Glacial period
Encyclopedia
A glacial period is an interval of time (thousands of years) within an ice age
that is marked by colder temperatures and glacier
advances. Interglacial
s, on the other hand, are periods of warmer climate within an ice age. The last glacial period ended about 15,000 years ago;
epoch is the current interglacial.
Within the Quaternary
glaciation (2.58 Ma to present), there have been a number of glacials and interglacials.
In the British Isles
the Pleistocene
extent of the Quaternary ice age, has been subdivided into the following stages and superstages.
The Cromerian consists of multiple glacial and interglacial periods. Other stages, the Anglian and Hoxnian, consist either of single glacial or interglacial periods.
This subdivision is valid for the British Isles and hence has a local significance. Other areas have different subdivisions that partly correlate with the British subdivision.
, occurring in the Pleistocene
epoch
, which began about 70,000 and ended about 15,000 years ago. The glaciations that occurred during this glacial period covered many areas of the Northern Hemisphere
, and have different names, depending on their geographic distributions: Wisconsin (in North America
), Devensian (in Great Britain
), Midlandian (in Ireland
), Würm (in the Alps
), Weichsel (in northern central Europe
) and Llanquihue in Chile
. The glacial advance reached its maximum extent
about 18,000 BP. In Europe
, the ice sheet reached northern Germany
.
) are likely to exert a larger influence over the short term; and that the mechanism by which orbital forcing
influences climate is not well understood.
Work by Berger and Loutre suggests that the current warm climate may last another 50,000 years.
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
that is marked by colder temperatures and glacier
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
advances. Interglacial
Interglacial
An Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...
s, on the other hand, are periods of warmer climate within an ice age. The last glacial period ended about 15,000 years ago;
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
epoch is the current interglacial.
Quaternary ice age
Quaternary
The Quaternary Period is the most recent of the three periods of the Cenozoic Era in the geologic time scale of the ICS. It follows the Neogene Period, spanning 2.588 ± 0.005 million years ago to the present...
glaciation (2.58 Ma to present), there have been a number of glacials and interglacials.
In the British Isles
British Isles
The British Isles are a group of islands off the northwest coast of continental Europe that include the islands of Great Britain and Ireland and over six thousand smaller isles. There are two sovereign states located on the islands: the United Kingdom of Great Britain and Northern Ireland and...
the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
extent of the Quaternary ice age, has been subdivided into the following stages and superstages.
- Preludhamian
- Ludhamian
- Thurnian
- Antian
- Bramertonian
- Prepastonian
- Pastonian
- BeestonianBeestonian stageThe Beestonian Stage is the name for an early Pleistocene stage used in the British Isles. It precedes the Cromerian Stage and follows the Pastonian Stage. This stage consists of alternating glacial and interglacial phases instead of being a continuous glacial epoch. It is equivalent to the...
(glacial) - Cromerian
- Anglian (glacial)
- Hoxnian
- Wolstonian (glacial)
- Ipswichian
- Devensian (glacial)
The Cromerian consists of multiple glacial and interglacial periods. Other stages, the Anglian and Hoxnian, consist either of single glacial or interglacial periods.
This subdivision is valid for the British Isles and hence has a local significance. Other areas have different subdivisions that partly correlate with the British subdivision.
Last glacial period
The last glacial period was the most recent glacial period within the current ice ageQuaternary glaciation
Quaternary glaciation, also known as the Pleistocene glaciation, the current ice age or simply the ice age, refers to the period of the last few million years in which permanent ice sheets were established in Antarctica and perhaps Greenland, and fluctuating ice sheets have occurred elsewhere...
, occurring in the Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
epoch
Epoch
-An epoch :* Epoch , a moment in time chosen as the origin of a particular era* Epoch or geologic epoch, a span of time smaller than a "period" and larger than an "age"...
, which began about 70,000 and ended about 15,000 years ago. The glaciations that occurred during this glacial period covered many areas of the Northern Hemisphere
Northern Hemisphere
The Northern Hemisphere is the half of a planet that is north of its equator—the word hemisphere literally means “half sphere”. It is also that half of the celestial sphere north of the celestial equator...
, and have different names, depending on their geographic distributions: Wisconsin (in North America
North America
North America is a continent wholly within the Northern Hemisphere and almost wholly within the Western Hemisphere. It is also considered a northern subcontinent of the Americas...
), Devensian (in Great Britain
Great Britain
Great Britain or Britain is an island situated to the northwest of Continental Europe. It is the ninth largest island in the world, and the largest European island, as well as the largest of the British Isles...
), Midlandian (in Ireland
Ireland
Ireland is an island to the northwest of continental Europe. It is the third-largest island in Europe and the twentieth-largest island on Earth...
), Würm (in the Alps
Alps
The Alps is 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....
), Weichsel (in northern central Europe
Central Europe
Central Europe or alternatively Middle Europe is a region of the European continent lying between the variously defined areas of Eastern and Western Europe...
) and Llanquihue in Chile
Chile
Chile ,officially the Republic of Chile , is a country in South America occupying a long, narrow coastal strip between the Andes mountains to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far...
. The glacial advance reached its maximum extent
Last Glacial Maximum
The Last Glacial Maximum refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and...
about 18,000 BP. In Europe
Europe
Europe is, by convention, one of the world's seven continents. Comprising the westernmost peninsula of Eurasia, Europe is generally 'divided' from Asia to its east by the watershed divides of the Ural and Caucasus Mountains, the Ural River, the Caspian and Black Seas, and the waterways connecting...
, the ice sheet reached northern Germany
Northern Germany
- Geography :The key terrain features of North Germany are the marshes along the coastline of the North Sea and Baltic Sea, and the geest and heaths inland. Also prominent are the low hills of the Baltic Uplands, the ground moraines, end moraines, sandur, glacial valleys, bogs, and Luch...
.
Next glacial period
Since orbital variations are predictable, computer models that relate orbital variations to climate can predict future climate possibilities. Two caveats are necessary: that anthropogenic effects (global warmingGlobal warming
Global warming refers to the rising average temperature of Earth's atmosphere and oceans and its projected continuation. In the last 100 years, Earth's average surface temperature increased by about with about two thirds of the increase occurring over just the last three decades...
) are likely to exert a larger influence over the short term; and that the mechanism by which orbital forcing
Orbital forcing
Orbital forcing is the effect on climate of slow changes in the tilt of the Earth's axis and shape of the orbit . These orbital changes change the total amount of sunlight reaching the Earth by up to 25% at mid-latitudes...
influences climate is not well understood.
Work by Berger and Loutre suggests that the current warm climate may last another 50,000 years.
See also
- Timeline of glaciationTimeline of glaciationThere have been five known ice ages in the Earth's history, with the Earth experiencing the Quaternary Ice Age during the present time. Within ice ages, there exist periods of more severe glacial conditions and more temperate referred to as glacial periods and interglacial periods, respectively...
- GlacierGlacierA glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
- Geologic time scaleGeologic time scaleThe geologic time scale provides a system of chronologic measurement relating stratigraphy to time that is used by geologists, paleontologists and other earth scientists to describe the timing and relationships between events that have occurred during the history of the Earth...
- Glacial history of MinnesotaGlacial history of MinnesotaThe glacial history of Minnesota is most defined since the onset of the last glacial period, which ended some 10,000 years ago. Within the last million years, most of the Midwestern United States and much of Canada were covered at one time or another with an ice sheet. This continental glacier had...
- Milankovitch cyclesMilankovitch cyclesMilankovitch theory describes the collective effects of changes in the Earth's movements upon its climate, named after Serbian civil engineer and mathematician Milutin Milanković, who worked on it during First World War internment...
- CyclostratigraphyCyclostratigraphyCyclostratigraphy is the study of astronomically forced climate cycles within sedimentary successions . Astronomical cycles are variations of the Earth's orbit around the sun due to the gravitational interaction with other masses within the solar system. Due to this cyclicity solar irradiation...
- ClimateClimateClimate encompasses the statistics of temperature, humidity, atmospheric pressure, wind, rainfall, atmospheric particle count and other meteorological elemental measurements in a given region over long periods...
- Precession (astronomy)
- Greenhouse and Icehouse EarthGreenhouse and Icehouse EarthFor the past millions of years, the earth has been fluctuating between two different states of dominant climate: Greenhouse and Icehouse. These two climate sets are complete opposites from each other and is on a continuing, uneven cycle between the two...
- Snowball EarthSnowball EarthThe Snowball Earth hypothesis posits that the Earth's surface became entirely or nearly entirely frozen at least once, some time earlier than 650 Ma . Proponents of the hypothesis argue that it best explains sedimentary deposits generally regarded as of glacial origin at tropical...
- InterglacialInterglacialAn Interglacial period is a geological interval of warmer global average temperature lasting thousands of years that separates consecutive glacial periods within an ice age...
and Interstadial periods - Yarkovsky effectYarkovsky effectThe Yarkovsky effect is a force acting on a rotating body in space caused by the anisotropic emission of thermal photons, which carry momentum...
- YORP effect
- Quaternary glaciationQuaternary glaciationQuaternary glaciation, also known as the Pleistocene glaciation, the current ice age or simply the ice age, refers to the period of the last few million years in which permanent ice sheets were established in Antarctica and perhaps Greenland, and fluctuating ice sheets have occurred elsewhere...
- last glacial period
- Last Glacial MaximumLast Glacial MaximumThe Last Glacial Maximum refers to a period in the Earth's climate history when ice sheets were at their maximum extension, between 26,500 and 19,000–20,000 years ago, marking the peak of the last glacial period. During this time, vast ice sheets covered much of North America, northern Europe and...
- Ice ageIce ageAn ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...