Terrestrial planet evolution—The importance of adaptive behaviour

• Published in: Physics and chemistry of the earth Vol. 23; no. 7; pp. 831 - 840
• Main Author: Tozer, D.C.
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 1998
• ISSN: 0079-1946; 1879-3568
• DOI: 10.1016/S0079-1946(98)00097-4

With its self-contradictory emphasis on ‘rigid’ plates, the plate tectonic account of current endogenous geotectonic activity has greatly muddled the point that such activity in any terrestrial planet's surface rocks only continues for as long as internal heat transfer can induce an irrecoverable deformability in rocks too cold to have a significant intrinsic deformability. This paper explores the inconsistencies that exist between this tectonic manifestation of internal heat transfer and deeply entrenched views on planetary thermal history and the cause of volcanism. The difficulties are seen to arise from previous neglect of the ability of planetary heat transfer to regulate the properties of the media it involves. Such ‘adaptive’ behaviour includes one of regulating the capacity of planetary shell material to retain volatiles like water and carbon dioxide which can greatly increase the deformability of rocks. It is suggested that Venus is a planet where a major greenhouse effect has interfered with such ‘adaptive’ behaviour, and Earth's prolonged tectonic history is attributed to it being as yet just too far from the Sun to suffer a similar devolatilisation of its shell material. An essential element in my account is the attribution of magmatism to shear instabilities and the consequent unrepresentativeness of magma temperatures as an indicator of horizontally averaged internal temperatures in any terrestrial planet.