Editing Continental drift (section)

=== Rejection of Wegener's theory, 1910s–1950s ===
Although now accepted, and even with a minority of scientific proponents over the decades, the theory of continental drift was largely rejected for many years, with evidence in its favor considered insufficient. One problem was that a plausible driving force was missing.<ref name="pubs.usgs.gov" /> A second problem was that Wegener's estimate of the speed of continental motion, {{cvt|250|cm/y|round=10}}, was implausibly high.<ref name="UniCalifMusPaleontology" /> (The currently accepted rate for the separation of the Americas from Europe and Africa is about {{cvt|2.5|cm/y|0}}.)<ref name="Unavco-2015" /> Furthermore, Wegener was treated less seriously because he was not a geologist. Even today, the details of the forces propelling the plates are poorly understood.<ref name="pubs.usgs.gov" />

The English geologist [[Arthur Holmes]] championed the theory of continental drift at a time when it was deeply unfashionable. He proposed in 1931 that the Earth's mantle contained convection cells which dissipated heat produced by radioactive decay and moved the crust at the surface.<ref name="Holmes-1931" /> His ''Principles of Physical Geology'', ending with a chapter on continental drift, was published in 1944.<ref name="Holmes-1944" />

Geological maps of the time showed huge [[land bridge]]s spanning the Atlantic and Indian oceans to account for the similarities of fauna and flora and the divisions of the Asian continent in the Permian period, but failing to account for glaciation in India, Australia and South Africa.<ref name="Wells-1931" />

====The fixists====
[[Hans Stille]] and [[Leopold Kober]] opposed the idea of continental drift and worked on a "fixist"<ref name="Sen30" /> [[geosyncline]] model with [[Contracting Earth|Earth contraction]] playing a key role in the formation of [[orogen]]s.<ref name="Sen28" /><ref name="Sen29" /> Other geologists who opposed continental drift were [[Bailey Willis]], [[Charles Schuchert]], Rollin Chamberlin, Walther Bucher and [[Walther Penck]].<ref name="Sen31" /><ref name="Bremer-1983">{{Cite journal|title=Albrecht Penck (1858–1945) and Walther Penck (1888–1923), two German geomorphologists|journal=[[Zeitschrift für Geomorphologie]]|last=Bremer|first=Hanna|volume=27|pages=129–138|issue=2|year=1983|doi=10.1127/zfg/27/1983/129|bibcode=1983ZGm....27..129B}}</ref> In 1939 an international geological conference was held in [[Frankfurt]].<ref name="Frankel403" /> This conference came to be dominated by the fixists, especially as those geologists specializing in tectonics were all fixists except Willem van der Gracht.<ref name="Frankel403" /> Criticism of continental drift and mobilism was abundant at the conference not only from tectonicists but also from sedimentological (Nölke), paleontological (Nölke), mechanical (Lehmann) and oceanographic ([[Carl Troll|Troll]], [[Georg Wüst|Wüst]]) perspectives.<ref name="Frankel403" /><ref name="Frankel405" /> [[Hans Cloos]], the organizer of the conference, was also a fixist<ref name="Frankel403" /> who together with Troll held the view that excepting the [[Pacific Ocean]] continents were not radically different from oceans in their behaviour.<ref name="Frankel405" /> The mobilist theory of [[Émile Argand]] for the [[Alpine orogeny]] was criticized by Kurt Leuchs.<ref name="Frankel403" /> The few drifters and mobilists at the conference appealed to [[biogeography]] (Kirsch, Wittmann), [[paleoclimatology]] ([[Kurt Wegener|Wegener, K]]), [[paleontology]] (Gerth) and [[geodesy|geodetic]] measurements (Wegener, K).<ref name="Frankel407" /> F. Bernauer correctly equated [[Southern Peninsula (Iceland)|Reykjanes]] in south-west [[Iceland]] with the [[Mid-Atlantic Ridge]], arguing with this that the floor of the Atlantic Ocean was undergoing [[extensional tectonics|extension]] just like Reykjanes. Bernauer thought this extension had drifted the continents only {{cvt|100-200|km|round=10}} apart, the approximate width of the [[Volcanism of Iceland|volcanic zone in Iceland]].<ref name="Frankel409" />

[[David Attenborough]], who attended university in the second half of the 1940s, recounted an incident illustrating its lack of acceptance then: "I once asked one of my lecturers why he was not talking to us about continental drift and I was told, sneeringly, that if I could prove there was a force that could move continents, then he might think about it. The idea was moonshine, I was informed."<ref name="McKie-2012" />

As late as 1953—just five years before [[Samuel Warren Carey|Carey]]<ref name="Carey-1958" /> introduced the theory of [[plate tectonics]]—the theory of continental drift was rejected by the physicist Scheidegger on the following grounds.<ref name="Scheidegger-1953" />
* First, it had been shown that floating masses on a rotating [[geoid]] would [[Polflucht|collect at the equator]], and stay there.  This would explain one, but only one, mountain building episode between any pair of continents; it failed to account for earlier [[Orogeny|orogenic]] episodes.
* Second, masses floating freely in a fluid substratum, like icebergs in the ocean, should be in [[Isostasy|isostatic]] equilibrium (in which the forces of gravity and buoyancy are in balance). But gravitational measurements showed that many areas are not in isostatic equilibrium.
* Third, there was the problem of why some parts of the Earth's surface (crust) should have solidified while other parts were still fluid. Various attempts to explain this foundered on other difficulties.