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Da Terra Supercontinentes: As “Pangeas” Da Terra

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Da Terra Supercontinentes: As “Pangeas” Da Terra [60] [60] Jan. 2013 Jan. 2013 Pangeas Pangeas Supercontinentes: As “Pangeas” da Terra Supercontinentes: As “Pangeas” da Terra O que é um supercontinente? O que é um supercontinente? O termo supercontinente é utilizado pela geologia para designar grandes O termo supercontinente é utilizado pela geologia para designar grandes massas de terra emersas no planeta Terra. Eles formam-se quando os conti- massas de terra emersas no planeta Terra. Eles formam-se quando os conti- nentes se juntam, devido à movimentação de placas tectónicas, processo que nentes se juntam, devido à movimentação de placas tectónicas, processo que acontece em ciclos que duram várias centenas de milhar de anos. acontece em ciclos que duram várias centenas de milhar de anos. A Terra já presenciou o nascimento de vários supercontinentes ao longo do A Terra já presenciou o nascimento de vários supercontinentes ao longo do tempo geológico pelo que aquilo que presenciamos atualmente, quanto à for- tempo geológico pelo que aquilo que presenciamos atualmente, quanto à for- ma e posição dos continentes, já foi bem diferente no passado e prevê-se que ma e posição dos continentes, já foi bem diferente no passado e prevê-se que o seja, também, no futuro. o seja, também, no futuro. Rodínia Rodínia Há cerca de 1 100 milhões de anos (M.a.) os Há cerca de 1 100 milhões de anos (M.a.) os continentes estavam agrupados formando um continentes estavam agrupados formando um supercontinente, a Rodínia, cujas dimensões supercontinente, a Rodínia, cujas dimensões exatas e configuração não são bem conhecidas, exatas e configuração não são bem conhecidas, rodeado por um oceano, a Pantalassa. Pensa-se rodeado por um oceano, a Pantalassa. Pensa-se que a parte central deste supercontinente era que a parte central deste supercontinente era constituída pela América do Norte, cuja costa constituída pela América do Norte, cuja costa oriental se ligava à parte ocidental da América do oriental se ligava à parte ocidental da América do Sul. A parte oeste da América do Norte estava Sul. A parte oeste da América do Norte estava conectada com a Austrália e com a Antárctica. conectada com a Austrália e com a Antárctica. A Rodínia era uma terra gelada e hostil. Esta terá A Rodínia era uma terra gelada e hostil. Esta terá sobrevivido cerca de 350 M.a., tendo sido vítima sobrevivido cerca de 350 M.a., tendo sido vítima da dinâmica interna da Terra que a quebrou e da dinâmica interna da Terra que a quebrou e subdividiu, primeiramente em três continentes. subdividiu, primeiramente em três continentes. Pangea Pangea Formou-se no Paleozóico e há 237 M.a., no fim Formou-se no Paleozóico e há 237 M.a., no fim do Pérmico/início do Triássico, começou sua do Pérmico/início do Triássico, começou sua fragmentação, originando dois supercontinentes, fragmentação, originando dois supercontinentes, a Laurásia e a Gondwana, que foram rodeados a Laurásia e a Gondwana, que foram rodeados pelo mar de Tétis. Essa fragmentação prosse- pelo mar de Tétis. Essa fragmentação prosse- guiu até os continentes atingirem a posição atual. guiu até os continentes atingirem a posição atual. Amásia Amásia Supõe que embarcaste numa máquina do Supõe que embarcaste numa máquina do tempo para daqui a 250 M.a. O Homem há tempo para daqui a 250 M.a. O Homem há muito que se extinguiu mas a Terra está muito que se extinguiu mas a Terra está ativa e irreconhecível! ativa e irreconhecível! Os continentes estão de novo unidos for- Os continentes estão de novo unidos for- mando uma massa continental gigantesca mando uma massa continental gigantesca cercada por um mar global. cercada por um mar global. A Amásia é o suposto supercontinente que A Amásia é o suposto supercontinente que se poderá formar daqui a 250 milhões de se poderá formar daqui a 250 milhões de anos. Este supercontinente foi descrito por anos. Este supercontinente foi descrito por Chris Hartnady e Paul Hoffman, em 1992. Chris Hartnady e Paul Hoffman, em 1992. Este supercontinente do futuro não será o último, uma vez que os geólogos Este supercontinente do futuro não será o último, uma vez que os geólogos suspeitam que estas grandes massas continentais se formam a cada 500 ou suspeitam que estas grandes massas continentais se formam a cada 500 ou 700 milhões de anos. 700 milhões de anos. Sabias que… Sabias que… Devido à grande dinâmica da Terra, pressupõe-se que a Devido à grande dinâmica da Terra, pressupõe-se que a Rodínia e a Pangeia não tenham sido os únicos supercon- Rodínia e a Pangeia não tenham sido os únicos superconti- tinentes a formarem-se no passado da Terra. nentes a formarem-se no passado da Terra. A lista inclui: A lista inclui: Vaalbara (4000 milhões de anos): Vaalbara (4000 milhões de anos): Kenorland (2700 milhões de anos); Kenorland (2700 milhões de anos); Columbia (1700 milhões de anos); Columbia (1700 milhões de anos); Pannótia (600 milhões de anos). Pannótia (600 milhões de anos). Afinal… sempre é verdade: nada se perde, tudo se transforma! Afinal… sempre é verdade: nada se perde, tudo se transforma! Trabalho realizado por: Trabalho realizado por: Cristiana Macedo Cristiana Macedo João Gomes João Gomes Miguel Laranjeira Miguel Laranjeira Pedro Azevedo Pedro Azevedo Sandra Ascenção Sandra Ascenção 12ºC (Jan. 2013) 12ºC (Jan. 2013) http://vsites.unb.br/ig/glossario/verbete/rodinia.htm http://vsites.unb.br/ig/glossario/verbete/rodinia.htm http://www.cienciahoje.pt/index.php?oid=49597&op=allhttp:// pt.wikipedia.org/wiki/Supercontinente http://www.cienciahoje.pt/index.php?oid=49597&op=allhttp:// pt.wikipedia.org/wiki/Supercontinente .
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