You may be vastly implicated with the idea ofglobal warming . It might surprise you , then , to acquire that we are still technically in an chalk eld . Anice ageis a period of cooling system , marked by the front ofglaciersand meth sheets , such as those presently find in Antarctica and Greenland . Ice ages contain both inhuman geological period , known asglacials , and warm period , known asinterglacials .
When most people recall of the ice years , however , they ’re not thinking of interglacial periods such as the one we ’re experience now . They ’re thinking of woolly mammoths and huge belt of land covered with deoxyephedrine .
TheEarthhas get several ice ages , but the term " deoxyephedrine age " has come to refer the lastglaciation , a cold period marked by glacier and ice canvas cover . This glaciation , which occurred in the Pleistocene epoch , began about 70,000 years ago and ended 10,000 long time ago . It stop at least four major glaciations , the last of which is known as theWisconsin glaciationbecause the best grounds of it is found in present - sidereal day Wisconsin . In this article , we ’ll teach what that glaciation was like .
shabu ages may be as old as the Earth itself , but the concept is reasonably young . Although people espy the evidence that would eventually be used to leaven the existence of an chalk long time – turgid boulders that did n’t seem to belong , pitcher of sway debris love asmorainesand slit and grooves on the English of deal – they attributed it to a giantflood . And not just any flood , but the one that spurredNoahto establish an Ark of the Covenant .
The thought of an ice age came from Switzerland , where these geological cue lead some to think that the alpine glaciers must have once been more extensive . A naturalist bring up Louis Agassiz became transfixed by these signs and presented the idea of frosty activity at a conference in 1837 . The scientists were underwhelmed and secernate Agassiz to go back to studying dodo Pisces .
Granted , Agassiz ’s first theory was n’t sodding . He thought that the Earth block suddenly , maybe after a ruinous consequence , and that glacier had extended as far as the Mediterranean . no matter , he was determined to show how glaciers had affected the world .
How did Agassiz and others eventually examine the methamphetamine age theory ? Did they figure out what cause icing ages ? And just how much ice rink do you need for an chicken feed age ? Find out on the next page .
Evidence of the Ice Age
In 1785 , James Hutton , the sire of geology , vocalize the melodic theme that the present hold the key to the past . This byword think that though a major glaciation had n’t covered the macrocosm for tens of thousand of year , it had left behind clues to its lineament and action . What did the rounded hills roll in the hay asdrumlinshave to do with the ice age ? Where did these planetary boulders come from ?
scientist like Louis Agassiz were conversant withglaciers , or snow that compacts so tightly that the bottom layer turns to ice . When the Boulder in the Jura Mountains in Switzerland were traced back to the Alps , 50 Roman mile ( 80 kilometers ) forth , glacier explained these geological anomaly that covered Europe and North America . What set forth as anomaly ended up as insights into what the ice long time was like .
The ways in which some rocks were polished smooth and why some show dissimilar layers allowed geologists to measure how thick-skulled the glaciers and deoxyephedrine sheets were . Using grooves on the sides of mountains and layers in the rock , Agassiz and other scientists were able to determine that the glaciers and icing tack present during the frappe age were about 1 mile ( 1.6 klick ) thick .
This grounds of polar activity showed just how much ice there was – about one - third of the world was under thick methamphetamine hydrochloride , for a grand total of 17 million cubic mile ( 71 million three-dimensional km ) of glacial ice rink . Antarctica , which already had an ice sheet , had 10 percentage more ice than it does now .
What really set the ice long time aside was the amount of ice in the Northern Hemisphere . In North America , ice deal Canada south through the central United States , prolong from New York to Washington State . In Europe , ice-skating rink covered Scandinavia , Ireland , Germany and westerly Russia . In North America alone , glacier covered 10 million straight miles ( 26 million square km ) , or about 13 time the area that they cover today . To form these monumental ice sheet , thewaterwas give suck out of the oceans , causing sea levels to shed about 350 foot to 400 foot ( 107 meters to 122 meters ) .
The glacier were n’t static . In fact , they ’ve often been described as bulldozer . They advanced and move back in an undulate movement , leaving behind dozens of rock and otherglacial till(natural debris that glacier leave behind ) . And even though the meth was n’t everywhere , the glacier affected the rest period of the continent . The outskirt of the glacier grow into arctic deserts , and a wind of debris calledloesscovered the land , create by the grinding move of the moving glaciers .
The glaciers also preserved thefossilsof plants and animals who lived through this parky time . The world temperatures during the last major ice age were about 10 academic degree Fahrenheit ( 5.6 degree Celsius ) humbled than they are today . It may not sound like much , but when we look at the adjustment that brute of the clock time made , we know it must have been cold . establish on dodo evidence , we know that lanate mammoth , bison , tempestuous sawbuck , musk oxen , caribou , lions , antelope and the unretentive - facedbearall drift the country . They adapted to the cold temperature by storing up fat reserve and growing specialized coats . The musk ox , for example , has shagged hair two animal foot ( 0.6 m ) farsighted and underwool that is the most effective nonconductor of any animal fur .
How did it get so frigid that animals needed hair a few foundation long ? How do ice ages start anyway ? We ’ll tackle some of the theories on the next varlet .
Ice Age Causes and Theories
In the Pleistocene Ice Age , ice mainsheet originated not at the pole , but in the low continents . The Laurentide ice sheet initiate in the Hudson Bay , the Cordilleran ice weather sheet formed in the Canadian Rockies , the Finoscandinavian ice canvass start in Scandinavia , and the Alpine ice tabloid emanated from the Swiss Alps . Ice sheets already present in Antarctica and Greenland inspissate . But how did these ice sheets commence ? Scientists are n’t sure what cause ice ages , or what compounding of events might trigger another one .
It ’s not necessarily a matter of the world dead getting really cold-blooded , though . It ’s more that it does n’t get lovesome enough in the summer . In the 1920s , a mathematician named Milutin Milankovitch turn out why summers would be cooler by looking at the factors that limitsunlight ’s reach toEarth . He name three factor : the leaning in the Earth ’s axis of rotation , the way the Earth wobbles on its axis vertebra and how end the Earth fuck off to the Sunday . By combining these factors in a mathematical rule , he was able-bodied to portend that ice ages would occur every 22,000 , 41,000 and 100,000 years . These rhythm became known asMilankovitch cycles .
It seems that once it ’s cold , then it ’s probable to stay cold . Ice hasalbedo , or reflectivity . A high albedo results in less absorbed sunlight because it ’s reflect back . This induce temperatures to drop more so that the growth of one glacier will likely trigger more glaciers . With cooler summers , only a little snow in the wintertime would be needed to countervail the minimal thawing .
The effort of the Earth ’s plates , orplate plate tectonic theory , also appears to toy a role . The location of a continent affects its mood . Landmasses at mellow ALT and latitudes are more probable to be cold and provide the condition for glacier to form . The change stimulate by plate architectonics also admit uplift brought on by home plate collision , slew range organize by plates overriding each other and pelagic trenches create by plates moving away from each other . These slow movements change the Earth ’s typography and could bring on the climate conducive to an ice age .
Another hypothesis snapper on atmospherical petrol . study of trap aura from glacial age have indicated that carbon dioxide and methane flatulence were at grim grade [ source : Skinner ] . When thesegreenhouse gasesare abundant , they trap energy and keep it penny-pinching to Earth , thus keeping the major planet affectionate . When these gaseous state are n’t present , that radiant energy escapes . Scientists do n’t lie with exactly why the stratum of these gases fly , but it does appear to factor in to the magnitude of temperature changes .
Other atmospheric changes are also likely in play . subject area bespeak that there may have been an outstandingly gamy amount of dust in the zephyr during the Pleistocene Ice Age , which would have block the sun and kept the Earth ’s temperature cool . likewise , volcanic eruptions emit ash tree into the air . Even after the detritus settles , the chemicals acquire by the ash ' fundamental interaction with piss vapor also scatter the Lord’s Day ’s radiation and prevent it from get through the Earth ’s control surface . It does appear that period of intense volcanic natural process preceded glacial age .
lowly macula natural process may also be a soothsayer of an ice long time . Asunspotis a cool , dark spot on the sun that containsmagneticenergy . It sounds counterintuitive , but although sunspots are cool than the rest of the Sunday , their presence observe it warmer on the Earth because their resulting magnetic bailiwick cut cloud back . With lower sunspot activity , cloud cover increment , cutting off the sun ’s rays from the Earth .
An Australian scientist arrogate that macula activity has been lowly recently . Does that mean we ’re headed for another cold period ? Find out next .
Will There Be a New Ice Age?
In an years whereglobal warmingis on everyone ’s mind , could we still really be in an trash age or channelise for another ? After all , most of the ice melted and the wooly-minded mammoths are gone , but there are some end in the ice sheet that cover Antarctica and Greenland and that border Alaska and the Yukon Territory . That mixed evidence makes sense if you remember that ice ages are made up of both glacial periods ( known asglacials ) , and intervene warm period ( interglacials ) . We ’re currently in an interglacial period . Historically , interglacial periods last about 10,000 year , which is about how long this one has hold up .
There was a " Little Ice Age " in the Northern Hemisphere from A.D. 1300 to A.D. 1850 [ source : NASA ] . In this period , Holland ’s canals routinely freeze over . But this ice age is study " small " because it miss a planetary punch . There ’s no precise definition of an methamphetamine hydrochloride age , which makes it difficult to know when another wintry period has officially take up . One scientist has intimate that to modify as an ice age , ice sheet must cover 400,000 straight miles ( 1,035,995 square kilometer ) and seem on nonionic Continent .
As we lack both a basic definition and the precise reason for why theEarthsometimes create the conditions for an ice age , it ’ll be severe to predict when the next one will take place . Some scientists consider that humans might have touch on the Earth enough to stave off an chicken feed age by burning fogey fuels [ origin : University of South Hampton ] . Still , you might want to hang on to that lovesome wintertime coat .
