Izici Zesimo Sezulu Sasendulo Ezisekelwe Kudatha Yezwe
Isimo sezulu somhlaba asikaze sibe "simile" ngempela. Kudala ngaphambi kokuba abantu bavele, iplanethi yabhekana nezinkathi zokushisa okukhulu, izinkathi zeqhwa ezinde, amaphethini emvula ashintshashintshayo, izinguquko ekwakhekeni komkhathi, ngisho nokushintshashintsha kwezinga lolwandle. Ngenxa yokuthi azikho amarekhodi e-thermometer asezikhathini zasendulo, ososayensi bathembele kudatha ye-geological ukuze bakhe kabusha ukuthi isimo sezulu sasinjani esikhathini esidlule. Le datha igcinwa njengemikhondo emadwaleni, emafosilini, amaminerali, kanye nokwakheka kwamakhemikhali okwakhiwa ngaphansi kwezimo ezithile zemvelo. Ukusuka lapho, singaqonda izici zesimo sezulu sasendulo—ukuthi uMhlaba wake waba "yindlu yokushisa," ukuthi iqhwa elingakanani elimboze amazwekazi, nokuthi imijikelezo yesimo sezulu yenzeka kanjani eminyakeni eyizigidi.
1. Idatha ye-geological njenge-"archive" yezimo zezulu zesikhathi esidlule
Amatshe agcwele inhlabathi, i-ice cores (yesikhathi esincane), kanye namarekhodi amakhemikhali kumaminerali asebenza njengezindawo zokugcina izinto. Isimiso esiyisisekelo silula: izimo zezulu zithonya izinqubo ze-geological, njengokuguguleka kwenhlabathi, ukuguguleka komhlabathi, uhlobo lwenhlabathi elahliwe, kanye nezinto eziphilayo ezazihlala lapho. Uma sithola izinhlobo ezithile zama-deposit noma amaphethini amakhemikhali, singachaza izimo ezifana nokushisa, imvula, usawoti wolwandle, ngisho namazinga e-carbon dioxide.
Ukwakhiwa kabusha kwesimo sezulu sasendulo kuvame ukuhlanganisa izinkomba eziningi (ama-proxies) ukuqinisekisa imiphumela eqinile. Lokhu kungenxa yokuthi inkomba eyodwa ingathonywa yizici ezingezona isimo sezulu. Isibonelo, amatshe esihlabathi sasehlane asikisela isimo sezulu esomile, kodwa kusadingeka aqhathaniswe nezinsalela, amaminerali, kanye nama-isotope ukuqinisekisa incazelo.
2. Izinkomba zokungcola: iminonjana yendawo ehlala kuyo
Omunye wemithombo ecacile yolwazi mayelana nezimo zezulu zasendulo uvela ezinhlotsheni nasezinhlelweni zamadwala angaphansi komhlaba.
– Ama-vaporite (i-gypsum, i-halite): Akhiwa lapho amanzi olwandle noma amachibi ethola ukuhwamuka okuphezulu, okubangela ukuthi usawoti uvuthe. Lokhu kubonisa isimo sezulu esishisayo, esomile kanye nebhalansi yamanzi engalungile (ukuhwamuka kudlula ukutholakala).
– Amalahle: Akhiwe ngokuqongelela kwezitshalo ezindaweni ezigcwele izinto eziphilayo, ngokuvamile ngaphansi kwezimo ezinomswakama ezinokukhiqizwa okuphezulu kwe-biomass kanye nokubola okulinganiselwe. Ubuningi bamalahle ngesikhathi esithile bubonisa isikhathi esinezindawo ezibanzi ezinamaxhaphozi kanye nesimo sezulu esinomswakama olinganiselayo.
– Amatshe e-Eolian (itshe lesihlabathi lendunduma): Izakhiwo ezijwayelekile zokubeka umbhede ohlangene kanye nezinhlayiya zesihlabathi ezihlelwe kahle zibonisa ukubekwa komoya, okuvame ukuhlotshaniswa nezimo zasehlane nezomile.
– I-Tillite kanye ne-dropstone: I-Tillite iyi-glacial sediment eqinile; i-dropstone yidwala elikhulu “elawa” lisuka eshalofini leqhwa laya phansi kolwandle. Zombili zibonisa ukuba khona kweqhwa noma iqhwa lolwandle, ngaleyo ndlela zikhombisa isimo sezulu esibandayo.
Kusukela ekusatshalalisweni kwalezi zinhlabathi esikhaleni nasesikhathini, ososayensi bangakwazi ukumaka imingcele yezindawo zezulu zasendulo, isibonelo izindawo zasehlane ezindaweni ezithile noma ukusatshalaliswa kwezinguzunga zeqhwa kuwo wonke amazwekazi.
3. Izinsalela: izinto eziphilayo ezinquma izinga lokushisa kanye nomswakama
Izinto eziphilayo zinemingcele ekubekezeleleni kwazo izinga lokushisa, usawoti, kanye nokutholakala kwamanzi. Ngakho-ke, izinsalela ziwusizo kakhulu njengezinkomba zesimo sezulu.
– Izinsalela zezitshalo (impova, izinhlayiya, amaqabunga): Ukuma kwamaqabunga kunganikeza izinkomba zesimo sezulu. Amaqabunga anemiphetho eyisicaba avame kakhulu ezindaweni ezibandayo, kuyilapho amaqabunga anezimbotshana avame kakhulu ezindaweni ezipholile kuya kwezifudumele. Ukuhlukahluka kwempova kungabonisa nohlobo lwezitshalo (amahlathi emvula, i-savanna, i-tundra).
– I-Foraminifera kanye ne-plankton yasolwandle: Ubuningi bezinhlobo ezithile bubonisa izinga lokushisa lolwandle. Le miphakathi yamagciwane iyashintsha ngokuya ngezimo zamanzi.
– Ama-coral reefs asendulo: Ama-coral ngokuvamile adinga amanzi afudumele, angajulile, nacwebile. Ama-coral reefs asendulo angasebenza njengezinkomba zolwandle olushisayo futhi azinzile.
Ngokuhlanganisa izinsalela zomhlaba nezasolwandle, singaphetha ngokuthi inkathi ethile yayibuswa isimo sezulu esifudumele somhlaba wonke, noma inkathi yokubanda eyayigcizelela imvelo yasezindaweni ezishisayo.
4. Ama-isotope azinzile: “ama-thermometer” amakhemikhali esikhathi esidlule
Elinye lamathuluzi anamandla kakhulu ku-paleoclimatology ukuhlaziywa kwe-isotope okuzinzile, ikakhulukazi ama-carbonates asolwandle (amagobolondo ezinto eziphilayo) kanye neqhwa.
– Ama-isotope e-oxygen (δ¹⁸O): Isilinganiso se-isotope ye-oxygen kuma-carbonate asolwandle singabonisa izinto ezimbili eziyinhloko: izinga lokushisa lamanzi lapho ama-carbonate akheka khona kanye nomthamo weqhwa lomhlaba wonke. Amanani aphezulu e-δ¹⁸O avame ukuhlotshaniswa nezimo ezibandayo kanye/noma iqhwa eliningi (ngoba ama-isotope alula abambeke kakhulu eqhweni).
– Ama-isotope e-carbon (δ¹³C): Chaza umjikelezo we-carbon, umkhiqizo wezinto eziphilayo, kanye nezinguquko ezinkulu njengokukhishwa kwe-carbon kusuka e-volcanism noma i-methane. Ukushintshashintsha okukhulu kwe-δ¹³C kungabonisa ukuphazamiseka okukhulu kwesimo sezulu, okuhlanganisa nezehlakalo zokufudumala okusheshayo.
Ama-Isotopes asezindaweni zasolwandle ezinezingqimba avumela ukwakhiwa kabusha kokushintsha kwesimo sezulu eminyakeni eyizinkulungwane kuya kwezigidi ngesisombululo esihle impela.
5. Amaminerali kanye nesimo sezulu: izinkomba zemvula kanye nokushisa emhlabeni
Uhlobo lwamaminerali aguqukile lungabonisa izimo zezulu.
– I-Laterite ne-bauxite: Ngokuvamile kwakheka ngenxa yokushisa okukhulu ezindaweni ezishisayo ezinomswakama ezinemvula ephezulu kanye namazinga okushisa afudumele. Lokhu kuyisibonakaliso sezinqubo zamakhemikhali ezilawulayo kanye nokuphuma kwezakhi ezinamandla.
– I-Calcrete (ama-soil carbonate deposits): Akhiwa enhlabathini ezindaweni ezomile kuya ezomile, lapho ukuhwamuka kukhuthaza ukugcwala kwama-carbonates enhlabathini.
– I-Paleosol (inhlabathi yasendulo): Ungqimba lomhlabathi oluyi-fossil lugcina ulwazi mayelana nezitshalo, amanzi agelezayo, kanye nesimo sezulu. Isakhiwo sempande, amaqhubu e-carbonate, ngisho nokwakheka kwamakhemikhali kusiza ekunqumeni imvula emaphakathi.
Le datha ibalulekile ngoba iqopha izimo zomhlaba ezingaboniswanga ngokuqondile njalo ekuthuthweni kwenhlabathi yasolwandle.
6. Ukusatshalaliswa kwezinga lolwandle kanye neqhwa: izimpawu zesimo sezulu somhlaba wonke
Ukushintsha kwesimo sezulu emhlabeni jikelele kuvame ukuhambisana nokushintsha kwezinga lolwandle. Njengoba isimo sezulu sibanda futhi iqhwa lezwekazi likhula, amanzi olwandle "avalelwa" njengeqhwa, okubangela ukuba amazinga olwandle ehle. Ngokuphambene nalokho, njengoba kwenzeka ukufudumala, iqhwa liyancibilika futhi amazinga olwandle akhuphuke. Embhalweni we-geology, lezi zinguquko zivela kanje:
– Ukweqa (ulwandle oluya ezweni) kanye nokubuyela emuva (ulwandle olubuyela emuva)
– Izinguquko ezinhlotsheni ze-sedimentary kusuka olwandle olujulile kuya olwandle olungajulile (noma okuphambene nalokho)
- Ukungahambisani okubonisa ukumiswa okwesikhashana ngenxa yokwehla kwamazinga olwandle
Ukusatshalaliswa kwezinsalela zeqhwa kuwo wonke amazwekazi kusiza futhi ekuboneni izikhathi “zezindlu zeqhwa” (imihlaba eneqhwa eliningi) uma kuqhathaniswa nezikhathi “zezindlu zeqhwa” (imihlaba ecishe ingabi naqhwa).
7. Izici zesimo sezulu sasendulo: amaphethini amakhulu atholakele
Ngokusekelwe kudatha ye-geological ehlanganisiwe, izici eziningana eziyinhloko zesimo sezulu sasendulo zingafingqwa kanje:
1. Isimo sezulu siyashintshashintsha phakathi kwezifundazwe “zezindlu ezigcina ukushisa” kanye “nezindlu zeqhwa”.
Kuwo wonke umlando woMhlaba, kube nezikhathi ezifudumele kakhulu ezineqhwa elincane kakhulu, futhi kube nezikhathi ezibandayo kakhulu ezineqhwa elikhulu. Lokhu kushintsha kwenzeka ngenxa yokuhlanganiswa kwe-plate tectonics, ukwakheka komkhathi, ukujikeleza kolwandle, kanye ne-albedo feedback (ukukhanya okukhanyayo yiqhwa).
2. Ukushintsha kwesimo sezulu kungenzeka ngokushesha ngokwezinga le-geological.
Irekhodi le-isotope libonisa izehlakalo eziningana zokufudumala noma ukupholisa ezibukhali ezenzeke eminyakeni eyizinkulungwane kuya kwamakhulu ezinkulungwane—ezishesha kakhulu ngokwezindinganiso ze-geological. Izehlakalo ezinjalo zivame ukuhlotshaniswa nokuphazamiseka komjikelezo wekhabhoni noma izinguquko emifudlaneni yolwandle.
3. Izindawo zesimo sezulu ziyashintsha ngokuya ngesimo samazwekazi
Njengoba amazwekazi ehamba, izindawo ezaziseduze ne-equator zingashintshela ezindaweni eziphakeme. Ubufakazi obufana namalahle, ama-evaporites, noma ama-tillites ezindaweni manje "ezingafaneleki" ngesimo sezulu sazo bunikeza izinkomba ze-paleogeography kanye ne-paleoclimate.
4. Imvula kanye nezinkathi zonyaka kuncike endaweni kanye nokwakheka kwezwekazi nolwandle.
Ukuphakama kwezintaba kwathonya amaphethini ezimvula kanye nezithunzi zemvula. Amarekhodi e-Paleosol kanye ne-sediment yemifula abonisa ukuthi izimo zezulu zasendulo zazinganqunywanga nje kuphela amazinga okushisa omhlaba kodwa futhi nangokwesimo sesifunda.
8. Kungani ukuqonda izimo zezulu zasendulo kubalulekile?
Ukwakhiwa kabusha kwesimo sezulu sasendulo kungaphezu nje kwezindaba zesikhathi esidlule. Idatha ye-geological inikeza umongo wendlela uhlelo loMhlaba olwasabela ngayo ezinguqukweni ze-CO₂, umsebenzi omkhulu wentaba-mlilo, noma izinguquko ekujikelezeni kolwandle. Ngokuqonda izindlela ezasebenza esikhathini esidlule, sikwazi kangcono ukuhlola ukuzwela kwesimo sezulu kanye nemiphumela yesikhathi eside yokushintsha kwemvelo.
I-Penutup
Izici zezimo zezulu zasendulo zingafundwa ngobufakazi be-geological obusakazeke eMhlabeni wonke: kusukela ezidakeni zasehlane kanye nama-evaporites abonisa ukoma, kuya kumalahle nama-paleosols aqopha umswakama kanye nezitshalo, kuya kuma-isotopes azinzile asebenza njenge-"thermometer" yesikhathi esidlule. Zonke lezi zinkomba zisikisela ukuthi isimo sezulu soMhlaba siyisimiso esiguquguqukayo esizwela izinguquko ekwakhekeni komkhathi, ukukhukhuleka kwezwekazi, kanye nokusabela kwangaphakathi. Ngokuchaza ngokucophelela ingobo yomlando we-geological, sithola isithombe esicacile sendlela yesimo sezulu soMhlaba—kanye nezifundo ezibalulekile zokuqonda ushintsho lwesimo sezulu lwamanje nolwesikhathi esizayo.
Uma ufisa, ngingangeza ingxenye encane ezinikele exoxa ngezibonelo zezikhathi ezithile (isb., i-Quaternary Ice Age, i-Cretaceous "super-greenhouse," noma "i-Snowball Earth") kanye nezinhlobo zedatha ye-geological esetshenziswa enkathini ngayinye.
