Namuhla sizokhuluma ngohlobo lokwakheka kwe-geological olwakhiwe kusukela ekukhululekeni kweqhwa. Imayelana ne- isigubhu. Leli gama livela ku-Irish "droim" noma "drim" futhi lisho "i-crest of a hill". Ukwakheka kwayo kuvela ezinqabeni zeqhwa futhi akuyona nje into eyisiduli esincane esinemithambeka ebushelelezi emise okomkhomo olele. Zenziwa ngokumodeliswa kweqhwa elibhekise ekuhambeni kweqhwa ngezikhathi ze-glaciation.
Kulesi sihloko sizokutshela zonke izici, ukuqeqeshwa kanye nokufuna ukwazi kwedrumlin.
Izici eziyinhloko
Sikhuluma ngohlobo lwesiduli esincane esakhiwe ngamathambeka abushelelezi. Imithambeka ebushelelezi inalokhu kuthungwa selokhu iqhwa le-glaciation nezikhathi zokuncibilika kubangela ukuguguleka komhlabathi ngokuhuzuka. Isimo se-drumlin esomkhomo olele futhi senziwa ngu ukuqondiswa kokunyakaza okuthwalwa kakhulu yiqhwa ngezikhathi zeqhwa.
Ngoba i-drumlin itholakala eduze kwediphozithi ye-moraine, zithathwa njengezakhiwo ezivela ku-moraine ezenziwa ngaphansi kweqhwa. AmaMoraines ayisethi yezidalwa zeqhwa eziqongelela ezinhlangothini zesakhiwo seqhwa. Bangabonakala bodwa kodwa kuvame kakhulu ukuthola emaqenjini anjenge kwenzeka endaweni yaseChilean Patagonia. Futhi ukuthi iqoqo lezidalwa ezakha ama-moraines zihamba ziqonde ohlangothini lweqhwa nomoya okhona. Siyazi ukuthi iqhwa libuye libe nokunyakaza kwalo kuncike emthambekeni nasezikhathini ze-glaciation.
Ukwakhiwa kwesigubhu
Ake sibheke ukuthi iyiphi inqubo eyenziwa yi-drumlin. Siyazi ukuthi bayingxenye yendawo ebunjwe isenzo seqhwa. Kunezimpikiswano eziningi mayelana nemvelaphi yedrumlin, yize izinkolelo-mbono ezithinteke kakhulu yilezi ezilandelayo:
- Kungumkhiqizo owenziwe ngesikhukhula ngaphansi kweqhwa. Le alluvium iyakwazi ukuhambisa izinto eziningi ngomzuzwana owodwa futhi iqoqeka eziteshini ze-sub-ice. Lezi ziteshi kulapho amanzi egeleza khona, amile, kodwa avela engxenyeni engezansi nawo aqhubeke esimweni soketshezi. Siyazi ukuthi iqhwa linamathele entanjeni kodwa aliqandeki ngokuphelele. Ingxenye engezansi yeqhwa ejikelezisa izinsalela nomhlabathi imvamisa isesimweni soketshezi futhi inesibopho sokuhamba kweqhwa.
- Kwakhiwa iqhwa elikhulu kakhulu leqhwa elaliklwebha kancane kancane ubuso bomhlaba. Uma sikhuluma ngokuklwebheka ubuso bomhlaba sisuke sisho uhlobo lokuguguleka komhlaba olubizwa ngokuthi ukuhuzuka. Ukuhuzuka yinqubo ekhiqizwa ngokuhudulwa kweziduli nesisindo salowo nalowo. Ngamanye amagama, lapho iqhwa lingena ebusweni, likhiqiza umhuzuko ngenxa yesakhiwo sawo futhi inhlabathi iyaguguleka futhi inokushelela okubushelelezi.
Ukwakhiwa kwesigubhu kuhlotshaniswa nohlobo lwento eyakha la magquma. Futhi ukuthi ukungena kweziduli kubonakala kudlala indima ebalulekile enqubeni yokubumba. Uma inhlabathi engaphansi kweqhwa eqoqwe ngezikhathi zeqhwa igcwele, kuba nzima kakhulu ukuthi ihudulwe ngoba izokuhlunga.
Izinto zokwakha iDrumlin
Ake sibheke ukuthi iziphi izinto ezisemqoka ezenziwe yidrumlin. Okokuqala kunakho konke ukwazi ukuthi yini eyenziwe ngodaka lwe-glacial. Lolu daka lweqhwa luyaziwa ngegama le-till. Kuyinhlanganisela yobumba, isihlabathi kanye nohlalu olunamaphethelo angular futhi kwesinye isikhathi lunamabhulokhi amadwala. Inguzunga yeqhwa idonsa futhi iphushe lezi zinto bese izifaka ezansi. Ngale ndlela, kwakuyizinto ezazitholakala ukuthi zingahanjiswa yinguzunga yeqhwa ene-alluvial ephansi.
Kwesinye isikhathi inzika ingakha isigubhu esidalwe ukuhamba kwamanzi ngemifula ezungeza ngaphansi kweqhwa. Njengoba sishilo ngaphambili, ngaphansi koqweqwe lukanoqweqwe lwamanzi esimweni samanzi njengomfula. Ezimweni ezimbalwa kakhulu iqhwa liba yiqhwa ngokuphelele ngokuphelele. Ikakhulukazi ngenkathi yokuncibilika, ingxenye eba uketshezi esheshayo yingxenye yangaphakathi yeqhwa. Kulokhu, lapho i-drumlin yakhiwa ngu Imifula ezungeza ngaphansi kweqhwa yakhiwe ngamatshe amatshe amatshe.
Amafomu wokuqongelela
Kusukela ukuqabuleka kokugcina, okwenzeka cishe eminyakeni eyi-18.000 eyedlule, iqhwa belilokhu lihlehla, lembula ukukhululeka okuzuzwe njengefa kulo lonke izinga ebelihlala kulo ngesikhathi sokugcina seqhwa. Lokho ukusho ukuthi, ngesikhathi sokuncibilika nokwehliswa kobuso obumbozwe yiso, kwembula ukukhululeka ngokumodeliswa kweqhwa.
Ama-glacial deposits aziwa ngokuthi yi-till ayizidalwa ezakhiwe ngezinto ezifakwe ngqo izinguzunga zeqhwa. Lezi zinto azinaso isigaxa futhi izingcezu zazo zibonisa ukukhishwa ngenxa yokufuduka nokungqubuzana nomhlabathi. Ama-moraines ukwakheka okwenziwe ngamathill aqoqana ezinhlangothini zamaqhwa. Uma inguzunga yeqhwa ihlehla ungqimba lwama-till amise okwe-wavy abizwa nge-basal moraine afakwa. Lapho umphambili uqhubeka nokuhlehla, ungazinza futhi wakhe i-moraine yokubuyisa.
Ama-moraines asemuva ngokuvamile ajwayelekile kakhulu eziqhwa zezigodi. Baphethe ukuhambisa zonke izidalwa emabhange aso futhi bafakwa ngemisele emide. Lapho ama-moraines e-lateral ehlanganiswa nokuhlangana kwezigodi ezimbili, kwakhiwa i-moraine emaphakathi.
Ekugcineni, lapho izinhlabathi sezifakwe ngaphandle kwendawo yeqhwa futhi zapheshulwa umoya nokusebenza kwamanye ama-geological agents, i-drumlin iyakhiwa. Kukhona okunye ukwakheka kwe-geomorphological okungumphumela wokukhululeka kweqhwa futhi okwakhiwe ngemfucumfucu eboshiwe futhi ama-kame, amathamo we-kame, nama-eskers.
Ngiyethemba ukuthi ngalolu lwazi ungafunda kabanzi nge-drumlin nezimpawu zayo.