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| Practical Exercises |
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Exercise 1: A continental lithosphere zl km thick with a crustal thickness zc is deformed. We called fc and fl the vertical strain factors for the crust and the whole lithosphere respectively: fc, fl>1=>thickening, fc, fl<1=>thinning. Assuming that isostatic equilibrium is verified and that the surface elevation of the undeformed lithosphere is at sea level, what would be the elevation h of a thickened and a thinned lithosphere? In other terms give h as a function of the densities and thicknesses of the various relevant geological layers.
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Numerical application 1: average density of the crust ρc=2700kg.m-3; average density of the lithospheric mantle ρm=3330kg.m-3; average density of the asthenospheric mantle ρa=3310 kg.m-3; zc=40km; zl=120km; fc= fl=2.
Numerical application 2: same as above excepted that fl=1
Numerical application 3: same as abve excepted that fc=fl=0.5. We will assume here that as h drops below sea level the basin in field with sea water. Density of sea water 1030 kg.m-3. |
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Exercise 2: Determine the gravitational force that the deformed lithosphere (fc=fl=2) and the same lithosphere in an undeformed state applied to one another assuming that densities in the crust, the lithospheric mantle and asthenospheric mantle are temperature and pressure independent. Repeat the calculation for fc=2 and fl=1, then for fc=fl=0.5.
NB: Those doing the calculation by hand may assume that the density of asthenospheric and lithospheric mantle is 3330 kg.m-3. |
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| Exercise 3: Assuming lithospheric rocks have a depth independent strength of 70MPa, would the gravitational forces determined in Exercise 2 produce any lithospheric deformation? We will see later on in that course than the lithospheric strength profile is more complex. |
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| NB2: |
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