Kutheni Ulwandle Lumtyuba?

UKUBA ityuwa eselwandle ibinokwandlalwa emhlabeni wonke, ibiya kulingana neemitha ezili-150 ukuphakama—malunga nesakhiwo esinemigangatho engama-45 ubude! Njengokuba yonke imilambo nemisinga enamanzi angenatyuwa ingena elwandle, ivela phi ke ityuwa engaka? Kuhlolisiso eziye zalwenza izazinzulu ziye zafumana iindawo ezininzi evela kuyo le tyuwa.

Enye indawo ngumhlaba lo siwunyathelayo. Njengokuba amanzi emvula equkuqela phezu komhlaba namatye, akhukulisa amasuntswana ezondlo, ityuwa namanye amachiza ukuze aphelele elwandle ngokuthwalwa yimilambo nemisinga (1). Kaloku, ityuwa incinane kakhulu emanzini asiwaselayo, yile nto ke ingavakali xa siwasela.

Enye indawo esuka kuyo ityuwa ngamachiza omhlaba oqinileyo ongaphantsi kolwandle. Amanzi angena ngaphantsi elwandle ngeentanda ezilapho, aze la manzi abe shushu, abuyele ngaphezu kolwandle namachiza anyibilikileyo. La manzi ashushu anyibilikisa amachiza omhlaba ongaphantsi kwamanzi aze awabuyisele emanzini olwandle (2).

Kwenye inkqubo enemiphumo efanayo, amanzi angaphantsi kolwandle abangela ugqabhuko-dubulo, lona olukhupha amatye ashushu anemichiza ephumela elwandle (3). Ezinye izondlo zivela emoyeni, wona utyhalela amasuntswana asuka emhlabeni ukuze aye elwandle (4). Zonke ezi nkqubo zenza amanzi olwandle abe nazo zonke izimbiwa ezisemhlabeni. Elona chiza liphambili letyuwa yisodium chloride, okanye ityuwa esetyenziswa ekhaya. Yona iyilwe ngama-85 ekhulwini ezinye iityuwa ezinyibilikileyo yaye esi sisizathu sokuba amanzi olwandle avakale emtyuba.

Yintoni Egcina Ityuwa Ikumlinganiselo Ofanayo?

Ityuwa iqokelelana elwandle ekubeni ubukhulu becala amanzi omphunga ecocekile. Amanye amachiza asala elwandle. Kwangaxeshanye, amanye amachiza angena elwandle, ngaloo ndlela umlinganiselo wetyuwa awutshintshi, uhlala umalunga nesi-3,5 ekhulwini samanzi olwandle. Ngoko ke, ityuwa iphuma yaye ingena elwandle ngomlinganiselo ofanayo namanye amachiza. Le nto isishiya sinombuzo, Iyaphi yonke le tyuwa?

Ityuwa eninzi ifunxwa zizinto eziphilayo. Ngokomzekelo, iicoral polyp, iimollusk, kunye neecrustacean, zifunxa ikhalsiyam ukomeleza amaqokobhe namathambo azo. Ubulembu obuncinane obubizwa ngokuba yidiatom bufunxa isondlo kwilitye elibizwa ngokuba yisilica. Ezinye iintsholongwane eziphila elwandle zitya ezinye izinto eziphilayo. Xa ezi zinto ziphilayo zisifa okanye zityiwa zezinye izilwanyana, ityuwa kunye nezondlo zizikela ezantsi elwandle kodwa ezifileyo zinyukela ngaphezu kwamanzi (5).

Ezinye iityuwa ezingakhange zinyibilikiswe zishenxiswa ngezinye iindlela. Ngokomzekelo, udongwe nezinye zinto ezivela emhlabeni ezingena elwandle ngemilambo, umoya kunye nogqabhuko-dubulo zinokuba zinetyuwa yaye zingena nayo elwandle. Enye ityuwa ifumaneka ematyeni. Ngenxa yale nkqubo, ityuwa eninzi iphelela ngaphantsi kwamanzi (6).

Abaphengululi abaninzi bakholelwa kwelokuba inguqu ezenziwa yindalo zithabatha ixesha elide. Uqweqwe lomhlaba luyilwe ngamacandelo amakhulu. Amanye amacandelo ayadibana yaye elinye icandelo lingena ngaphantsi kwelinye lize lizikele kummandla oshushu. Ngokuqhelekileyo elona candelo lisixwexwe lingena ngaphantsi kwelilula yaye ngelo xesha lithwele iityuwa ngokungathi libhanti elikhulu. Ngale ndlela uqweqwe lomhlaba lwenziwa lutsha (7). Iinyikima zomhlaba, nogqabhuko-dubulo nemimandla eneentlambo konke oku kuyimiphumo yoku.a

Ukuzinza Okumangalisayo

Umlinganiselo wetyuwa yolwandle uyahluka kuxhomekeka kuloo ndawo, ngamanye amaxesha kuxhomekeka kumaxesha onyaka. Awona manzi anetyuwa ngawoLwandle Olubomvu naweNyoba yasePersia, apho amanzi aguquka abe ngumphunga ngomlinganiselo ophezulu. Imimandla yolwandle efumana amanzi angenatyuwa okanye iimvula ezinkulu, inomlinganiselo omncinane wetyuwa. Oku kunjalo ke nakulwandle nakwincam ekuMntla nekuMzantsi apho kukho amanzi angenatyuwa angumkhenkce. Phofu ke, xa ulwandle lusiba nomkhenkce amanzi aba netyuwa eninzi. Sekunjalo, ulwandle lona luhlala lunomlinganiselo ongaguquguqukiyo wetyuwa.

Amanzi olwandle anomlinganiselo ongaguquguqukiyo wehydrojini (pH), nto leyo esixelela ubungakanani beasidi netyuwa esemanzini, yaye xa isisi-7, ikumlinganiselo ophakathi. Umlinganiselo wehydrojini emanzini aselwandle uphakathi kwesi-7,4 nesi-8,3, nto leyo ethetha ukuba amtyuwa kancinane. (Igazi lomntu linomlinganiselo wehydrojini omalunga nesi-7,4) Ukuba umlinganiselo wehydrojini ekumanzi olwandle ibinokuba ngaphezu koku, ulwandle lunokuba yingozi. Eneneni yiloo nto kanye ezinye izazinzulu zinexhala layo. Ikharbon diokside eninzi ebangelwa ngabantu iphelela elwandle, apho idibana namanzi ize yenze iasidi yekharboni. Ngoko ke, izinto ezenziwa ngabantu zisenokulwenza ulwandle lube neasidi eninzi ngokuthe ngcembe.

Izinto ezenza iasidi yamanzi olwandle ihlale ingaguquguquki ayaziwa ngokupheleleyo. Nakuba kunjalo, oko siye sakufunda kukha phantsi isitya sizele xa kuthelekiswa nobulumko boMdali, oyikhathaleleyo imisebenzi yezandla zakhe.—ISityhilelo 11:18.

[Umbhalo osemazantsi]

[Umzobo/Imifanekiso ekwiphepha 16, 17]

(Ukuba ufuna inkcazelo ehlahlelwe kakuhle, yiya kwimpapasho)

Imvula

↓↓

↓↓

4 Umoya

↑ ↓ ↓

․․․․․․․․․․․․↑․․․․․․․․․․․․․↑․․․UMGANGATHO․․․․․↓․․ ․․․․․↓․․․․

↑ ↑ WOLWANDLE 7 ←← UMMANDLA EKUDIBANA

↑ UQWEQWE LOMHLABA ←← KUWO AMACANDELO

↑ ←←

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[Inkcazelo]

Uthanda: © Science VU/Visuals Unlimited; ugqabhuko-dubulo: REUTERS/Japan Coast Guard/Handout

Diatoms: Dr. Neil Sullivan, USC/NOAA Corps; ifoto yentaba-mlilo: Dept. of Interior, National Park Service

[Ibhokisi/Umzobo okwiphepha 18]

Iityuwa Ezifumaneka Elwandle

Nakuba izazinzulu ziye zafunda ngamanzi olwandle ngaphezulu kwenkulungwane, iseyinkohla nangoku kubo indlela amachiza olwandle asebenza ngayo. Noko ke, ziye zakwazi ukucalula iityuwa ezahlukahlukeneyo nomlinganiselo wobungakanani bazo. Ezi ziquka:

[Umzobo]

Ikloride engama-55 ekhulwini

Isodiyam engama-30,6 ekhulwini

Isulfate esisi-7,7 ekhulwini

Imagnesiyam esisi-3,7 ekhulwini

Ikhalsiyam esisi-1,2 ekhulwini

Ipotasiyam esisi-1,1 ekhulwini

Ibikharbonate eli-0,4 ekhulwini

Ibromide eli-0,2 ekhulwini

kunye nezinye ezimbalwa ezifana neborate, istrontium nefluoride.

[Ibhokisi/Umfanekiso okwiphepha 18]

Zinetyuwa Eninzi Kunolwandlekazi

Ezinye iindawo zinetyuwa eninzi kunolwandlekazi. Ngokomzekelo, uLwandle Olufileyo lunawona manzi anetyuwa emhlabeni. Amanzi aqukuqelela kuLwandle Olufileyo, olwalubizwa ngokuba luLwandle lweTyuwa ngamaxesha okubhalwa kweBhayibhile, athwele iityuwa kunye namanye amachiza. (Numeri 34:3, 12) Ngenxa yokuba unxweme loLwandle Olufileyo luyeyona ndawo isezantsi yomileyo emhlabeni, amanzi anokuphuma kuphela ngendlela enye—ngokuba ngumphunga, nto leyo enokuphungula amanzi ngeemilimitha ezinokuba ngama-25 ehlotyeni ngosuku nje olunye.

Ngoko ke, ubungakanani betyuwa emanzini angaphezulu bunokuba ngama-30 ekhulwini—nto leyo ewuphindaphinda kalishumi umlinganiselo wetyuwa kuLwandle lweMeditera. Njengokuba amanzi esiba ngqindilili ngenxa yetyuwa, abantu abaqubhayo badada ngaphezulu emanzini. Eneneni, basenokujongisa iqebe phezulu baze bafunde iphephandaba kodwa bangaziki emanzini.

[Ibhokisi ekwiphepha 18]

Ityuwa Inceda Ekucoceni Umoya

Uphando luye lwabonisa ukuba ukungcola okusemoyeni kuthintela umjikelo wemvula kwiindawo ezikude nolwandle. Noko ke, amafu anokungcola ngaphezu kolwandle aguquka msinyane abe yimvula. Umahluko wenziwa ngumphunga onetyuwa osuka elwandle.

Amathontsi amanzi ayileka kukungcola okusemoyeni mancinane kakhulu ukuba anganetha okwemvula, kungenxa yoko lento ephelel’ emoyeni. Lo mphunga unetyuwa wamanzi olwandle udibana nala mathontsi uze ube ngamaqabaza amakhulu. Ngaloo ndlela kuna imvula, ecoca izinto ezingcolileyo ezikwimeko-bume.