Ixesha loqeqesho

Kwizithuba zangaphambili sihlalutye ukuba isebenza njani Ixesha lejoloji kwaye yajonga ezona ziganeko zibalulekileyo ezenzeka kwi Ixesha leMesozoic kunye I-Precambrian Aeon. Namhlanje sibuyela Ixesha leCenozoic apho siza kuhlalutya okwenzekayo kuyo ixesha koqeqesho. Imalunga nexesha lokugqibela leCenozoic Era kwaye iquka ezona zimbini “zala maxesha”, iPleistocene neHolocene.

Ngaba uyafuna ukwazi ezona ziganeko zibalulekileyo ezenzekileyo ngeli xesha? Qhubeka ufunda kuba sikuxelela yonke into.

Ukufika komkhenkce nomntu

Emva kokudlula kwezigidi zeminyaka, sisondela koko bekuye "namhlanje". KwiQuaternary, ethi yaqala kwiminyaka ezi-2,59 yezigidi eyadlulayo, lixesha esiphila kulo namhlanje. IQuaternary ayibandakanyi iPleistocene kunye neHolocene kuphela, kodwa ukungqinelana xa kusenziwa ukufumanisa malunga notshintsho olwenzeka emhlabeni, ubudala beGelasian bungabandakanywa. Ngeli xesha bekukho utshintsho olubalulekileyo kubomi kwiplanethi, imozulu kunye neelwandle ngenxa yeziqendu zobudala bomkhenkce.

Amaxesha amabini eQuaternary yiPleistocene kunye neHolocene. IPleistocene yeyona inde kwaye ibandakanya iinkulungwane kunye neenkulungwane zomkhenkce. Yaziwa njenge Ixesha lomkhenkce. Ukuya kwixesha lakutshanje sine-Holocene, ethathelwa ingqalelo njengenxalenye yasemva komkhenkce kwaye yile nto sinayo namhlanje.

Xa bethetha ngePleistocene, abantu abaninzi bathetha ngayo "Ubudala bomntu" okoko uhlobo lweHomo lwaqala ukuvela ngeli xesha. Sele ilapho kwi-Holocene, umntu ophuhla ubomi ahlelwe ngokwamaqela ezentlalo abizwa ngokuba yimpucuko.

Iimpawu zePleistocene

Siqala ngokuchaza iQuaternary kunye nexesha layo lokuqala. Iminyaka engama-2,59 yezigidi eyadlulayo inika indlela ekuqaleni kwePleistocene ephela kwiminyaka eyi-12.000 eyadlulayo. Ngeli xesha umkhenkce usasazeka ngohlobo lomkhenkce de hlala ngaphezulu kwekota yomhlaba. Umkhenkce wafikelela kwiindawo ezingazange zifikelelwe ngaphambili. Kwaye kukuthi xa sithetha ngomkhenkce okanye ubudala bomkhenkce ekucingelwa ukuba ilizwe liphela ligutyungelwe ngumkhenkce, kubandakanya neelwandle. Oku akunje. Phantse iipesenti ezingama-25 zomhlaba wonke ogqunywe ngumkhenkce ngokungaqhelekanga.

Ngenxa yesixa esikhulu somkhenkce emhlabeni, inqanaba lolwandle lehla laya kwiimitha ezili-100 kwaye ubomi kwiplanethi kwafuneka buguquke kwimeko entsha yokusingqongileyo okanye banyamalale. Kwimimandla apho kwakungekho mkhenkce, phantse zonke izilwanyana kunye nezilwanyana zazifana kwixesha elidlulileyo (Pliocene).

Kwakukho ezinkulu iinkqubo zomkhenkce saa kwiindawo ezibandayo nezinomkhenkce. Eyokuqala yayiliqhekeza lomkhenkce eScandinavia elalithe tyaba emazantsi nasempuma kuwo wonke umantla weJamani nasentshona Russia. Ifikelele kwiiBritish Isles, ke unokuthelekelela ubungakanani baloo glacier.

Kwelinye icala, sikwafumana enye inkqubo enkulu yomkhenkce ebekwe ikakhulu eSiberia. Enye inkqubo ye-glacial isasazeka ukusuka eCanada ukuya eUnited States. Zonke ezi zakhiwo zomkhenkce, emva kokudaleka kwazo kunye nokwakheka kwazo, ziye zakhokelela kwizakhiwo zomkhenkce esinokuthi sizigcine namhlanje kuzo zonke ezi ndawo.

Ukuqaqamba, iintyatyambo kunye nezilwanyana

Njengoko unokuthelekelela, imimandla yeArctic kunye neAntarctic nayo yayigutyungelwe ngumkhenkce, njengoko uninzi lweentaba zijikeleze iplanethi. Inqanaba lekhephu lehle laya kumazinga angazange abonwe namhlanje. Njengoko besenditshilo ngaphambili, zonke izinto ezenziwa ngumkhenkce kunye nokunyibilika kwazo kungabonakala nanamhlanje kwiindawo ezininzi zehlabathi.

Kwakungekho kuphela i-glaciation ngexesha le-Pleistocene, kodwa kwakukho ezintandathu. Phakathi kwazo nganye yazo kwakukho amaxesha apho imozulu yayifudumele ngxi kwaye umkhenkce wabuya kwakhona. Okwangoku, sithathwa njengelinye lala maxesha "okuphumla" omkhenkce.

Ngokubhekisele kwizityalo nezilwanyana ekuye kwafuneka ziqhelane neendawo ezinomkhenkce ngokupheleleyo, safumana iimammoth, iinyamakazi, amaxhama amakhulu kunye neebhere ezimhlophe. Uhlaza kule ndawo lwalunee-lichen kunye ne-mosses. Yayifana ngokupheleleyo netundra yangoku. Kumanqanaba ahlukeneyo, anamaqondo aphezulu obushushu kunye nomgangatho ongaphantsi womkhenkce, banokuphila amahashe, amatakane namabamba amakhulu kunye nemikhombe.

Ezinye iintlobo ezimbalwa zezilwanyana zilungelelaniswe kakuhle notshintsho lwemozulu ukuze ziphile ixesha elide. Sithetha nge-bison, i-elk, i-fox kunye ne-wildcat. Kwiindawo ezibandayo zaseNyakatho Melika, iintlobo ezinje nge inkamela, yak, ilama, itapir kunye nehashe. Ngexesha lokuphela kwePleistocene, iintlobo zezilwanyana ezanyisayo ezinje ngemastodon, ingwe edumileyo enamazinyo, kunye nexhama elikhulu sele liphelile emhlabeni.

Indaleko yabantu kunye neHolocene

Ngoku sithetha ngendaleko yabantu apho sinePaleolithic kwiPleistocene, apho homo habilis waqala ukuqokelela nokuzingela. Kamva, Homo erectus benze ezinye izixhobo eziphucukileyo kwaye bazingelwa bengamaqela. i-homo neanderthalensis yayiluhlobo olwaqhelaniswa nokubanda okwavela kwiminyaka engama-230.000 eyadlulayo.

Siyaqhubeka nokuchaza elona xesha litsha leQuaternary: iHolocene. Kulapho sikhoyo namhlanje. Iqale iminyaka eyi-12.000 eyadlulayo kunye nokuhamba kwayo kotshintsho lwamaqondo obushushu kwaqala ixesha lokunyibilika kwiplanethi yonke. Lo mnyibiliko ubangele ukunyuka kwenqanaba lolwandle ngeemitha ezimashumi mathathu.  Kuthiwa eli xesha lokuhlangana linokuphela kwinqanaba elitsha lomkhenkce.

Kule minyaka ingama-12.000, ukucinywa kwezinto kuqhubekile kwaye kukhawuleziswe ngakumbi kule minyaka ili-100 idlulileyo bubukho babantu kunye nophuhliso lwetekhnoloji. Emhlabeni kubekho ukuphela kwezinto ezi-5. Ngesi sizathu, ukubulawa kwabantu ngoku okubizwa ngokuba namhlanje ukuphela kwesithandathu.

Ubomi bokuhambahamba bomntu buphelile ngophuhliso lwezolimo kunye nemfuyo. Ukuloba kukwaluthanda kakhulu ukukhula kwabantu. Okokugqibela, iHolocene ihlala ifundiswa kude kuyilwe ukubhala, apho oko sikubiza ngokuba yiMbali kuqala ukufunda.

Ndiyathemba ukuba esi sithuba sikwazise ngakumbi malunga nexesha lokugqibela loMhlaba.