The climate of the Quaternary period showed several decreases in global temperature glacial periods separated by warm interglacial periods. Core samples taken from sea beds elude to at least sixteen glaciations during the Quaternary period.
The current warm and ice free conditions of the Holocene Epoch may be a result of the end of the last glaciation or the climate may be a part of an interglaciel period. The constantly changing climate of the Quaternary period resulted in some environmental changes.
Changes in the amounts of rainfall during the Great Ice Age corresponded with the cyclic changes in the environment. These changes in rainfall were important in tropic and subtropic regions of the globe because of the resulting shift in bondries between tropical forest, savanna and arid vegetation zones. In areas where glaciers were progressing and receding plants and animals were displace be the ice, migrating to warmer areas as the ice sheets advanced.
Plant and animal life was essentially the same during the early Quaternary Period as it is today accept for the presence of the megafauna such as mastodons which have since become extinct. Continental drift During the Great Ice Age the land masses of Earth had achieved the basic shapes and global positions in which we see them today.
The cycle of glacier melting in forming resulted in the rise and fall of the world's water levels. Traditionally it was preceded by Tertiary which is no longer recognized as a formal geological unit but is still in colloquial use. This relatively short geological period is characterized by a series of glaciations and by the appearance and expansion of anatomically modern humans. The Quaternary Period follows the Neogene Period and extends to the present. The Quaternary covers the time span of glaciations classified as the Pleistocene, and includes the present interglacial period, the Holocene.
This places the start of the Quaternary at the onset of Northern Hemisphere glaciation approximately 2. Prior to , the Pleistocene was defined to be from 1. Quaternary stratigraphers usually worked with regional subdivisions. The Quaternary subdivisions were defined based on biostratigraphy instead of paleoclimate. This led to the problem that the proposed base of the Pleistocene was at 1.
In , it was decided to make the Quaternary the youngest period of the Cenozoic Era with its base at 2. The 2. Over this short time period, there has been relatively little change in the distribution of the continents due to plate tectonics. The major geographical changes during this time period included the emergence of the Strait of Bosphorus and Skagerrak during glacial epochs, which respectively turned the Black Sea and Baltic Sea into fresh water, followed by their flooding and return to salt water by rising sea level; the periodic filling of the English Channel, forming a land bridge between Britain and the European mainland; the periodic closing of the Bering Strait, forming the land bridge between Asia and North America; and the periodic flash flooding of Scablands of the American Northwest by glacial water.
The climate was one of periodic glaciations with continental glaciers moving as far from the poles as 40 degrees latitude. There was a major extinction of large mammals in Northern areas at the end of the Pleistocene Epoch. Many forms such as saber-toothed cats, mammoths, mastodons, glyptodonts, etc. Others, including horses, camels and American cheetahs became extinct in North America.
Glaciation took place repeatedly during the Quaternary Ice Age — a term coined by Schimper in that began with the start of the Quaternary about 2. In , a Swiss engineer, Ignaz Venetz, presented an article in which he suggested the presence of traces of the passage of a glacier at a considerable distance from the Alps.
A year later, Agassiz raised the hypothesis of a great glacial period that would have had long-reaching general effects. It is clear that Homo sapiens and Homo neanderthalensis were contemporaries for a time. Dental evidence indicates that H. This suggests that a longer childhood allowed more time for social development and transmission of knowledge and technology to new generations.
This possibly led to division of labor allowing females and young to forage for more diverse food sources. Diversification in diet could have been a species advantage for H. The most recent Neanderthal remains are about 28, years old. For whatever reason, Homo sapiens weathered the drastic climate changes and continued to disperse throughout the Earth while Neanderthals became extinct.
Between 13, to 10, years ago, at the beginning of the Holocene Epoch, lowered sea levels exposed the Bering Land Bridge between Siberia and Alaska. Snowfall in this area would have been relatively light due to the rain shadow effects of the Alaska Range, so with the glaciers covering most of Europe, it was natural for H.
Then, about 12, years ago, nearly three-fourths of North America's large animals, including woolly mammoths, horses and camels were wiped out. Scientists have long debated what caused this catastrophic extinction event. One explanation is that increasing global temperatures caused the glaciers to retreat.
Increasing sea levels submerged the land bridge again, and forests began to replace the mammoth steppes. Changes in habitat undoubtedly put stress on animal populations. The mass extinction also coincided with the arrival of humans in the area.
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