Ukulamana Kwejiyoloji
Eminyakeni engaphezulu kwesigidi eyadlulako, iphasi lathoma ukuphola ngendledlana ethileko begodu nama-celestial bombardment ehla, ngonobangela wokobana ama-bolides amanengi aku-solar sysytem besele awele phezu kwentwethileko nofana besele aphelile. I-water vapour, carbon dioxide kunye namanye amarhasi (gasses) avela emabharasini angaphasi kwephasi bekathoma ukubumba umoya endaweni (atmosphere). Izulu lathoma ukuna begodu amalwandle athoma ukuzala eenzibeni ezinamatje ngaphasi. Amanzi wangaphasi bevele akhona eminyaka engaba yi 3.9 yamabhiliyoni eyadlulako.
Isikhathi Somlando we-Archaean
Lesi sithomo sesikhathi somlando we-Archaean (okutjho bona emandulo) begodu sadosa kufikela eminyakeni angaba yi 2.5 yamabhiliyoni eyadlulako. Ngesikhathi lesi, amabhande wamalarha wamatje abizwa nge- Granite-Greenstone abumbeka, enza ingaphasi lawo woke amajiyoloji alandelako. Isibonelo esihle esibulungiweko somlando we-Archaean esisabonakalako ephasini sitholakala eMpumalanga, edorobheni le-Barberton, lapho ama- Granite-Greenstone strata wemandulo, aqaliswe phasi-phezulu avela phasi. Amatje wentaba evutha umlilo (volcano), abizwa nge-komatiities, abumbeka ku-seabed yemandulo hlangana kweminyaka eyi 3.6 ne 3.2 yamabiliyoni ubudala. Ukwakheka kwawo kutjengisa bona abunjwa ngesikhathi lapho amazinga womtjhisa ku-mantle bekaphezulu khulu kunangendla angakhona namhlanjesi, okutjengisa bona amazinga womtjhiso wephasi aragela phambili ngokuphola eminyekeni eyikulungwana ngokulandelana.
Njengombana i-crust iragela phambili ngokuqina, amametheriyali aregileko we-silica (egade angakaminyani khulu ukudlula i-molten matter engaphasi) avamise ukuya phezulu begodu ahlangane phezulu kwe-mantle. Njengombana beyilula kune-mantle kunye nephasi lelwandle elikhulu, amatje aregileko we-silica akhenge anamathele phasi begodu asala athaya phasi, bekwafika lapho abadege ngokulingene bona angaya ngaphezulu kwamazinga wamanzi njengeSihlengele.
Ama-Cratons
Ngokukhamba kwesikhathi, iinhlengele egade zibumbekile zaragela phambili ngokuhlukana kuma-tectonic plates, zatjhayisana bezahlangana, kufikela lapho kubumbeka inarha ekulu eendaweni ezihlukahlukeneko ephasini. Iinhlanganisela lezi zibizwa nge- ‘micro-continents’. Kanye kanye, amatje avela ngaphezulu kwamanzi aragela phambili ngokukhukhulwa mumoya namanzi akhambako, begodu amacezu womatje aphukileko akhukhuleka akhamba nelwandle elikhulu njenge- gravel conglomerates, sandstones kunye ne-mudstones. Ngalokhu ikhontinendi yokuthoma yabumbeka.
Ukuqunta indaba ede, amakhontinendi wokuthoma abumbekako aragela phambili akhula, ngombana bekangakaminyani khulu kunengaphasi lelwandle elikhulu. Ezinye iingcenye zama-continental crusts zasala zahlala iminyaka elandelako eyi 3 bhiliyoni. Kungenzeka bona zahlukana zabuye zahlangana amahlandla ambalwa, kodwana akhenge zimotjheke nofana zisetjenziswe godu. Namhlanjesi sibiza iincetjhana lezi ze-crust yemandulo ngama-‘cratons’.
I-Kaapvaal Craton
Enye yama-craton wokuthoma kuplanethi yi-Kaapvaal Craton, esahleli phakathi eSewula Afrika. Ubukhulu be-craton lee abaziwa, kodwana ukuhlolisisa kuveze bona incenye yepumalanga yeSewula Afrika, incenye yepumalamga ye-Austrilia, India kunye neye-Madagascar zazihlangene kuyikhontinendi yinye emandulo. Ngokukhamba kweeminyaka, amatje wamalarha amatja bekahleli phasi kwengaphazulu le-craton’s Granite-Greenstone, kunye namaminerali amanengi anentengo ephezulu. I-Kaapvaal Craton yabakhona ngokubethana kwamandla we-Vreedefort.
Ilarha lokuthoma lamatje amatja abumbeka ku-Kaapvaal craton libizwa nge- Dominion group. Linamalarha ondileko aneenrhirirhiri zamatje ezinamathele amatje adege. Iinrhirirhiri zamatje zenzeka lokha iincephu zamatje akhukhulekileko ziphelela endaweni etja bezigcine ziphenduka amatje, ngekambiso ebizwa nge-lithification. Ngakwelinye ihlangothi, amatje kuthiwa ma-igneous rocks enzeka lokha intaba evutha umlilo (volcano) phezulu ku-mantle ne-crust, lapho i-magma ingenelela emabharasini we-crust kufikela lapho iphola beyiqina khona. I-lava egelezako evela iphuma ngaphasi kwephasi nayo ingabumba amatje okuthiwa ma-igneous rocks.
Translated by Busisiwe Skhosana