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Effect of erosion on mountain building Background on work budget Background on erosion Erosion exercise Data analysis
whatever Do fault systems evolve in order to minimize the total work? Is the Earth Lazy?
Evidence of lazy Earth Geometry of spreading centers [Sleep, 1979] and mudcracks reflects work minimization • Faults become more smooth with greater slip • Strike-slip traces [e.g. Wesnousky, 1988], extensional fault traces [Gupta et al., 1998], and lab [Scholz, 1990].
Underthrust-Accretion Cycle • Accretion: new forethrust • Underthrusting • Accretion: new forethrust • Underthrusting
Sandbox experiments • Adams et al. 2001, JSG • Particle Integrated Velocity records the development of accreting forethrust within10 cm of contraction
Forethrust Model Set-Up • Simulate 0.5 cm of contraction
Conclusions thus far… • Sandboxes are lazy! • The Earth might be lazy. ?
Equilibrium • At equilibrium the ratio of wedge thickness to wedge length is constant. • Erosion can disrupt this equilibrium
Erosion • Iceland
Implications • After erosion the wedge thickens rather than lengthening. Can accommodate contraction efficiently along the old faults • On the non-erosion side, wedge must constantly lengthen because the old faults are buried under heavy sand. • Fault system adjusts to slip along the most efficient path <- earth is lazy!