JOURNAL OF QUATERNARY SCIENCE (2010) 25(5) 824–825Copyright � 2010 John Wiley & Sons, Ltd.Published online 12 March 2010 in Wiley InterScience(www.interscience.wiley.com) DOI: 10.1002/jqs.1374

Correspondence

Reply: Defending and testinghypotheses: a response to JohnShaw’s paper ‘In defence of themeltwater (megaflood)hypothesis for the formation ofsubglacial bedform fields’

JOHN SHAW (2010)Journal of Quaternary Science 25: 249–260

In response to Evans’ criticism on my science, I first point outperceptual problems in his comment, whereby he gives falseaccounts of my research by twisting its meaning. For example,he writes:

According to Shaw (2010), the detailed glacial geomorphologypresented by Evans et al. (2006, 2008) is merely a ‘backcloth’.In fact, I wrote the opposite:

Consequently, deposition and glaciotectonic thrusting, fold-ing and faulting were merely backcloths to much landscapeevolution; they give information on events that precededpresent-day geomorphology. (Shaw, 2010)

Furthermore, I fail to see how he arrives at the conclusionthat this statement implies that glacial geomorphologists work-ing in Western Canada must view the glacial landscape asresulting from a flood. How could I insist that others adoptmy interpretation? (my italics throughout this reply).

In another misrepresentation, I did not write that Evans et al.(2006, 2008) missed the point because sediments in glaciallandforms were truncated by the flood. I suggested that theymissed the point because, whether or not there were floods,the sediment is truncated and the landforms are erosional.

Again, despite Evans’ assertion, I did not revoke any notion thatsubglacial deformation operates at the base of glaciers; for me tothink so would be idiotic in light of much theory and many obser-vations of deformation beneath glaciers and ice sheets (e.g.Clarke, 2005). Incredibly, he asks why I totally exclude subgla-cial deformation in my interpretation of subglacial landforms.Evidently, he overlooked my discussion of this topic with respectto the Schiller and Blackspring fluting, sediment transport in flowpaths, and groove-ploughing.

Evans returns yet again to hypothesis testing, stressing oncemore the roles of falsification and ad hoc protection devices.He alleges that, because the meltwater hypothesis is unfalsifi-able, it cannot be a true hypothesis. But Evans et al. (2006,p. 1643) claimed to have falsified the hypothesis on the basisof cross-cutting lineations! He remains adamant that testing ahypothesis ‘involves the identification of observations that have

the potential to prove it wrong’. He acknowledges no alternative.However, Kuhn (1967, p. 145), for example, argued that no the-ory ever solves all the puzzles with which it is confronted andconcluded that, according to falsification, any failure calls forthe rejection of a theory; therefore, all theories should berejected. Kuhn went on to suggest a more pragmatic test wherebytwo theories (hypotheses) are compared (p.145):

It makes a great deal of sense to ask which of two actual andcompeting theories fits the facts better.

This is precisely the test I used to compare the explanatorypower of the glacial and meltwater hypotheses.

In terms of this test, Evans appears to support the meltwaterhypothesis, conceding that proponents of the megaflood theorypresent an explanation that is unquestionably consistent withtheir chosen observations. He claims, however, that thisrelationship arises only because we constantly create ad hocprotection devices, presumably ad hoc hypotheses, to accom-modate anomalous observations. Rather than constantly call-ing for ad hoc hypotheses, in the last 25 years we haveadded just one: direct erosion by meltwater.

Why would defending the megaflood hypothesis becounterproductive when Evans et al. (2006, 2008 subject it toharsh assessment? Naturally, I responded to this unwarrantedcriticism. If anything, this discussion is counterproductive.

Some modern glacial landscapes compare closely to Qua-ternary glacial landscapes and, by analogy, they provide excel-lent models of landscape evolution. In viable models, the twolandscapes must be similar. But Benn and Evans (2006) used anIcelandic glacial landscape to model a Quaternary Prairie land-scape with virtually no resemblance between the two; that is,there is no analogy (see Shaw, 2010, Fig. 4).

In conclusion, Evans first parades his familiar barb that themegaflood hypothesis is ‘outrageous’. I have nothing more tosay on this topic than we have said before (see Shaw andMunro-Stasiuk, 2006). He then dismissively describes thescience in Shaw (2010) as ‘hypothesis defending’, as thoughthis were a novel insight. What else could it be about? The titlereads ‘In defence of the meltwater (megaflood) hypothesis . . .’Finally, though hypothesis testing is the principal method I usedto compare hypotheses, Evans concludes speciously that thereis no testing in Shaw (2010).

References

Benn DI, Evans DJA. 2006. Subglacial megafloods: outrageoushypothesis or just outrageous? In: Glacier Science and EnvironmentalChange, Knight PG (ed.). Blackwell: Oxford: 42–46.

Clarke GKC. 2005. Subglacial Processes. Annual Review of Earth andPlanetary Sciences 33: 247–276.

Evans DJA, Rea BR, Heimstra JF, O Cofaigh C. A critical assessment ofsub-glacial megafloods: a case study of subglacial sediments andlandforms in south-central Alberta. Quaternary Science Reviews 25:1638–1667.

Evans DJA, Clark CD, Rea BR. 2008. Landform and sediment imprintsof fast glacier flow in the southwest Laurentide Ice Sheet. Journal ofQuaternary Science 23: 249–272.

Kuhn TS. 1967. The Structure of Scientific Revolutions. University ofChicago Press: Chicago, IL.

Shaw J. 2010. In defence of the meltwater (megaflood) hypothesis forthe formation of subglacial bedform fields. Journal of QuaternaryScience 25: 249–260.

Shaw J, Munro-Stasiuk M. 2006. Reply to Benn and Evans. In GlacierScience and Environmental Change, Knight PG (ed.) Blackwell:London; 46–50.

JOHN SHAWFaculty of Science, University of Alberta Edmonton,

Alberta, Canada

CORRESPONDENCE 825

Copyright � 2010 John Wiley & Sons, Ltd. J. Quaternary Sci., Vol. 25(5) 824–825 (2010)