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"Bond Event", in Wikipedia.

Bond events are North Atlantic climate fluctuations occurring every ≈1,470 ± 500 years throughout the Holocene. Eight such events have been identified, primarily from fluctuations in ice-rafted debris. Bond events may be the interglacial relatives of the glacial Dansgaard–Oeschger events, with a magnitude of perhaps 15–20% of the glacial-interglacial temperature change.

Gerard C. Bond of the Lamont–Doherty Earth Observatory at Columbia University, was the lead author of the 1997 paper that postulated the theory of 1,470-year climate cycles in the Holocene, mainly based on petrologic tracers of drift ice in the North Atlantic.

The existence of climatic changes, possibly on a quasi-1,500 year cycle, is well established for the last glacial period from ice cores. Less well established is the continuation of these cycles into the holocene. Bond et al. (1997) argue for a cyclicity close to 1470 ± 500 years in the North Atlantic region, and that their results imply a variation in Holocene climate in this region. In their view, many if not most of the Dansgaard–Oeschger events of the last ice age, conform to a 1,500-year pattern, as do some climate events of later eras, like the Little Ice Age, the 8.2 kiloyear event, and the start of the Younger Dryas.

The North Atlantic ice-rafting events happen to correlate with most weak events of the Asian monsoon for at least the past 9,000 years,[4][5] while also correlating with most aridification events in the Middle East for the past 55,000 years (both Heinrich and Bond events). Also, there is widespread evidence that a ≈1,500 yr climate oscillation caused changes in vegetation communities across all of North America.

For reasons that are unclear, the only Holocene Bond event that has a clear temperature signal in the Greenland ice cores is the 8.2 kyr event.

The hypothesis holds that the 1,500-year cycle displays nonlinear behavior and stochastic resonance; not every instance of the pattern is a significant climate event, though some rise to major prominence in environmental history. Causes and determining factors of the cycle are under study; researchers have focused attention on variations in solar output, and “reorganizations of atmospheric circulation.” Bond events may also be correlated with the 1800-year lunar tidal cycle.

0 ≈0.5 ka Little Ice Age
1 ≈1.4 ka Migration Period
2 ≈2.8 ka early 1st millennium BC drought in the Eastern Mediterranean, possibly triggering the collapse of Late Bronze Age cultures.
3 ≈4.2 ka 4.2 kiloyear event; collapse of the Akkadian Empire and the end of the Egyptian Old Kingdom.
4 ≈5.9 ka See 5.9 kiloyear event;
5 ≈8.2 ka See 8.2 kiloyear event;
6 ≈9.4 ka Erdalen event of glacier activity in Norway, as well as with a cold event in China.
7 ≈10.3 ka 8 ≈11.1 ka transition from the Younger Dryas to the boreal.

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"Migration Period", in Wikipedia.

The Migration Period, better known as the Barbarian Invasions and also referred to as the Völkerwanderung (in German), was a period of intensified barbarian invasion in Europe, often defined from the period when it seriously impacted the Roman world, as running from about 376 to 800 AD during the transition from Late Antiquity to the Early Middle Ages. This period was marked by profound changes both within the Roman Empire and beyond its “barbarian frontier”. The barbarians who came first were Germanic tribes such as the Goths, Vandals, Angles, Saxons, Lombards, Suebi, Frisii, Jutes and Franks; they were later pushed westwards by the Huns, Avars, Slavs, Bulgars and Alans. Later barbarian invasions (such as the Viking, Norman, Hungarian, Moorish, Turkic, and Mongol invasions) also had significant effects (especially in North Africa, the Iberian peninsula, Anatolia and Central and Eastern Europe); however, they are outside the scope of the Migration Period.

Germanic peoples moved out of southern Scandinavia and Germany to the adjacent lands between the Elbe and Oder after 1000 BC. The first wave moved westward and southward (pushing the resident Celts west to the Rhine by about 200 BC) and moving into southern Germany up to the Roman provinces of Gaul and Cisalpine Gaul by 100 BC, where they were stopped by Gaius Marius and Julius Caesar. It is this western group which was described by the Roman historian Tacitus (56–117 AD) and Julius Caesar (100–44 BC). A later wave of Germanic tribes migrated eastward and southward from Scandinavia between 600 and 300 BC to the opposite coast of the Baltic Sea, moving up the Vistula near the Carpathians. During Tacitus’ era they included lesser known tribes such as the Tencteri, Cherusci, Hermunduri and Chatti; however, a period of federation and intermarriage resulted in the familiar groups known as the Alemanni, Franks, Saxons, Frisians and Thuringians.

The Barbarian Invasions may be divided into two phases. The first phase, occurring between a.d. 300 and 500, is partly documented by Greek and Latin historians but difficult to verify archaeologically. It put Germanic peoples in control of most areas of the then-Western Roman Empire. The Tervingi entered Roman territory (after a clash with the Huns) in 376. Some time thereafter in Marcianopolis, the escort to Fritigern (their leader) was killed while meeting with Lupicinus. The Tervingi rebelled, and the Visigoths, a group derived either from the Tervingi or from a fusion of mainly Gothic groups, eventually invaded Italy and sacked Rome in 410, before settling in Gaul, and then, 50 years later, in Iberia, founding a kingdom that lasted for 250 years. They were followed into Roman territory first by a confederation of Herulian, Rugian, and Scirian warriors, under Odoacer, that deposed Romulus Augustulus on 4 September AD 476, and later by the Ostrogoths, led by Theodoric the Great, who settled in Italy. In Gaul the Franks (a fusion of western Germanic tribes whose leaders had been aligned with Rome since the a.d. 3rd century) entered Roman lands gradually during the 5th century, and after consolidating power under Childeric and his son Clovis’s decisive victory over Syagrius in 486, established themselves as rulers of northern Roman Gaul. Fending off challenges from the Allemanni, Burgundians, and Visigoths, the Frankish kingdom became the nucleus of the future France and Germany. The initial Anglo-Saxon settlement of Britain occurred during the fifth century, when Roman control of Britain had come to an end.. The Burgundians settled in North Western Italy, Switzerland and Eastern France in the 5th century.

The second phase took place between 500 and 700 and saw Slavic tribes settling in central and eastern Europe (notably in eastern Magna Germania), gradually making it predominantly Slavic. Additionally, Turkic tribes such as the Avars became involved in this phase. In 567, the Avars and the Lombards destroyed much of the Gepid Kingdom. The Lombards, a Germanic people, settled in Italy with their Herulian, Suebian, Gepid, Thuringian, Bulgarian, Sarmatian and Saxon allies in the 6th century They were later followed by the Bavarians and the Franks, who conquered and ruled most of Italy. The Bulgars, originally a Turkic group from Central Asia, had occupied the Pontic steppe north of Caucasus since the second century, but after, pushed by the Khazars, the majority of them migrated west and dominated Byzantine territories along the lower Danube in the seventh century.

During the early Byzantine–Arab Wars Arab armies attempted to invade southeast Europe via Asia Minor during the late seventh and early eighth centuries, but were defeated at the siege of Constantinople (717–718) by the joint forces of Byzantium and the Bulgars. During the Khazar–Arab Wars, the Khazars stopped the Arab expansion into Europe across the Caucasus (7th and 8th centuries). At the same time, the Moors (consisting of Africans like the Haratin Moors of the African country of Mauritania (Mooritania), Arabs and Berbers) invaded Europe via Gibraltar (conquering Hispania—the Iberian Peninsula—from the Visigothic Kingdom in 711), before being halted. These battles broadly demarcated the frontiers between Christendom and Islam for the next millennium. The following centuries saw the Muslims successful in conquering most of Sicily from the Christians by 902.

The Hungarian conquest of the Carpathian Basin from around 895, and the Viking expansion from the late 8th century conventionally mark the last large movements of the period. Christianity gradually converted the non-Islamic newcomers and integrated them into the medieval Christian order.

A number of contemporary historical references worldwide refer to an extended period of extreme weather during 535–536. Evidence of this cold period is also found in dendrochronology and ice cores. The consequences of this cold period are debated.

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