Literature

Box Canyon in Idaho, US, is an amphitheatre-headed canyon that is a classic example of its type. With no obvious flow of water into the canyon, geomorphologists in the past have looked at possible mechanisms of erosion and have come up with groundwater seepage. The idea was that groundwater flows were high enough to weaken the rock and to give loose particles sufficient movement to commence canyon formation. However, recent research has shifted the emphasis from slow erosion processes to something catastrophic.

"We fully expected to find Box Canyon was carved by groundwater, but then all the evidence we found pointed at a megaflood," said Michael Lamb, a geomorphologist at the University of California, Berkeley. [. . .] "The entire canyon seems to have been cut out of the earth by this flood," Lamb said. Although hardened lava, or basalt, is hard, "it's very fractured material. When lava cools, it contracts and cracks just like mud does. All this cracking makes the basalt like a pile of stacked blocks. So while small floods might cause little erosion, a large enough flood can pull these blocks out of place."

High-resolution topographic map of Box Canyon, Idaho. (Image credit: Michael P. Lamb and New Scientist. Larger image.)

What stimulated a rethink about Box Canyon was a critical evaluation of the favoured model:

"But when Lamb and his colleagues looked closer, the sapping hypothesis fell apart. Their calculations indicate that flowing spring water is too feeble by a factor of 22 to move the existing bouldery rubble downstream and make room for more. Moreover, spring water is chemically incapable of eroding the rubble by dissolution. And rock dating showed that erosion of the canyon's head wall ceased 45,000 years ago - further evidence that the present water flow isn't up to the job of cutting a canyon."

Fortified by this scepticism, the researchers looked again at the field evidences. Three features at the canyon head convinced them that surface water once flowed into the canyon and that the timescale for formation was only 35 to 160 days.

"First, three concentric semicircles of boulders within the canyon head appear to be waterfall plunge pools with ~2 m of relief. Second, a small notch (~300 m3) in the center of the headwall rim has linear flutelike abrasion marks, millimeters in width and several centimeters long, that follow the local curvature of the notch, indicating past overspill. The scours appear as divots on the inferred upstream end that gradually fan outward and diminish in relief downstream. Third, this scoured rock extends at least 1 km upstream of the canyon head and delineates flow toward the canyon."

The new mechanism brings a paradigm shift to geomorphological thinking about all box canyons. This includes Mars - which has numerous examples of these structures. This is a potential problem for those who are seeking evidences for past life on Mars. Richard Kerr comments: "If martian canyons were gouged out only by rare floods rather than many millennia of slow seepage, Mars may have lacked the continually warm and wet climate needed for the origin and evolution of life." In other words, the quiet warm pools may not have existed: just raging infernos over very short timescales.

However, the idea that a "continually warm and wet climate [is] needed for the origin and evolution of life" is not a scientific statement. We have no evidence that favours the idea that a warm pool can provide the conditions for the spontaneous formation of life. Indeed, all the evidence we have favours the opposite conclusion: whatever chemicals are in the pool, the outcome will be a state of equilibrium rather than an event of extraordinarily low probability. Despite all the discussion over past years, there is still no apparent appreciation of the central issue of generating biologically meaningful information.

One last thought: the researchers have made their breakthrough after realising that the proposed mechanisms for forming box canyons were inadequate. Then they went out to search for new data that would lead them to more satisfying solutions. This is where many of us are with Darwinism. We do not find the proposed mechanisms convincing and we have looked again at the data to find more satisfying solutions. It has led us to a paradigm shift which, we argue, operates within the realm of science.

Formation of Box Canyon, Idaho, by Megaflood: Implications for Seepage Erosion on Earth and Mars
Michael P. Lamb, William E. Dietrich, Sarah M. Aciego, Donald J. DePaolo, and Michael Manga.
Science 320, 23 May 2008: 1067-1070.

Abstract: Amphitheater-headed canyons have been used as diagnostic indicators of erosion by groundwater seepage, which has important implications for landscape evolution on Earth and astrobiology on Mars. Of perhaps any canyon studied, Box Canyon, Idaho, most strongly meets the proposed morphologic criteria for groundwater sapping because it is incised into a basaltic plain with no drainage network upstream, and approximately 10 cubic meters per second of seepage emanates from its vertical headwall. However, sediment transport constraints, 4He and 14C dates, plunge pools, and scoured rock indicate that a megaflood (greater than 220 cubic meters per second) carved the canyon about 45,000 years ago. These results add to a growing recognition of Quaternary catastrophic flooding in the American northwest, and may imply that similar features on Mars also formed by floods rather than seepage erosion.

See also:

Chandler, D.L. Earth canyon hints at ancient megafloods on Mars, NewScientist.com, 22 May 2008.

Choi, C.Q. Ancient Flash Floods Sculpted Earth, Mars, Space.com,, 22 May 2008.

Kerr, R.A. Martian Canyons by a Trickle or a Gush? ScienceNOW Daily News, 22 May 2008.