Abahanga mu bumenyi bw’Isi bemeza ko  kera, kera cyane Nyabarongo yambukiranyaga umujyi wa Musanze, mpaka no muri Lac Edouard.

Bihabanye cyane n’ibivugwa mu gitabo cy’Intangiriro ku bijyanye n’iremwa ry’Isi, abahanga mu bumenyi bw’Isi ( geologues), bo bemeza ko iyi Isi yatangiye kubaho hashyize imyaka itabarika ingana na miliyari 4,54

Aba bahanga bemeza ko iyi Si yabayeho bihereye ku bihu by’uruvange rwa gaz n’ivumbi ( nouage de gaz et de poussieres) bita “nebuleuse solaire” mu rurimi rw’igifransa, uru ruvange rukaba rwaraje kwishyira hamwe rugahinduka ikintu gikomeye ( solide).

Nyuma yaho,  iki cyari kimaze kuvuka cyagiye kigira imihindagurikire inyuranye,yaganishije ku Isi tubona  ubu ifite ikirere, ubutaka n’inyanja.

Aba bahanga bemeza kandi ko n’ubu butaka tubona mu Rwanda, imisozi, ibibaya n’utununga, byagiye bibaho kuva iyi SI yatangira kwiremarema kugeza mu myaka miliyoni 542 ishyize. Iki  gihe nicyo aba bahanga bise “ precambrien”,cyamaze imyaka miliyari 4 uhereye nyine kuva Isi yatangira kwiremarema.

Naho ku bijyanye n’ibirunga dusanga mu majyaruguru y’U Rwanda, ngo byaba byaratangiye kubaho mu myaka miliyoni 2 ishyize mu gihe cyiswe “ pleistocene”.  Ivuka ry’ibi birunga rikabarbyaragize ingaruka zikomeye ku miterere y’inzuzi n’imigezi zo mu karere. Tubabwire kandi ko abahanga nanone bemeza ko umuntu wa mbere wiswe “homo habilis”, yabayeho hashyize hagati y’imyaka miliyoni 2 na 1,6, bishatse kuvuga koi bi birunga byavutse n’ikiremwamuntu gitangiye kwigaragaza ku Isi.

Nyabarongo yahinduye icyerekezo kubera iruka ry’ikirunga cya Muhabura

Nk’uko byemezwa nanone n’aba bahanga, iri vuka ry’ibirunga twavuze haruguru ryabimburiwe n’ikirunga cya Sabyinyo, riherukwa n’ivuka rya Nyamulagira.

Ubwo Ikirunga cya Muhabura Cyavukaga, ngo cyaba cyarohereje amahindure menshi mu bice bigikikije biherereye kuri ubu mu gihugu cya Uganda n’ U Rwanda ku buryo aya mahindure yageze no mu bice bya za Kabale muri Uganda ndeste no mu bice biherereye mu Ntara y’amajyepfo y ‘ U Rwanda za Muhanga, aho bita mu Masangano.

Iri ruka kandi uretse kohereza amahinduremu bice binyuranye twavuze,  ryagiye rituma habaho n’ukwiyongera k’ubutumburuke ( soulevement de la croute terrestre) k’ubutaka buherereye muri kariya gace, ibyatumaga byanze bikunze habaho imihindagurikire y’imiterere y’inzuzi n’imigezi yo muri turiya duce.

Mbere y’uko ibi birunga bivuka ariko, U Rwanda rw’ubu, icyo gihe rwari rugizwe n’imisozi ndeste n’ibibaya byanyurwaga n’imigezi, Nyabarongo y’ubu ikaba yari umugezi munini wavaga mu gice cy’amajepfo werekeza mu majyaruguru.

Aha mu majyaruguru, niho wambukiranyaga ahari buno umujyi wa Musanze ubanje  guhura n’utundi tugezi twavaga ahari Urugezi buno no mu bice birwegereye, hanyuma  iyi Nyabarongo ikambuka igana muri Congo y’ubu aho yisukaga mu mugezi wa Rutchuru ya buno, bigakomeza mpaka no mu kiyaga cya Edouard. Aya mazi akaba yongera kuva muri Lac Edouard ajya kurema Nil nk’uko tuyizi ubu.

Iruka ritavaho rya  Muhabura ryaba ryararangiye mu myaka hafi ibihumbi 12 ishyize ( periode helocene), rikaba rero ryaratumye  Nyabarongo ihindura icyerekezo,ishakisha izindi nzira mu majyepfo igana iya lac Victoria y’ubu.

Ivuka ry’ibiyaga mpanga bya Burera na Ruhondo

Hagati aho ariko, amahindure Muhabura yerekezaga mu gice cya Ndorwa n’urukiga by’ubu, yaje kuzibira twa tugezi twavuze twavaga mu Rugezi no mu bice bikikje kariya gace, maze hatangira kwikora mu bikombe byo muri turiya duce ikiyaga aricyo  kiyaga cya Burera cya none.

Kera ngo kabaye, nyuma y’imyaka nk’amagana, iki gikombe cyaje kuzura, maze gitangira kumena aya mazi mu kindi gikombe, bitari bifite ubutumburuke bumwe( kimwe gisa n’ikiri hejuru y’ikindi, ku kinyuranyo cya metero ijana) aricyo cya Ruhondo y’ubu.

Iki gikombe nacyo uko imyaka yagiye yiyongera cyaje kuzura, maze amazi atangira kwerekeza muri za nzira za mbere twa tugezi twavaga mu rurgezi twanyuragamo mbere y’ivuka ry’ikirunga cya Muhabura.

Aya mazi yafashe inzira ya Mukungwa tuzi ubu, iyi nzira yaje kuyahuza na Nyabarongo yari yahinduriwe icyerekezo n’amahindure ya Muhabura, biza guhurira aho bita kuri ubu mu Masangano ya Mukungwa na Nyabarongo.

Uretse iri hinduka ry’ icyerekezo ry’ako kanya ryabaye kuri Nyabarongo nk’ikimenyetso cy’ingaruka ry’ivuka rya muhabura ku mazi n’imigezi y’  U Rwanda, aba bahanga bemeza ko n’ubugari bw’ikibaya cya Mukungwa kuri ubu, ari ikimenyetso simasiga ko Nyabarongo ariyo yanyuraga muri iki kibaya, Mukungwa nk’umugezi muto kuri Nyabrongo, ukaba utari bugire ikibaya gifite buriya binini.

Ikindi kigaragaza ko Nyabarongo yaba yarahinduriwe inzira n’ibimeyetso bya kera ( sediment, alluvions)  byakuwe muri kariya gace ka za Nyakinama, ibimeyetso biranga ahahoze hanyura inzuzi n’imigezi.

 

Twifashishije imbuga:

www.kigalitoday.com na rw.wikipedia.org

Umwanditsi: Musengimana Emmanuel