: The newly-formed Arabic Rashidun Caliphate . By Heraclius' death in 641, the empire had been severely reduced economically as well as territorially—the loss of the wealthy eastern provinces had deprived Constantinople of three-quarters of its revenue. The next seventy-five years are poorly documented. Arab raids into Asia Minor began almost immediately, and the Byzantines resorted to holding fortified centres and avoiding battle at all costs; although it

10998-555: The outset of his reign, Alexios faced a formidable attack from the Normans under Guiscard and his son Bohemund of Taranto , who captured Dyrrhachium and Corfu and laid siege to Larissa in Thessaly . Guiscard's death in 1085 temporarily eased the Norman problem. The following year, the Seljuq sultan died, and the sultanate was split due to internal rivalries. By his own efforts, Alexios defeated

11115-521: The patriarch Nicholas , the powerful Simeon I of Bulgaria , and other influential figures jockeyed for power. In 920, the admiral Romanos I used his fleet to secure power, crowning himself and demoting Constantine to the position of junior co-emperor. His reign, which brought peace with Bulgaria and successes in the east under the general John Kourkouas , was ended in 944 by the machinations of his sons, whom Constantine soon usurped in turn. Constantine's ineffectual sole rule has often been construed as

11232-410: The pope and Western Christian kingdoms, and he successfully handled the passage of the crusaders through his empire. In the East, Manuel suffered a major defeat in 1176 at the Battle of Myriokephalon against the Turks. These losses were quickly recovered, and in the following year Manuel's forces inflicted a defeat upon a force of "picked Turks". The Byzantine commander John Vatatzes , who destroyed

11349-590: The ports of southern Italy, he sent an expedition to Italy in 1155, but disputes within the coalition led to the eventual failure of the campaign. Despite this military setback, Manuel's armies successfully invaded the southern parts of the Kingdom of Hungary in 1167, defeating the Hungarians at the Battle of Sirmium . By 1168, nearly the whole of the eastern Adriatic coast lay in Manuel's hands. Manuel made several alliances with

11466-506: The same actual ages in different regions where they were deposited, (continental, near-shore, open sea). In Arizona, the Toroweap formation is found in two transgressions eastwards, with easternmost 'strand-lines' locating the shoreline, Toroweap west, and Coconino sand dunes or beach deposits, east. Halfway through the Grand Canyon (north side of Colorado River), at Toroweap Valley, with Toroweap Lake (a playa lake), an outcrop, or point overlooks

11583-447: The sulfates it contains can be reduced back to sulfide by sulfate-reducing bacteria . This can lead to accumulation of elemental sulfur in oil-bearing formations, such as salt domes, where it can be mined using the Frasch process Electric power stations burning coal with flue gas desulfurization produce large quantities of gypsum as a byproduct from the scrubbers. Orbital pictures from

11700-543: The throne. Alexios was highly incompetent in the office, and with his mother Maria of Antioch 's Frankish background, his regency was unpopular. Eventually, Andronikos I Komnenos , a grandson of Alexios I, overthrew Alexios II in a violent coup d'état . After eliminating his potential rivals, he had himself crowned as co-emperor in September 1183. He eliminated Alexios II and took his 12-year-old wife Agnes of France for himself. Andronikos began his reign well; in particular,

11817-442: The unpopular Irene was overthrown by Nikephoros I ; he reformed the empire's administration but died in battle against the Bulgars in 811. Military defeats and societal disorder, especially the resurgence of iconoclasm, characterised the next eighteen years. Stability was somewhat restored during the reign of Theophilos ( r.  829–842 ), who exploited economic growth to complete construction programs, including rebuilding

11934-561: The water source, can also be important considerations in distillation , as well as in heat exchangers , where either the salt solubility or concentration can change rapidly. A new study has suggested that the formation of gypsum starts as tiny crystals of a mineral called bassanite (2CaSO 4 ·H 2 O). This process occurs via a three-stage pathway: The production of phosphate fertilizers requires breaking down calcium-containing phosphate rock with acid, producing calcium sulfate waste known as phosphogypsum (PG). This form of gypsum

12051-458: The west, the warlord Odoacer deposed Romulus Augustulus in 476, killed his titular successor Julius Nepos in 480, and the office of western emperor was formally abolished. Through a combination of luck, cultural factors, and political decisions, the Eastern empire never suffered from rebellious barbarian vassals and was never ruled by barbarian warlords—the problems which ensured the downfall of

12168-483: The western parts of the empire became increasingly Latinised , while the eastern parts largely retained their preexisting Hellenistic culture . This created a dichotomy between the Greek East and Latin West . These cultural spheres continued to diverge after Constantine I ( r.  324–337 ) moved the capital to Constantinople and legalised Christianity . Under Theodosius I ( r. 379–395 ), Christianity became

12285-422: The zenith of Byzantine learning , but while several works were compiled, they were largely intended to legitimise and glorify the emperor's Macedonian dynasty . His son and successor died young; under two soldier-emperors, Nikephoros II ( r.  963–969 ) and John I Tzimiskes ( r.  969–976 ), the Roman army claimed numerous military successes, including the conquest of Cilicia and Antioch , and

12402-592: Was besieged in August 1068 and fell in April 1071 . About 1053, Constantine IX disbanded what the historian John Skylitzes calls the "Iberian Army", which consisted of 50,000 men, and it was turned into a contemporary Drungary of the Watch . Two other knowledgeable contemporaries, the former officials Michael Attaleiates and Kekaumenos , agree with Skylitzes that by demobilising these soldiers, Constantine did catastrophic harm to

12519-560: Was captured. Alp Arslan treated him with respect and imposed no harsh terms on the Byzantines. In Constantinople a coup put in power Michael Doukas , who soon faced the opposition of Nikephoros Bryennios and Nikephoros III Botaneiates . By 1081, the Seljuks had expanded their rule over virtually the entire Anatolian plateau from Armenia in the east to Bithynia in the west, and had established their capital at Nicaea , just 90 kilometres (56 miles) from Constantinople. The Komnenian dynasty attained full power under Alexios I in 1081. From

12636-550: Was given credit for his predecessor's achievements. Basil I ( r.  867–886 ) continued Michael's policies. His armies campaigned with mixed results in Italy but defeated the Paulicians of Tephrike . His successor Leo VI ( r.  886–912 ) compiled and propagated a huge number of written works. These included the Basilika , a Greek translation of Justinian I's law-code which included over 100 new laws of Leo's devising;

12753-573: Was his fourth son, Manuel I Komnenos , who campaigned aggressively against his neighbours both in the west and east. In Palestine, Manuel allied with the Crusader Kingdom of Jerusalem and sent a large fleet to participate in a combined invasion of Fatimid Egypt . Manuel reinforced his position as overlord of the Crusader states, with his hegemony over Antioch and Jerusalem secured by agreement with Raynald , Prince of Antioch, and Amalric of Jerusalem . In an effort to restore Byzantine control over

12870-540: Was invaded annually, Anatolia avoided permanent Arab occupation. The outbreak of the First Fitna in 656 gave Byzantium breathing space, which it used wisely: some order was restored in the Balkans by Constans II ( r.  641–668 ), who began the administrative reorganisation known as the " theme system ", in which troops were allocated to defend specific provinces. With the help of the recently rediscovered Greek fire , Constantine IV ( r.  668–685 ) repelled

12987-556: Was marked by the theological dispute over Nestorianism , which was eventually deemed heretical , and by the formulation of the Codex Theodosianus law code. It also saw the arrival of Attila 's Huns , who ravaged the Balkans and exacted a massive tribute from the empire; Attila however switched his attention to the rapidly-deteriorating western empire , and his people fractured after his death in 453. After Leo I ( r.  457–474 ) failed in his 468 attempt to reconquer

13104-406: Was not esteemed by the "soldier-emperors" who ruled from the frontiers or by the empire's population who, having been granted citizenship , considered themselves "Roman". Constantine extensively reformed the empire's military and civil administration and instituted the gold solidus as a stable currency. He favoured Christianity , which he had converted to in 312. Constantine's dynasty fought

13221-506: Was occupied by conflicts against two prominent generals, Bardas Skleros and Bardas Phokas , which ended in 989 with the former's death and the latter's submission. Between 1021 and 1022, following years of tensions, Basil II led a series of victorious campaigns against the Kingdom of Georgia , resulting in the annexation of several Georgian provinces to the empire. Basil's successors also annexed Bagratid Armenia in 1045. Importantly, both Georgia and Armenia were significantly weakened by

13338-450: Was only used to describe the inhabitants of that city; it did not refer to the empire, which they called Romanía —"Romanland". After the empire's fall, early modern scholars referred to the empire by many names, including the "Empire of Constantinople", the "Empire of the Greeks", the "Eastern Empire", the "Late Empire", the "Low Empire", and the "Roman Empire". The increasing use of "Byzantine" and "Byzantine Empire" likely started with

13455-490: Was overthrown in 695 after attempting to exact too much from his subjects; over the next twenty-two years, six more rebellions followed in an era of political instability . The reconstituted caliphate sought to break Byzantium by taking Constantinople, but the newly crowned Leo III managed to repel the 717–718 siege , the first major setback of the Muslim conquests. Leo and his son Constantine V ( r.  741–775 ), two of

13572-515: Was soon at war on many fronts. The Lombards , fearing the aggressive Avars , conquered much of northern Italy by 572. The Sasanian wars restarted that year, and continued until the emperor Maurice finally emerged victorious in 591; by that time, the Avars and Slavs had repeatedly invaded the Balkans , causing great instability. Maurice campaigned extensively in the region during the 590s, but although he managed to re-establish Byzantine control up to

13689-726: Was the norm. For this reason, he has been called the Byzantine Marcus Aurelius . During his twenty-five-year reign, John made alliances with the Holy Roman Empire in the West and decisively defeated the Pechenegs at the Battle of Beroia . He thwarted Hungarian and Serbian threats during the 1120s, and in 1130 he allied himself with Lothair III , the German Emperor against the Norman King Roger II of Sicily . In

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