Editing Plate tectonics (section)

=== Driving forces related to mantle dynamics ===
{{Main|Mantle convection}}
For much of the first quarter of the 20th century, the leading theory of the driving force behind tectonic plate motions envisaged large scale convection currents in the upper mantle, which can be transmitted through the asthenosphere. This theory was launched by [[Arthur Holmes]] and some forerunners in the 1930s<ref>{{Cite journal |last=Holmes |first=Arthur |author-link=Arthur Holmes |year=1931 |title=Radioactivity and Earth Movements |url=http://www.mantleplumes.org/WebDocuments/Holmes1931.pdf |url-status=live |journal=[[Transactions of the Geological Society of Glasgow]] |volume=18 |issue=3 |pages=559–606 |doi=10.1144/transglas.18.3.559 |s2cid=122872384 |archive-url=https://web.archive.org/web/20191009101823/http://www.mantleplumes.org/WebDocuments/Holmes1931.pdf |archive-date=2019-10-09 |access-date=2014-01-15}}</ref> and was immediately recognized as the solution for the acceptance of the theory as originally discussed in the papers of [[Alfred Wegener]] in the early years of the 20th century. However, despite its acceptance, it was long debated in the scientific community because the leading theory still envisaged a static Earth without moving continents up until the major breakthroughs of the early sixties.

Two- and three-dimensional imaging of Earth's interior ([[seismic tomography]]) shows a varying lateral density distribution throughout the mantle. Such density variations can be material (from rock chemistry), mineral (from variations in mineral structures), or thermal (through thermal expansion and contraction from heat energy). The manifestation of this varying lateral density is [[mantle convection]] from buoyancy forces.{{sfn|Tanimoto|Lay|2000}}

How mantle convection directly and indirectly relates to plate motion is a matter of ongoing study and discussion in [[geodynamics]]. Somehow, this [[energy]] must be transferred to the lithosphere for tectonic plates to move. There are essentially two main types of mechanisms that are thought to exist related to the dynamics of the mantle that influence plate motion which are primary (through the large scale convection cells) or secondary. The secondary mechanisms view plate motion driven by friction between the convection currents in the asthenosphere and the more rigid overlying lithosphere. This is due to the inflow of mantle material related to the downward pull on plates in subduction zones at ocean trenches. Slab pull may occur in a geodynamic setting where basal tractions continue to act on the plate as it dives into the mantle (although perhaps to a greater extent acting on both the under and upper side of the slab). Furthermore, slabs that are broken off and sink into the mantle can cause viscous mantle forces driving plates through slab suction.

==== Plume tectonics ====
In the theory of [[plume tectonics]] followed by numerous researchers during the 1990s, a modified concept of mantle convection currents is used. It asserts that super plumes rise from the deeper mantle and are the drivers or substitutes of the major convection cells. These ideas find their roots in the early 1930s in the works of [[Vladimir Belousov|Beloussov]] and [[Reinout Willem van Bemmelen|van Bemmelen]], which were initially opposed to plate tectonics and placed the mechanism in a fixed frame of vertical movements. Van Bemmelen later modified the concept in his "Undation Models" and used "Mantle Blisters" as the driving force for horizontal movements, invoking gravitational forces away from the regional crustal doming.{{sfn|Van Bemmelen|1976}}{{sfn|Van Bemmelen|1972}}

The theories find resonance in the modern theories which envisage [[hotspot (geology)|hot spots]] or [[mantle plumes]] which remain fixed and are overridden by oceanic and continental lithosphere plates over time and leave their traces in the geological record (though these phenomena are not invoked as real driving mechanisms, but rather as modulators).

The mechanism is still advocated to explain the break-up of supercontinents during specific geological epochs.{{sfn|Segev|2002}} It has followers amongst the scientists involved in the [[Expanding Earth|theory of Earth expansion]].{{sfn|Maruyama|1994}}{{sfn|Yuen|Maruyama|Karato|Windley|2007}}{{sfn|Wezel|1988}}

==== Surge tectonics ====
Another theory is that the mantle flows neither in cells nor large plumes but rather as a series of channels just below Earth's crust, which then provide basal friction to the lithosphere. This theory, called "surge tectonics", was popularized during the 1980s and 1990s.{{sfn|Meyerhoff|Taner|Morris|Agocs|1996}} Recent research, based on three-dimensional computer modelling, suggests that plate geometry is governed by a feedback between mantle convection patterns and the strength of the lithosphere.{{sfn|Mallard|Coltice|Seton|Müller|2016}}