Late Pleistocene Ice Ages and the Holocene Epoch
The Late Pleistocene Ice Ages were a worldwide series of events that resulted in extreme climatic cycles. In the vicinity of the Gregory Rift, climate changes were accompanied by intensive volcanism. In comparison, the rapid explosion in population numbers of Homo sapiens that ushered in the Holocene occurred in a time of modest climatic fluctuations and less intense volcanism. Significant climatic cycles did, however, occur in the Holocene of East Africa. Evidence includes ice cores from Kibo (Kilimanjaro) and changes in the size and depth of lakes in the rift valley. The Early Holocene was dominated by the African Humid Period, a relatively hot and wet phase that lasted from 11,700 BP until approximately 6,000–5,000 BP. This period was interrupted by an intensely dry phase at approximately 8,300 BP. The Late Holocene included a second extremely dry phase (4,000–3,700 BP) which affected civilisation in northern Africa and the Middle East so severely that it is known as the First Dark Age. During the hotter and more humid periods of the Early Holocene, giant palaeo-lakes developed in the Gregory Rift Valley. Conversely, many lakes dried up during the intervening arid phases. Since 3,700 years, the climate established similar patterns to those observed today although minor, relatively short-lived cycles are recognised, including the Medieval Warming and the Little Ice Age. Volcanism in the Holocene, which can be categorised as active or dormant, occurred both in the Gregory Rift Valley and on the Eastern Rift Platform. Several catastrophic events are recognised which would have affected evolution of the hominins as well as growth of some of the montane forests.
KeywordsActive volcanism Climatic cycles Holocene Montane forest Palaeo-lake Pleistocene Ice Ages
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