|
Results for Holocene
|
On this page:
|
Of or belonging to the geologic time, rock series, or sedimentary deposits of the more recent of the two epochs of the Quaternary Period, beginning at the end of the last Ice Age about 11,000 years ago and characterized by the development of human civilizations.
n.The Holocene Epoch or its system of deposits.
That portion of geologic time that postdates the latest episode of continental glaciation. The Holocene Epoch is synonymous with the Recent or Postglacial interval of Earth's geologic history and extends from 10,000 years ago to the present day. It was preceded by the Pleistocene Epoch and is part of the Quaternary Period, a time characterized by dramatic climatic oscillations from warm (interglacial) to cold (glacial) conditions that began about 1.6 million years ago. The term Holocene is also applied to the sediments, processes, events, and environments of the epoch.
As the interval of time closest to us, the Holocene Epoch is very convenient to study. Holocene sediments cover virtually every part of the Earth's surface and represent almost every environment of deposition. With the development of 14C dating (a method of age determination based on the measurement of radioactive carbon decay), Holocene sediments are relatively easy to date. From a scientific standpoint, the Holocene Epoch is of great interest because it provides a recent analog for past environments and processes. Its sediments and landforms provide important clues to changes that occurred as a result of the last shift from the glacial to the nonglacial climatic mode. See also Depositional systems and environments; Radiocarbon dating.
The Pleistocene/Holocene transition was a time of dramatic environmental change. The huge ice sheets that had developed over the northern and western parts of North America (Laurentide and Cordilleran, respectively) and most of Scandinavia were at their maximum geographic extent about 18,000 14C years B.P. (before present, where present is defined as the year 1950) and in full retreat by 14,000 14C years B.P. By 10,000 14C years B.P., the Laurentide ice sheet had withdrawn from the Great Lakes. The ice sheets survived in the northern latitudes for another 3000 14C years or so. The progress of deglaciation was complex, because the overall glacial meltback was interrupted by intervals of glacier readvance. It remains unclear whether these readvances were synchronous on a hemispheric or global scale and what role ice sheet/oceanic interactions played in the deglaciation. See also Pleistocene.
The early phase of the Holocene was geologically the most eventful. The periglacial (near the edge of the ice) landscape was unstable and very dynamic. As the Pleistocene ice sheets melted, enormous volumes of water, stored as glacier ice for many thousands of years, returned to the oceans via meltwater streams or by way of ice streams that flowed directly to the ocean.
As the ice sheets shrank, sea level rose an average of 130 m (426 ft), drowning the continental margins and closing many land bridges, including the land bridge across the Bering Strait between Asia and North America that had enabled humans to migrate to the Americas. In parts of Canada and Scandinavia, temporary marine invasions occurred when the ice melted from low areas where the Earth's crust had been depressed by the weight of the ice sheets.
As the ice sheets waned, the Earth's crust rose, rebounding from the release of the weight of thousands of meters of glacier ice and creating uplifted shoreline features and sediments. Parts of Hudson Bay and Scandinavia were uplifted several hundred meters. Maximum uplift occurred in the early Holocene, but uplift continues even today although at much slower rates.
The middle phase of the Holocene has been called the hypsithermal, a name for the warmest interval of the present interglacial episode. It has also been referred to as the climatic optimum, a term which is more appropriately applied to the peak warmth of the hypsithermal phase. At the climatic optimum, world temperature was probably 2 or 3°C (3.6 or 5.4°F) higher than today. The climate was warm enough to melt much of the sea ice in the Arctic Ocean, as indicated by the occurrence of fossil driftwood (dated at 4000–6000 14C years B.P.) on uplifted beaches.
After the climatic optimum, the Earth experienced climatic cooling. The shift to a cooler, moister climate began about 5000–4000 14C years B.P. in the midcontinent. In western North America at about 5000 14C years B.P., the mountain glaciers began to expand again. This renewed glacial activity is called Neoglaciation. At least three intervals of glacial expansion have occurred in the late Holocene. The glacial advances are cyclic. In the mountains of the western United States, the three advances have been dated at about 5000, 2800, and 300 14C years B.P. The most impressive of the three glacial intervals is the last, called the Little Ice Age. It is well documented because it occurred in historic time. Between the intervals of glacier expansion were times of climatic warming. One, called the Little Climatic Optimum to differentiate it from the hypsithermal of the middle Holocene, peaked about 1800 14C years B.P.
During the late Holocene, human populations expanded and human culture developed into the complex agricultural, industrial, and technological society of today. The result is that humans have become significant factors in altering the Earth's surface environment, including, most believe, Holocene climate. See also Geologic time scale; Glacial epoch; Quaternary.
The most recent geological epoch, stretching from 12 000 years ago to the present day. This epoch has seen the development of early man.
The later of two chronostratigraphic units or epochs forming the Quaternary system (the earlier one is the Pleistocene) dating from 10 000 years ago down to the present day. The series of deposits represented are simply the latest major interglacial stage following the Devensian Stage stage at the end of the Pleistocene, known in Britain as the Flandrian Stage although in other areas (rather confusingly) as the Holocene.
| This time period is part of the Holocene epoch. |
Pleistocene
|
Holocene
|
The Holocene epoch is a geological period, which began approximately 11,550 calendar years BP (about 9600 BC) and continues to the present. The Holocene is part of the Neogene and Quaternary periods. Its name comes from the Greek words ὅλος (holos, whole or entire) and καινός (kainos, new), meaning "entirely recent". It has been identified with MIS 1 and can be considered an interglacial in the current ice age.
The Holocene has also been referred to as the "Alluvium Epoch", but this name has fallen into disuse.
The Holocene starts late in the retreat of the Pleistocene glaciers.
Human civilization dates entirely within the Holocene. The Blytt-Sernander classification of climatic periods defined, initially, by plant remains in peat mosses, is now of purely historical interest. The scheme was defined for north Europe, but the climate changes have been claimed to occur more widely. The periods of the scheme include a few of the final, pre-Holocene, oscillations of the last glacial period and then classify climates of more recent prehistory.
The Holocene was preceded by the Younger Dryas cold period, the final part of the Pleistocene epoch. However, evidence for the Younger Dryas is not clear cut anywhere other than in the Northern Hemisphere. [citation needed]
Paleontologists have defined no faunal stages for Holocene. If subdivision is necessary, periods of human technological development such as the Mesolithic, Neolithic, and Bronze Age are usually used.
Climatically, the Holocene may be divided evenly into the Hypsithermal and Neoglacial periods; the boundary coincides with the start of the Bronze Age in western civilisation. According to some scholars, a third division, the Anthropocene began in the 18th Century [1]. It is debatable whether this is an age within, or follows, the Holocene epoch. [citation needed]
Continental motions are less than a kilometre over a span of only 10 ka. However, ice melt caused world sea levels to rise about 35 m (110 ft) in the early part of the Holocene. In addition, many areas above about 40 degrees north latitude had been depressed by the weight of the Pleistocene glaciers and rose as much as 180 m (600 ft) over the late Pleistocene and Holocene, and are still rising today.
The sea level rise and temporary land depression allowed temporary marine incursions into areas that are now far from the sea. Holocene marine fossils are known from Vermont, Quebec, Ontario, and Michigan. Other than higher latitude temporary marine incursions associated with glacial depression, Holocene fossils are found primarily in lakebed, floodplain, and cave deposits. Holocene marine deposits along low-latitude coastlines are rare because the rise in sea levels during the period exceeds any likely upthrusting of non-glacial origin.
Post-glacial rebound in the Scandinavia region resulted in the formation of the Baltic Sea. The region continues to rise, still causing weak earthquakes across Northern Europe. The equivalent event in North America was the rebound of Hudson Bay, as it shrank from its larger, immediate post-glacial Tyrrell Sea phase, to near its present boundaries.
Although geographic shifts in the Holocene were minor, climatic shifts were very large. Ice core records show that before the Holocene there were global warming and cooling periods, but climate changes became more regional at the start of the Younger Dryas. However, the Huelmo/Mascardi Cold Reversal in the Southern Hemisphere began before the Younger Dryas, and the maximum warmth flowed south to north from 11,000 to 7,000 years ago. It appears that this was influenced by the residual glacial ice remaining in the Northern Hemisphere until the latter date.
The hypsithermal was a period of warming in which the global climate became 0.5–2°C warmer than today. However, the warming was probably not uniform across the world. This period ended about 5,500 years ago, when the earliest human civilizations in Asia and Africa were flourishing. This period of warmth ended with the descent into the Neoglacial. At that time, the climate was not unlike today's, but there was a slightly warmer period from the 10th–14th centuries known as the Medieval Warm Period. This was followed by the Little Ice Age, from the 13th or 14th century to the mid 19th century, which was a period of significant cooling, though not everywhere as severe as previous times during neoglaciation.
The Holocene warming is an interglacial period and there is no reason to believe that it represents a permanent end to the Pleistocene glaciation. However, the current global warming may result in the Earth becoming warmer than the Eemian Interglacial, which peaked at roughly 125,000 years ago and was warmer than the Holocene. This prediction is sometimes referred to as a super-interglacial.
Compared to glacial conditions, habitable zones have expanded northwards, reaching their northernmost point during the hypsithermal. Greater moisture in the polar regions has caused the disappearance of steppe-tundra.
Animal and plant life have not evolved much during the relatively short Holocene, but there have been major shifts in the distributions of plants and animals. A number of large animals including mammoths and mastodons, saber-toothed cats like Smilodon and Homotherium, and giant sloths disappeared in the late Pleistocene and early Holocene—especially in North America, where animals that survived elsewhere (including horses and camels) became extinct. This extinction of American megafauna has been explained as caused by the arrival of the ancestors of Amerindians; though most scholars assert that climatic change also contributed.
Throughout the world, ecosystems in cooler climates that were previously regional have been isolated in higher altitude ecological "islands."
The 8.2 ka event, an abrupt cold spell recorded as a negative excursion in the δ18O record lasting 400 years, is the most prominent climatic event occurring in the Holocene epoch, and may have marked a resurgence of ice cover. It is thought that this event was caused by the final drainage of Lake Agassiz which had been confined by the glaciers, disrupting the thermohaline circulation of the Atlantic [1].
The beginning of the Holocene corresponds with the beginning of the Mesolithic age in most of Europe; but in regions such as the Middle East and Anatolia with a very early neolithisation, Epipaleolithic is preferred in place of Mesolithic. Cultures in this period include: Hamburgian, Federmesser, and the Natufian culture.
Both are followed by the aceramic Neolithic (Pre-Pottery Neolithic A and Pre-Pottery Neolithic B) and the pottery Neolithic.
Within the Holocene numerous meteorite events have been recently discovered in Europe; but also in oceans such as the Indian Ocean and remote Siberia. The Burckle crater and even within Phaëton cited in Greek mythology as one of those possible impact events Chiemgau Impact crater[2]. Burckle crater[3] also find evidence of such events possibly dramatically affecting human culture directly and early history by the creation of megatsunamis in ancient times triggering deluge or inundation stories of the past such as Noah's Flood. A wash out effect from such waves may have breached land bridges or strips with sudden massive erosion along with violent weather changes. Competing reasons for the various basin floods also include climate change and earthquake fault lines weakening the barriers to ocean encroachment.
| Neogene period | ||
|---|---|---|
| Quaternary | ||
| Pliocene | Pleistocene | Holocene |
| ← Neogene | Gelasian | Early | Middle | Late | |
This entry is from Wikipedia, the leading user-contributed encyclopedia. It may not have been reviewed by professional editors (see full disclaimer)
Join the WikiAnswers Q&A community. Post a question or answer questions about "Holocene" at WikiAnswers.
Copyrights:
 |
 | Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved. Read more |
 |
| Sci-Tech Encyclopedia. McGraw-Hill Encyclopedia of Science and Technology. Copyright © 2005 by The McGraw-Hill Companies, Inc. All rights reserved. Read more |
 |
| Geography Dictionary. A Dictionary of Geography. Copyright © Susan Mayhew 1992, 1997, 2004. All rights reserved. Read more |
|
| Archaeology Dictionary. The Concise Oxford Dictionary of Archaeology. Copyright © 2002, 2003 by Oxford University Press. All rights reserved. Read more |
 |
| Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Holocene". Read more |
Search for answers directly from your browser with the FREE Answers.com Toolbar!
Click here to download now. 
Get Answers your way! Check out all our free tools and products.
Mentioned In:
