Eemian, once called the Eemian Interglacial period, is temporally equivalent to the
Sangamonian StageThe Sangamonian Stage, also known as the Sangamon interglacial, is the name used by Quaternary geologists to designate the last interglacial period in North America...
(sensu stricto) in
North AmericaNorth America is the northern continent of the Americas, situated in the Earth's northern hemisphere and in the western hemisphere. It is bordered on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the southeast by the Caribbean Sea, and on the west by the North Pacific...
, the Ipswichian Stage in the
UKThe United Kingdom of Great Britain and Northern Ireland is a sovereign state located off the northwestern coast of continental Europe. It is an island country, spanning an archipelago including Great Britain, the northeastern part of Ireland, and many small islands...
, and the
Riss-Würm interglacial in the
AlpsThe Alps are one of the great mountain range systems of Europe, stretching from Austria and Slovenia in the east; through Italy, Switzerland, Liechtenstein and Germany; to France in the west....
. It is the second-to-latest interglacial period of the
Ice AgeThe general term "ice age" or, more precisely, "glacial age" denotes a geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in an expansion of continental ice sheets, polar ice sheets and alpine glaciers. Within a long-term ice age, individual...
. It began about 130,000 years ago. Changes in orbital parameters from today (greater obliquity and eccentricity, and perihelion), known as the Milankovitch cycle, probably led to greater seasonal temperature variations in the Northern Hemisphere, although global annual means temperatures were probably similar to those of the Holocene. The Eemian climate is believed to have been about as stable as, but probably warmer than, that of the
HoloceneThe Holocene is a geological epoch which began approximately 11 700 years ago . According to traditional geological thinking, the Holocene continues to the present. The Holocene is part of the Neogene and Quaternary periods. Its name comes from the Greek words and , meaning "entirely...
(see
ice coreAn ice core is a core sample from the accumulation of snow and ice over many years that have re-crystallized and have trapped air bubbles from previous time periods...
). The warmest peak of the Eemian was around 125,000 years ago, when forests reached as far north as
North CapeNorth Cape is a cape on the island of Magerøya in northern Norway, in the municipality of Nordkapp. Its 307 m high, steep cliff is often referred to as the northernmost point of Europe, located at , 2102.3 km from the North Pole. However, the neighbouring point Knivskjellodden is actually 1,457...
(which is now
tundraIn physical geography, tundra is a biome where the tree growth is hindered by low temperatures and short growing seasons. The term tundra comes from Kildin Sami tūndâr, which means "uplands, treeless mountain tract." There are two types of tundra: Arctic tundra and alpine tundra...
) in northern
NorwayNorway , officially the Kingdom of Norway, is a country in Northern Europe occupying the western portion of the Scandinavian Peninsula, as well as Jan Mayen and the Arctic archipelago of Svalbard under the Spitsbergen Treaty...
well above the Arctic Circle at .
HardwoodThe term 'hardwood' is used to describe wood from angiosperm trees . It may also be used for those trees themselves: these are usually broad-leaved; in temperate and boreal latitudes they are mostly deciduous, but in tropics and subtropics mostly evergreen.Hardwood contrasts with softwood which...
trees like
hazelThe hazels are a genus of deciduous trees and large shrubs native to the temperate northern hemisphere. The genus is usually placed in the birch family Betulaceae, though some botanists split the hazels into a separate family Corylaceae.They have simple, rounded leaves with double-serrate margins...
and
oakAn oak is a tree or shrub in the genus Quercus , of which about 400 species exist. "Oak" may also appear in the names of species in related genera, notably Lithocarpus...
grew as far north as
OuluOulu is a city and municipality of inhabitants in the province of Oulu and the region of Northern Ostrobothnia, in Finland. It is the largest city in Northern Finland and the sixth largest city in the country. Its population growth rate is almost comparable with that of the Helsinki Metropolitan...
,
FinlandFinland , officially the Republic of Finland
, is a Nordic country and democracy situated in the Fennoscandian region of northern Europe. It borders Sweden on the west, Russia on the east, and Norway on the north, while Estonia lies to its south across the Gulf of Finland...
. Sea levels at that time were 4-6 meters higher than they are now, indicating greater deglaciation than today (mostly from partial melting of the
ice sheetAn ice sheet is a mass of glacier ice that covers surrounding terrain and is greater than 50,000 km² . The only current ice sheets are in Antarctica and Greenland; during the last glacial period at Last Glacial Maximum the Laurentide ice sheet covered much of Canada and North America, the...
s of
GreenlandGreenland is an autonomous constituent country within the Kingdom of Denmark located between the Arctic and Atlantic Oceans, east of the Canadian Arctic Archipelago...
and
Antarctica| style="border-top:solid 1px #ccd2d9; padding:0.4em 1em 0.4em 0; vertical-align:top;" | 14,000,000 km
2 280,000 km
2 13,720,000 km
2 |-! style="border-top: solid 1px #ccd2d9; padding: 0.4em 1em 0.4em 0; vertical-align: top;...
). One study published in July 2007 found evidence that
Dye 3An ice core is a core sample from the accumulation of snow and ice that has re-crystallized and trapped air bubbles over many years. The composition of these ice cores, especially the presence of hydrogen and oxygen isotopes, provides a picture of the climate at the time...
was glaciated during the Eemian, which implies that Greenland could have contributed at most to sea level rise.
ScandinaviaScandinavia is a geographical region in northern Europe that includes, and is named after, the Scanian Province. It consists of the kingdoms of Norway, Sweden, and Denmark...
was an island due to the inundation of vast areas of
northern EuropeNorthern Europe is the northern part or region of Europe. The United Nations defines Northern Europe as including the following countries and dependent regions:** ** ** Ireland** Svalbard and Jan Mayen** ** Channel Islands: and...
and the
West Siberian PlainThe West Siberian Plain is a large plain that occupies the western portion of Siberia and Russia, between the Ural Mountains in the west and the Yenisei River in the east, and by the Eastern Sayan Mountains and the Baikal Mountains on the south. Much of the plain is poorly drained and consists of...
.
At the peak of the Eemian, the northern hemisphere winters were generally warmer and wetter than now, though some areas were actually slightly cooler than today. The
HippopotamusThe hippopotamus or hippo is a large, mostly plant-eating mammal in sub-Saharan Africa, and one of only two extant species in the family Hippopotamidae...
was distributed as far north as rivers
RhineThe Rhine is one of the longest and most important rivers in Europe, at , with an average discharge of more than ....
and Thames. Trees grew as far north as southern
Baffin IslandBaffin Island in the territory of Nunavut is the largest member of the Canadian Arctic Archipelago. It is the largest island in Canada and the fifth largest island in the world, with an area of and has a population of 11,000...
in the
CanadianCanada is a country occupying most of northern North America, extending from the Atlantic Ocean in the east to the Pacific Ocean in the west and northward into the Arctic Ocean...
Arctic Archipelago instead of only as far north as Kuujjuaq in northern
QuebecQuebec is a province in east-central Canada. It is the only Canadian province with a predominantly French-speaking identity and the only one whose sole official language is French at the provincial level....
, and the prairie-forest boundary in the
Great PlainsThe Great Plains are the broad expanse of prairie and steppe which lie west of the Mississippi River and east of the Rocky Mountains in the United States and Canada. This area covers parts of the U.S...
of the
United StatesThe United States of America is a federal constitutional republic comprising fifty states and a federal district...
lay further west — near
Lubbock, TexasLubbock is an American city in the state of Texas. Located in the northwestern part of the state, a region known historically as the Llano Estacado, it is the county seat of Lubbock County, and the home of Texas Tech University. According to the 2000 U.S. Census, the city population was 199,564,...
, instead of near
Dallas, TexasDallas , with a population of 1,279,910, is the third-largest city in Texas and the 8th-largest in the United States. The city is the main economic center of the 12-county Dallas–Fort Worth–Arlington metropolitan area that according to the March 2009 U.S. Census Bureau release, had a population of...
, where the boundary now exists. The era closed as temperatures steadily fell to conditions cooler and drier than the present, with 468-year long aridity pulse in central Europe, and by 114,000 years ago, a glacial era had returned.
Kaspar
et al. (GRL, 2005) perform a comparison of a coupled general circulation model (GCM) with reconstructed Eemian temperatures for Europe. Central Europe (north of the Alps) is found to be 1–2
°CCelsius is a temperature scale that is named after the Swedish astronomer Anders Celsius , who developed a similar temperature scale two years before his death...
warmer than present; south of the alps conditions are 1–2 °C cooler than today. The model (forced with observed GHG concentrations and Eemian orbital parameters) generally reproduces these observations, and hence they conclude that these factors are enough to explain the Eemian temperatures.
Definition of the Eemian
The Eemian Stage was first recognized from
boreholeA borehole is the generalised term for any narrow shaft drilled in the ground, either vertically or horizontally. A borehole may be constructed for many different purposes, including the extraction of water or other liquid or gases , as part of a geotechnical investigation or environmental site...
s in the area of the city of
AmersfoortAmersfoort is a municipality and the second largest city of the province of Utrecht in central Netherlands. The city is growing quickly and has a well-preserved medieval core. Amersfoort is one of the largest railway junctions in the country, because of its location on two of the Netherlands' main...
(The Netherlands) by Harting (1875). He named the beds "Système Eémien", after the river
EemThe Eem is a river in the north of the Utrecht Province in the Netherlands with a length of approximately .The river is fed by the Vallei Canal and a number of Veluwe creeks, the most important of which are the Heiligenberger, the Barneveldse and the Lunterse, all of which come together in...
on which Amersfoort is located. Harting noticed the marine molluscan assemblages to be very different from the modern fauna that occurs in the
North SeaThe North Sea is a marginal, epeiric sea on the European continental shelf. The Dover Strait and the English Channel in the south and the Norwegian Sea in the north connect it to the Atlantic Ocean. It is more than long and wide, with an area of around...
. Many species from the Eemian layers nowadays show a much more southern distribution, ranging from South of the
Strait of DoverThe Strait of Dover or Dover Strait is the strait at the narrowest part of the English Channel. The shortest distance across the strait is from the South Foreland, some 4 miles north east of Dover in the county of Kent, England, to Cap Gris Nez, a cape near to Calais in the French of...
, to
PortugalPortugal , officially the Portuguese Republic , is a country located in southwestern Europe on the Iberian Peninsula. Portugal is the westernmost country of mainland Europe and is bordered by the Atlantic Ocean to the west and south and by Spain to the north and east...
(
LusitanianLusitanian may refer to:*Lusitanians, an ancient people of western Iberian Peninsula.**Lusitanian language, the language of the ancient Lusitanians.**Lusitanian mythology, the mythology of the ancient Lusitanians....
faunal province) and even into the Mediterranean (Mediterranean faunal province). More information about the molluscan assemblages is given by Lorié (1887), and Spaink (1958). Since its discovery, Eemian beds in the Netherlands have mainly been recognized on their marine molluscan content combined with their stratigraphical position and other palaeontology. In the type-area the marine beds are often underlain by
tillthumb|right|Glacial till with tufts of grassTill is unsorted glacial sediment. Glacial drift is a general term for the coarsely graded and extremely heterogeneous sediments of glacial origin. Glacial till is that part of glacial drift which was deposited directly by the glacier. It may vary from...
s that are considered to date from the Saalian, and overlain by local fresh water or wind-blown deposits from the Weichselian. Contrary to for instance the deposits in Denmark, the Eemian deposits in the type area have never been found overlain by tills, nor in ice-pushed position.
Van Voorthuysen (1958) described the
foraminiferaThe Foraminifera, or forams for short, are a large group of amoeboid protists with reticulating pseudopods, fine strands of cytoplasm that branch and merge to form a dynamic net. They typically produce a test, or shell, which can have either one or multiple chambers, some becoming quite elaborate...
from the type site, whereas Zagwijn (1961) published the
palynologyPalynology is the science that studies contemporary and fossil palynomorphs, including pollen, spores, orbicules, dinoflagellate cysts, acritarchs, chitinozoans and scolecodonts, together with particulate organic matter and kerogen found in sedimentary rocks and sediments...
, providing a subdivision of this stage into pollenstages. At the end of the twentieth century, the type site was re-investigated using old and new data in a multi-disciplinary approach (Cleveringa et al., 2000). At the same time a parastratotype was selected and multidisciplinary investigated in the
AmsterdamAmsterdam is the capital and largest city of the Netherlands, located in the province of North Holland in the west of the country...
glacial basin in the Amsterdam-Terminal borehole (Van Leeuwen, et al., 2000). These authors also published a U/Th age for late Eemian deposits from this borehole of 118.2 ±6.3 Ka. A historical review of Dutch Eemian research is provided by Bosch, Cleveringa and Meijer, 2000.
Sea level
Sea level at peak was probably 4-6m higher than today (references in Overpeck et al., 2006), with much of this extra water coming from Greenland but some likely to have come from Antarctica. Global mean
sea surface temperatureSea surface temperature is the water temperature close to the surface.In practical terms, the exact meaning of surface varies according to the measurement method used...
s are not thought to have been significantly higher than in the Holocene, hence the thermal expansion difference from today is small. Because of the sea level drop since the Eemian, exposed fossil coral reefs are common in the tropics, especially in the Caribbean and along the Red Sea coastlines. These reefs often contain internal erosion surfaces showing significant sea level instability during the Eemian.
Ipswichian Stage
This name is used by British
geologistFor other uses, see Geologist .A geologist is a scientist who studies the solid and liquid matter that constitutes the Earth and terrestrial planets...
s and archaeologists who named it after the town of
IpswichIpswich is a non-metropolitan district and the county town of Suffolk, England on the estuary of the River Orwell. Nearby towns are Felixstowe in Suffolk and Harwich and Colchester in Essex...
in the English county of
SuffolkSuffolk is a non-metropolitan county of historic origin in East Anglia, England. It has borders with Norfolk to the north, Cambridgeshire to the west and Essex to the south. The North Sea lies to the east...
, where some of the deposits it created were first found.
See also
- Bay mud
Bay mud consists of thick deposits of soft, unconsolidated silty clay, which is saturated with water; these soil layers are situated at the bottom of certain estuaries, which are normally in temperate regions that have experienced cyclical glacial cycles...
- Ice age
The general term "ice age" or, more precisely, "glacial age" denotes a geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in an expansion of continental ice sheets, polar ice sheets and alpine glaciers. Within a long-term ice age, individual...
- Interglacial period
- Glacial period
A glacial period is an interval of time within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate within an ice age...
- Last glacial period
- Timeline of glaciation
There have been four major periods of glaciation in the Earth's past. The second, and possibly most severe, is estimated to have occurred from 850 to 635 Ma ago, in the late Proterozoic Age) and it has been suggested that it produced a second
Further reading
/ Netherlands Journal of Geosciences |volume=79 |issue=2/3 |pages=135–145 |id= |url=http://www.njgonline.nl/publish/articles/000085/article.pdf |accessdate= |quote= }}
- Cleveringa, P., Meijer, T., van Leeuwen, R.J.W., de Wolf, H., Pouwer, R., Lissenberg T. and Burger, A.W., 2000. The Eemian stratotype locality at Amersfoort in the central Netherlands: a re-evaluation of old and new data. Geologie & Mijnbouw / Netherlands Journal of Geosciences, 79(2/3): 197-216.
- Harting, P., 1875. Le système Éemien Archives Néerlandaises Sciences Exactes et Naturelles de la Societé Hollandaise des Sciences (Harlem), 10: 443-454.
- Harting, P., 1886. Het Eemdal en het Eemstelsel Album der Natuur, 1886: 95-100.
- Lorié, J., 1887. Contributions a la géologie des Pays Bas III. Le Diluvium plus récent ou sableux et le système Eémien Archives Teyler, Ser. II, Vol. III: 104-160.
- Spaink, G., 1958. De Nederlandse Eemlagen, I: Algemeen overzicht. Wetenschappelijke Mededelingen Koninklijke Nederlandse Natuurhistorische Vereniging 29, 44 pp.
- Van Leeuwen, R.J. , Beets, D., Bosch, J.H.A., Burger, A.W., Cleveringa, P., van Harten, D., Herngreen, G.F.W., Langereis, C.G., Meijer, T., Pouwer, R., de Wolf, H., 2000. Stratigraphy and integrated facies analysis of the Saalian and Eemian sediments in the Amsterdam-Terminal borehole, the Netherlands. Geologie en Mijnbouw / Netherlands Journal of Geosciences 79, 161-196.
- Van Voorthuysen, J.H., 1958. Foraminiferen aus dem Eemien (Riss-Würm-Interglazial) in der Bohrung Amersfoort I (Locus Typicus). Mededelingen Geologische Stichting NS 11(1957), 27-39.
- Wilson, M.A., Curran, H.A. and White, B., 1998. Paleontological evidence of a brief global sea-level event during the last interglacial. Lethaia 31, 241-250.
- Zagwijn, W.H., 1961. Vegetation, climate and radiocarbon datings in the Late Pleistocene of the Netherlands. Part 1: Eemian and Early Weichselian. Mededelingen Geologische Stichting NS 14, 15-45.
External links