Uko kwikubanaho kw’ibyo bice no gutandukana k’ubutaka bigira ingaruka zigera ku mibereho y’ibinyabuzima ku Isi, cyane cyane nk’imihindaguirikire y’ibihe no kuba byakwisanga bituye ahantu hatandukanye (imigabane).

Abahanga mu by’ubumenyi bw’Isi ntibahamya neza igihe nyacyo ibyo byaba byaratangiriye, ariko bagereranya ko haba ari hagati y’imyaka miliyoni 700 na miliyari 4 ishize, ubwo Isi yari ikiri mu itangira. Bagereranya ko icyo gihe Isi yari imeze nk’umwana.

Umushakashatsi akaba n’umwarimu muri Kaminuza ya Texas, Robert Stern, aherutse kubwira Live Science ko ikimenyetso simusiga kiganisha ku gusobanura igihe byaba byaratangiriye, ari icyo mu myaka iri hagati ya miliyari 1 na miliyoni 541 ishize.

Muri iyo myaka ngo ni bwo ubushakashatsi bwerekana ko hagaragaye utuvungukira twinshi tw’ibitare byiremera mu gace kabereyemo ukwikubanaho kw’ibice bigize ubutaka bw’Isi.

Utwo tuvungukira (ophiolites) turacyafatwa nk’ikimenyetso cy’uko habayeho ukwikubanaho kw’ibice by’ubutaka bw’Isi.

Ku rundi ruhande, hari abandi bashakashatsi benshi babona ubusesenguzi bwa Stern nk’aho butajyanye n’igihe.

Bemera ko ibitare bifatwa nk’ibimenyetso by’uko ibice by’ubutaka bw’Isi byikubanaho byagaragaye cyane bwa mbere hagati y’imyaka miliyoni 700 na miliyoni 900 ishize. Gusa bakongera ko ibyo bitare bishobora kuba byarabayeho mu myaka yabanje ariko bikaza gusaza bitewe n’igihe.

Mark Harrison wigisha muri Kaminuza ya California avuga ko nk’urugero ‘Indian subcontinent’ yikubanyeho n’igice cy’Amajyepfo ya Asia mu myaka hafi miliyoni 55 ishize, kandi ibyinshi mu bitare byerekana ko habaye uko kwikubanaho bikaba bitakigaragara.

‘Indian subcontinent’ ni igice kiriho inyanja y’Abahinde n’ibihugu bya Bangladesh, Bhutan, u Buhinde, Maldives, Nepal, Pakistan, na Sri Lanka.

Harrison asobanura ko kwikubanaho kw’ibyo bice byombi kutararangira, aho ahera yibaza ukuntu bimwe mu bimenyetso by’uko kwikubanaho byaba bitakigaragara kandi kukiba, hanyuma bakizera ko hazaboneka ibimenyetso by’ukwikubanaho kwabayeho mu myaka ya kera cyane.

Abashakashatsi benshi bahuriza ku kuba ukwikubanaho kw’ibice by’ubutaka bw’Isi kwaba kwaratangiye mu myaka ya kera cyane, kuko hari ibimenyetso byinshi byerekana ko kwatangiye hagati y’imyaka miliyari 4 na miliyari 2.5 ishize.

Babishingira ku kuba mu bimenyetso by’uko kwikubanaho bikigaragara uyu munsi, harimo icyo mu myaka miliyari 2.5 ishize.

Ikindi gifatwa nk’ikimenyetso gishingira ku binyabutabire bigize igice cyo hejuru cy’ubutaka bw’Isi (Crust), gifite ibitare bikomoka ku iruka ry’ibirunga.

Iyo bibayeho ko kwikubanaho kw’ibice by’ubutaka bw’Isi gutuma ‘Crust’ ishonga ikongera ikagaruka bushya, bya binyabutabire biyigize birahinduka. Inyigo ya 2012 yagaragaje ko ‘Crust’ yaba yaratangiye gushonga cyane mu myaka miliyari eshatu ishize.

Ubushakashatsi ku mabuye y’agaciro yitwa ‘zircons’ akomeza kugaragara n’ubwo ‘Crust’ yashonga, bugaragaza ko ‘Crust’ yatangiye guhindagurika kera cyane, nko mu myaka miliyari 3.8 ishize.

Indi nyigo yakozwe kuri ayo mabuye mu 2023, yerekanye ko yagumye aho yari kuva mu myaka miliyari 3.4 ishize. Ibyo byatumye hakomeza kwibazwa niba iryo hindagurika rya ‘Crust’ ryashingirwaho mu kumenya neza igihe ukwikubanaho kw’ibice by’ubutaka bw’Isi kwatangiriye.

Ubushakashatsi buheruka buvuga kuri uko kwikubanaho bwagaragaje ko kwaba kwaratangiye mu myaka miliyari 4.5 na miliyari 4 ishize, ariko bwakuruye impaka ndende.

Bwashingiye ku bimenyetso by’uko Isi ikibaho yari ifite imiterere ijya kumera nk’iyo ifite uyu munsi, kuko yagiraga inyanja n’imigabane.

Magingo aya ubushakashatsi bwose bugaragaza igihe ukwikubanaho kw’ibice bigize ubutaka bw’Isi kwaba kwaratangiriye, bwagiye bugaragaramo icyuho mu gutanga ubusobanuro bwuzuye. Muri rusange nta na bumwe buremeranywaho na bose.