Inligting

Jagters gesmelte en gevormde ivoor 12.000 jaar gelede


In 'n verslag wat hierdie week verskyn het, is daar bewyse dat ivoor versag word vir die skep van gereedskap en sierdiere wat meer as 12 000 jaar gelede deur ou mense bereik is. Die Siberiese wetenskaplike wat hierdie ontdekking gemaak het, verduidelik egter heeltemal hoe die ou jagters die speelgoedagtige materiaal gemaak het wat gebruik is om ou diervorme te versamel. Hierdie bewyse dui daarop dat antieke mense baie meer ingewikkelde vaardighede het as wat voorheen geglo is.

Dr Evgeny Artemyev beweer dat die ivoorstawe gemaak is met behulp van 'n vooraf tegniek wat dit 'vloeibaar' gemaak het, amper soos playdoh. Bron: Evgeny Artemyev / Russiese Akademie vir Wetenskappe

Antieke wetenskap wat moderne wetenskaplikes verstom

Die ivoordiere is in die vroeë 2000's ontdek deur argeoloë wat op die archeologiese terrein van Afontova Gora-2, by die rivier Yenisey in Krasnoyarsk, gegrawe het, wat dikwels as die mooiste stad in Siberië beskou word. Twaalf ivoorstawe is ontdek wat “gevorm is nadat dit versag is”. Die Siberiese tye berig dat die feit dat ou mense geweet het hoe om sulke gereedskap en versierings te maak “die moderne wetenskap nog steeds verbaas”.

Die ivoorversierings is onlangs ondersoek deur dr. Evgeny Artemyev van die Krasnoyarsk Laboratory of Archaeology and Paleogeography of Middle Siberia, Institute of Archaeology and Ethnography van die Siberiese tak van die Russiese Akademie van Wetenskappe. Die navorser meen die beeldjies is óf 'ystyd speelgoed' gemaak deur mense wat hierdie gebied van die hedendaagse Siberië bevolk het, 'óf 'n vorm van oerkuns'. Hy het ontdek dat die argeoloog gesê het dat as hulle elkeen uit verskillende hoeke kyk, 'hulle op verskillende soorte diere' lyk, met behulp van tegnologieë waarvan die internasionale wetenskaplike gemeenskap nog nie bewus is nie.

Die dieragtige figure wat in Siberië ontdek is, is gemaak van sponsagtige dele van wollerige mammoet en beertjies. (Evgeny Artemyev / Russiese Akademie vir Wetenskappe )

Hervorming van "Fluid Like" ivoor

Dr Artemyev sê twee van die dieragtige beeldjies wat van sponsagtige dele van wollerige mammoet en beertjies gemaak is. Wat meer is, as jy na een van hulle aan sy sy kyk, lyk dit soos 'n slapende mens. As ons terugkeer na die playdoh-verwysing, het dit gebeur omdat sommige van die falliese vormige ivoorstawe wat op dieselfde plek ontdek is, gemaak is met 'n tegniek wat hulle 'amper vloeistofagtig' gemaak het.

  • Eiers van dinosourusse, meteoriete, tekens van 'n antieke beskawing: wat is hierdie reuse -balle?
  • Antieke Siberiese gesnyde mammoet -ivoor lewer ongelooflike nuwe inligting!
  • Kan antieke Peruane klip versag?

Spore van klipwerktuie wat op die "vloei" van die smeebare stof gemerk is voordat dit verstyf het, het aangedui dat die wesens se slagtande "aansienlik versag het, dat die konsekwentheid taai was", het dr. Artemyev gesê. Hoewel wetenskaplikes nog nie seker is hoe ou mense dit reggekry het om die semi-gesmelte toestand te bewerkstellig nie, het dr. Artemyev gesê dat 'n spesifieke reuse-slagtand "versag het in die mate dat dit soos die huidige playdoh lyk."

Dr Artemyev het gesê dat argeoloë nog nooit so iets op hedendaagse paleolitiese terreine teëgekom het nie en dat tradisionele sienings van ou mense wat meer primitief as ons is, moet opgedateer word. Die wêreld sien sulke artefakte selde omdat wetenskaplike spanne “selde publiseer oor items wat nie behoorlik verduidelik kan word nie”, het die argeoloog beweer. Hierdie langwerpige ivoorstawe kan spasies wees wat gereedskap of toekomstige speelgoed maak, maar die wetenskaplikes kan nog nie begryp hoe hierdie vorms gemaak is nie. Maar hulle aanvaar nou dat die ou mense baie groter vaardighede gehad het as wat hulle ooit kon dink.

Die artefakte, insluitend die ivoorstawe, is in die vroeë 2000's ontdek deur argeoloë wat op die Afontova Gora-2 argeologiese terrein gegrawe het Krasnojarsk, Siberië. (Evgeny Artemyev / Russiese Akademie vir Wetenskappe )

Hoe om sagte ivoor te maak?

'N Paar antwoorde is gevind in 'n ondersoek na die raaisel van hoe ou jagters ivoor versag het Wetenskaplike Amerikaner artikel getiteld Hoe om sagte ivoor te maak . Mettertyd word ivoor bros (maklik verkrummel) en kan dit sag word en deurskynend word deur dit in gelatien te kook en in 'n bad fosforsuur te lê voordat dit in suiwer linne droog word. As die behandelde ivoor verhard is, kan dit weer versag word met 'n bad warm water en melk. Hierin lê die raaisel.

Ons weet dat die ou mense toegang gehad het tot water, melk en gelatien, uit diere hoewe, maar waar op aarde het 12 000-jarige jagters in Siberië fosforsuur gekry? Hierdie noodsaaklike bestanddeel is verkrygbaar uit voedsel wat hoog is in proteïene, soos vleis, bone, eiers, hoender en vis, wat almal baie fosfor bevat, maar hoe jagters die suur versamel en verfyn het om ivoor smeebaar te maak, is dit die sleutel tot die verstaan ​​daarvan hele situasie. Vandaar die gevolgtrekking "hierdie eertydse mense het baie groter vaardighede as wat hulle hulle kon voorstel."


Clovis -kultuur

Die Clovis -kultuur is 'n prehistoriese Paleo -Amerikaanse kultuur, vernoem na duidelike klipgereedskap wat in die 1920's en 1930's in noue samewerking met die fauna van die Pleistoseen gevind is in Blackwater -omgewing nr. 1 naby Clovis, New Mexico. Dit verskyn ongeveer 11 500–11 000 ongekalibreerde RCYBP [1] aan die einde van die laaste ystydperk, en word gekenmerk deur die vervaardiging van "Clovis -punte" en kenmerkende been- en ivoorwerktuie. Argeoloë se mees presiese bepalings tans dui daarop dat hierdie radiokoolstofouderdom ongeveer 13 200 tot 12 900 kalenderjare gelede is. Clovis -mense word beskou as die voorouers van die meeste inheemse mense van die Amerikas. [2] [3] [4]

Clovis
Geografiese omvangGroot vlaktes
TydperkLities
Datumsc. 13,000 - 11,000 BP
Tik werfBlackwater -plek nr
Voorafgegaan deurPaleo-Indiërs
Gevolg deurFolsom tradisie

Die enigste menslike begrafnis wat direk verband hou met gereedskap uit die Clovis-kultuur, sluit in die oorskot van 'n babaseunnavorser met die naam Anzick-1. [5] [6] Paleogenetiese ontledings van die antieke kern-, mitochondriale en Y-chromosoom-DNA van Anzick-1 [7] toon aan dat Anzick-1 nou verwant is aan moderne inheemse Amerikaanse bevolkings, wat die Beringia-hipotese ondersteun vir die vestiging van die Amerikas. [8]

Die Clovis-kultuur is vervang deur nog meer gelokaliseerde streeksgenootskappe vanaf die jonger Dryas-koue klimaatperiode. Post-Clovis-kulture sluit in die Folsom-tradisie, Gainey, Suwannee-Simpson, Plainview-Goshen, Cumberland en Redstone. Daar word vermoed dat elkeen hiervan direk afkomstig is van Clovis, wat in sommige gevalle blykbaar slegs verskil in die lengte van die fluit op hul projektielpunte. Alhoewel dit oor die algemeen die gevolg is van normale kulturele verandering deur die tyd, [9] is talle ander redes aangevoer as dryfkragte om veranderinge in die argeologiese rekord te verduidelik, soos die jonger Dryas postglaciale klimaatsverandering wat talle fauna -uitwissings vertoon het.

Na die ontdekking van verskeie Clovis -terreine in die oostelike Noord -Amerika in die dertigerjare, word die Clovis -mense beskou as die eerste menslike inwoners wat 'n wydverspreide kultuur in die Amerikas geskep het. Verskeie argeologiese ontdekkings het egter beduidende twyfel getrek oor die Clovis-eerste teorie, insluitend terreine soos Cactus Hill in Virginia, Paisley Caves in die Summer Lake Basin van Oregon, die Topper-terrein in Allendale County South Carolina, Meadowcroft Rockshelter in Pennsylvania, die Friedkin [10] perseel in Texas, Cueva Fell in Chili, en veral Monte Verde ook in Chili. [11] Die oudste menslike argeologiese terrein in Amerika is die Pedra Furada -vuurherde, 'n plek in Brasilië wat die Clovis -kultuur voorafgaan en die ander terreine wat reeds 19.000 tot 30.000 jaar genoem is. Hierdie bewering het 'n twispunt geword tussen Noord -Amerikaanse argeoloë en hul Suid -Amerikaanse en Europese eweknieë, wat nie saamstem of dit beslis 'n ouer menslike terrein is nie. [12] [13] [14]


'N Komeet het hierdie paleolitiese dorpie 12 800 jaar gelede vernietig

Abu Hureyra is 'n belangrike argeologiese terrein in Sirië, bekend vir artefakte wat die vroeë aanvaarding van landbou in die streek dokumenteer. Dit kan ook erken word as die enigste menslike nedersetting wat deur 'n fragment van 'n komeet getref is.

Die terrein, nou onder die waters van die Assadmeer, is vinnig tussen 1972 en 1973 opgegrawe voordat die bou van die Tabqa -dam die gebied oorstroom het. Tydens die opgrawing het argeoloë besef dat daar werklik twee terreine is, die een bo -op die ander. Die eerste was 'n paleolitiese nedersetting van jagter-versamelaars, en die tweede was 'n boerdery met nuwe geboue in 'n ander styl.

Die navorsers dink dat die komeet wat reeds gebreek het, by die aarde se atmosfeer binnegekom het, waarskynlik in nog meer stukke opgebreek het, waarvan baie nie die grond bereik het nie. In plaas daarvan het hulle 'n reeks ontploffings in die atmosfeer veroorsaak, bekend as lugstortings. Elke lugaanval was so kragtig soos 'n kernontploffing, wat die grond en plantegroei daaronder onmiddellik verdamp en kragtige skokgolwe veroorsaak wat alles vir tien kilometer verwoes het. Die dorpie in Abu Hureyra is deur een van hierdie skokgolwe getref.

Toe ons die werf in 1973 teruggrawe, het ek opgemerk dat daar in een gebied sterk brand, maar natuurlik het ek destyds nie gedink aan komete of asteroïdes of iets dergeliks nie, ” het Andrew gesê Moore, 'n argeoloog en professor aan die Rochester Institute of Technology in New York, wat die opgrawing by Abu Hureyra gelei het. Moore is die eerste skrywer van die nuwe studie, wat op 6 Maart in die internet verskyn het Wetenskaplike verslae. Dit blyk nou dat swaar verbranding die gevolg was dat die hele dorp in rook opgegaan het as gevolg van hierdie lugstorting wat die hele plek verbrand het. ”

'N Multidissiplinêre groep wetenskaplikes het nou gevind dat sommige grondmonsters uit Abu Hureyra gevul is met klein stukkies smeltglas en klein stukkies verdampte grond wat vinnig stol na die ontploffing. Hulle het smeltglas gevind tussen die sade en graankorrels wat uit die terrein gevind is, asook spat in die buis wat die geboue bedek het. Die meeste van hierdie stukkies smeltglas is tussen 1 en 2 millimeter in deursnee. Die span het ook 'n hoë konsentrasie mikroskopiese nanodiamante, klein koolstofbolletjies en houtskool gevind, waarvan almal waarskynlik tydens 'n kosmiese impak gevorm is.

Ons het gevind dat die glas op klein stukkies been wat by die haard was, spat, sodat ons weet dat die gesmelte glas in hierdie dorpie geland het terwyl mense daar gewoon het, sê mede -outeur Allen West, lid van die Comet Research Group, 'n organisasie sonder winsbejag wat daarop gemik is om hierdie spesifieke kosmiese impak en die gevolge daarvan te bestudeer.

Kosmiese oorsprong

Die impak oorsprong van die smeltglas word ondersteun deur die minerale wat dit bevat. Smeltglas wat in Abu Hureyra gevind word, bevat gesmelte korrels van minerale soos kwarts, chromferied en magnetiet, wat slegs kan smelt by temperature van 1,720 °C tot 2,200 °C.

U moet baie gesofistikeerde wetenskaplike analitiese tegnieke gebruik om hierdie dinge te sien, maar as u dit eers sien, is daar absoluut geen twyfel oor wat u teëkom nie, en daar is slegs een verklaring daarvoor, ’ 8221 het Moore gesê. Hierdie smeltglas het enorme hitte geverg, ver bo alles wat 'n groep jagters en versamelaars ooit op hul eie kon opwek. ”

Natuurlike bronne soos vuur of vulkanisme is ook uitgesluit omdat dit nie die vereiste temperatuur kan bereik nie. Weerlig bereik wel temperature wat sedimente smelt en glas produseer, maar dit skep ook magnetiese afdrukke wat nie in Abu Hureyra se smeltglas voorkom nie.

Dit kan nie die gevolg wees van brande nie, het Peter Schultz, 'n geoloog en planeetwetenskaplike aan die Brown -universiteit in Rhode Island, gesê wat nie by die nuwe studie betrokke was nie. Hulle resultate ondersteun hul gevolgtrekkings sterk dat 'n impak of, meer waarskynlik, 'n lugstorting in die streek plaasgevind het. ”

“ Hierdie temperature sou u motor in minder as 'n minuut in 'n gesmelte poel metaal verander, het West 82 gesê.

Komete jaag

Abu Hureyra lê in die oostelike deel van die gebied wat bekend staan ​​as die gebied van die jonger Dryas -grens, 'n reeks plekke in Amerika, Europa en die Midde -Ooste waar bewyse gevind is van 'n kosmiese impak teen die einde van die Pleistoseen. Hierdie bewys bevat 'n koolstofryke laag, bekend as die “black mat ”, wat groot hoeveelhede nanodiamante, metaalbolletjies en hoër konsentrasies van seldsame elemente soos iridium, platinum en nikkel bevat. Dit bevat ook houtskool, wat dui op wydverspreide veldbrande wat tot 10% van alle beboste gebiede op die planeet kon verbrand het.

Die jonger Dryas Grens -impakhipotese beweer dat die impak die aarde se klimaat verander het, wat 'n koue periode van 1300 jaar veroorsaak het. Temperature het gemiddeld met 10 °C gedaal, en die klimaat het droër geword, veral in die Midde -Ooste.

Sommige navorsers meen dat die impak en die gevolglike klimaatsverandering die uitwissing van die meeste groot diere op die planeet kan versnel, insluitend mammoete, sabeltande katte en Amerikaanse perde en kamele. Dit kan ook die Clovis -kultuur in Noord -Amerika versterk het, wat omstreeks daardie tyd verdwyn het.

Boere word

Argeoloë verbind die gebeurtenis Younger Dryas ook met die begin van sistematiese landbou in die Midde -Ooste. Ons het reeds geweet dat die verandering van jag en versameling na boerdery saamval met die begin van die jonger Dryas, so ons het reeds geweet dat dit lyk asof klimaatsverandering 'n rol gespeel het om die mense in die dorp te oorreed om te begin boer, ” het Moore gesê. “ Natuurlik weet ons nie wat die jonger Dryas veroorsaak het nie. ”

Radiokoolstofdatering in Abu Hureyra het aan die lig gebring dat die dorp baie kort herbou is na die impak deur mense wat dieselfde soort been- en vuurgereedskap gebruik het as die eerste bewoners van die nedersetting. Daar was absoluut geen verandering in die kultuurtoerusting nie, het Moore gesê, wat daarop dui dat dit dieselfde groep mense was wat die dorp weer gevestig het. Miskien, dink Moore, was sommige lede van die dorp besig om te jag of kos te versamel en kon hulle terugkeer.

Slegs hierdie keer het hulle aansienlike veranderinge in hul ekonomie aangebring. Ek dink nie die mense in Abu Hureyra het dit noodwendig uitgevind nie, en Moore het gesê, maar Abu Hureyra is die vroegste webwerf waar ons kan sê dat iets soos sistematiese landbou werklik aan die gang is. ”

In die heeltemal veranderende klimaatstoestande het hulle begin boer, rogvelde begin verbou, en mettertyd koring en gars, en uiteindelik het hulle ook begin vee by skape en bokke, en#8221 het Moore gesê . Mettertyd het die ding ontwikkel tot 'n enorme nedersetting met etlike duisende inwoners, en dit het nogal die dominante dorp in daardie deel van Sirië geword.

Hierdie artikel is oorspronklik gepubliseer deur Eos, 'n bron vir nuus en perspektiewe oor aarde- en ruimtewetenskap.


Die opkoms van mense in Noord -Amerika

Gedurende die laat Pleistoseen was die Bering Land Bridge (Beringia) 'n belangrike verbinding tussen Asië en Noord -Amerika. die mammoet, kon tussen die twee kontinente reis.

Beringia is vandag onder water en ons ken dit as die Beringsee, 'n koue en onherbergsame arktiese gebied waar oorblyfsels van antieke plante byna perfek in prehistoriese modder oorleef. Slegs met groot moeite woon die Inuit- en Aleoetiese mense langs die oewers daarvan.

Maar hoe was Beringia tydens die Pleistoseen?

Russiese en Amerikaanse wetenskaplikes het geleer deur die kuslyn te bestudeer en see -kerne van die Beringsee te neem, dat Beringia tydens die Pleistoseen ten minste twee keer gewissel het van 'n droë landmassa toe die gletsers versprei het, wat die seewater toegesluit het, see toe as gletsers het gesmelt. Vir twee lang tydperke: van 75 000 tot 45 000 jaar gelede, en weer van 25 000 tot 14 000, is die Bering -landbrug blootgestel.

Gedurende die duisende jare was Beringia 'n dorre, verlate land met dun sneeubedekking en sterk winterwinde en storms. Die meeste plante is baie lae struike.

Miskien sal die diere gedurende die jaarlikse groeiseisoen van vier of vyf maande van die een gunsteling na die ander beweeg. land wemel van troppe herbivore . Waarskynlik was die diere versprei oor die landskap, gekonsentreer op baie spesiale plekke. een keer . Hulle sou mekaar opgevolg het, op dieselfde plekke, maar op verskillende plante en in verskillende maande.

So, watter diersoorte sou in Beringia teenwoordig gewees het? As gevolg van Asië na Beringia sou mammoete, bisons, kariboe, muskus, takbokke, vreeslike wolwe, sabeltandkatte, daalskape, saiga-bokke, jak, elande, vlieënde eekhorings, lynx, leeu, dhole, honde, rivierotters, frette, bere, jaguars, lemmings, muise en volse, jakkalse, konyne en wolwe. en hierdie kameel. 'n ander van enige diersoort . Die Pleistoseen -soogdiere het dwarsdeur Beringia geleef en slegs toevallig sou hulle reis na Asië en Noord -Amerika gevolg het. Reis verder na Noord -Amerika is gereeld geblokkeer deur ysplate wat soms die omvang van Pleistoseen -soogdiere wat in Beringia woon, beperk.

Wat van mense? Waar pas hulle in die plek wat Beringia genoem word?

35 000 jaar gelede het mense uit Europa na Siberië verhuis . Daar is twee gebiede in Siberië waar argeologiese oorblyfsels van vroeë mense gevind word. .

Opkoms

In die Baikalmeer kom die bekendste argeologiese oorblyfsels van Mal'ta aan die Angara -rivier. geweier en bedek met huide of sooi. Malthe is bekend vir sy ivoorsnywerk van mammoet, vroue en voëls. ook opgegrawe is.

In die middel -Aldan -vallei is oorblyfsels van 'n groep nedersettings gevind. burines, lemme en groot klipkappers. Omdat die grot ongestoord was, het betroubare radiokoolstofdatums aangedui dat Dyukhtai van 14 000 tot 12 000 jaar gelede deur Siberiese jagters gebruik is. en ander grootwild teen 11 000 jaar gelede in Noord -Amerika . Hierdie bewering is nie wetenskaplik bewys nie, omdat geen ander bewyse opgegrawe is deur argeologiese ondersoeke wat sou aantoon dat die Dyukhtai -mense oor Beringia gereis het nie.

Nog 'n argument wat daarop dui dat die voorouers van die inheemse mense uit Amerika uit Siberië gekom het, kom van Cristy Turner, 'n wetenskaplike wat die fisiese eienskappe van menslike tande bestudeer. jagters en moderne inheemse Amerikaanse mense . Hy het gevind dat die tande van die Pleistoseen -mense wat by Dyukhtai gewoon het, anders is as die tande van die mense wat oor Beringia gereis het . Turner stel voor dat die Siberiese jagters wat die diere na Noord -Amerika gevolg het, nie dieselfde as die jagters wat in Mal'ta en Dyukhtai woon nie, maar is jagters wat in die noordooste van Siberië gewoon het, nader aan Beringia. Bo -Lena -bekken, oor die oostelike Siberië en vandaar na Beringia.

Argeologiese en anatomiese (tande) bewyse toon dat daar moontlik verskillende groepe mense gedurende die laat Pleistoseen in Siberië gewoon en gejag het en dat hierdie verskillende groepe mense oor die tegnologie beskik het sodat hulle die diere kon jag wat oor die Beringia getrek het. maar stewige bewyse wat toon watter groep Pleistoseenjagters Beringia oorsteek, is maar min, hoewel dit seker is dat Amerika se eerste mense wel uit Siberië geëmigreer het.

Die emigrasie uit Siberië het die Pleistoseenjagters en hul gesinne na Alaska gelei en uiteindelik dieper na Noord- en Suid -Amerika. hoef nie hul kulturele gewoontes baie te verander nie. Maar mettertyd het toestande begin verander.

Eerstens het die klimaat van die Pleistoseen droër en warmer geword namate die ys ongeveer 10 000 jaar gelede in die Arktiese gebied teruggetrek het. diere waarop die mense afhanklik was, het uitgesterf. Tweedens het die mense self baie vaardig geword om die groot diere met spiese en atlatl te jag. en habitat, het bygedra tot die uitwissing van die mammoet, kameel, perd en reuse -luiaard. . Om 10.000 jaar gelede moes die mense hul jagpatrone verander. ke hert, elande en konyne. Die mense moes ook streke verlaat wat voor 10 000 jaar genoeg hulpbronne verskaf het, maar nadat dit 10 000 jaar droog geword het, woestyngebiede wat nie genoegsame hulpbronne verskaf het nie.

Hierdie veranderende klimaat het die maklike eenvoudige leefstyl van die jagters verander en die mense gedwing om met ander kulturele oplossings te eksperimenteer . Een oplossing wat sommige stamme aangeneem het, was om plante, soos mielies, pampoentjies en boontjies, te mak en te begin eksperimenteer met tuinbou . Tuinbou beteken om in sedimentêre dorpe te woon en slegs te jag om die plantgewas aan te vul. slote om water uit verafgeleë gebiede te voorsien. Die risiko's en arbeidsinvestering verbonde aan tuinbou was groter as die risiko's van jag.

Geografiese verskeidenheid hulpbronne

Natuurlik het die Siberiese jagters wat tydens die Pleistoseen uit Siberië na Alaska gekom het, nie besef dat hulle 'n nuwe kontinent binnegekom het nie. Hulle oorlewingsbehoeftes het dieselfde gebly. was die verskeidenheid, soorte en konsentrasies van hulpbronmateriale terwyl hulle van die een geografiese gebied na die ander gereis het . Dit is duidelik dat elke streek in Amerika verskillende plante, diere en gesteentes het waaruit materiale gemaak kan word. net in Idaho. Die woude en mere in die panhandle in vergelyking met die woestyn-, bekken- en gebied van die suide van Idaho. Elke streek het verskillende rou hulpbronne aan die mense gebied wat hulle kon gebruik vir voedsel, klere, skuiling, gereedskap en wapens. Die gemene deler was egter tegnologie.

Voorgeskiedenis van Suid -Idaho

Die vroegste onbetwiste argeologiese bewyse van menslike besetting in die suide van Idaho is afkomstig van die Wasden -terrein (ook na verwys as die uilgrot), wes van Idaho Falls. hierdie datums is klip- en beengereedskapfragmente, insluitend gegroefde projektielpunte wat as Folsom geklassifiseer is. . Die opvallendste van hierdie terreine is die Simon Site naby Fairfield, Idaho, wat talle Clovis -punte en gepaardgaande bifaces bevat het.

Woestynbewoners in Idaho

Klimate het na die einde van die Pleistoseen aanhou droog en warm word. . Daardie groepe, wat al duisende jare woestynbewoners was, het die kennis en tegnologie opgedoen om voordeel te trek uit die groot verskeidenheid plant- en diersoorte wat 4000 jaar gelede gedy het in die droë en warm klimaat van die suide van Idaho . Hulle het hert en bokke uitgebuit af en toe bison in kombinasie met kleiner diere, insluitend visse en watervoëls.

Belangrike terreine wat hierdie veranderende lewenswyse beskryf, sluit in die voorheen genoemde Wasden- en Simon -terreine saam met Wahmuza, wat aan die Fort Hall Indian Reservation geleë is, en Dagger Falls, op die middelvurk van die Salmonrivier . Die kenmerkende styl van spies hierdie tydperk is die groot hoekpunte van die Elko-reeks.

Shoshoni pyl en boog. Met vergunning van die Idaho Museum of Natural History, Pocatello Idaho

Boë en amp Pyle en ampte

Die woestynlewe het tot in die historiese tye voortgeduur namate die klimaat in die moderne tyd afgekoel het. Tegnieke om te jag en kos te maak, het verander namate nuwe tegnologie ontwikkel is. vorige spiestegnologie was steeds 'n belangrike deel van jag en visvang. . Op daardie plek het Shoshoni meer as 60 visspesies, watervoëls en landsoogdiere in die winterkampe geoes. Kenmerkende pylpunte, soos die Rosespring-hoek en die woestynkant, en erdewerk dui op hierdie tydperk.


Terug in die tyd gebel

Twintig duisend jaar gelede was die sneeu diep in Maine. Regtig diep.

Amerika vir ongeveer 60 000 jaar. Nie veel daarvan het gesmelt nie. Sneeuval na sneeuval opgebou, verpak die lae in ys en nog meer ys. Ongeveer 21 000 jaar gelede bedek 'n myl-en-'n-half-dik laag ys hierdie deel van die wêreld en strek oor berge en ooswaarts oor die oseaan tot 180 myl van die huidige kuslyn. Geoloë noem dit die Laurentide -ysblad. Die res van ons, wat nie veel meer kan doen as om kop te krap oor soveel ys nie, noem dit net 'n gletser.

Soveel ys was swaar. Dit het op die grond daaronder gedruk en dit honderde voet laer gedruk as wat dit vandag is. Tussen ongeveer 12 000 en 20 000 jaar gelede het die atmosfeer begin warm word en die gletser het teruggetrek toe die ystydperk, bekend as die Wisconsin -tydperk van gletsering, tot 'n einde gekom het. Ongeveer 16 000 jaar gelede begin die kuslyn wys, en teen 14 000 jaar gelede steek die top van Cadillac en ander berge uit.

Ons sê die gletser het 'teruggetrek', maar dit is 'n bietjie meer misleidend, maar wat gebeur het, is dat die gletser van sy kant af in die binneland gesmelt het. Die ys self het die hele tyd seewaarts gestroom, selfs al het dit in stukke gesmelt en afgebreek (soos gletsers nou in Alaska en ander dele van die wêreld doen). Namate die ys se gewig afneem, het die land weer opgeskiet. Teen 10 000 tot 12 000 jaar gelede was ons laaglandgebiede duidelik.

Afvallende gletsers laat alle groottes, vorms en toestande van rots agteruit - gekap, geskend, afgeskuur. Net om 'n paar geologiese voorbeelde te gee: Daar is grond, wat sanderige, sandagtige rommel is, die stukke wat onder die gletser gemaal is, word basale bewerking genoem. Akkumulasies van grond en rotsagtige materiaal wat deur die gletser gelaat word, word morene genoem. Sand- en gruisafsettings van gesmelte water wat in tonnels vloei, word genoem eskers.

Baie van die materiaal wat tot, morene en eskers bestaan, is honderde miljoene jare oud. Die gletser was net die mees onlangse verwerkingsvorm. Trouens, die kus van Maine het begin vorm aanneem in sy huidige kronkelende vorm toe dwalende landmassas ongeveer 430 miljoen jaar gelede gebots het. 'N Fragment van die kontinentale land (of terrane) genaamd Avalonia - wat verbind was met grond wat nou dele van Europa uitmaak - het op die proto -Noord -Amerikaanse vasteland, of Laurentia, ingeploeg.

In die stadige botsing het sedimentêre, stollings- en metamorfe gesteentes wat reeds daar was, uit die seebodem opgeduik en oor en onder gevou. As hundreds of millions of years churned by, the continents continued to drift, until what’s now the Atlantic Ocean opened up around 1.7 million years ago. Periods of glaciation over the next million and a half years sculpted the rocks and stones we see now, from the sandy beaches of southern Maine to the cliffs of Monhegan, mountains of Mount Desert, and Washington County coast.


Cave art

The Upper Paleolithic period dates from between 50,000 and 10,000 years ago, depending on the region. This was the time when anatomically modern humans — Homo sapiens — replaced earlier lineages throughout the world, such as Neanderthals and Denisovans — although DNA studies show that they sometimes interbred with them.

The Upper Paleolithic period was marked by big changes in stone tools. Instead of the general-purpose stone tools used for hundreds of thousands of years, specialized stone tools began to be developed for specific tasks — such as hafted axes for cutting wood.

This period also saw a big increase in figurative artworks, including cave paintings, rock sculptures, and bone, antler and ivory carvings. The natural pigment paintings on the walls of the Altamira cave in northern Spain date from the Upper Paleolithic period, around 30,000 years ago.


The Rise of Civilization - 15,000 BC

This article theorises the rise of civilization in approximately 15,000 BC not 4000 BC.

During the last ice age, when sea levels were low, the combined Tigris-Euphrates river flowed through a wide flat plain-like landscape. The Persian Gulf today has an average depth of only 35 m. During the most recent glaciation, which ended 12,000 years ago, worldwide sea levels dropped 120 to 130 m, leaving the bed of the Persian Gulf well above sea level during the glacial maximum. It had to have been a slightly swampy freshwater floodplain, with small lakes where water was retained in the hollows.


The drainage of the combined glacial era Tigris-Euphrates made its way down the marshes and lakes of this plain to the Strait of Hormuz into the Arabian Sea. Reports of the exploration ship "Meteor" have confirmed that the Gulf was an entirely dry basin about 15,000 BC. Close to the steeper Iranian side a deep channel apparently marks the course of the ancient extended Shatt al-Arab, called the "the Atlantis river". A continuous shallow shelf across the top (north) of the Gulf and down the west side (at 20 m) suggests that this section was the last to be inundated at roughly 5500 BC. At the Straits of Hormuz the bathymetric profile indicates a convergence into one main channel which continued across the Bieban Shelf before dropping to a depth of c 400 m in the Gulf of Oman the deeper parts of this channel may be due to delta deposits at the edge of the deep ocean collapsing in a succession of big underwater landslides, causing underwater erosion by the resulting turbidity currents.


15,500 BC, in the lower Atlantis valley a small band of hunters and gatherers settle on the marshy bankside and start herding wild sheep and goats, within ten years they have started growing wild wheat and barley, this marks the beginning of agriculture on Earth.


15,400 BC, the small village formed by the first farmers has now expanded to 650 people, around the village (called Atlantis after the nearby river) there are 55 farms producing crops fro the village population. The Atlantians also develop the wheel around this time.


15,250 BC, the small village has expanded into several small towns with a total population of 10,000 people, smaller villages have been set up by the Atlantians along the course of the Atlantis River. total population of the Atlantians is 25,000 people. In a small village 20 miles south of Atlantis a young man discovers how to smelt copper starting the copper age.


15,200 BC, some copper smelters discover by putting a small proportion tin in with the molten copper they form a harder metal, the call it bronze, this starts the bronze age. Due to copper tools farmers start basic irrigation of the dry areas away from the main river channel.


14,550 BC Atlantians in the mountains of OTL Iran start trying new ores to see what can be smelted, during this time they discover iron, this starts the iron age. Due to the improvements in the plowing technology and oxen to pull the new iron plows, the amount of farmland that can be cultivated leads to a population explosion. Due to their improved weapon technology the Atlantian army is vastly superior to any other army on earth.


14,156 BC This is the year that is expected the first text to be written with cuneiform technique.


14,000 BC the Atlantians invade south Mesopotamia and colonise it. They found the towns of Ur and Uruk. The Atlantian population is now 800,000. Whilst invading Mesopotamia the Atlantians discover how to domesticate cattle and pigs.


13,750 BC, whilst exploring lands to the north of Atlantis, the Atlantians discover that the Przewalski's Horse (Equus ferus przewalskii) can be domesticated. Special breds are created to be used as heavy war horses and chariot horses.


13,500 BC the Atlantians colonise the Indian sub continent, as far as the Ganges delta, and the east coast of the Mediterranean. They start building vessels capable of oceanic voyages. Asian elephants are trained as heavy war elephants, replacing war horses. (Altantians reach level of third century BC level Romans)


13,000 - 12,500 BC, Atlantians settle the Nile delta and valley, northern Africa including the savanna of the Sahara, southern Italy and the Anatolian mainland and Greek mainland and islands. (Atlantians reach technological levels of first century BC Romans)

12,000 - 11,750 BC, Atlantians conquer various tribes that inhabit southern mainland Europe (OTL southern Spain, Portugal, France, and Italy) these tribes adopt Atlantian ways.


11,750 BC, Atlantians colonise Sundaland (between the modern islands of Borneo and Sumatra)


10,500 BC, Atlantians discover north-western Australia. They encounter local aborigines and form colonies along the east coast of the continent.


8000 BC as the ice age ends sea levels start to rise, major river floods inundate the city of Atlantis, destroying and burying the majority of city. five of these floods devastate the city in less than eight years, after the last of these floods the council of Atlantis decide to abandoned the city and build a new capital at the junction of the Tigris and Euphrates. They name the new capial Querna Atlantis (meaning new Atlantis).


Due to the ending of the ice age inland Europe starts to become habitable the Atlantian peoples start following rivers inland.

7000 BC The lower Atlantis river basin floods, submerging the former capital eventually under 35 metres of water.


6938 BC The first Belic conflict is registered by an historian, it was between two Atlantian-inheritance kingdoms in South Europe


6000 BC The Atlantis gulf is flooded totally.


5900 BC The First Democratic nation (leaded by an old men council) is founded in the Ganges valley.


4300 BC The first researches with gunpowder are made in OTL south China, by an Atlantian-inheritance alchemist


How Two Rival Mammoths Lost an Epic Duel 12,000 Years Ago

Twelve thousand years ago, there was an epic duel on the plains of western Nebraska. Both participants most likely suffered slow, painful deaths. Adding insult to injury, their bodies have been locked together face-to-face for 120 centuries and counting.

The players in this drama were two adult Columbian mammoths (Mammuthus columbi). A larger relative of the woolly mammoth, this species had long tusks and relatively little hair. By land mammal standards, the Columbian was a giant: Full-grown individuals could weigh 10 tons (9 metric tons) and stand more than 13 feet (3.9 meters) in height.

In 1962, land surveyors Ben Ferguson and George McMillan came across the bodies of those mammoth duelists. The two skeletons were complete and buried just north of Crawford, a city in the Nebraskan panhandle.

A team of fossil hunters from the University of Nebraska-Lincoln was quickly dispatched to recover the bones. Over a month-long period, they painstakingly removed all that was left of Benny and George — that's what they were dubbed — from the badland soil. While digging, the excavators made an astonishing discovery: The two mammoths had died with their tusks intertwined.

Daniel Fisher, a University of Michigan paleontologist who specializes in mammoths and mastodons, analyzed the tangled-up fighters in the early 2000s. Elephant tusks contain growth lines that develop at regular intervals (sort of like tree rings). By studying ivory samples from both of the dueling Nebraska mammoths, Fisher determined that they were each around 40 years old when they perished.

Male African elephants are subject to periods of intense, hormone-induced aggression at this age. Zoologists and animal caretakers call the phenomenon "musth." While experiencing musth, a male's testosterone levels may be 10 times higher than normal. Male elephants in this state are liable to fight viciously at the slightest provocation, especially if females are around.

So it seems probable that the two male Columbian mammoths were duking it out in a musth-induced rage. And they fought dirty: One of them died with a tusk tip lodged inside his rival's eye socket. Ai.

Both animals had one short tusk and one long tusk. By hitting each other head-on at just the right angle, the weapons became permanently entangled. If the mammoths proceeded to slip and fall over, it would have been impossible for them to stand up or pull the tusks apart. Unable to move, they apparently stayed intertwined until starvation set in.

It was a tragic tale, but at least there's a nice epilogue. After spending 43 years in storage at a facility in Lincoln, Nebraska, the tangled skulls were returned to Crawford in 2005. Today, the dueling mammoths are on display at the Trailside Museum of Natural History, where nearly 10,000 people from all over the world come to visit them every year. Crawfordites are rightly proud of their one-of-a-kind fossil.


Argaïes

Approximately 8,000 years ago, the climate turned drier and warmer and lifestyles had to change. Archaeologists call the culture of this time the Archaic.

Archaic people were hunters and gathers, usually moving around as they followed food sources. Their shelters were usually caves or wickiups made from brush.

People at this time made baskets, which they used for collecting seeds, pinyon nuts and other plants. They also used baskets for cooking.

Archaic people made several kinds of spear points. An atlatl, or spear-thrower, helped them hurl small spears faster and farther. They also would have eaten insects.

The Archaic people left behind petroglyphs, and you can see echoes of their lives in the Barrier Canyon style marks left behind in sites around the San Rafael Swell and Canyonlands National Park.

Friends of Gold Butte board members Byron George, right, and Tom Cluff, examine petroglyphs covering a boulder at the Falling Man Petroglyph site in the Gold Butte Area of Critical Environmental Concern Friday, Jan. 15, 2016. (Photo: Jud Burkett / The Spectrum & Daily News)


Inhoud

The last glacial period is often colloquially referred to as the "last ice age", though the term ice age is not strictly defined, and on a longer geological perspective the last few million years could be termed a single ice age given the continual presence of ice sheets near both poles. Glacials are somewhat better defined, as colder phases during which glaciers advance, separated by relatively warm interglacials. The end of the last glacial period, which was about 10,000 years ago, is often called the end of the ice age, although extensive year-round ice persists in Antarctica and Greenland. Over the past few million years the glacial-interglacial cycles have been "paced" by periodic variations in the Earth's orbit via Milankovitch cycles.

The last glacial period has been intensively studied in North America, northern Eurasia, the Himalaya and other formerly glaciated regions around the world. The glaciations that occurred during this glacial period covered many areas, mainly in the Northern Hemisphere and to a lesser extent in the Southern Hemisphere. They have different names, historically developed and depending on their geographic distributions: Fraser (in the Pacific Cordillera of North America), Pinedale (in the Central Rocky Mountains), Wisconsinan of Wisconsin (in central North America), Devensian (in the British Isles), [5] Midlandian (in Ireland), Würm (in the Alps), Mérida (in Venezuela), Weichselian of Vistulian (in Northern Europe and northern Central Europe), Valdai in Russia and Zyryanka in Siberia, Llanquihue in Chile, and Otira in New Zealand. The geochronological Late Pleistocene includes the late glacial (Weichselian) and the immediately preceding penultimate interglacial (Eemian) period.

Northern Hemisphere Edit

Canada was nearly completely covered by ice, as well as the northern part of the United States, both blanketed by the huge Laurentide Ice Sheet. Alaska remained mostly ice free due to arid climate conditions. Local glaciations existed in the Rocky Mountains and the Cordilleran Ice Sheet and as ice fields and ice caps in the Sierra Nevada in northern California. [6] In Britain, mainland Europe, and northwestern Asia, the Scandinavian ice sheet once again reached the northern parts of the British Isles, Germany, Poland, and Russia, extending as far east as the Taymyr Peninsula in western Siberia. [7] The maximum extent of western Siberian glaciation was reached by approximately 18,000 to 17,000 BP and thus later than in Europe (22,000–18,000 BP) [8] Northeastern Siberia was not covered by a continental-scale ice sheet. [9] Instead, large, but restricted, icefield complexes covered mountain ranges within northeast Siberia, including the Kamchatka-Koryak Mountains. [10] [11]

The Arctic Ocean between the huge ice sheets of America and Eurasia was not frozen throughout, but like today probably was only covered by relatively shallow ice, subject to seasonal changes and riddled with icebergs calving from the surrounding ice sheets. According to the sediment composition retrieved from deep-sea cores there must even have been times of seasonally open waters. [12]

Outside the main ice sheets, widespread glaciation occurred on the highest mountains of the Alps−Himalaya mountain chain. In contrast to the earlier glacial stages, the Würm glaciation was composed of smaller ice caps and mostly confined to valley glaciers, sending glacial lobes into the Alpine foreland. The Pyrenees, the highest massifs of the Carpathian Mountains and the Balkanic peninsula mountains and to the east the Caucasus and the mountains of Turkey and Iran were capped by local ice fields or small ice sheets. [13]

In the Himalaya and the Tibetan Plateau, glaciers advanced considerably, particularly between 47,000 and 27,000 BP, [14] but these datings are controversial. [15] [16] The formation of a contiguous ice sheet on the Tibetan Plateau [17] [18] is controversial. [19]

Other areas of the Northern Hemisphere did not bear extensive ice sheets, but local glaciers in high areas. Parts of Taiwan, for example, were repeatedly glaciated between 44,250 and 10,680 BP [20] as well as the Japanese Alps. In both areas maximum glacier advance occurred between 60,000 and 30,000 BP. [21] To a still lesser extent glaciers existed in Africa, for example in the High Atlas, the mountains of Morocco, the Mount Atakor massif in southern Algeria, and several mountains in Ethiopia. In the Southern Hemisphere, an ice cap of several hundred square kilometers was present on the east African mountains in the Kilimanjaro massif, Mount Kenya and the Rwenzori Mountains, still bearing remnants of glaciers today. [22]

Southern Hemisphere Edit

Glaciation of the Southern Hemisphere was less extensive. Ice sheets existed in the Andes (Patagonian Ice Sheet), where six glacier advances between 33,500 and 13,900 BP in the Chilean Andes have been reported. [23] Antarctica was entirely glaciated, much like today, but unlike today the ice sheet left no uncovered area. In mainland Australia only a very small area in the vicinity of Mount Kosciuszko was glaciated, whereas in Tasmania glaciation was more widespread. [24] An ice sheet formed in New Zealand, covering all of the Southern Alps, where at least three glacial advances can be distinguished. [25] Local ice caps existed in Western New Guinea, Indonesia, where in three ice areas remnants of the Pleistocene glaciers are still preserved today. [26]

Small glaciers developed in a few favorable places in Southern Africa during the last glacial period. [27] [A] [B] These small glaciers would have developed in the Lesotho Highlands and parts of the Drakensberg. [29] [30] The development of glaciers was likely aided by localized cooling indebted to shading by adjacent cliffs. [30] Various moraines and former glacial niches have been identified in the eastern Lesotho Highlands, above 3,000 m.a.s.l. and on south-facing slopes, a few kilometres west of the Great Escarpment. [29] Studies suggest the mountains of Southern Africa were mostly subject to mild periglaciation during the last glacial cycle and the annual average temperatures were about 6 °C colder than at present. The estimated 6 °C temperature drop for Southern Africa is in line with temperature drops estimated for Tasmania and southern Patagonia during the same time. [27] [28] The environment of the Lesotho Highlands during the Last Glacial Maximum was one of a relatively arid periglaciation without permafrost but with deep seasonal freezing on south-facing slopes. Periglaciation in the Eastern Drakensberg and Lesotho Highlands produced solifluction deposits, blockfields and blockstreams, and stone garlands. [27] [28]

Scientists from the Center for Arctic Gas Hydrate, Environment (CAGE) and Climate at the University of Tromsø, published a study in June 2017 [31] describing over a hundred ocean sediment craters, some 3,000 meters wide and up to 300 meters deep, formed by explosive eruptions of methane from destabilized methane hydrates, following ice-sheet retreat during the last glacial period, around 12,000 years ago. These areas around the Barents Sea still seep methane today. The study hypothesized that existing bulges containing methane reservoirs could eventually have the same fate.

Antarctica glaciation Edit

During the last glacial period Antarctica was blanketed by a massive ice sheet, much as it is today. The ice covered all land areas and extended into the ocean onto the middle and outer continental shelf. [32] [33] According to ice modelling, ice over central East Antarctica was generally thinner than today. [34]

Europa Wysig

Devensian and Midlandian glaciation (Britain and Ireland) Edit

British geologists refer to the last glacial period as the Devensian. Irish geologists, geographers, and archaeologists refer to the Midlandian glaciation as its effects in Ireland are largely visible in the Irish Midlands. The name Devensian is derived from the Latin Dēvenses, people living by the Dee (Dēva in Latin), a river on the Welsh border near which deposits from the period are particularly well represented. [35]

The effects of this glaciation can be seen in many geological features of England, Wales, Scotland, and Northern Ireland. Its deposits have been found overlying material from the preceding Ipswichian stage and lying beneath those from the following Holocene, which is the stage we are living in today. This is sometimes called the Flandrian interglacial in Britain.

The latter part of the Devensian includes Pollen zones I–IV, the Allerød oscillation and Bølling oscillation, and Oldest Dryas, the Older Dryas and Younger Dryas cold periods.

Weichselian glaciation (Scandinavia and northern Europe) Edit

Alternative names include: Weichsel glaciation of Vistulian glaciation (referring to the Polish river Vistula or its German name Weichsel). Evidence suggests that the ice sheets were at their maximum size for only a short period, between 25,000 and 13,000 BP. Eight interstadials have been recognized in the Weichselian, including: the Oerel, Glinde, Moershoofd, Hengelo and Denekamp however correlation with isotope stages is still in process. [36] [37] During the glacial maximum in Scandinavia, only the western parts of Jutland were ice-free, and a large part of what is today the North Sea was dry land connecting Jutland with Britain (see Doggerland).

The Baltic Sea, with its unique brackish water, is a result of meltwater from the Weichsel glaciation combining with saltwater from the North Sea when the straits between Sweden and Denmark opened. Initially, when the ice began melting about 10,300 BP, seawater filled the isostatically depressed area, a temporary marine incursion that geologists dub the Yoldia Sea. Then, as post-glacial isostatic rebound lifted the region about 9500 BP, the deepest basin of the Baltic became a freshwater lake, in palaeological contexts referred to as Ancylus Lake, which is identifiable in the freshwater fauna found in sediment cores. The lake was filled by glacial runoff, but as worldwide sea level continued rising, saltwater again breached the sill about 8000 BP, forming a marine Littorina Sea which was followed by another freshwater phase before the present brackish marine system was established. "At its present state of development, the marine life of the Baltic Sea is less than about 4000 years old", Drs. Thulin and Andrushaitis remarked when reviewing these sequences in 2003.

Overlying ice had exerted pressure on the Earth's surface. As a result of melting ice, the land has continued to rise yearly in Scandinavia, mostly in northern Sweden and Finland where the land is rising at a rate of as much as 8–9 mm per year, or 1 meter in 100 years. This is important for archaeologists since a site that was coastal in the Nordic Stone Age now is inland and can be dated by its relative distance from the present shore.

Würm glaciation (Alps) Edit

Die term Würm is derived from a river in the Alpine foreland, approximately marking the maximum glacier advance of this particular glacial period. The Alps were where the first systematic scientific research on ice ages was conducted by Louis Agassiz at the beginning of the 19th century. Here the Würm glaciation of the last glacial period was intensively studied. Pollen analysis, the statistical analyses of microfossilized plant pollens found in geological deposits, chronicled the dramatic changes in the European environment during the Würm glaciation. During the height of Würm glaciation, c. 24,000 – c. 10,000 BP, most of western and central Europe and Eurasia was open steppe-tundra, while the Alps presented solid ice fields and montane glaciers. Scandinavia and much of Britain were under ice.

During the Würm, the Rhône Glacier covered the whole western Swiss plateau, reaching today's regions of Solothurn and Aarau. In the region of Bern it merged with the Aar glacier. The Rhine Glacier is currently the subject of the most detailed studies. Glaciers of the Reuss and the Limmat advanced sometimes as far as the Jura. Montane and piedmont glaciers formed the land by grinding away virtually all traces of the older Günz and Mindel glaciation, by depositing base moraines and terminal moraines of different retraction phases and loess deposits, and by the pro-glacial rivers' shifting and redepositing gravels. Beneath the surface, they had profound and lasting influence on geothermal heat and the patterns of deep groundwater flow.

Noord -Amerika Redigeer

Pinedale or Fraser glaciation (Rocky Mountains) Edit

Die Pinedale (central Rocky Mountains) or Fraser (Cordilleran Ice Sheet) glaciation was the last of the major glaciations to appear in the Rocky Mountains in the United States. The Pinedale lasted from approximately 30,000 to 10,000 years ago and was at its greatest extent between 23,500 and 21,000 years ago. [38] This glaciation was somewhat distinct from the main Wisconsin glaciation as it was only loosely related to the giant ice sheets and was instead composed of mountain glaciers, merging into the Cordilleran Ice Sheet. [39] The Cordilleran Ice Sheet produced features such as glacial Lake Missoula, which would break free from its ice dam causing the massive Missoula Floods. USGS geologists estimate that the cycle of flooding and reformation of the lake lasted an average of 55 years and that the floods occurred approximately 40 times over the 2,000 year period between 15,000 and 13,000 years ago. [40] Glacial lake outburst floods such as these are not uncommon today in Iceland and other places.

Wisconsin glaciation Edit

The Wisconsin Glacial Episode was the last major advance of continental glaciers in the North American Laurentide Ice Sheet. At the height of glaciation the Bering land bridge potentially permitted migration of mammals, including people, to North America from Siberia.

It radically altered the geography of North America north of the Ohio River. At the height of the Wisconsin Episode glaciation, ice covered most of Canada, the Upper Midwest, and New England, as well as parts of Montana and Washington. On Kelleys Island in Lake Erie or in New York's Central Park, the grooves left by these glaciers can be easily observed. In southwestern Saskatchewan and southeastern Alberta a suture zone between the Laurentide and Cordilleran ice sheets formed the Cypress Hills, which is the northernmost point in North America that remained south of the continental ice sheets.

The Great Lakes are the result of glacial scour and pooling of meltwater at the rim of the receding ice. When the enormous mass of the continental ice sheet retreated, the Great Lakes began gradually moving south due to isostatic rebound of the north shore. Niagara Falls is also a product of the glaciation, as is the course of the Ohio River, which largely supplanted the prior Teays River.

With the assistance of several very broad glacial lakes, it released floods through the gorge of the Upper Mississippi River, which in turn was formed during an earlier glacial period.

In its retreat, the Wisconsin Episode glaciation left terminal moraines that form Long Island, Block Island, Cape Cod, Nomans Land, Martha's Vineyard, Nantucket, Sable Island, and the Oak Ridges Moraine in south central Ontario, Canada. In Wisconsin itself, it left the Kettle Moraine. The drumlins and eskers formed at its melting edge are landmarks of the Lower Connecticut River Valley.

Tahoe, Tenaya, and Tioga, Sierra Nevada Edit

In the Sierra Nevada, there are three named stages of glacial maxima (sometimes incorrectly called ice ages) separated by warmer periods. These glacial maxima are called, from oldest to youngest, Tahoe, Tenaya, en Tioga. [41] The Tahoe reached its maximum extent perhaps about 70,000 years ago. Little is known about the Tenaya. The Tioga was the least severe and last of the Wisconsin Episode. It began about 30,000 years ago, reached its greatest advance 21,000 years ago, and ended about 10,000 years ago.

Greenland glaciation Edit

In Northwest Greenland, ice coverage attained a very early maximum in the last glacial period around 114,000. After this early maximum, the ice coverage was similar to today until the end of the last glacial period. Towards the end, glaciers readvanced once more before retreating to their present extent. [42] According to ice core data, the Greenland climate was dry during the last glacial period, precipitation reaching perhaps only 20% of today's value. [43]

Suid -Amerika Redigeer

Mérida glaciation (Venezuelan Andes) Edit

Die naam Mérida Glaciation is proposed to designate the alpine glaciation which affected the central Venezuelan Andes during the Late Pleistocene. Two main moraine levels have been recognized: one with an elevation of 2,600–2,700 m (8,500–8,900 ft), and another with an elevation of 3,000–3,500 m (9,800–11,500 ft). The snow line during the last glacial advance was lowered approximately 1,200 m (3,900 ft) below the present snow line, which is 3,700 m (12,100 ft). The glaciated area in the Cordillera de Mérida was approximately 600 km 2 (230 sq mi) this included the following high areas from southwest to northeast: Páramo de Tamá, Páramo Batallón, Páramo Los Conejos, Páramo Piedras Blancas, and Teta de Niquitao. Approximately 200 km 2 (77 sq mi) of the total glaciated area was in the Sierra Nevada de Mérida, and of that amount, the largest concentration, 50 km 2 (19 sq mi), was in the areas of Pico Bolívar, Pico Humboldt [4,942 m (16,214 ft)], and Pico Bonpland [4,983 m (16,348 ft)]. Radiocarbon dating indicates that the moraines are older than 10,000 BP, and probably older than 13,000 BP. The lower moraine level probably corresponds to the main Wisconsin glacial advance. The upper level probably represents the last glacial advance (Late Wisconsin). [44] [45] [46] [47] [48]

Llanquihue glaciation (Southern Andes) Edit

The Llanquihue glaciation takes its name from Llanquihue Lake in southern Chile which is a fan-shaped piedmont glacial lake. On the lake's western shores there are large moraine systems of which the innermost belong to the last glacial period. Llanquihue Lake's varves are a node point in southern Chile's varve geochronology. During the last glacial maximum the Patagonian Ice Sheet extended over the Andes from about 35°S to Tierra del Fuego at 55°S. The western part appears to have been very active, with wet basal conditions, while the eastern part was cold based. Cryogenic features like ice wedges, patterned ground, pingos, rock glaciers, palsas, soil cryoturbation, solifluction deposits developed in unglaciated extra-Andean Patagonia during the Last Glaciation. However, not all these reported features have been verified. [49] The area west of Llanquihue Lake was ice-free during the LGM, and had sparsely distributed vegetation dominated by Nothofagus. Valdivian temperate rain forest was reduced to scattered remnants in the western side of the Andes. [50]


Kyk die video: Ek is Jagter 2019 #tawnilodge (Januarie 2022).