Izilwandle ziyakugcina ukushisa
NGOKWEDLULE sigcine sikhuluma ngesakhiwo sangaphakathi soMhlaba. Namuhla siyiqala ekushiseni kwawo.
UKUSHISA okungama-20% kwasemathunjini oMhlaba kuvela enhlanganiseleni yezinsalela zokushisa okwakheka ngesikhathi kwenzeka umabuthelanazakhiwomkhathi ( accretion), okungama-80% kudalwa “wukuxebuka” kwesithelongcwele ( nucleous) bese kukhiqizeka amandla ( energy) nogqulunzulu ( matter) - okuyisimo esibizwa nge- radioactive decay ngesiNgisi.
Izingqulugqulwanamaphahla ( isotopes) - okuyizingqulu ( atoms) ezinogqulwanyana ( proton) olunesibalo esifanayo nogqulwana ( neutrons) olunesingafani [isibonelo - Protium 1 proton - 1 neutron/ Deuterium 1 proton - 2 neutrons/ tritium 1 proton - 3 neutrons] - ezingosondonzima ekukhiqizeni ukusha emathunjini oMhlaba, yipotassium-40, i- uranium 238 nethorium 232.
Enkabeni yethambo ( core) loMhlaba, ukushisa kuyizi-6 000°C. Ngenxa yokuthi ukushisa okuningi kukhiqizeka ngokuxebuka kwesithelongcwele - bese kukhiqizeka amandla nongqulunzulu - ososayensi bacabanga ukuthi ngesikhathi uMhlaba useyiklume, ngaphambi kokuba izingqulugqulwanamaphahla ezinempilo emfushane zishabalale, ukukhiqizeka kokushisa (koMhlaba) kwakwenzeka ngamandla.
Cishe eminyakeni eyizi-3 billion eyedlule, sekushisa okungaphindwa kabili kokuphuma manje emathunjini oMhlaba. Uqweqwe loMhlaba oluthanda okuba ngaphandle, lubizwa ngenzikandilinga ( lithosphere), njengoba sike sasho phambilini, luhlukene izicucu eziningi ezibizwa ngezingqokolozi, ezinyakaza “ngokuhloniphana” emingceleni emithathu eyahlukene okuyinzikamngceleni ( convergent boundaries).
(Lapho izingqokolozi ezimbili zingqubuzana enye izike enyameni enye ishone phezulu oqweqweni ( cast) - umajokolemngceleni ( divergent boundaries) lapho izingqokolozi ezimbili zihlukana, enye ishone kolunye uhlangothi nenye ngokunjalo - nomagudlanemngceleni ( transform boundaries), lapho izingqokolozi ezimbili zigudlana, enye ishone kwelinye icala nenye ngokunjalo.
Ukuzamazama komhlaba, izintabamlilo, ukwakheka kwezintaba nemisele yasolwandle ( ocean trenches) kungakheka ngenxa yale mingcele yezingqokolozi.
Njengoba besishilo ngokudlule, izingqokolozi lezi “ziqhwakele” kwintekentekendilinga ( asthenosphere) okuyingxenye esasixavathi yenyama - ekwazi “ukugobhoza” ihambisane nezingqokolozi.
Ubusomhlaba boMhlaba bulinganiselwa ezi-510 million km2. Ama70.8% noma izi-361.13 million km2 obusomhlaba angaphansi kwesilinganiso solwandle ( sea level), ambozwe ngamanzi alo. Ingxenye elimekayo yoMhlaba ili-10.9% kanti u-1.3% kuvele kutshaliwe kuwona.
Ilinganiselwa ema-40% ingxenye yobusomhlaba esetshenziselwa ukulima, kuklabe kuyona nezilwane ezidla utshani nezimila - okulinganiselwa ezi-1.3×107 km2 okulinywe kuwona ne3.4×107 km2 wamadlelo. Amanzindilinga ( hydrosphere)
ebuswenimhlaba boMhlaba, yinto ewenza wehluke kozakwabo abasesimeninkanyezi ( star system) seLanga. Ingxenye enkulu yamanzindilinga yakhiwe wulwandle - yize ihlanganisa nemifula, amachibi namanzi angaphansi ekujuleni okungaba yizi-2000m. Indawo enamanzi asekujuleni ngendlela eba- bazekayo, yiChallenger Deep eseMaiana Trench, olwandle iPacific - ijule ngezi-10 911.4m. Isisindo sezilwandle zihlangene silinganiselwa e-1.35×1018 tons.
Amanzi angama-97.5% anosawoti kanti lawa “adliwayo” ayisi-2.5%. Amanzi amaningi adlekayo, angama-68.7%, ayiqhwa. Ulinganiselwa ema-35 grams usawoti otholakala kwikhilo ngekhilo lamanzi olwandle. Omningi walo sawoti wakhiqizwa yizintabamlilo nedwala lohlobo lwe-Igneous elipholile.
Izilwandle zibuye zibe yithala lamagesi asuke encibilike kwingubomkhathi ( atmosphehere), abamba elikhulu iqhaza empilweni yasolwandle. Amanzi olwandle anomthelela omkhulu esimeni sezulu eMhlabeni - izilwandle ziyithala elikhulu eligcina ukushisa.
Ukuguquka kwendlela okukhiqizeka ngayo amazinga okushisa olwandle, kungaholela ekushintsheni kwesimo sezulu kudaleke iziphepho ezinamandla.
Sizoyiqhuba ngokuzayo Umthombo ngabe: en.wikipedia.org