O modelo criacionista de novo no pedaço: cânion formado rapidamente em 3 dias

segunda-feira, junho 21, 2010

Canyon Carved in Just Three Days in Texas Flood: Insight Into Ancient Flood Events on Earth and Mars

ScienceDaily (June 20, 2010) — In the summer of 2002, a week of heavy rains in Central Texas caused Canyon Lake -- the reservoir of the Canyon Dam -- to flood over its spillway and down the Guadalupe River Valley in a planned diversion to save the dam from catastrophic failure. The flood, which continued for six weeks, stripped the valley of mesquite, oak trees, and soil; destroyed a bridge; and plucked meter-wide boulders from the ground. And, in a remarkable demonstration of the power of raging waters, the flood excavated a 2.2-kilometer-long, 7-meter-deep canyon in the bedrock.

According to a new analysis of the flood and its aftermath -- performed by Michael Lamb, assistant professor of geology at the California Institute of Technology (Caltech), and Mark Fonstad of Texas State University -- the canyon formed in just three days.

A paper about the research appears in the June 20 advance online edition of the journal Nature Geoscience.

Our traditional view of deep river canyons, such as the Grand Canyon, is that they are carved slowly, as the regular flow and occasionally moderate rushing of rivers erodes rock over periods of millions of years.

Read more here/Leia mais aqui: Science Daily


Nature Geoscience
Published online: 20 June 2010 | doi:10.1038/ngeo894

Rapid formation of a modern bedrock canyon by a single flood event

Michael P. Lamb1 & Mark A. Fonstad2

Deep river canyons are thought to form slowly over geological time (see, for example, ref. 1), cut by moderate flows that reoccur every few years2, 3. In contrast, some of the most spectacular canyons on Earth and Mars were probably carved rapidly during ancient megaflood events4, 5, 6, 7, 8, 9, 10, 11, 12. Quantification of the flood discharge, duration and erosion mechanics that operated during such events is hampered because we lack modern analogues. Canyon Lake Gorge, Texas, was carved in 2002 during a single catastrophic flood13. The event offers a rare opportunity to analyse canyon formation and test palaeo-hydraulic-reconstruction techniques under known topographic and hydraulic conditions. Here we use digital topographic models and visible/near-infrared aerial images from before and after the flood, discharge measured during the event, field measurements and sediment-transport modelling to show that the flood moved metre-sized boulders, excavated ~7 m of limestone and transformed a soil-mantled valley into a bedrock canyon in just ~3 days. We find that canyon morphology is strongly dependent on rock type: plucking of limestone blocks produced waterfalls, inner channels and bedrock strath terraces, whereas abrasion of cemented alluvium sculpted walls, plunge pools and streamlined islands. Canyon formation was so rapid that erosion might have been limited by the ability of the flow to transport sediment. We suggest that our results might improve hydraulic reconstructions of similar megafloods on Earth and Mars.

1. California Institute of Technology, Geological and Planetary Sciences, 1200 E. California Blvd., Pasadena, California 91125, USA

2. Texas State University, Department of Geography, 601 University Dr., San Marcos, Texas 78666, USA

Correspondence to: Michael P. Lamb1 e-mail: mpl@gps.caltech.edu


Subscription or payment needed/Requer assinatura ou pagamento: Nature Geoscience


The Grand Canyon Image Gallery - Live Science



Gente, alguém me belisque, nem estou acreditando no que leio na literatura científica especializada, mas em menos de uma semana, o modelo do criacionismo (pseudociência) 'lança luz' (eu não pude resistir...) na explicação de eventos sobre a realidade. Será que deu a louca na Nomenklatura científica? Ou será que são rumores de anjos na epistemologia?

Eu queria ver a cara da Galera dos meninos e meninas de Darwin: o modelo criacionista servindo de referencial teórico em biologia evolutiva e em geologia? Cruz, credo! Darwin (agnóstico -- ateu que não saiu do armário por conveniência) uma hora dessas já deve estar todo borrado no seu túmulo na Abadia de Westminster (que sacrilégio contra o homem que teve a maior ideia que toda a humanidade já teve).

Charles Lyell, onde foi que você errou com sua geologia uniformitarista??? O presente é a chave do passado??? É mesmo? Me engana que eu gosto...

Fui, nem sei por que, rindo da cara Nomenklatura científica que parece ter perdido de vez o Norte epistêmico... Ué, será que eu exagerei na dose de ironia???