Isikhathi seCretaceous

Kuyo yonke inkathi ye- Mesozoic sithola izinkathi ezi-3: the I-Triassic, the I-Jurassic futhi i Okuhle kakhulu. Namuhla sizogxila ekukhulumeni ngesikhathi seCretaceous. Kuyisigaba sesilinganiso sesikhathi esihambelana ne- isikhathi sokuma komhlaba ukuba yisikhathi sesithathu nesokugcina seMesozoic. Kwaqala cishe eminyakeni eyizigidi eziyi-145 edlule futhi kwaphela cishe eminyakeni eyizigidi ezingama-65 edlule. Lesi sikhathi sihlukaniswe izingxenye ezimbili ezaziwa njengeLower Cretaceous ne-Upper Cretaceous. Lesi ngesinye sezikhathi ezinde kakhulu ngaphakathi kwe-Phonerozoic eon.

Kulesi sihloko sizokutshela konke odinga ukukwazi mayelana nesikhathi seCretaceous.

Izici eziyinhloko 

Lesi sikhathi sinegama laso elivela esiLatini ngesi- eta okusho ukuthi ushoki. Leli gama lisuselwa kumucu otholakala e-Parisian Basin eFrance. Kule nkathi impilo olwandle nasemhlabeni yavela njengenhlanganisela yamafomu wesimanje kanye namafomu asendulo. Ihlala cishe iminyaka eyizigidi ezingama-80 cishe, yisikhathi eside kakhulu se-Phonerozoic eon.

Njengezinkathi eziningi zokwakheka komhlaba esizifundile, ukuqala kwalesi sikhathi akuqinisekile, kuneminyaka eyizigidi ezimbalwa ngaphezulu noma ngaphansi. Zonke iziqalo neziphetho zezikhathi zokuma kwezwe zinqunywa isenzakalo esithile esikhulu somhlaba wonke, kungakhathaliseki ukuthi kungenxa yezinguquko zesimo sezulu, izitshalo, izilwane, noma i-geology. Ukujola kokuphela kwalesi sikhathi kunembile ngokuphathelene nasekuqaleni. Lokhu kungenxa yokuthi uma ifana nenye yezendlalelo ze-geological enobukhona obuqinile be-iridium futhi ebonakala ihambisana nayo. ukuwa kwe-meteorite kulokho manje okuhambisana neNhlonhlo Yucatan neGulf of Mexico.

Le yi-meteorite edumile engagcina idale ukuqothulwa okukhulu okwenzeke ekupheleni kwalesi sikhathi lapho iningi lezilwane lanyamalala khona, kufaka phakathi ama-dinosaurs. Lo ngumcimbi obaluleke kakhulu omemezela ukuphela kwenkathi yeMesozoic. Kungemva kweJurassic nangaphambi kwe- I-Paleocene.

I-athikili ehlobene:

ukushabalala okukhulu

I-geology e-Cretaceous

Maphakathi nesikhathi seCretaceous, ngaphezu kwengxenye yemithombo kawoyela yomhlaba esinayo namuhla yakhiwa. Ukugxila okuningi okudume kakhulu kutholakala ePersian Gulf nasendaweni ephakathi kweGulf of Mexico kanye nogu lwaseVenezuela.

Phakathi naso sonke lesi sikhathi, amazinga olwandle ayelokhu ekhuphuka ngenxa yokukhuphuka kwezinga lokushisa emhlabeni. Lokhu kukhula kwenza amazinga olwandle afinyelela ezingeni eliphakeme kunawo wonke ake alotshwa emlandweni weplanethi yethu. Izindawo eziningi ebeziyihlane phambilini seziphenduke amathafa agcwele amanzi. Izinga lolwandle lafinyelela izinga kangangokuthi yi-18% kuphela yomhlaba ebingaphezu kwezinga lamanzi. Namuhla sine-29% yendawo yomhlaba evelile.

I-supercontinent eyaziwa ngokuthi yiPangea yahlukaniswa phakathi nayo yonke inkathi yeMesozoic ukunikeza amazwekazi esiwaziyo namuhla. Izikhundla ababeziphethe emuva ngaleso sikhathi zazihluke kakhulu. Ekuqaleni kweCretaceous kwase kunama-supercontinents amabili abaziwa ngeLaurasia neGondwana. Lezi zindimbane zomhlaba ezinkulu zahlukaniswa uLwandle lwaseThetis. Ekupheleni kwalesi sikhathi amazwekazi aqala ukuthola amafomu acishe afane nawamanje. Ukwehlukaniswa okuqhubekayo kwamazwekazi kubangelwe isenzo se- Ukukhukhuleka kwezwekazi futhi kuhambisane nokwakhiwa kwamapulatifomu abanzi nemifula.

Uhlelo lwamaphutha olwalukhona kwiJurassic yangaphakathi lwaluhlukanise iYurophu, i-Afrika nezwekazi laseNyakatho Melika. Kodwa-ke, lawa mhlaba ahlala esondelene. I-India neMadagascar babehamba besuka ogwini lwaseMpumalanga Afrika. Esinye seziqephu ezibaluleke kakhulu zokuqhuma kwentaba-mlilo okukhulu kwenzeka phakathi kokuphela kweCretaceous nokuqala kwePaleocene eNdiya. Ngakolunye uhlangothi, i-Antarctica ne-Australia zazisahlangene futhi zazisuka eNingizimu Melika, zikhukhuleka zibheke empumalanga.

I-athikili ehlobene:

Ukuthi ama-dinosaurs ashabalala kanjani

Konke lokhu kunyakaza kudale imizila emisha yasolwandle njengeNyakatho yasendulo neNingizimu Atlantic futhi, uLwandle lweCaribbean nolwandle i-Indian. Ngenkathi i-Atlantic Ocean yayisanda, ama-orogenies ayesekhule ngesikhathi seJurassic aqhubeka esuka ezintabeni zaseNyakatho Melika ngenkathi i-orogeny yeNevada ilandelwa ngamanye ama-orogenies afana neLaramide.

Isimo sezulu seCretaceous

Amazinga okushisa ngalesi sikhathi akhuphuka aze afike ezingeni eliphezulu cishe eminyakeni eyizigidi eziyi-100 edlule. Ngaleso sikhathi lalingekho iqhwa ezigxotsheni. Izinsalela ezitholwe kulesi sikhathi zibonisa ukuthi amazinga okushisa olwandle olushisayo kufanele ukuthi abephakathi kuka-9 no-12 degrees Celsius, afudumele kunanamuhla. Amazinga okushisa olwandle olujulile kufanele ukuthi abe ngisho nangama-degree angama-15 nangu-20 ngaphezulu.

Iplanethi bekungafanele ifudumale kakhulu kunangesikhathi se-Triassic noma i-Jurassic, kodwa kuyiqiniso ukuthi i-gradient lokushisa phakathi kwezigxobo ne-Equator bekufanele libe bushelelezi. Le gradient ebushelelezi yokushisa ibangele ukuthi imisinga yomoya weplanethi inciphe futhi yaba nomthelela ekwehliseni imisinga yolwandle. Ngalesi sizathu, bekukhona izilwandle eziningi ebezime kakhulu kunanamuhla.

Lapho isikhathi seCretaceous sesiphelile, amazinga okushisa ajwayelekile aqala ukwehla okuhamba kancane okwakusheshisa ngokuqhubekayo futhi ezigidini zeminyaka zokugcina isilinganiso sonyaka sehle sisuka kuma-20 degrees saya kuma-10 degrees.

I-athikili ehlobene:

Umthelela we-Chicxulub asteroid kanye nokushabalala kwama-dinosaurs

Izimbali nezilwane

Umphumela odale ukuthi uMhlaba uhlukane ube ngamasimu womhlaba ayi-12 noma ngaphezulu kukhethwe ukuthuthukiswa kwezilwane nezitshalo. Kulezi zizwe, bazakhela ezabo iziqhingana zamazwekazi eziqhingini zase-Upper Cretaceous futhi bavela ukuze bakhiqize okunhlobonhlobo okuningi kokuphila kwasemhlabeni nokwasolwandle esikwaziyo namuhla.

I-athikili ehlobene:

Nezilwane Cretaceous