030111 Faults & Terrestrial Planets

030111 Faults & Terrestrial Planets - 1 03/01/11...

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1 03/01/11 Faults & Terrestrial Planets Questions to remember and contemplate (!) 1) What is tectonics? When considering the Earth, what is plate tectonics? 2) What are the surface features of planets that we can use to investigate tectonic processes and what do they tell us about terrestrial planetary tectonics? 3) What are the internal processes of planets that relate to tectonics and what do they tell us about terrestrial planetary tectonics? 4) Are the terrestrial planets tectonically active now? Whatever the answer, Why? 5) Also, if the answer is not the same for all terrestrial planets, why? Today, we will focus on observations derived from features formed directly by tectonic forces: map-scale faults and fault-related folds. The occurrence of these structures should enable us to gain a sense of the overall tectonic behavior of each planet and to speculate about the occurrence of plate tectonics on Venus & Mars. A “fault primer” is also provided at the class Blackboard site for those of you who would appreciate a review of these structures in the context of planetary tectonics. Surface Faults on Earth Concentrated at plate boundaries with important role for strike-slip faults (slides 3, 4) Continents contain fault systems spanning at least 3.5 b.y. of tectonic activity Many major normal and reverse faults have low dips and large displacements Class activity – How do we recognize the presence and displacement of map-scale faults on the Earth from only surface information? (consider Slide 24) (see also Faults Primer document) Surface faults on Mars Extensional and contractional faults are abundant on Mars (Slide 5 –about 8500 faults with >4km lengths from population of over 25,000 identified faults), but strike-slip faults rare. Maximum age of faults versus size indicates that most faults are late Noachian to middle late Hesperian in age (Slides 6, 7). Class activity – Why is it maximum age that we can determine? Why is that a limitation to knowing when faults initiated? Extensional faults (normal faults - Slides 8, 9, 11) Steeply dipping rift faults forming large graben systems (e.g., Valles Marineris). Some faults ornamented by pits, so faulting involves volume increase.
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030111 Faults & Terrestrial Planets - 1 03/01/11...

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