Indlela Isakhiwo Somhlaba Esithinta Ngayo Imicimbi Yemvelo
Umhlaba awuyona nje ibhola elikhulu ledwala "elithule" esikhaleni. Ngaphansi kobuso bawo obubonakala buzinzile kunesistimu enamandla, enezingqimba eziningi: ezinye ziqinile, ezinye ziyipulasitiki, njengenhlama ejiyile, kanye nomongo oshisayo kakhulu. Lesi sakhiwo sangaphakathi silawula indlela amandla okushisa ahamba ngayo, indlela amapuleti e-tectonic ashintsha ngayo, kanye nendlela izenzakalo zemvelo ezahlukahlukene—njengokuzamazama komhlaba, ukuqhuma kwezintaba-mlilo, ama-tsunami, ngisho nokwakheka kwezintaba—ezenzeka ngayo. Ukuqonda isakhiwo soMhlaba kusisiza sichaze ukuthi kungani izinhlekelele zemvelo zenzeka kaningi ezindaweni ezithile nokuthi imiphumela yazo ingabikezelwa futhi incishiswe kanjani.
1. Izendlalelo eziyinhloko zoMhlaba
Kalula nje, isakhiwo soMhlaba singahlukaniswa sibe yizingqimba eziningana ezinkulu: uqweqwe, i-mantle, kanye nomongo. Ingqimba ngayinye inezakhiwo ezihlukile zomzimba nezamakhemikhali, futhi lokhu kwehluka kunquma ukuthi uMhlaba "usebenza kanjani."
Ungqimba loMhlaba luyingqimba engaphandle nencane kakhulu. Ubukhulu balo buyahlukahluka: ungqimba lolwandle lungaba ngu-5–10 km, kanti ungqimba lwezwekazi lungafinyelela ku-30–70 km. Ungqimba lolwandlekazi luvame ukuba luncane futhi luncane, kanti ungqimba lwezwekazi lulula futhi ludala. Lolu ngqimba "luyisigaba" sokuphila komuntu, kodwa empeleni luyisikhumba esincane emshinini omkhulu.
Ngaphansi koqweqwe kukhona i-mantle, ungqimba olukhulu kakhulu (cishe amakhilomitha angu-2.900). I-mantle yakhiwe ngamatshe ashisayo aminyene, kodwa ngokwezinga le-geological, ingageleza kancane kakhulu. I-mantle ayiyona "uketshezi" njengamanzi, kodwa iyipulasitiki eyanele kwezinye izindawo ukuvumela ukunyakaza kwezinto nokushisa.
Ingxenye engaphakathi yoMhlaba ingumgogodla woMhlaba, oqukethe umgogodla wangaphandle (owuketshezi) kanye nomgogodla wangaphakathi (oqinile). Umgogodla wakhiwe ngokuyinhloko ngensimbi ne-nickel. Amazinga okushisa aphezulu kanye nokucindezela okungaphakathi kuhlinzeka ngomthombo wamandla okushisa oqhubeka nokuqhuba amandla oMhlaba, okuhlanganisa nokwakheka kwamandla awo kazibuthe.
2. I-Lithosphere kanye ne-asthenosphere: isihluthulelo sokunyakaza kwamapuleti
Uma ukuhlukaniswa kwe-crust-mantle-core "kuyikhemikhali" kakhulu, kukhona okunye ukuhlukaniswa okuwusizo kakhulu ekuqondeni izenzakalo zemvelo, okusekelwe ezimpawini zemishini: i-lithosphere kanye ne-asthenosphere.
I-lithosphere ihlanganisa uqweqwe kanye nengxenye engenhla eqinile ye-mantle. Yilokhu okuhlukaniswe ngamapuleti amaningana amakhulu namancane e-tectonic. I-lithosphere iyaphuka; uma icindezelwa ngaphezu kwamandla ayo, iyaphuka—futhi kungokuqhekeka lokhu okuvame ukuvela kukho ukuzamazama komhlaba.
Ngaphansi kwe-lithosphere kukhona i-asthenosphere, ingxenye yepulasitiki futhi "egeleza kalula" (nakuba isaqinile) ye-mantle engenhla. I-asthenosphere ivumela amapuleti e-lithospheric angaphezulu kwayo ukuba anyakaze, ashintshe, futhi ashayisane. Ngaphandle kwalolu ngqimba lwepulasitiki, amapuleti abeyoba nesikhathi esinzima kakhulu sokuhamba, futhi umsebenzi we-tectonic ubungancishiswa.
3. Imisinga ye-convection ye-Mantle: amandla ashukumisayo e-tectonics
Enye yethonya elibaluleke kakhulu esakhiweni soMhlaba kanye nezehlakalo zemvelo ukuba khona kwemisinga ye-convection ku-mantle. Ukushisa okuvela enkabeni kanye nokubola kwezinto ezinemisebe eMhlabeni kubangela ukuthi i-mantle ihlale ithola amandla. Izinto ezishisayo zivame ukukhuphuka, kuyilapho izinto ezipholile zicwila. Lokhu kujikeleza okuhamba kancane kudala imisinga ye-convection esunduza futhi idonse amapuleti e-tectonic kusuka ngaphansi.
Imiqondo emibili ebalulekile ekuhambeni kwepuleti yile:
– Ukusunduza kwe-Ridge: ukusunduza kusuka ogwini oluphakathi nolwandle, lapho kwakheka khona amapuleti amasha futhi ahlukane.
– Ukudonsa kwe-slab: ukudonsa kwepuleti lolwandle ngaphansi kwelinye ipuleti endaweni engaphansi; lokhu kuvame ukubhekwa njengamandla amakhulu kakhulu kumapuleti ahambayo.
Ngenxa yokuthi isakhiwo soMhlaba sivumela ukuhlangana kwe-mantle kanye nokuba khona kwe-lithosphere ephukile, uMhlaba uyiplanethi ene-active plate tectonics—into enquma kakhulu iphethini yezinhlekelele ze-geological.
4. Ukuzamazama komhlaba: ngenxa yokucindezeleka koqweqwe olubuthakathaka
Ukuzamazama komhlaba kwenzeka lapho ukucindezeleka okwakhiwe emadwaleni kukhishwa ngokuzumayo. Ukuqina koqweqwe kanye ne-lithosphere kuvumela amandla okunwebeka ukuthi agcinwe aze afinyelele umkhawulo; lapho iphutha lishintsha, la mandla aguqulwa abe amagagasi okuzamazama komhlaba.
Isakhiwo soMhlaba sithinta ukuzamazama komhlaba ngezindlela eziningana:
1. Izindawo zokuzamazama komhlaba zilandela imingcele yamapuleti, njengoba kulapho ukucindezeleka okukhulu kwenzeka khona. Isibonelo, i-Indonesia itholakala lapho kuhlangana khona amapuleti amakhulu amaningana (i-Eurasian, i-Indo-Australian, iPacific, kanye nePhilippine), okuholela ekusebenzeni okukhulu kokuzamazama komhlaba.
2. Ukujula kokuzamazama komhlaba kuthonywa yizindawo ezingaphansi komhlaba. Ukuzamazama komhlaba okungajulile kuvamile ezindaweni eziphansi, kuyilapho ukuzamazama komhlaba okuphakathi nendawo kuya kokujulile (kufika emakhilomitha angamakhulu) kuhlotshaniswa namapuleti angaphansi komhlaba.
3. Uhlobo lwedwala kanye nokushisa kuthonya ukuthi amatshe ayaphuka noma aqinile yini. Ekujuleni okuthile, amatshe aba yipulasitiki eyengeziwe, okuwavumela ukuthi ageleze kunokuba aqhekeke, okunciphisa amathuba okuzamazama komhlaba.
5. I-Tsunami: umphumela owengeziwe we-crustal kanye ne-sea dynamics
Ama-tsunami avame ukuba umphumela wokuzamazama komhlaba okukhulu ngaphansi kwamanzi, ikakhulukazi lawo asezindaweni ezingaphansi komhlaba. Isakhiwo soMhlaba sidlala indima ngoba:
– Izindawo ezingaphansi komhlaba zivumela ukushintsha okuqondile phansi kolwandle njengoba amapuleti ecindezelana.
– Lapho ulwandle luphakama noma luwa ngokuzumayo, ikholomu yamanzi ngaphezu kwalo iyacindezelwa, okubangela amagagasi amade angahamba ngokushesha olwandle.
Ama-tsunami amakhulu awaveli kuzo zonke izinyikima zomhlaba ngaphansi kwamanzi; ngokuvamile adinga inhlanganisela ethile: ubukhulu obukhulu, indlela yokwenza iphutha ephakamisa/ehlisa phansi kolwandle, kanye nokujula okungajulile. Konke lokhu kuhlobene ngqo ne-plate geometry kanye nezakhiwo ze-mechanical ze-lithosphere.
6. Izintaba-mlilo: indlela ye-magma ephuma esicongweni
Intaba-mlilo incike kakhulu esakhiweni soMhlaba, ikakhulukazi izinqubo ezakha ngazo i-magma kanye nokuhamba kwayo. I-Magma ngokuvamile yakha ezindaweni ezintathu eziyinhloko ze-tectonic:
1. Indawo yokunciphisa: ipuleti lolwandle elinciphisa uketshezi lithwala amanzi namaminerali. Amanzi ehlisa iphuzu lokuncibilika kwedwala elingaphezulu, akhiqize i-magma. Lokhu kuchaza uchungechunge lwezintaba-mlilo ezigudle "iPacific Ring of Fire," okuhlanganisa ne-Indonesia.
2. Unqenqema oluphakathi nolwandle: amapuleti ayasuka komunye nomunye (ahlukane), ingcindezi iyancipha, i-mantle iyancibilika kancane (ukuncibilika kwe-decompression), kwakha uqweqwe olusha lolwandle.
3. Indawo Eshisayo: ikholomu yokushisa evela ku-deep mantle (i-mantle plume) ingakha izintaba-mlilo phakathi kwepuleti, njengeHawaii.
Ngaphezu kwendawo, isakhiwo soMhlaba sithonya uhlobo lokuqhuma. I-magma eqinile, egcwele i-silica ivame ukukhiqiza ukuqhuma okuqhumayo ngenxa yamagesi avalelekile; kuyilapho i-magma encane ivame ukukhiqiza ukugeleza kwe-lava. Ukusebenzisana phakathi kwe-magma, amanzi, namatshe oqweqweni nakho kunquma izinga lengozi.
7. Ukwakheka kwezintaba namaphutha: izinguquko ebusweni yi-tectonics
Izintaba ezinkulu zivame ukwakheka ngenxa yokushayisana kwe-continental plate (ukushayisana kwe-convergent plate). Ngenxa yokuthi uqweqwe lwe-continental lulula kakhulu, kunzima ukuthi lubekwe phansi kakhulu; ngenxa yalokho, amatshe ayagoqwa futhi aphakanyisiwe, akha izintaba. Isibonelo esidumile kakhulu yi-Himalayas, eyakheka ngenxa yokushayisana kwe-India ne-Eurasia.
Ngaphezu kwalokho, isakhiwo esibuthakathaka soMhlaba ku-lithosphere sakha inethiwekhi yamaphutha. La maphutha awagcini nje ngokubangela ukuzamazama komhlaba kodwa futhi akha indawo: izigodi zamaphutha, izibazi zamaphutha, kanye nezinguquko ekugelezeni kwemifula. Ngokuhamba kwesikhathi, i-tectonics isebenza ngokubambisana nokuguguleka komhlaba ukuze "iqophe" ubuso boMhlaba.
8. Ukudilika komhlaba kanye nokucwiliswa kwamanzi: imiphumela engaqondile yezinqubo zangaphakathi
Ezinye izenzakalo zemvelo zivela "phezu komhlaba," kodwa izimbangela zazo zivame ukuhlotshaniswa nezinqubo zangaphakathi. Ukudilika komhlaba kungabangelwa yimvula, kodwa ukuzamazama komhlaba okubangelwa ukunyakaza kwamapuleti kuvame ukubangela ukudilika komhlaba okukhulu ezindaweni zezintaba. Ukuchitheka kwamanzi—lapho inhlabathi enesihlabathi egcwele amanzi ilahlekelwa amandla ayo futhi isebenza njengoketshezi lapho inyakaziswa—kuvame ukwenzeka ngesikhathi sokuzamazama komhlaba okunamandla. Ngamanye amazwi, isakhiwo soMhlaba esenza ukuzamazama komhlaba kwenzeke siphinde sibangele ukuqubuka kwemiphumela emibi yesibili.
9. Kungani ukuqonda isakhiwo soMhlaba kubalulekile ekunciphiseni izingozi?
Ukufunda isakhiwo soMhlaba akuyona nje inkolelo-mbono. Ulwazi mayelana nemingcele yamapuleti, izinhlobo zamaphutha, umlando wokususwa kwezindawo, kanye nezakhiwo zamadwala kusiza ososayensi ukuthi babhale izindawo ezivame ukuzamazama komhlaba kanye nezindawo ezivame ukukhukhulwa yi-tsunami, baqaphe izintaba-mlilo, futhi bathuthukise amazinga okwakha amelana nokuzamazama komhlaba. Nakuba izinhlekelele zemvelo zingenakuvinjelwa, izingozi zazo zingancishiswa uma abantu beqonda amaphethini azo kanye nezimbangela zazo.
I-Penutup
Isakhiwo soMhlaba—kusukela ku-lithosphere yawo ephukile kuya ku-asthenosphere yawo yepulasitiki kanye nemisinga ye-convection ye-mantle kuya enkabeni yawo eshisayo—yisimiso esinquma cishe zonke izehlakalo zemvelo ze-geological. Ukuzamazama komhlaba, ukuqhuma kwezintaba-mlilo, ama-tsunami, ukwakheka kwezintaba, ngisho nezinhlekelele zemvelo njengokudilika komhlaba kanye noketshezi konke kusekelwe endleleni uMhlaba odlulisela ngayo ukushisa futhi ulawule ingcindezi yawo yangaphakathi. Ngokuqonda "umshini" ongaphansi kwezinyawo zethu, asigcini nje ngokuqonda ukuthi kungani uMhlaba ushintsha njalo, kodwa futhi singaphila sikulungele futhi siphephile kule planethi enamandla.
