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Patrice Rey Room: 407 [email protected] Tel: 12060 •Lecturers are guides, they open doors and show paths to knowledge... …but it’s up to you to do the journey. •Consider lectures and practical classes for what they really are: introductions to knowledge. •1 hour of lecture should be followed by 2 hours of work involving reading and synthesizing information gathered from textbooks and other resources. Use the web and make the library your second home! •Become an independent learner. •Do not work alone. •There is no bad students, only bad learning habits. •Most importantly: Get organized, work steadily, and have fun! Lecture 1: Lithosphere, asthenosphere, and Archimedes (287212 BC) Aims: A brief reminder about he earth and lithospheric plates Structural geology deals with deformation of earth materials: From minerals to tectonic plates • ~15 plates travel at the surface of the earth @ a speed of a few cm/y • Plates travel at various speed and in various direction ...=> • …seismicity and deformation at plates boundaries Plate boundaries features • Topography Plate boundaries features • Seismicity Plate boundaries features • Volcanism Australian plate Plate tectonics and things that happen @ plate boundaries Divergent plate boundaries Convergent plate boundaries Transform fault, and strike slip fault boundaries Transform fault, and strike slip fault boundaries Earth’s structure Continental lithosphere: Some physical characteristics Temperature Radiogenic upper crust Radiogenic elements U, Th, K Continental lithosphere: Some physical characteristics Density Density lithosphere ? (zc/zl)*rc+(zlm/zl)*rlm Isostasy and surface topography Isostasy and surface topography Isostasy: A surface exists at a certain depth where the pressure, from the column of earth material above, is the same across and underneath the surface. Continental lithosphere: Some physical characteristics Strength •Strong upper crust •Weak upper crust •Strong upper mantle •Weak lower lithospheric mantle •Very weak asthenosphere Lecture 1 at a glance ~15 plates move at the surface of the earth. Plate boundaries: locus of seismicity +/- magmatic activities, and high topography. Divergent, convergent, and transform plate boundaries. Lithospheric plates: oceanic lithosphere only, or both oceanic and continental lithosphere, they float on the asthenosphere. •Thickness Continental lithosphere: 180 +/- 100 km thick; Oceanic lithosphere: 0-100 km Continental crust: 35+/-10 km; Oceanic crust: 5-7 km •Temperature Temperature at continental Moho: 500+/-150ºC Temperature at base of lithosphere: 1300 +/-100ºC •Density Density continental crust: 2800 +/-100 kg.m-3 Density lithospheric mantle: 3350 +/-100 kg.m-3 Density asthenosphere: 3300 +/-100 kg.m-3 •Strength of continental lithosphere Strong upper crust, weak lower crust, strong upper mantle, weak lower lithospheric mantle, very weak asthenosphere.