Zealandia : Amakarata ya nyuma y’uno mugabane ugira umunani w’isi

Ubushakashatsi bushasha ku bigize Zealandia burerekana ingene yabayeho n’ingene yamizwe.

Mu 1820, ubwato bw’Uburusiya bwari bwuzuye abahinga hamwe, mu bintu bitangaje, n’inyoni zizwi nka pingouins – zari imfungurwa z’aba bantu – barabutswe hirya urutare rw’ibarafu.

Ni co kibarafu ca mbere cari kizwi nka Fimbul cari kibonetse, ari naco cabaye ifatiro mu kwerekana ko bari babonye umugabane mushasha uzwi kw’izina rya Antarctica. Ni muri ico gihe nyene havutse iciyumviro ca none, gishigikiwe n’ibihugu hafi vyose bikoresha ururimi rw’icongereza, ko hari imigabane indwi nyamukuru.

Uno musi, abana biga mu mashure, abashakashatsi, hamwe n’abanyaporitike, baremera mu bisanzwe ko isi igabuye muri ibi bice, ari vyo Ubulaya, Aziya, Afrika, Amerika y’Uburaruko, Amerika y’Ubumanuko, Australia hamwe na Antarctica.

Ariko mu 2017, habaye impinduka zitari zitezwe mu vyo abantu bari bazi : ic’uko isi igizwe n’imigabane indwi kwabaye ukwihenda kuva mu ntango. Haje Zealandia, ubutaka bwazimiye, buherereye amaja mu bumanuko bushira ubuseruko bwa Australia, ikizwi nk’umugabane w’isi wibagiranywe ugira umunani.

Abahinga bari baramaze kumenyesha kuva kera ko hariho uru rusirusi rwo mu bumanuko, ariko ko rubaka rwamaze imyaka 375 rutaboneka kubera rwari rwaramizwe hafi rwoze n’amazi gushika ku birometero hagati ya 1 na 2 musi y’amazi. Ubu rero baratanguye guhishura ibinyegezwa vyarwo.

Mu kwezi guheze, umurwi w’abashakashatsi mpuzamakungu wasohoye amakarata yerekana neza na neza Zealandia gushika uno musi, yerekana ubutaka bw’uru rusi rw’ibirometero kwadarato imiriyoni zitanu n’ibirugize.

Muri ubu bushakashatsi, bashize ahagaragara ibimenyetso vyerekana ingene uno mugabane w’amayobera wabayeho – n’ivyatumye umara imyaka imiriyoni 25 ya nyuma uzibiriwe mu mikuba y’amazi.

Imaze imyaka n’imyaka

Bibaza ko haciye imyaka yababa imiriyoni 83 Zealandia ibayeho. Hagati aho, urugendo rwayo rwo kubaho rwatanguye imyaka imiriyoni 100 imbere y’aha, igihe umugabane wa Gondwana munini cane – uno ukaba ari wo wari ugizwe n’igice kinini c’ubutaka bwa kino gihe bwari bugize urusirusi rutariga iherezo – watangura gusambuka.

Mu gihe wariko urasambuka, umugabane muto kandi wa vuba gusumba iyindi yose waciye uja ukwawo, mu gihe uturere twa Gondwana twari duherereye mu buraruko bushira uburengero n’ubumanuko bushira uburengero twagiye kuvamwo Australia na Antarctica.

Bibaza ko igice kimwe ca Zealandia canke yose, gishobora kuba carabayeho nk’izinga mu gihe gitoya. Ariko mu nyuma caciye kimirwa n’amazi, haraciye imyaka imiriyoni yababa 25.

Ibimenyetso nyavyo vya mbere vyerekana ko Nouvelle-Zélande/New Zealand ishobora kuba ari agace gato cane kaboneka k’urusi runini cane vyagiye ahabona mu 2002, igihe abahinga bakoresha ubuhinga bwa bathymétrie – ubuhinga bwo kwiga uburebure bw’amazi – mu kwiga aka karere.

Ibahari iri hejuru y’ico ubu twita Zealandia ntigera kure cane, ari co gishobora kuba cerekana ko aka karere kadahagaze ku gisate co musi y’ibahari (plaque tectonique océanique).

Icemezo c’imvaho cagiye kuboneka mu 2017, igihe abahinga begeranya ivyemezo bitari bike, harimwo amakuru ku bijanye n’ubwoko bw’ibinonko (roches) biwugize hamwe n’ubunini bwavyo kugira ngo bashobore kwemeza ko koko ari umugabane mushasha. Iki si agace gato k’umugabane canke gusa akagabane gato, nk’uko vyahora bivugwa imbere y’aha, ahubwo ni umugabane nyawo, aho 95% vyawo vyamizwe n’amazi.

Hagati aho, n’aho habaye umunezero w’uko hatowe umugabane mushasha, inyuma y’ubushakashatsi bw’urutavanako bwamaze imyaka irenga cumi, amakuru menshi ajanye n’ingene Zealandia yatanguye kubaho aracari ibisigabwenge. Ibi biva ku ruhande rumwe n’ikintu kidasanzwe cabaye igihe uno mugabane wiyonkora kuri Gondwana.

Gutora inyishu mu buryo butoroshe

Mu 2019, umurwi w’abahinga mpuzamakungu wasohoye ikarata y’igice c’ubumanuko bwa Zealandia. Ubushakashatsi bwabo bwerekana ko hageze igihe kimwe Zealandia ikiyonkora – kubera inguvu za tektoniki (ugusekana kw’ibi bisate), ivyatumye uno mugabane unyunyuka ugereranije n’ibisate vy’imigabane (plaques continentales), haca haduka imigaga yavuyemwo amabahari.

Muri iki gikorwa, uno mugabane warikubiranije, bituma bigorana kumenya kahise kawo kugira ngo inyubako yawo kama imenyekane.

Umwihwezo wakozwe n’abashakashatsi ku bigize uno mugabane werekana ko uku gukweguka kwabaye mu mice ibiri.

Umuce wa mbere watanguye haraciye imyaka igera ku miriyoni 89 gushika ku miriyoni 101, wateje umugaga wavuyemwo ikiyaga ca Tasmanie (mer de Tasmanie), hagati ya Australia na Nouvelle-Zélande.

Umuce wa kabiri watanguye mu myaka imiriyoni 80-90 iheze ukaba watumye Zealandia itandukana na Antarctica y’uburengero, haca havuka ihabari Pasifike.

Ariko hari amayobera menshi atarashobora kuronka insiguro, mu gihe n’ikindi gice c’uno mugabane kitarashobora kwigwako mu buryo burambuye.

Yagiye imirwa buke buke

Muri iki cigwa giheruka, uwundi murwi w’abashakashatsi – ugizwe ahanini n’aba bahinga nyene mu bijanye n’inyubako y’isi (geologists) bakoze ubushakashatsi ku gice c’uburaruko bwa Zealandia.

Aha rero, bihweje ibinonko vyacukuwe mu misozi ya Fairway, akarere kari muri Pasifike y’ubumanuko mu mazi akukira Australia kagize isonga rya Zealandia mu buraruko.

Ibi bisigarira vya kera bitigeze bimenya umusi n’umwe ukakaraye kuva imyaka imiriyoni 25 iheze, rwari uruvangatirane rw’ibinonko vyavuye mu birunga (roches magmatiques) n’ivyavuye mu mirundo y’ibinonko vyatembanywe n’inkukura (roches sédimentaires) vyiyegeranirije mu nkengera z’amazi ya Zealandia.

Mu kwihweza inyubako y’ibi bibuye, aba bahinga barashoboye kumenya imyaka yavyo n’ingene vyabayeho.

Ivya kera cane bimaze imyaka hagati y’imiriyoni 130 na 110, ibikurikira bikaba bimaze imyaka yababa imiriyoni 95, ivya nyuma bikaba bimaze imyaka imiriyoni 40.

Amakarata ya Zealandia yerekana urusirusi rutagira imforo ruhinduka rukavamwo ibihimba bitandukanye kuva mu buraruko bushira uburengero gushika mu bumanuko bushira ubuseruko. Ibi bihimba bihuye n’ingene Antarctica y’uburengero yubatse nk’urufatangane rw’ibihimba bitandukanye, ibi bikerekana ko aka karere hamwe na Zealandia vyari bifatanye.

Igice gikurikira c’ubu bushakashatsi cabaye ukwihweza ibintu bidasanzwe mu bigize inguvu rukuruzi (forces magnétiques) hasi mw’ibahari izungurutse Zealandia.

Ihindagurika ry’izi nguvu rukuruzi z’isi zirerekana, mu buryo butaboneka, ukungene ibi bisate vy’isi vyagiye vyimuka uko imyaka yagenda. Ryatumye hamenyekana ingene uno mugabane wa kera wagiye ukweguka, birabandanya mu myaka imiriyoni n’iyindi kandi bihindura n’inzira, bituma havuka akagabane gato cane vyagiye kurangira kamizwe.

Zealandia iratanguye rero kwerekana ibinyenezwa vyayo. Ariko rero kubera ko igice kinini c’uru rusirusi rw’igitangaza ruri ku birometero musi y’amazi, bizofata igihe kitari gito kugira no ivyerekane vyose.