Kugeza aka kanya u Rwanda ni kimwe mu bihugu bidakora ku Nyanja. Ariko abahanga mu bumenyi bw’isi bavuga ko bishoboka ko u Rwanda rwazaba muri bimwe mu bihugu bizakora ku nyanza. Bakemeza ko ibyo bishobora kuba mu mwaka wa 2200.

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Amateka agaragaza ko mu myaka miliyoni 300 ishize, Isi itari ifite imigabane irindwi nk’uko bimeze ubu, ahubwo yari ifite icyakwitwa nk’umugabane umwe, cyitwaga Pangaea kizengurutswe n’Inyanja imwe yitwaga Panthalassa.

Ubusanzwe Isi igira ibice bitatu uvuye ku butaka duhinga ukagera kuri cya gikoma gishyushye kiba gifite ubushyuhe bwa dogere Celsius buri hagati ya 700 na 1300, ari na cyo kigira uruhare mu kurema iyo migabane bivuye ku ngufu zabwo.

Ibyo bice birimo ikizwi ka Crust akenshi tuba dukandagiraho, kigakurikirwa na Mantle kiba kigizwe n’ibibuye ariko bishyushye hagaheruka ikizwi nka Core.

Abahanga mu by’Ubumenyi bw’Isi bagaragaza ko iyi migabane irindwi dufite uyu munsi yaturutse ku gushwanyukamo ibice kwa Crust bigizwemo uruhare n’ingufu zituruka mu nda y’Isi kuri cya gice kizwi nka Mantle, kiba kigizwe n’ibitare bishyushye ari na byo bibyara ibikoma bizwi nka magma.

Kugira ngo ubyumve neza, uzarebe iyo imvura ihise, ahitetse amazi hagakama, hatangira kwisaturamo ibice bitandukanye, uko ni na ko Isi imeze. Ibyo bice ubona hejuru byiyashije bisa neza n’ibi dutuyeho biba bisa n’ibireremba kuri uwo muriro.

Igitabo kigaruka ku mateka y’Isi n’uko yagiye yicamo ibice cyiswe ‘Ancient Supercontinents and the Paleogeography of Earth’ cyanditswe n’abahanga mu by’Ubumenyi bw’Isi barimo Trond Torsvik, Mathew Domeier na Robin Cocks, kigaragaza ko Pangaea yatangiye kwitandukanya hagati y’imyaka miliyoni 195 na miliyoni 170 ishize.

Ni ibintu byabaye mu gihe cya Jurassic Period, igihe cyaranzwemo na za nyamaswa nini zizwi nka “dinosaurs”, ari na ho Inyanja ya Atlantique yavumbutse n’indi migabane ivuka ityo.
Igice cyitwaga Gondwana cyahuzaga Afurika, Amerika y’Amajyepfo, Antarctica, u Buhinde na Australia by’ubu na cyo cyiyomoye ku gice cyitwaga Laurasia cyari kibumbatiye Eurasia (ubu ni u Burayi na Azia) ndetse na Amerika y’Amajyaruguru.

Mu myaka miliyoni 150 ishize Gondwana yacitsemo ibice, u Buhinde butandukana na Antarctica ndetse na Afurika yitandukanya na Amerika y’Amajyepfo nk’uko ubushakashatsi bwanyujijwe mu Kinyamakuru Geophysical Research bubigaragaza.

Nyuma mu myaka miliyoni 60 ishize Amerika y’Amajyaruguru na yo yitandukanyije na Eurasia biba imigabane ibiri itandukanye.

Ishingiro ry’ibi ni uko iyo witegereje usanga imimerere y’abatuye ku mpera z’umugabane umwe, ijya gusa n’iy’abatuye ku ntangiriro zo ku wundi byahoze bifatanye.

Urugero rwa hafi ni Amajyaruguru ya Afurika aho usanga bajya kumera kimwe n’abo mu Majyepfo y’u Burayi, cyangwa abo ku mpera za Angola ugasanga bafite imico ijya gusa n’iyo muri Brésil. Ntabwo byapfuye kwizana.

Ibihugu bisanzwe bidakora ku nyanja birimo u Rwanda, Uganda, u Burundi, Repubulika Iharanira Demokarasi ya Congo, RDC (ikoraho gato), Malawi na Zambia umunsi umwe bizisanga amateka yahindutse na byo bikora ku mazi magari.

Ibi bijyanye n’Ubushakashatsi bugaragaza ko Afurika iri kugenda yigabanyamo ibice bibiri, aho igice giherereye mu ruhererekane rw’ikibaya cya Afurika y’Uburasirazuba (East African Rift System: EARS) kiri kugenda cyitandukanya n’ikindi gice cy’uyu mugabane.

Abahanga mu by’Ubumenyi bw’Isi bagaragaza ko uku gutandukana kuzahereza mu Majyaruguru y’Uburasirazuba bwa Afurika kugana mu majyepfo y’u Burasirazuba, icyo gice kikazisanga mu Nyanja y’Abahinde.

Ni ukuvuga ko bizahera muri Ethiopia, bikamanuka muri Kenya bigakomereza muri RDC no muri Uganda, mu Rwanda, u Burundi, Tanzania na Malawi bigasoreza muri Mozambique.

Umuryango wo mu Bwongereza wiga ibijyanye n’ubumenyi bw’Isi, ugaragaza ko iki kibaya cya EARS cyabayemo mu myaka miliyoni 22, ukagaragaza ko uku gucikamo ibice kwatangiye kugaragara mu 2005.

Byabaye ubwo Ubutayu bwa Afar muri Ethiopia bwiyashije hakabamo umuhora munini, ibyabaye nyuma y’uko Ikirunga cya Dabbahu giherereye mu Majyaruguru ya Ethiopia cyarukaga hafi y’Ikibaya cya Afurika y’Uburasirazuba (East African Lift Valley).

Ibi byatumye kwa kugendagenda kwa bya bisheshe (plates) birimo ikizwi nka Somali Plate kigizwe n’ibihugu nka Comores, Eswatini, Kenya, Madagascar, Ibirwa bya Maurices, Mozambique, Seychelles na Somalia.

Byarimo kandi icya Arabian Plate kigizwe n’ibihugu nka Yemen, Oman, Saudi Arabia, Reta Zunze Ubumwe z’Abarabu, Qatar, Bahrain, Kuwait na Jordan ndetse na Nubian Plate kigizwe n’ibindi bihugu bisigaye.

Mu 2018 na bwo abahanga mu Bumenyi bw’Isi bahamije uku gutandukana ubwo uko kwiyasa kwabaga mu gace ka Narok gaherereye mu bilometero 142 uvuye mu Murwa Mukuru wa Kenya, Nairobi, ibyakomeje kwaguka bijyanye n’uko imvura yakomezaga kugwa.

Ibyo biri mu byatumye abahanga bashimangira iby’uko gucikamo kabiri bakagaragaza ko nibimara kuba ibihugu nka Ethiopia, Kenya na Tanzania bizakora ku Nyanja y’Abahinde ku mpande zabyo ebyiri.

Ibihugu nk’u Rwanda, u Burundi na RDC byishingikirizaga ku byambu bya Mombasa muri Kenya ndetse na Dar es Salaam muri Tanzania bizaba bibonye uburyo bwiza bwo kugeza ibicuruzwa byabyo bivuye nko mu Burayi na Azia byoroshye, kuko icyo gihe amafaranga yagendaga mu bwikorezi n’ibindi azaba akuweho.

Abashakashatsi ntibazi niba uku gucikamo ibice kuzageraho kukihuta nk’uko byagenze ku itandukana rya Amerika na Afurika kuri ubu iyi ntera ikaba ibarirwa ibirometero 9325.

Ubu bushakashatsi bushya bwamuritswe mu Kinyamakuru cya Geophysical Research: Solid Earth bwerekanye ko uku kwigabamo ibice bibiri kwa Afurika kuri guterwa n’imbaraga zo ku Isi cyane cyane iz’iki gice cya lithosphere zizwi nka ‘lithospheric buoyancy forces’ ndetse n’izo mu nda y’Isi ziterwa na kwa gutembera kwa wa muriro uba mu nda yayo.

Umuhanga mu bijyanye n’Ubumenyi bw’Isi, akaba n’Umusenateri mu Nteko Ishinga Amategeko y’u Rwanda, Havugimana Emmanuel yavuze ko ibi bintu byatangiye ndetse ngo ntibyigeze bihagarara n’ubwo bigenda gake.

Senateri Havugimana yerekana ko bizaba nko mu 2200 iri imbere. Ati “ibyumvikana neza ko nta muntu uriho ubu uzabibona ariko bizaba. Isi iri ku bisheshe (plaques, plates) binini icyenda bireremba hejuru y’umuriro waka mu nda yayo. Uwo muriro iyo ubonye aho unyura nibwo havuka ibirunga.”