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Effect of erosion on mountain building
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  1. Effect of erosion on mountain building Background on work budget Background on erosion Erosion exercise Data analysis

  2. whatever Do fault systems evolve in order to minimize the total work? Is the Earth Lazy?

  3. 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].

  4. Forces within wedges

  5. Work terms

  6. Underthrust-Accretion Cycle • Accretion: new forethrust • Underthrusting • Accretion: new forethrust • Underthrusting

  7. Sandbox experiments • Adams et al. 2001, JSG • Particle Integrated Velocity records the development of accreting forethrust within10 cm of contraction

  8. Forethrust Model Set-Up • Simulate 0.5 cm of contraction

  9. Thrust Sheet Growth

  10. Conclusions thus far… • Sandboxes are lazy! • The Earth might be lazy. ?

  11. Equilibrium • At equilibrium the ratio of wedge thickness to wedge length is constant. • Erosion can disrupt this equilibrium

  12. Erosion • Iceland

  13. Erosion

  14. Watch Mario movie

  15. Erosion Experiment

  16. 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!