Bumi Bola Salji

Anggaran tempoh glasier Proterozoik.^[1] Pentarikhan glasiasi pra-Gaskier tidak pasti. Adapun Kaigas, kewujudannya diragukan oleh beberapa orang. Fasa bola salji yang lebih awal dan lebih lama, glasiasi Huron, tidak ditunjukkan.

Hipotesis Bumi Bola Salji mencadangkan bahawa permukaan Bumi menjadi sepenuhnya atau hampir sepenuhnya beku sekurang-kurangnya sekali, lebih awal daripada 650 juta tahun yang lalu. Penyokong hipotesis itu berpendapat bahawa ia terbaik menjelaskan deposit endapan yang umumnya dianggap sebagai asal usul glasiat pada palaeolatitud tropika dan ciri-ciri enigmatik lain dalam rekod geologi. Lawan pertandingan hipotesis implikasi bukti geologi untuk glasiasi global dan kemungkinan geofizik lautan atau lereng yang dilindungi^[2]^[3] dan menekankan kesukaran melarikan diri dari keadaan yang beku. Sejumlah soalan yang tidak dijawab kekal, termasuk sama ada Bumi adalah bola salji penuh, atau "slushball" dengan kumpulan khatulistiwa tipis air terbuka (atau terbuka).

Episod bola salji-Bumi berlaku sebelum radiasi tiba-tiba bioforma multiselular, yang dikenali sebagai letupan Kambria. Episod bola salji yang paling terkini mungkin telah mencetuskan evolusi multiselulariti. Satu lagi episod bola salji yang lebih awal dan lebih lama, glasiasi Huron, yang berlaku 2400 hingga 2100 juta tahun lalu, mungkin telah dicetuskan oleh penampilan pertama oksigen di atmosfera, "Peristiwa Pengoksidaan Besar".

Lihat juga sunting

Rujukan sunting

^ Smith, A. G. (2009). "Neoproterozoic timescales and stratigraphy". Geological Society, London, Special Publications. 326: 27–54. Bibcode:2009GSLSP.326...27S. doi:10.1144/SP326.2.
^ Kirschvink, J. L. (1992). "Late Proterozoic low-latitude global glaciation: The snowball Earth". Dalam Schopf, J. W.; Klein, C. (penyunting). The Proterozoic Biosphere: A Multidisciplinary Study (PDF). Cambridge University Press. m/s. 51–2.
^ Allen, Philip A.; Etienne, James L. (2008). "Sedimentary challenge to Snowball Earth". Nature Geoscience. 1 (12): 817–825. Bibcode:2008NatGe...1..817A. doi:10.1038/ngeo355.

Bacaan lanjut sunting

Tziperman, E.; Halevy, I.; Johnston, D. T.; Knoll, A. H.; Schrag, D. P. (2011). "Biologically induced initiation of Neoproterozoic snowball-Earth events". Proceedings of the National Academy of Sciences. 108 (37): 15091–15096. doi:10.1073/pnas.1016361108. PMC 3174660. PMID 21825156.
Etienne, J.L.; Allen, P.A.; Rieu, R.; Le Guerroué, E. (2007). "Neoproterozoic glaciated basins: A critical review of the Snowball Earth hypothesis by comparison with Phanerozoic glaciations". Glacial Sedimentary Processes and Products. IAS Special Publication. 39. Malden, MA: IAS/Blackwell. m/s. 343–399. doi:10.1002/9781444304435.ch19. ISBN 978-1-4051-8300-0. Unknown parameter |editors= ignored (bantuan); Unknown parameter |last-author-amp= ignored (bantuan)
Gabrielle Walker (2003). Snowball Earth. Bloomsbury Publishing. ISBN 0-7475-6433-7.
Micheels, A.; Montenari, M. (2008). "A snowball Earth versus a slushball Earth: Results from Neoproterozoic climate modeling sensitivity experiments". Geosphere. 4 (2): 401–10. doi:10.1130/GES00098.1. (Geol. Soc. America).
Roberts, J.D. (1971). "Late Precambrian glaciation: an anti-greenhouse effect?". Nature. 234 (5326): 216–7. Bibcode:1971Natur.234..216R. doi:10.1038/234216a0.
Roberts, J.D. (1976). "Late Precambrian dolomites, Vendian glaciation, and the synchroneity of Vendian glaciation". Journal of Geology. 84: 47–63. Bibcode:1976JG.....84...47R. doi:10.1086/628173.
Sankaran, A.V. (2003). "Neoproterozoic "snowball earth" and the "cap" carbonate controversy" (PDF). Current Science. 84 (7): 871. Dicapai pada 6 May 2007.
Torsvik, T.H.; Rehnström, E.F. (2001). "Cambrian palaeomagnetic data from Baltica: Implications for true polar wander and Cambrian palaeogeography". J. Geol. Soc. Lond. 158 (2): 321–9. doi:10.1144/jgs.158.2.321.

Pautan luar sunting

The Snowball Earth Diarkibkan 2010-06-13 di Wayback Machine 1999 overview by Paul F. Hoffman and Daniel P. Schrag, 8 August 1999
Snowball Earth web site Exhaustive on-line resource for snowball Earth by pro-snowball scientists Hoffman and Schrag.
New Evidence Puts 'Snowball Earth' Theory Out In The Cold sciencedaily.com. 2007. Analyses in Oman produce evidence of hot-cold cycles in the Cryogenian period, roughly 850-544 million years ago. The UK-Swiss team claims that this evidence undermines hypotheses of an ice age so severe that Earth's oceans completely froze over.
Channel 4 (UK) documentary, Catastrophe: Snowball Earth episode 2 of 5, first screened Dec 2008, documentary narrated by Tony Robinson, advocates snowball Earth and contains interviews with proponents.
First breath: Earth's billion-year struggle for oxygen New Scientist, #2746, 5 February 2010 by Nick Lane. Posits an earlier much longer snowball period, c2.4 - c2.0 Gya, triggered by the Great Oxygenation Event.
'Snowball Earth' theory melted BBC News online (2002-03-06) report on findings by geoscientists at the University of St Andrews, Scotland that casts doubt on the snowball Earth hypothesis due to evidence of sedimentary material, which could only have been derived from floating ice on open oceanic waters.
Life may have survived 'snowball Earth' in ocean pockets BBC News online (2010-12-14) report on research presented in the journal Geology by Dr Dan Le Heron (et al.) of Royal Holloway, University of London who studied rock formations in Flinders Ranges in South Australia, formed from sediments dating to the Sturtian glaciation, which bear the unmistakable mark of turbulent oceans.

[Smith2009-1] Smith, A. G. (2009). "Neoproterozoic timescales and stratigraphy". Geological Society, London, Special Publications. 326: 27–54. Bibcode:2009GSLSP.326...27S. doi:10.1144/SP326.2.

[Kirschvink1992-2] Kirschvink, J. L. (1992). "Late Proterozoic low-latitude global glaciation: The snowball Earth". Dalam Schopf, J. W.; Klein, C. (penyunting). The Proterozoic Biosphere: A Multidisciplinary Study (PDF). Cambridge University Press. m/s. 51–2.

[nature_geo-3] Allen, Philip A.; Etienne, James L. (2008). "Sedimentary challenge to Snowball Earth". Nature Geoscience. 1 (12): 817–825. Bibcode:2008NatGe...1..817A. doi:10.1038/ngeo355.

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