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Topic: Varangian glaciation


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  Glaciation - Wikipedia, the free encyclopedia   (Site not responding. Last check: 2007-11-05)
Glaciation, often called an ice age, is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator.
The causes of glaciations have been much debated ever since the phenomenon was clearly identified in the 17th century.
An ice age is sometimes used to refer to a single glaciation, or to an entire period of repeated glaciations such as the recent 30 million years of the Cenozoic period, especially the Pleistocene glaciations.
www.peekskill.us /project/wikipedia/index.php/Glaciation   (504 words)

  
 [No title]   (Site not responding. Last check: 2007-11-05)
A glaciation (a created composite term meaning Glacial Period, referring to the Period or Era of, as well as the process of High Glacial Activity), often called an ice age, is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator.
It is probable that glacial periods other than those above have been overlooked because of the paucity of exposed rocks from high latitudes from older periods.
The term ice age is used to refer either to a single glaciation or to an entire period of repeated glaciations such as the recent 30 million years of the Cenozoic period, especially the Pleistocene glaciations.
mindwallet.com /wiki/Interglacial   (550 words)

  
 Snowball Earth - Wikipedia, the free encyclopedia
Brian Harland pointed out that glacial till deposits of this period can be found on all continents, and first proposed that the Earth must have been in an ice age at this time.
Proponents of the theory point out that oxygen in the Earth's atmosphere is not naturally stable, and must receive continuous maintenance (replenishment) from the biosphere as it is constantly leached out of the atmosphere in a wide variety of chemical reactions, particularly iron and silicon.
A tremendous glaciation would curtail plant life on Earth, thus letting the atmospheric oxygen be drastically depleted and perhaps even disappear, and thus allow (non-oxidized) iron-rich rocks to form.
en.wikipedia.org /wiki/Varangian_glaciation   (1601 words)

  
 Read about Sturtian-Varangian at WorldVillage Encyclopedia. Research Sturtian-Varangian and learn about ...   (Site not responding. Last check: 2007-11-05)
The Sturtian-Varangian is a late Precambrian world-wide glaciation episode ranging from 950Ma to 600Ma, represented by tillite deposits in Congo, Australia, China, North America, Sahara and Norway.
The population of acritarchs crashed during this glaciation and it is claimed that oxygen levels in the
Evidence of the glaciation is found in various places and times: The Congo River basin from 950-750Ma and 620-600Ma.
encyclopedia.worldvillage.com /s/b/Varanger_glaciation   (239 words)

  
 Glaciers
A glacier is defined as a body of ice that flows under its own mass due to gravity.
Glaciers are powerful enough to transport vast quantities of sediment of all sizes, though there is differential erosion and sedimentation through the glacier profile.
Evidence from the Illinoian and Wisconsinan glacial periods are easier to interpret than older ones because sediment deposits are directly accessible on the glacially shaped landscape.
jove.geol.niu.edu /faculty/fischer/429_info/429trips/NIF/Glaciers.htm   (3107 words)

  
 Sturtian-Varangian - Wikipedia, the free encyclopedia   (Site not responding. Last check: 2007-11-05)
The Sturtian-Varangian (also known as the Cryogenian) is a late Precambrian world-wide glaciation episode ranging from 950Ma to 600Ma, represented by tillite deposits in Congo, Australia, China, North America, Sahara and Norway.
The population of acritarchs crashed during this glaciation and it is claimed that oxygen levels in the atmosphere increased after the glaciation.
Other known world wide glaciations include the from 2400Ma to 2100Ma, from 450-420Ma, the Karoo glaciation from 360Ma to 260Ma, and the Cenozoic glaciation which started 30Ma in Antarctica and are not over.
kernersville.us /project/wikipedia/index.php/Cryogenian   (298 words)

  
 glaciation   (Site not responding. Last check: 2007-11-05)
Glaciations are characterized by cool, wet climates and thick ice sheets extending south of each pole.
Known periods of glaciation include the Huronian (2400Ma-2100Ma), Sturtian-Varangian (950Ma-570Ma), Andean-Saharan (450Ma-420Ma), Karoo (360Ma-260Ma), Cenozoic (30Ma-Present).
Not every year in each interval was a time of complete or even partial glaciation.
www.yourencyclopedia.net /glaciation.html   (470 words)

  
 CONK! Encyclopedia: Precambrian   (Site not responding. Last check: 2007-11-05)
A number of glacial periods have been identified going as far back as the Huronian epoch, roughly 2200 Ma.
The best studied is the Sturtian-Varangian glaciation, around 600 Ma, which may have brought glacial conditions all the way to the equator, resulting in a "Snowball Earth".
The atmosphere of the early Earth is poorly known, but it is thought to have been smothered in noxious gases, containing very little free oxygen.
www.conk.com /search/encyclopedia.cgi?q=Precambrian   (769 words)

  
 Snowball Earth -- Facts, Info, and Encyclopedia article   (Site not responding. Last check: 2007-11-05)
The Snowball Earth, also known as the (Click link for more info and facts about Varangian) Varangian glaciation, is an hypothesis that has been around for several decades but which has recently been reformulated by Paul F. Hoffman, Sturgis Hooper Professor of Geology at (A university in Massachusetts) Harvard University.
In the Earth's (A nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas; constitutes 21 percent of the atmosphere by volume; the most abundant element in the earth's crust) oxygen (The envelope of gases surrounding any celestial body) atmosphere, iron naturally rusts.
Proponents of the theory point out that oxygen in the Earth's atmosphere is not naturally stable, and must receive continuous maintenance from the (The regions of the surface and atmosphere of the Earth (or other planet) where living organisms exist) biosphere.
www.absoluteastronomy.com /encyclopedia/s/sn/snowball_earth.htm   (1013 words)

  
 Glaciation - ArtPolitic Encyclopedia of Politics : Information Portal
Glaciation is a geological phenomenon in which massive ice sheets form in the Arctic and Antarctic and advance toward the equator.
The best studied glaciation -- that of the recent past appears to have taken place in at least four separate ice incursions and retreats.
This has lead to a recent Snowball Earth hypothesis that the Earth froze over completely in the late Proterozoic then thawed very rapidly as trapped water and carbon dioxide were returned to atmosphere.
www.artpolitic.org /infopedia/gl/Glaciation.html   (425 words)

  
 ES 331/767 Lab III   (Site not responding. Last check: 2007-11-05)
Glacial strata are known from all modern continents (except Antarctica) with an overall time range of about 950 to 600 million years old.
Glaciation is known from Arabia, central Sahara, western Africa, the lower Amazon of Brazil, and the Andes of western South America.
Glaciation began in the early Carboniferous (360 Ma), reached a peak in late Carboniferous, continued into early Permian, and mostly came to an end by late Permian (260 Ma) time, thus spanning 100 million years.
academic.emporia.edu /aberjame/ice/labs/lab03.htm   (1629 words)

  
 Chapter 7, part 3, Lecture Notes, The Proterozoic Eon, Levin: The Earth Through Time - Wiley   (Site not responding. Last check: 2007-11-05)
They contain striated (scratched and grooved) pebbles and boulders, and other features indicative of glaciation, such as glacial dropstones or chunks of rock dropped by melting icebergs, and varves or layers of sediment formed in glacial lakes.
Glacial deposits are so widespread at this time that geologists refer to it as "snowball Earth".
The glaciation was associated with a decrease in atmospheric CO and increase in O
www3.interscience.wiley.com:8100 /legacy/college/levin/0470000201/chap_tutorial/ch07/chapter07-3.html   (425 words)

  
 Snowball Earth   (Site not responding. Last check: 2007-11-05)
The Snowball Earth, also known as the Varangian glaciation, is a recent hypothesis which proposes that the Ice Age which took place in the Precambrian was so severe that the Earth's oceans froze over completely, with only heat from the planetary core causing some liquid water to exist under ice more than a kilometer thick.
Paleontologist W. Brian Harland pointed out that glacial till deposits can be found on all continents, and proposed that the Earth must have been in an ice age at this time.
A tremendous glaciation would obviously curtail life on Earth, thus allowing the atmospheric oxygen to disappear, and iron-rich rocks to form.
www.theezine.net /s/snowball-earth.html   (858 words)

  
 Palaeos Proterozoic : Neoproterozoic: Ediacaran : Ediacaran Period - 1
This was supposed to take the age of the Ediacaran fauna, while the Varangian sub-period took in the age of the Varangian glaciation -- presumably the first half of the Vendian.
Nostoc-like balls) is possible but is difficult to reconcile with the morphology and relatively high relief of the remains, their occurrence at the bottom of turbidite beds, and the lack of a carbonaceous film outlining them, particularly in view of the of the fact that carbonaceous compressions are present in the formation." Hofmann et al.
The published age constraints on these fossils are from 595 Ma (Varangian glacial diamictites of the Gaskiers Formation) to 565 Ma (well-dated Ediacaran fossils at Mistaken Point occurring 1.5 km stratigraphically higher).
www.palaeos.com /Proterozoic/Neoproterozoic/Ediacaran/Ediacaran.htm   (2724 words)

  
 [No title]   (Site not responding. Last check: 2007-11-05)
Areas influenced by Varangian glaciation in Scotland, Greenland, Scandinavia, and Australia appear to have been in the Tropics by the Late Cambrian because thick and extensive limestones of that and younger Paleozoic ages occur there.
In the present ocean, essentially glacial times with permanent ice at high latitudes, the major factor in forming water masses is the wide variation in temperature as the variation in open ocean salinity is small.
This paradox is due to the conservation of the average salinity and the change in surface salinity related to the zonal change in evaporation minus precipitation.
www.marscigrp.org /pv82.html   (5944 words)

  
 Glaciation latitude Earth ice Equator ice age glacier Snowball Earth Mountain Sturtian-Varangian carbon dioxide   (Site not responding. Last check: 2007-11-05)
Glaciation : is the modification of the land surface by the action of glaciers.
Paleoenvironments and Glaciation in Beringia Research funded by the National Science Foundation (Office of Polar Programs) and the National Park Service (Beringian Heritage Project) Click on the letters...
Glaciation Practice exam questions written by Timothy H. Heaton, Professor of Earth Sciences, University of South Dakota Click the circle by an answer with the mouse, then click on the Submit button to...
en.powerwissen.com /hwgFlUVVuagMQis7ITxktQ==_Glaciation.html   (556 words)

  
 Sturtian-Varangian explained   (Site not responding. Last check: 2007-11-05)
Generally considered to be divisible into at least two (Sturtian around 800Ma and Minoan/Varanger 650Ma) or four significant glaciation extremes.
The tillite deposits occurred also in what is believed to be low latitudes, which lead to the hypothesis of Snowball Earth The population of acritarchs crashed during this glaciation and it is claimed that oxygen levels in the atmosphere increased after the glaciation.
Paleomagnetism seems to indicate very high continental drift rates leading some geologists to question whether some of the phenomena might be due to magnetic pole wandering rather than plate motion and low latitiude glaciation.
www.wordspider.net /st/sturtian-varangian.html   (275 words)

  
 TESTING THE HIGH OBLIQUITY HYPOTHESIS AS AN EXPLANATION FOR THE SNOWBALL EARTH MODEL   (Site not responding. Last check: 2007-11-05)
Many papers dealing with Neoproterozoic glaciation have recently been published, thanks to the renewed interest in the hypothesis of a snowball Earth.
Here we use an AGCM coupled with a slab ocean to test the simplest solution proposed by G. Williams to explain the glaciation and the increased seasonal cycle at low latitudes : a higher obliquity of the Earth's rotation axis.
In this paper, we show that a soft snowball Earth is easily simulated for the Sturtian episode (750 Ma), due to the location of continental masses in the tropical areas, but not for the Varangian episode when the continental mass is mainly located over the mid and high latitudes of the Southern Hemisphere.
gsa.confex.com /gsa/2002RM/finalprogram/abstract_33916.htm   (346 words)

  
 Search Tuna Report for Snowball Earth   (Site not responding. Last check: 2007-11-05)
Description: Snowball Earth The Snowball Earth, also known as the Varangian glaciation, is a recent hypothesis, largely formulated by Paul F....
Description: The Snowball Earth, also known as the Varangian glaciation, is a recent hypothesis, largely formulated by Paul F. Hoffman, Sturgis Hooper Professor of Geology at Harvard University.
Kirshvink's argument was that the reduced interaction between the ocean and atmosphere due to global glaciation aided in the build up of reduced iron and manganese in great concentrations in the oceans....
www.searchtuna.com /ftlive2/833.html   (2514 words)

  
 CHAPTER 8: Cryptozoic (Precambrian) History
The occurrence of glacial tillite over an exceptionally broad latitudinal range suggests that the planet nearly became a frozen, lifeless world during the Late Proterozoic.
3) Some workers suggest that the Varangian glaciation event resulted from the earth's orbit becoming highly elliptical whereas others attribute the glaciation event to extreme tilting of the earth's axis.
Eventually, the abundant atmospheric CO caused global warming which, in turn, melted the glaciers.
www.uh.edu /~geos6g/1376/cryptozoic8.html   (2727 words)

  
 Vendian Period
The principal significance of this occurrence of cnidarian-grade metazoans is their stratigraphic position below Varangian glaciomarine tillites (Aitken 1988, 1989).
This is the only Ediacaran-like assemblage found below Varanger glacial deposits anywhere, and provides a useful test for those models positing metazoan evolution to have been arrested during one or more of the Neoproterozoic glaciations (e.g.
Of principal significance is this occurrence of cnidarian-grade metazoans in pre-Varanger sediments, since the Varanger glaciation is sometimes cited as an evolutionary 'bottleneck' which arrested metazoan evolution.
www.peripatus.gen.nz /paleontology/Vendian.html   (4246 words)

  
 Upto11.net - Wikipedia Article for Precambrian
The supercontinent, known as Rodinia, broke up around 600 million years BP.
A number of glacial periods have been identified going as far back as the Huronian epoch, roughly 2200 million years BP.
The best studied is the Sturtian-Varangian glaciation, around 600 million years BP, which may have brought glacial conditions all the way to the equator, resulting in a "Snowball Earth".
upto11.net /generic_wiki.php?q=pre-cambrian   (866 words)

  
 Search Tuna Report for Snowball Earth   (Site not responding. Last check: 2007-11-05)
Toulkeridis,, Babinski,, Buchwaldt,., De Brito Neves,, Todt,, Santos, 1999 : Are Varangian Or Sturtian The Glacial Deposits On The Sao Francisco Craton?...
Glaciers That Came As Far South As New York And Wisconsin, As Some Did 18,000 Years Ago, Were Not The Problem....
Once There, glaciers Would Have Formed And Drop Stones Would Be Common In All Rocks Of This Era, And After Those Drop Stones Had Been Formed At The Poles The Land, And The Drop Stones, Would Have Been Carried Back Down To The Tropics By Continental Drift....
searchtuna.com /ftlive2/2092.html   (1674 words)

  
 Search Tuna Report for Snowball Earth   (Site not responding. Last check: 2007-11-05)
There the proposed mechanism is the first appearance of atmospheric oxygen, which would have absorbed any methane in the air....
Aside from grinding glaciers and groaning sea ice, the only stir comes from a smattering of volcanoes forcing their hot heads above the frigid surface....
Although global glaciation would have drastically curtailed biological productivity, melting of the oceanic ice would also have induced a cyanobacterial bloom, leading to an oxygen spike in the euphotic zone and to the oxidative precipitation of iron and manganese....
searchtuna.com /ftlive2/833.html   (2514 words)

  
 Glaciation - www.catalogofcasinos.com   (Site not responding. Last check: 2007-11-05)
Such a period between glacial maxima is known also, as an interglacial.
These can be further divided by location and time (eg: the names Riss (180,000 - 130,000 years bp) and Würm (70,000-10,000 years bp) refer specifically to glaciation at the headwaters of the Donau / Rhine rivers.) Not every year in each interval was a time of complete or even partial glaciation.
CVO Menu - Glaciers and Glaciations, Ice Sheets and Glacial Lakes
www.catalogofcasinos.com /Glaciation.html   (922 words)

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