Editing Plate tectonics (section)

=== Continental drift ===
{{Further|Continental drift}}
In the late 19th and early 20th centuries, geologists assumed that Earth's major features were fixed, and that most geologic features such as basin development and mountain ranges could be explained by vertical crustal movement, described in what is called the [[geosyncline|geosynclinal theory]]. Generally, this was placed in the context of a contracting planet Earth due to heat loss in the course of a relatively short geological time.
[[File:Wegener Expedition-1912 008.jpg|thumb|Alfred Wegener in Greenland in the winter of 1912–13]]
It was observed as early as 1596 that the opposite [[coasts]] of the Atlantic Ocean—or, more precisely, the edges of the [[continental shelves]]—have similar shapes and seem to have once fitted together.{{sfn|Kious|Tilling|1996}}

Since that time many theories were proposed to explain this apparent complementarity, but the assumption of a solid Earth made these various proposals difficult to accept.{{sfn|Frankel|1987}}

The discovery of [[radioactivity]] and its associated [[exothermic|heating]] properties in 1895 prompted a re-examination of the apparent [[age of Earth]].{{sfn|Joly|1909}} This had previously been estimated by its cooling rate under the assumption that Earth's surface radiated like a [[black body]].{{sfn|Thomson|1863}} Those calculations had implied that, even if it started at [[thermal radiation|red heat]], Earth would have dropped to its present temperature in a few tens of millions of years. Armed with the knowledge of a new heat source, scientists realized that Earth would be much older, and that [[Earth's core|its core]] was still sufficiently hot to be liquid.

By 1915, after having published a first article in 1912,{{sfn|Wegener|1912}} Alfred Wegener was making serious arguments for the idea of continental drift in the first edition of ''The Origin of Continents and Oceans''.{{sfn|Wegener|1929}} In that book (re-issued in four successive editions up to the final one in 1936), he noted how the east coast of [[South America]] and the west coast of [[Africa]] looked as if they were once attached. Wegener was not the first to note this ([[Abraham Ortelius]], [[Antonio Snider-Pellegrini]], [[Eduard Suess]], [[Roberto Mantovani]] and [[Frank Bursley Taylor]] preceded him just to mention a few), but he was the first to marshal significant [[fossil]] and paleo-topographical and climatological evidence to support this simple observation (and was supported in this by researchers such as [[Alex du Toit]]). Furthermore, when the rock [[stratum|strata]] of the margins of separate continents are very similar it suggests that these rocks were formed in the same way, implying that they were joined initially. For instance, parts of [[Scotland]] and [[Ireland]] contain rocks very similar to those found in [[Newfoundland and Labrador|Newfoundland]] and [[New Brunswick]]. Furthermore, the [[Caledonian Mountains]] of Europe and parts of the [[Appalachian Mountains]] of North America are very similar in [[Structural geology|structure]] and [[lithology]].

However, his ideas were not taken seriously by many geologists, who pointed out that there was no apparent mechanism for continental drift. Specifically, they did not see how continental rock could plow through the much denser rock that makes up oceanic crust. Wegener could not explain the force that drove continental drift, and his vindication did not come until after his death in 1930.<ref>{{Cite web |title=Pioneers of Plate Tectonics |url=https://www.geolsoc.org.uk/Plate-Tectonics/Chap1-Pioneers-of-Plate-Tectonics/Alfred-Wegener |url-status=live |archive-url=https://web.archive.org/web/20180323155937/https://www.geolsoc.org.uk/Plate-Tectonics/Chap1-Pioneers-of-Plate-Tectonics/Alfred-Wegener |archive-date=23 March 2018 |access-date=23 March 2018 |website=[[The Geological Society]]}}</ref>