Cenozoic Ice Age

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The Cenozoic Ice Age is the current ice age , the ice age of the Cenozoic (New Earth Age) as distinct from the Ice Ages of the Paleozoic and Precambrian . Its beginning corresponds to the gradual glaciation of the Antarctic around 34 million years ago. About 2.7 million years ago, the increased ice formation in the Arctic began. From this point in time (longer) cold periods (glacials) alternate with (shorter) warm periods (interglacials).

The Quaternary Ice Age is the most recent segment of the Cenozoic Ice Age. It spans the Quaternary from 2.588 million years before today and is characterized by the formation of extensive continental ice sheets throughout the northern hemisphere during this time.

Formation of the Antarctic Ice Sheet

Topographic map of Antarctica without ice cover. The isostatic land elevation and the increased sea level are taken into account ; the representation corresponds roughly to the situation 35 million years ago.

After the heat anomalies and the climatic optimum of the early Eocene (around 56 to 49 mya ), a clear but temporary cooling phase occurred in the Antarctic for the first time 41 million years ago. The climatic fluctuations were more pronounced during the Eocene- Oligocene transition from 33.9 to 33.7 million years ago. A major factor in this change was the creation of the Drake Strait , which is now 480 nautical miles wide and connects the Atlantic with the Pacific Ocean . A land bridge existed between Antarctica and South America until the later Eocene , before the Drake Passage gradually opened. This created the strongest ocean current on earth in the Southern Ocean , the Antarctic Circumpolar Current , which from now on circled Antarctica in a clockwise direction, cut off the continent from the supply of warmer seawater and possibly had a direct effect on the global cooling process.

In the course of the Grande Coupure ("Big Gorge") there was a major extinction of species , which was linked to a marked drop in temperature on land and in the oceans. About 60 percent of the Eocene mammal genera in Europe were affected by the rapid climate change and its consequences. At the global level, the temperature of the oceans fell by 4 to 5 ° C down to the deeper regions, and the sea level dropped by about 30 meters within a relatively short time. What is striking in this context is the steep drop in the atmospheric CO 2 concentration. If this reached values ​​of 700 to 1,000 ppm towards the end of the Eocene, this level dropped abruptly by around 40 percent (and was possibly even lower for a very short geological period). The glaciation of the southern polar mainland 33.7 million years ago at a CO 2 threshold of 600 to 900 ppm, partly influenced and accelerated by the changing parameters of the Earth's orbit , marks the beginning of the Cenozoic Ice Age . In the north polar region, too, a significant cooling was observed. Finds of dropstones show the temporary existence of Greenlandic continental ice. In addition, it is assumed that the Arctic Ocean , which was isolated for a long time, found a connection to the global ocean circulation after a transition phase as a brackish sea in the early Oligocene (≈ 32 mya) with the influx of salty North Atlantic water .

Development in the Miocene and Pliocene

The cooling trend that began around 34 million years ago, coupled with a gradual reduction in atmospheric carbon dioxide, was not linear, but was first interrupted by a warming phase in the late Oligocene and then by a climatic optimum in the Miocene 19 to 15 million years ago. During this time, the C 4 plants adapted to arid conditions began to spread (especially grasses ), which require considerably less carbon dioxide for photosynthesis than C 3 plants . At the height of the Miocene climatic optimum, the CO 2 content rose from 350 ppm at the beginning of the Miocene to 500 ppm (according to other sources to over 600 ppm).

In the course of global warming associated with arid conditions, in which massive CO 2 emissions from the Columbia Plateau basalt were probably significantly involved, the forest habitats were pushed back, and steppes and grasslands took their place . At the same time, the Antarctic glaciers of that time lost some of their mass, but without melting completely. Simulations including the CO 2 level at the time indicate that the core areas of the East Antarctic Ice Sheet were hardly affected by the warming in the Middle Miocene. Under the influence of strong erosion and weathering processes, the CO 2 concentration fell again to 350 to 400 ppm towards the end of the optimum 14.8 million years ago, and a cooler climatic phase began with a renewed increase in inland Antarctic icing. Nevertheless, 14 to 12.8 million years ago the temperatures in this region were 25 ° C to 30 ° C above the current values ​​before the continent was hit by a cold snap.

Although the global temperature was 2 to 3 ° C above the pre-industrial level over large parts of the Pliocene , the Antarctic Ice Sheet reached its current size of 14 million km² in the course of the epoch. In the period that followed, and increasingly since the beginning of the Quaternary Glacial, the mass of the ice cover increased steadily, up to a thickness of 4,500 meters in places.

Arctic glaciation

The Mendenhall Glacier in Alaska

More or less extensive ice caps have sporadically formed on Greenland since the Eocene . An intense phase of Arctic glaciation, including the formation and expansion of the Greenland Ice Sheet, began about 2.7 million years ago. The complete closure of the Isthmus of Panama 2.76 million years ago caused the redirection of warm ocean currents to the north and thus the formation of the Gulf Stream with an increase in humidity in the arctic regions. In the more recent specialist literature, the Isthmus of Panama and the associated influence of the Gulf Stream only play a role as a side effect. It is predominantly assumed that the increasing arctic glaciation during the Pliocene-Quaternary transition is based on a significant decrease in the global CO 2 concentration.

The now increasing global cooling led to a reduction in forest stocks, which were pushed back to warmer refuges . The temperate forests were replaced by steppes and grasslands, while savannahs expanded into the subtropical areas. Due to this fragmentation of the habitats , new species and subspecies emerged in the fauna area (see also speciation ) . The apparently less favorable living conditions during the Ice Age resulted in new evolutionary developments with an increase in biodiversity in the warmer periods that followed.

Structure of the current ice age

During the Cenozoic Ice Age , relatively warm periods alternated with very cold periods. The cold phases ( cold periods or glacials ) are characterized by massive glacier advances. They are significantly longer than the warm periods ( warm periods or interglacials ), which only last around 15,000 years on average. Warm periods often require a very short “start-up time”, while the cooling process tends to be gradual.

A cycle from one warm period to the next currently lasts a little more than 100,000 years and, according to scientific opinion, is therefore linked to changes in the earth's orbit ( eccentricity ) of the same length . This period occurred in full expression for the first time in the early Middle Pleistocene around 700,000 years ago. Before - that is, since the beginning of the Quaternary (2.6 mya) - the cycle duration was only 41,000 years and at that time correlated with the fluctuations in the earth's axis of rotation . Until recently, only speculation was expressed about the reasons for this “jumping over” to a longer warm-cold cycle. A study published in March 2019, based on the analysis of sediment cores, postulates a significant weakening of the deep water circulation, especially in the subpolar regions of the southern ocean, as the main cause, resulting in 50 percent less carbon dioxide from the deep sea to the sea surface and from there compared to the present got into the atmosphere. Due to the reduced CO 2 outgassing, the cold-time conditions were extended, even if the constellation of the orbital parameters signaled the beginning of a warming phase. An additional aspect of this development was the increasing expansion and stability of the continental ice sheets, which only lost part of their mass during the relatively short warm periods.

The current glaciation of the earth at both poles (with sea ​​ice )

The current interglacial, called the Holocene on the geological time scale , is the most recent warm period of the Cenozoic Ice Age, with a previous duration of about 11,700 years. Even in the warm phases of an Ice Age, the climate remains at a relatively cool level in geological comparison. The ice cover of the polar regions and high mountains mostly remains, but glacier advances up to middle latitudes are receding, and there is a clearly temperate climate with milder winters in these areas.

Eleven interglacials have been identified and described in detail for the past 800,000 years. The duration of these interglacials was normally around 10,000 to 30,000 years, only for the period of the interglacial marine isotope level 11c (MIS 11c) a maximum of 40,000 years is estimated. In this respect, the Holocene seems to occupy a special position. Although the cooling trend of around 0.12 ° C per millennium that has prevailed since the climatic optimum of the Holocene is considered to be a harbinger and first sign of an approaching Ice Age climate, various studies, including the gradually changing Earth's orbit parameters, come to the conclusion that a new cold period is below normal Framework conditions will only occur in 30,000 to 50,000 years.

This duration, which is unusually long for an interglacial, could possibly extend to a total of 100,000 years and thus almost double if there was a further increase in anthropogenic CO 2 emissions. This would mean the failure of a complete Ice Age cycle due to human interference in the climate system.

Causes of the Ice Age

The main reasons for the cooling tendency since the middle and increasingly since the late Eocene are terrestrial factors, while the short-term climate changes in the course of a cold-age cycle are mainly controlled by the periodic changes in the Earth's orbit parameters and the associated solar radiation .

Earthly causes

The main drivers for the weakening of the warm climate in the Palaeogene and Neogene were plate tectonic processes such as the continental drift in connection with mountain formations ( orogenesis ) as well as phases of intensive weathering with correspondingly high CO 2 reduction, but also plant organisms, which by fixation and deposition ( sedimentation ) extensive amounts exerted climate-relevant effects on carbon .

Oceanic current systems

Desiccation of the Mediterranean Sea in the course of the Messinian salinity crisis

The closing or opening of the ocean routes has a lasting impact on thermohaline circulation and thus on global heat transport. As a result of the separation of Australia and later South America from Antarctica, two straits of the sea emerged around the Eocene-Oligocene border : the Tasmanian Passage and the Drake Strait . These tectonic processes created the geographic and climatic conditions for the formation of the Antarctic ice sheet .

A geologically significant event with far-reaching climatic effects was the repeated drying up of the Mediterranean on the border between the Miocene and Pliocene 6 to 5 million years ago. The repeated closure of the Strait of Gibraltar due to tectonic shifts interrupted the exchange of water between the Atlantic and the remainder of the Tethys Sea between Africa and Eurasia and caused the Mediterranean basin to be temporarily converted into a salt desert ( Messinian salinity crisis ).

Formation of high mountains

As a result of the collision of continental plates, an intensified phase of mountain formation began in the early Neogene . These unfolding processes , such as those of the Alps , the Rocky Mountains or the Himalayas , changed the atmospheric flow patterns on a large and small scale and, with the transport of moist air masses to the mainland, favored the glaciation of large parts of the northern hemisphere. At the same time, the high mountains themselves are preferred regions for glacier formation.

One theory assigns a central role to the highlands of Tibet , since it postulates an almost complete glaciation of the highlands. Through the significant increase in the albedo , this led to an intensification of the cooling process worldwide. However, the closed glaciation of Tibet is partially rejected. Changes in the albedo in connection with the duration and extent of the snow cover in the highlands are, however, undisputed.

Azolla event

The Azolla event (50/49 mya) marks the end of the Eocene climatic optimum and is considered to be one of the turning points in the climatic history of the Cenozoic . The family of salviniaceae scoring Azolla ( Azolla ) can store large amounts of nitrogen and carbon dioxide and massively proliferate under favorable conditions. This case occurred due to a chain of special circumstances when Azolla "colonized" the then Arctic Ocean over an area of ​​4 million km². Since in the Eocene the Arctic sea basin was cut off from the global cycle of thermohaline circulation and therefore became , so to speak , standing water , a thin but nutrient-rich freshwater layer could have formed on its surface due to rain and the entry of the rivers, which enabled the explosive growth of Azolla . The floating vegetation carpet of the algae ferns existed under moderate climatic conditions for about 800,000 years and during this time caused an initial significant reduction in CO 2 by absorbing large amounts of carbon dioxide and integrating it into sedimentation processes .

Volcanism

Although around 40 volcanic eruptions of the highest category VEI-8 have been documented from the Neogene and Quaternary , these did not have the potential to have a lasting impact on climate development. In contrast, so-called Magmatic Large Provinces (English Large Igneous Provinces ) were multiple causes of serious and relatively rapid global warming. This involved the large-volume escape of igneous rocks from the earth's mantle , predominantly in the form of flood basalts , which over the course of several hundred thousand to millions of years spilled over an area of ​​millions of km². Depending on the extent and duration of the volcanic activity, considerable climate-affecting amounts of carbon dioxide were released, occasionally with the help of the strong greenhouse gas methane or methane hydrate from oceanic deposits.

For example, the tropical climate of the Middle Cretaceous Period is said to be associated with long-lasting superplume activity in the western Pacific, while the optimal climate of the Eocene may reflect the influence of the North Atlantic Magmatic Greater Province, whose activity cycles were linked to the formation and expansion of the North Atlantic . Independently of this, “normal” volcanism in the Mesozoic and early Cenozoic Era could have been more active than in recent geological history, with the consequence of a generally higher atmospheric CO 2 concentration.

Astronomical causes

Earth's orbit geometry

The change in the geometry of the earth's orbit is caused by reciprocal gravitational forces in the sun , earth and moon system . They change the shape of the earth's elliptical orbit ( eccentricity ) around the sun with a period of around 100,000 or 405,000 years, the inclination of the earth's axis to orbit with a period of around 41,000 years (obliqueness of the ecliptic ), while the day-and-night Same on the elliptical orbit takes up the same position on the ellipse again after about 25,780 years ( precession ). With regard to the changes in eccentricity, the gravitational effect of the gas giants Jupiter and Saturn is also important.

As recent studies show, some of the Earth's orbit parameters are integrated into a stable time frame over the duration of geological time periods and are apparently not subject to any changes. In this way, the major cycle of 405,000 years could be traced back to the Upper Triassic about 215 million years ago and arranged chronologically on the basis of polarity reversal events of the terrestrial magnetic field.

Inspired by the meteorologist and geographer Wladimir Peter Köppen , Milutin Milanković formulated in his 1941 work "The Canon of Earth Radiation and its Application to the Ice Age Problem" with regard to recent geological history, the hypothesis that a glacial period always occurs when the intensity of the summer sunshine in decreases in high northern latitudes. Cool summers are therefore more decisive for ice build-up than cold winters.

Maximum and minimum inclination range of the earth's axis
Orbit parameters Cycle duration Fluctuation range Current status
Precession of the earth's axis of rotation approx. 025,780 years 360 ° (full circle) within a complete cycle Development for the more concise formation of the seasons in the northern hemisphere with longer winters
Angle of inclination of the earth's axis to the ecliptic approx. 041,000 years between 22.1 ° and 24.5 ° 23.43 ° (tending towards the minimum)
Eccentricity of the earth's orbit approx. 100,000 or 405,000 years 1) from 0.0006 (almost circular) to 0.058 (slightly elliptical) 0.016 (with a tendency to circular orbit)
1) Next minimum of eccentricity with 0.0023 in 27,500 years, absolute minimum with 0.0006 in over 400,000 years

The relatively weak influence of the Milanković cycles was the impetus for the alternation of warm and cold periods during the Quaternary Ice Age , the effect of which, however, was reinforced by several feedback factors . For example, the atmospheric CO 2 concentration played an essential role, which was closely linked to climate change, as has been shown by analyzes of ice cores in Antarctica and Greenland over the past 800,000 years. According to this, the decrease in the concentration of the greenhouse gas carbon dioxide (together with methane and nitrous oxide ) should account for around a third of the temperature fluctuations between warm and cold periods, and even for half, according to another publication. Positive feedback processes such as ice-albedo feedback, vegetation cover and the variability of the water vapor content in the atmosphere were also important.

Activity cycles of the sun

In the last glacial period there were two dozen significant climatic changes, during which the air temperature in the North Atlantic area rose by ten to twelve degrees Celsius within just a decade. These Dansgaard-Oeschger events mostly occurred every 1470 years. Their periodicity is tried to be explained by the cyclical correspondence of two known phases of activity of the sun of 87 and 210 years. After 1470 years, the 210 cycle has expired seven times and the 86.5 cycle seventeen times. In the warm period of the Holocene, Dansgaard-Oeschger events no longer occurred, as the weak fluctuation in solar radiation could no longer overlay the stable Atlantic currents of the last 10,000 years.

Structure and nomenclature

Outline problems

Originally, the current Ice Age was broken down on the basis of terrestrial (continental) deposits. A distinction was made between the individual, superimposed deposits of the various cold and warm periods. However, problems have arisen and continue to occur with the comparison and correlation of the Ice Age deposits over long distances. For example, it is still not certain whether the deposits of the Saale Ice Age in northern Germany and those of the Rift Ice Age in the Alpine foothills were formed at the same time. For this reason, every region on earth has its own quaternary stratigraphic structure.

The numerous local divisions with their proper names, which can hardly be overlooked even by experts, often seem confusing to non-experts. The most recent cold-age ice advance with its peak a little more than 20,000 years ago in northern Central Europe is known as the Vistula , in the northern Alps as the Würm , in northern Russia as the Waldai , on the British Isles as the Devensian , in North America as the Wisconsin Ice Age . There is also an abundance of local names for older cold and warm periods.

One difficulty in analyzing Ice Age deposits on the mainland is that there is no continuous stratification. Rather, phases of rapid sedimentation (as with glacier advances) were followed by phases without sedimentation or even erosion events. In Northern Germany, for example, there is no known place where all the marl boulder of the three major glaciation phases occur together with the deposits of the various warm periods on top of each other. Here, too, the correlation has to take place over great distances and can have errors.

International divisions

The internationally recognized structure of the Ice Age is based on the analysis of marine deposits. These have the advantage that they settle continuously at favorable points and include both warm and cold stratifications.

Marine Oxygen Isotope Stratigraphy

Reconstruction of the mean temperature curve over the last 5 million years

The most important aid in structuring the Ice Age is the ratio of the stable isotopes of oxygen 16 O and 18 O in calcareous microorganisms ( foraminifera ). Since the lighter isotope 16 O is enriched in comparison to the heavier 18 O during evaporation , an isotopic fractionation of the oxygen occurs. Due to the storage of the light isotope 16 O in the continental ice masses during the cold periods, the ocean is isotopically heavier during this time (ice effect). From this a stratigraphy for marine sediments was developed, the marine oxygen isotope stratigraphy.

The entire Ice Age is subdivided into 103 isotope stages. Odd numbers are assigned to warm periods (interglacials) and even to cold periods (glacials). The current warm period is therefore referred to as marine oxygen isotope stage 1 (international Marine Isotope Stage 1 or MIS 1 ), the peak of the last glacial period as MIS 2 . Since further isotope fluctuations were added after the establishment of this system, additional levels are defined by adding a letter, for example MIS 5e for the Eem warm period .

Magnetostratigraphy

The Magnetostratigraphy is a branch of paleomagnetism or the stratigraphy . Your task is to analyze the regularly occurring polarity changes (“normal” and “reverse”) of the earth's magnetic field and, on this basis, to carry out a relative age dating of these events. About 2,580,000 and 780,000 years ago clear polarity reversals of the magnetic field could be ascertained (“polarity reversal” is not to be understood literally, but rather as a slow decrease in the magnetic field and its build-up in a different polarity). Furthermore, there were short reversal phases in the course of various geological epochs, such as in the Old Pleistocene 1.77 million years ago. If traces of it are found, for example through the alignment of magnetic minerals in glacial deposits, the deposits can be dated. This method is suitable for both mainland and marine debris. That is why one of the limits of the Ice Age to the Pliocene, recognized by many scientists, is the great reversal of the polarity of the earth's magnetic field 2.58 million years ago, which corresponds well with the first appearance of glaciations in the northern hemisphere.

Structure in Central Europe

Oxygen isotope data for the last 300,000 years according to Martinson et al.

In Central Europe , the cold ages are named after rivers, which generally indicate the largest extent of the respective ice sheets . In southern Germany the icing started from the alpine glaciers, in northern Germany the ice came from the Scandinavian region . With the exception of the recent glacial period, it is not certain whether the glaciations in the Alpine region and in northern Germany really happened synchronously . Therefore the stated values ​​can be changed with further research.

Quaternary cold periods in the Alpine region and northern Germany
Alpine region
(namesake) 		Northern Germany
(namesake) 		Period
(thousand years before today) 		MIS
- Brüggen Cold Age ( Brüggen ) approx. 2200 ?
Beaver Cold Age ( Biberbach ) - approx. 1900–1800, or approx. 1500–1300 MIS 68-66, or MIS 50-40
- Eburon Ice Age ( Eburonen ) circa 1400 ?
Danube Ice Age ( Danube ) - approx. 1000-950 MIS 28-26
- Menap Ice Age ( Menapier ) 990-800 ?
Günz Cold Age ( Günz ) - 800-600 MIS 20-16
Mindel cold time ( Mindel ) - 475-370 MIS 12
- Elster Cold Age ( White Magpie ) 400-320 MIS 10
Crack cold time ( crack ) Saale Cold Age ( Saale ) 350–120 (Riss), 300–130 (Saale) MIS 10–6 (Riß), MIS 8–6 (Saale)
Würm Cold Age ( Würm ) Vistula glacial period ( Vistula ) 115-10 MIS 4-2

Impact on the earth

Glaciations

Minimum (warm period, black) and maximum (cold period, gray) icing of the northern hemisphere
Minimum (warm period, black) and maximum (cold period, gray) icing of the southern hemisphere

During the cold periods of the current Ice Age, the inland ice sheets and mountain glaciers increased significantly in size and volume and eventually covered about 32 percent of the mainland. Currently, only about 10 percent of the continental area is covered by glaciers. Large parts of Europe , Asia and North America were glaciated, especially in the northern hemisphere . Many traces of ice (for example trough valleys , moraines , glacier cuts , the glacial series ) have been preserved there to this day.

The change in the Antarctic ice sheet was less noticeable during the Quaternary Glaciation compared to the Arctic. One reason for this is that ice formation on land and flat shelves in the northern hemisphere is more effective than in the circumantarctic ocean areas. In addition, the Antarctic is almost completely glaciated today. Increasing the ice cover there was therefore only possible to a limited extent.

While in the last stage of the Pleistocene, the cold snap of the Younger Dryas period , a strong glacier growth set in, the current interglacial ( Holocene ) recorded a clear decline up to the disappearance of some glaciers. This is especially true of the Holocene Optimum Climate , around 7,000 years ago, and affected many glaciers in Iceland and probably some on the Scandinavian Peninsula. Most of the glaciers in the Alps during this period were probably smaller than they were at the end of the 20th century. It is widely assumed that today's glaciers in the Alps or in Scandinavia are remnants of the last glaciation, but this is not the case for most of them, as their age is 6,000 years or less. Many glaciers reached their greatest expansion a few hundred years ago during the Little Ice Age .

Sea level

The formation of continental ice masses deprived the oceans of massive amounts of water. During the height of the most recent Ice Age, the sea ​​level was 120 to 130 m lower than it is today. This resulted in numerous land bridges. Shelf seas like the North Sea fell dry over large areas. The land bridge over today's Bering Strait , which connected North Asia with North America (see → Beringia ), became very important . The exchange of numerous animal and plant species as well as human settlement on the American continent took place above or along this land bridge.

Climate and atmosphere

From a global perspective, during the cold periods there was significantly less precipitation than during the warm periods due to the lower temperatures. The changes in precipitation during the cold periods, however, varied greatly between regions and zones. While it tended to be drier in the high and middle latitudes, the subtropics were largely humid. The marginal tropical deserts were also extremely dry at this time, while the extent of the humid tropics was clearly restricted at this time. The available water supply in the high and middle latitudes was partly higher during the ice ages than it is today, as the evaporation rates were considerably lower due to the low temperature level and the reduced forest areas.

The last glacial maximum (LGM) was about 21,000 years ago. The global average temperature was about 5 to 6 K lower than today. Gas inclusions in polar ice indicate that the atmospheric concentration of the greenhouse gases carbon dioxide (CO 2 ) was only 70 percent and methane (CH 4 ) only 50 percent of the pre-industrial value (CO 2 in the LGM: 200 ppmv , pre-industrial: 288 ppmv, today (2019): 412 ppmv; CH 4 in the LGM: 350 ppbv , pre-industrial: 750 ppbv, today: almost 1,900 ppbv).

During the final phases of the individual glacial periods, it was probably changes in the Earth's orbit parameters and, as a result, in solar radiation (Milanković cycles) that acted as “pacemakers” and triggered the first climate changes. There was an almost parallel rise in the concentrations of the greenhouse gases methane and CO 2 - the latter was probably released from the deep sea of the southern ocean - and in temperatures. At least after the last glacial maximum, the global temperature rise followed that of the CO 2 concentrations. The changing greenhouse gas concentrations and albedo changes intensified the climate changes in a feedback process until equilibrium was finally reached.

The temperature rise according to the LGM was not even: it occurred earlier in Antarctica, and long-range effects probably mediated by oceanic current systems then later caused the northern hemisphere temperatures to rise. The increase in CO 2 concentrations reconstructed from ice cores occurred before the temperature increase in the north, but later than the Antarctic warming. The time differences cannot be precisely determined due to different dating methods and ice formation rates at the location where the drill cores were taken; they range from almost synchronously to several hundred years.

Lifeworld

The woolly mammoth ( Mammuthus primigenius ) as a representative of the megafauna during the last glacial period in the northern hemisphere

The climatic fluctuations of the Cenozoic Ice Age had a significant impact on the fauna and flora of their time. With the cooling and rewarming, the living beings adapted to the corresponding climate were forced to relocate their habitats. Numerous animal and plant species were therefore unable to repopulate large areas or became completely extinct. This effect was significantly greater in Africa and Europe, where the Mediterranean Sea and the east-west mountain ranges were obstacles to the migration of species, than in North America and East Asia.

Characteristic of this ice age were animals such as mammoths , mastodons , saigas , saber-toothed cats , cave lions , cave bears and other forms. Homo heidelbergensis , the Neanderthals that emerged from him and the modern man (Homo sapiens) who immigrated from Africa around 40,000 years ago also lived in Europe during the cold ages of this Ice Age.

See also

literature

Web links

Individual evidence

  1. ^ Felix Gradstein, James Ogg & Alan Smith: A Geologic Time Scale 2004 . Cambridge University Press, New York 2004, ISBN 978-0-521-78673-7 , pp. 412 .
  2. ↑ Linda C. Ivany, Kyger C. Lohmann, Franciszek Hasiuk, Daniel B. Blake, Alexander Glass, Richard B. Aronson, Ryan M. Moody: Eocene climate record of a high southern latitude continental shelf: Seymour Island, Antarctica . (PDF) In: The Geological Society of America (GSA) Bulletin . 120, No. 5/6, pp. 659-678. doi : 10.1130 / B26269.1 .
  3. ↑ Mark Pagani, Matthew Huber, Zhonghui Liu, Steven M. Bohaty, Jorijntje Henderiks, Willem Sijp, Srinath Krishnan, Robert M. DeConton: The Role of Carbon Dioxide During the Onset of Antarctic Glaciation . (PDF) In: Science . 334, No. 6060, December 2011, pp. 1261-1264. doi : 10.1126 / science.1203909 .
  4. ↑ Simone Galeotti, Robert DeConto, Timothy Naish, Paolo Stocchi, Fabio Florindo, Mark Pagani, Peter Barrett, Steven M. Bohaty, Luca Lanci, David Pollard, Sonia Sandroni, Franco M. Talarico, James C. Zachos: Antarctic Ice Sheet variability across the Eocene-Oligocene boundary climate transition . (PDF) In: Science . 352, No. 6281, April 2016, pp. 76-80. doi : 10.1126 / science.aab0669 .
  5. ↑ a b James S. Eldrett, Ian C. Harding, Paul A. Wilson, Emily Butler, Andrew P. Roberts: Continental ice in Greenland during the Eocene and Oligocene . (PDF) In: Nature . 446, March 2007, pp. 176-179. doi : 10.1038 / nature05591 .
  6. ↑ Michael Starkz, Wilfried Jokat, Gregor Knorr, Gerrit Lohmann: Threshold in North Atlantic-Arctic Ocean circulation controlled by the subsidence of the Greenland-Scotland Ridge . In: Nature Communications (online) . June 8, 2017. doi : 10.1038 / ncomms15681 .
  7. ^ Madelaine Böhme: The Miocene Climatic Optimum: evidence from ectothermic vertebrates of Central Europe . (PDF) In: Palaeogeography, Palaeoclimatology, Palaeoecology . 195, No. 3-4, June 2003, pp. 389-401. doi : 10.1016 / S0031-0182 (03) 00367-5 .
  8. ↑ Shiming Wan, Wolfram M. Kürschner, Peter D. Clift, Anchun Li, Tiegang Li: Extreme weathering / erosion during the Miocene Climatic Optimum: Evidence from sediment record in the South China Sea . In: Geophysical Research Letters . 36, No. 19, October 2009. doi : 10.1029 / 2009GL040279 .
  9. ↑ Wolfram M. Kürschner, Zlatko Kvaček, David L. Dilcher: The impact of Miocene atmospheric carbon dioxide fluctuations on climate and the evolution of terrestrial ecosystems . In: PNAS . 105, No. 2, 2007, pp. 449-453. doi : 10.1073 / pnas.0708588105 .
  10. ↑ Barbara P. Nash, Michael E. Perkins: Neogene Fallout Tuffs from the Yellowstone Hotspot in the Columbia Plateau Region, Oregon, Washington and Idaho, USA . In: PLOS One . October 2012. doi : 10.1371 / journal.pone.0044205 .
  11. ↑ Jennifer Kasbohm, Blair Schoene: Rapid eruption of the Columbia River flood basalt and correlation with the mid-Miocene climate optimum . (PDF) In: Science Advances . 4, No. 9, September 2018. doi : 10.1126 / sciadv.aat8223 .
  12. ↑ Edward Gasson, Robert M. DeConto, David Pollard, Richard H. Levy: Dynamic Antarctic ice sheet during the early to mid-Miocene . In: PNAS . 113, No. 13, March 2016, pp. 3459-3464. doi : 10.1073 / pnas.1516130113 .
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