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Growth and Decay of Boundary Undulations26

Growth and Decay of Boundary Undulations26 - 12.005 Lecture...

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12.005 Lecture Notes 26 Growth and Decay of Boundary Undulations Growth: Rayleigh - Taylor Instability • salt domes • diapirs • continental delamination X 3 λ = λ 0 cos η u , u η l , l = λ 0 coskx 2 x 1 X 1 Figure 26.1 Figure by MIT OCW. General problem: topography on an interface 2 π ξ = ξ 0 cos kx 1 k = λ t / τ (1) If ρ < ρ l topography decays as ξ 0 e . u (2) If ρ > ρ l topography grows. u t / τ Initially ξ = ξ 0 e . Eventually many wavelengths interact, problem is no longer simple. Characteristic time τ depends on ρ , η u , η l , thickness of layers, …
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Figure 26.2. Subsidence due to glaciation and the subsequent postglacial rebound. Ice Sheet Before glaciation Subsidence caused by glaciation Surface after melting of the ice sheet but prior to postglacial rebound Full rebound Figure by MIT OCW. Weight of ice causes viscous flow in the mantle. After melting of ice, the surface rebounds – “postglacial rebound”.
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