HR: 09:45h
AN: P31A-08    [PDF]
TI: Investigation of the Cooling Capacity of Plate Tectonics and Flood Volcanism in the Evolution of Earth, Mars and Venus
AU: * van Thienen, P
EM: thienen@geo.uu.nl
AF: Department of Theoretical Geophysics, Utrecht University, P.O. Box 80021, Utrecht, 3508 TA Netherlands
AU: Vlaar, N J
EM: vlaar@geo.uu.nl
AF: Department of Theoretical Geophysics, Utrecht University, P.O. Box 80021, Utrecht, 3508 TA Netherlands
AU: van den Berg, A P
EM: berg@geo.uu.nl
AF: Department of Theoretical Geophysics, Utrecht University, P.O. Box 80021, Utrecht, 3508 TA Netherlands
AB: The cooling of the terrestrial planets from their presumed hot initial states to the present situation has required the operation of one or more efficient cooling mechanisms. In the recent history of the Earth, plate tectonics has been responsible for most of the planetary cooling. The high internal temperature of the early Earth, however, prevented the operation of plate tectonics because of the greater inherent buoyancy of thicker oceanic lithosphere (basaltic crust and depleted mantle) produced from a hotter mantle. A similar argument is valid for Venus, and also for Mars. An alternative cooling mechanism may therefore have been required during a part of the planetary histories. Starting from the notion that all heat output of planets is through their surfaces, we have constructed two parametric models to evaluate the cooling characteristics of two cooling mechanisms: plate tectonics and basalt extrusion / flood volcanism. We have applied these models to the Earth, Mars and Venus for present-day and presumed early thermal conditions. Our model results show that for a steadily (exponentially) cooling Earth, plate tectonics is capable of removing all the required heat at a rate comparable to or even lower than its current rate of operation during its entire history, contrary to earlier speculations. The extrusion mechanism may have been an important cooling agent in the early Earth, but requires global eruption rates two orders of magnitude greater than those of known Phanerozoic flood basalt provinces. This may not be a problem, since geological observations indicate that flood volcanism was both stronger and more ubiquitous in the early Earth. Because of its smaller size, Mars is capable of cooling conductively through its lithosphere at significant rates. As a result may have cooled without an additional cooling mechanism during its entire history. Venus, on the other hand, has required the operation of an additional cooling agent for probably every cooling phase of its possibly episodic history, with rates of activity comparable to those of the Earth.
DE: 3210 Modeling
DE: 5418 Heat flow
DE: 5455 Origin and evolution
DE: 5475 Tectonics (8149)
DE: 5480 Volcanism (8450)
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting