Ixesha leCretaceous

Ngalo lonke ixesha le Mesozoic sifumana amaxesha amathathu: the Triassic, i IJurassic kunye Ukuthintela. Namhlanje siza kugxila ekuthetheni ngexesha leCretaceous. Kukwahlulwa kwinqanaba lesikali elihambelana ne Ixesha lejoloji ukuba lixesha lesithathu nelokugqibela leMesozoic. Iqale malunga ne-145 yezigidi zeminyaka eyadlulayo kwaye yaphela malunga ne-65 yezigidi zeminyaka eyadlulayo. Eli xesha lahlulwe laziziqingatha ezibini ezaziwa njenge-Lower Cretaceous kunye ne-Upper Cretaceous. Eli lelinye lawona maxesha mide kwi-Phonerozoic eon.

Kule nqaku siza kukuxelela yonke into ofuna ukuyifumana malunga nexesha leCretaceous.

Iimpawu eziphambili 

Eli xesha linegama elivela kwisiLatin kwi eta Oko kuthetha ukuba yitshokhwe. Eli gama lisekwe kumqolo obekwe kwi-Basisi yase-Paris e-France. Ngeli xesha ubomi elwandle nasemhlabeni babonakala njengomxube weefom zangoku kunye neefom zakudala. Ihlala iminyaka emalunga nezigidi ezingama-80 malunga, lelona xesha lide kwi-Phanerozoic eon.

Njengakwiindawo ezininzi zejoloji esizifundileyo, ukuqala kweli xesha akuqinisekanga ngeminyaka ezizigidi ezimbalwa ngaphezulu okanye ngaphantsi. Zonke iziqalo kunye neziphelo zamaxesha e-geological zichongwa sisiganeko esithile esibalulekileyo sehlabathi, nokuba kungokutshintsha kwemozulu, iintyatyambo, izilwanyana okanye igeology. Ixesha lokuphela kweli xesha lichanekile malunga nesiqalo. Kungenxa yokuba ukuba utshatisa enye yeengqimba ze-geologic ezinobungqina obomeleleyo be-iridium kwaye kubonakala ngathi ziyahambelana ukuwa kwe-meteorite kwinto ngoku ehambelana ne-Yucatan Peninsula kunye neGulf of Mexico.

Le yimeteorite edumileyo enokuthi ekugqibeleni ibangele ukutshabalalisa okuninzi okwenzekileyo ekupheleni kweli xesha apho uninzi lwezilwanyana zanyamalalayo, phakathi kwazo, iidinosaurs. Esi siganeko esibaluleke kakhulu esichaza ukuphela kwexesha leMesozoic. Kusemva kweJurassic naphambi kwe- Paleocene.

Ukuma komhlaba

Ngexesha eliphakathi kweCretaceous, ngaphezulu kwesiqingatha soovimba beoyile behlabathi esele sinabo namhlanje. Uninzi lwezona ndawo zidumileyo zibekwe kufutshane nePersian Gulf nakwingingqi ephakathi kweGulf yaseMexico kunye nonxweme lwaseVenezuela.

Ngalo lonke eli xesha, inqanaba lolwandle lalinyuka ngokuqhubekayo ngenxa yokunyuka kwamaqondo obushushu ehlabathi. Oku kukhula kwathatha amanqanaba olwandle aya kwelona nqanaba liphezulu lakha labhalwa kwimbali yomhlaba wethu. Iindawo ezininzi ezazifudula ziyintlango zaba ngamathafa ayizantyalantyala zemvula. Amanqanaba olwandle afikelela kwinqanaba lokuba yi-18% yomhlaba kuphela eyayingaphezulu kwenqanaba lamanzi. Namhlanje sine-29% yommandla womhlaba ovelileyo.

I-supercontinent eyaziwa ngokuba yiPangea yahlulahlulo lonke ixesha leMesozoic ukunika amazwekazi esiwaziyo namhlanje. Izikhundla ababezigcina ngelo xesha zahluke kakhulu. Ekuqaleni kweCretaceous kwakusele kukho amazwekazi amabini amakhulu abizwa ngokuba yiLaurasia neGondwana. Ezi ndawo zimbini zikhulu zahlulwa luLwandle lwaseThetis. Ekupheleni kweli xesha amazwekazi aqala ukufumana iifom ezifanayo kakhulu nezangoku. Ukwahlulwa okuqhubekayo kwamazwekazi kubangelwe sisenzo se Ukuhamba kwelizwekazi kwaye ihamba kunye nokwenziwa kwamaqonga abanzi kunye nemifula.

Inkqubo yesiphene ebikhona kwiJurassic yangaphakathi yahlule iYurophu, iAfrika, kunye nelizwekazi laseMntla Melika. Nangona kunjalo, le mihlaba ihlala isondelene. I-Indiya neMadagascar babefuduka kunxweme lweMpuma Afrika. Esinye seziqendu ezibaluleke kakhulu zokuqhuma kwentaba-mlilo kwenzeka phakathi kokuphela kweCretaceous kunye nokuqala kwePaleocene eIndiya. Kwelinye icala, iAntarctica kunye neAustralia zazihleli kunye kwaye babehamba besuka eMzantsi Melika, besiya ngasempuma.

Zonke ezi ntshukumo zenze iindlela ezintsha zaselwandle ezinje ngeNyakatho yokuqala kunye noMazantsi eAtlantic ngokunjalo, uLwandle lweCaribbean kunye noLwandlekazi lwaseIndiya. Ngelixa uLwandlekazi lweAtlantic lwalusanda, ii-orogenies ezazenziwe ngexesha leJurassic zaqhubeka ukusuka kwintaba yaseMntla Melika ngelixa i-Nevada orogeny yayilandelwa ngamanye ama-orogenies anjengeLaramide.

Imozulu eCretaceous

Amaqondo obushushu ngeli xesha anyukele kwelona liphezulu malunga neminyaka eyi-100 yezigidi eyadlulayo. Ngelo xesha, kwakungekho zii-ice kwiipali. Izidumbu ezifunyenwe ngeli xesha zibonisa ukuba amaqondo obushushu kumphezulu wolwandle olushushu kufuneka abephakathi kwe-9 ne-12 degrees, afudumele kunangoku. Amaqondo obushushu kulwandle olunzulu kufuneka ukuba abengu-15 nange-20 degrees ngaphezulu.

Iplanethi bekungafanelanga ukuba ishushu kakhulu kunangexesha leTriassic okanye iJurassic, kodwa kuyinyani ukuba iqondo lobushushu phakathi kweepali kunye ne-Equator bekufanele ukuba belugudile. Lo mgangatho wobushushu obugudileyo ubangele ukuba imisinga yomoya weplanethi yehle kwaye inegalelo ekunciphiseni imisinga yolwandle. Ke ngoko, zininzi iilwandle ezazime nkqo kunanamhlanje.

Emva kokuba ixesha leCretaceous liphelile, amaqondo obushushu aphakathi aqala ukwehla okucothayo okwakukhawulezisa ngokuthe ngcembe kwaye kwizigidi ezidlulileyo zeminyaka umndilili wonyaka wehlile ukusuka kwi-20 ukuya kwi-10 degrees.

Iintyatyambo kunye nezilwanyana

Iziphumo ezenze ukuba umhlaba wahlulwe ube zii-12 okanye ngaphezulu komhlaba uthanda ukuthanda ukukhula kwezilwanyana nezityalo. Kula bantu, bazenzela bodwa kumazwekazi esiqithi e-Upper Cretaceous kwaye bavela ukuze bavelise okuninzi kwezinto eziphilayo zasemhlabeni nezaselwandle esizaziyo namhlanje.

Ndiyathemba ukuba olu lwazi ungafunda ngakumbi malunga nexesha leCretaceous.