Ukuphonsa Kwenzungezilanga
Uma ubheka emkhathini ngobusuku obumnyama, konke kubonakala ngokuthula. Izinkanyezi zikhazimula esibhakabhakeni esimnyama esicacile futhi ububanzi bobukhulu baso bungaphezu kwekhanda lakho. Kodwa iqiniso lihlukile kakhulu. Umhlaba empeleni uqhunyiswa ngomsakazo wezinto zomkhathi, okukhishwa kakhulu ibhande lamatshe ashisayo phakathi kwe-Mars ne-Jupiter.Lokhu kuhlaselwa akupheli futhi, kuyilapho kucatshangwa ukuthi inani lokuphonsa kwenzungezilanga liphansi namhlanje kunalokhu lapho uMhlaba usungulwa, kulinganiselwa ukuthi amathani angu-30 000 wezimfucufucu zamaplanethi ayengena emkhathini wethu njalo ngonyaka.
Eziningi zalezi zingcezu nezicucu ziyashisa njengoba ziqhuma emkhathini, zishise ngaphezu kwamaphuzu azo okuncibilika ngokumelana nomoya. Ukukhanya okukhanyayo okukhishwa yilezi zinto kuzenza zibonakale njengezinkanyezi ezinomsila, noma izinkanyezi eziqhumayo. Uma inkanyezi enomsila inkulu ngokwanele, noma kunjalo, ingxenye yayo ingasinda ekusheni ingehlika emhlabeni njengenkanyezi ecibayo.
Ukuze Wazi, Inkanyezi ecibayo enkulu kunazo zonke ezitholakale kuze kube manje yi-Hoba Meteorite, etholiwengo-1920. Ishaye phansi ngaseGrootfontein, enyakatho yeNamibia, eminyakeni engaphezu kuka-80 000 edlule futhi ayizange ithi nyaka kusukela. I-Hoba iyinxenye eqinile yensimbi ne-nikheli, elinganisa ubude obungamamitha amathathu nobude bemitha enye.
Imithelela Emikhulu
Kodwa kuthiwani uma kukhona into enkulu kakhulu edumayo iza eMhlabeni? Yini eyokwenzeka uma inkanyezi eqhumayo elilinganiselwa amakhilomitha ayishumi noma ikhulu ngaphesheya ihlaselwa emhlabathini? Ukuhlolwa komthelela woksushayisana kwamandla yangaphambilini akudwebe isithombe esihle kakhulu.Imicimbi emikhulu yokushayana kwamandla ibonakala inamandla okubhubhisa hhayi nje indawo yomthelela, kodwa umhlaba wonke. Ukuzamazama komhlaba okukhulu izikhukhula, zezinto ezinjengomlilo ovela emthonjeni wawuzohlasela umhlaba nokuphila kuwo.Ngaphezu kwalokho, inqwaba enkulu yothuli namanxantathu aqhutshwa emkhathini kungavimbela ilanga, lenze umhlaba ube neskhathi sobusika esihlala izinyanga noma iminyaka. Ngamagama ambalwa, kuboniswe ukuthi umthelela wezenzakalo ungabangela ukuqedwa kwezimpilo emhlabeni wonke.
Ukuphela nya
Ukuqothulwa yingxenye yemvelo yenqubo yokuziphendukela kwemvelo. Eminyakeni eyizinkulungwane zezigidi, izinhlobo ezingenakubalwa ziye zafa ngenxa yezinguquko zezulu, izinhlekelele zemvelo nokuncintisana nezinye izinhlobo. Lokhu kuthathwa njengokuphela okujwayelekile (noma ngemuva) futhi kuseqhubeka nanamuhla - kusizwa abantu besimanje njengoba bephanga umhlaba. Kulinganiselwa ukuthi, ngaphansi kwemibandela evamile, phakathi kwemindeni emibili nenhlanu yezinhlobo ezehlukene izophela ezigidini zonke zeminyaka elandelayo, ngokungcola okuncane, singakwazi ukuthola lokho ngokwehlile. Kodwa-ke, irekhodi lezinto eziphilayo libonisa ukuthi, ngamaphuzu athile esikhathini esidlule, kwaba khona ukuphela okukhulu lapho amaphesenti amakhulu kakhulu kuwo wonke umhlaba eMhlabeni aphela khona ngokuzumayo.Lezi zikhathi ezithile zibizwa ngokuthi imingcele futhi ziboniswa ngokuphela kokubili emadwaleni, lapho uhlobo olulodwa lwefomu lokuphila lushintshwa ngokungazelelwe luthathe indawo yokunye. Lezi zenzakalo zomngcele zivame ukubonakala ezindaweni zamatshe ezihlukahlukene emhlabeni jikelele.
Ukuphela nya Okuyingqumbi
Njengoba sithembele kumlando wezinsalela ukuze sibone lezi zimingcele, ukuqhubekela phambili kwemicimbi yokuqothulwa kwemvelo kuvele kubonakale ngemva kokusakazeka kokuphila esikhathini seCambrian, cishe eminyakeni eyizigidi ezingu-550 edlule (Ma). Kusukela ngaleso sikhathi kuye kwaba khona ukuqothulwa okukhulu kwezinnhlanu: ukuguqulwa kwe-End-Ordovician (444 Ma: 84% ukulahlekelwa kwezinhlobo), i-Late Devonian (i-360 Ma: i-79% yokulahlekelwa kwezinhlobo), i-End-Permian (ama-250 Ma, ama-95% ukulahlekelwa - ukuphela kwesisindo esikhulu kunazo zonke emhlabeni), i-End-Triassic (i-200 Ma, i-79% yokulahlekelwa kwezinhlobo) kanye ne-End-Cretaceous (65 Ma, ukulahlekelwa kwezinhlobo ezingu-70%).Abanye abacwaningi banamuhla bathi ukuphela nya okwamanje, kushesha kunalokhu okubhaliwe.Kusizwa ngokuphathwa kabi kwemvelo, lokhu ukuphela kungasho ukuthi kuzophela uhafu yezinhlobo zokuphila eMhlabeni eminyakeni eyikhulu ezayo (ngokusho kwasosayensi omkhulu).
Ukucisha!
Izizathu zalezi zinkimbinkimbi eziningi zinzima ukuzinquma.Eyodwa Kuphela (i-End-Cretaceous, noma i-K-T Boundary) ixhunyaniswe ngokuqondile nesehlakalo somthelela. Ezinye zinemvelaphi encane, ngoba akukho zakhiwo ezithintekayo ezitholakele kuze kube manje. Ngaphandle kwemithelela, izimbangela ezihlongozwayo zihlanganisa: izinguquko zezulu (njengezinkathi zeqhwa), izenzakalo ezinkulu zezintabamlilo (okuyinto enobungozi emkhathini), nokuqhuma komthala osekudeni (okugazinga izinto eziphilayo eziphezulu) kanye nokunyakaza komhlaba(okuletha amazwekazi ndawonye futhi ngaleyo ndlela kuhlanganise izinhlobo zokuphila ezihlukile, okudala ukuvela kwezinhlobo ezintsha). Nokho, kubhekwa sengathi akunakwenzeka ukuthi noma yikuphi kwalokhu okucatshangelwayo kungaba imbangela nakho konke okwenzekayo ekuqothulweni okukhulu, futhi uinhlanganissela yezici kungathi isiphetho mhlawumbe esenzeka.Kunoma yikuphi, ucwaningo luye lwabonisa ukuthi ukuqothulwa kwezinto eziningi kwenzeka ngomjikelezo, mhlawumbe kaningi njengakuyonke iminyaka eminyakeni eyizigidi ezingamashumi amathathu kuya kwamashumi ayisithupha. Kumele futhi kuqashelwe ukuthi ngenxa yokuthi asinabo ubufakazi obuphawulekayo wesenzakalo sokuqothula obuningi ngaphambi kuka-500 Ma, akusho ukuthi akwenzanga.
Ngaphambi kwesikhathi sokuphila sasendulo, impilo yayinezimiso ezilula, ahlanganisa amafomu alula njengama-bhaktheriya, ama-brachiopods nama-trilobites. Lezi zinhlobo ezincane azishiyi ngemuva kwezinsalela ezinkulu, ngakho-ke izinombolo zazo kunzima ukulandelela. Ngaphezu kwalokho, ukuthola amadwala aneminyaka engaphezu kwezigidi ezingu-600 kuyinto engavamile, ngoba avame ukuvuselelwa ohlelweni lokunyakaza komhlaba. Lokhu kususa ubufakazi bomngcele ongasemuva ongase ukhombise izinkathi zenkinga yomhlaba jikelele. Kungakhathaliseki, uma kwakukhona izinhlobo eziyinkimbinkimbi zomhlaba ngesikhathi somthelela weVredefort, bekungasuswa!
Translated by Nsika Khoza