Energetics of the Earth: Mountain Building

1. Energetics of the Earth:Mountain Building Theresa Zajac, Haiyan Fu

2. Mountain Building model The Solar System began to form about 6 billion years ago and the Earth and other planetsabout 4.5 billion years ago. mountain building events expend energy on time scales of several hundred million years. whereas others, like earthquakes, expend energy on time scales of a few seconds Time Scales

3. Energy Source Mountain Building: Heat & Mechanical Energy First, is mountain building resulting primarily from heat. The uplift comes because heat from inside the earth heats the overlying lithosphere, causing it to expand, lifting and swelling the surface upward. Second is mechanical mountain building. tension (pulling apart) and compression (squeezing together). The relief (differences in elevation) come primarily because different blocks of earth move relative to each other, either falling or rising vertically, or one block being shoved (thrust) horizontally over another. The overall balance of energy in a steady state FTB:

4. Mechanical Energy The static equilibrium equation: Schematic cross -section of a critically tapered steady state fold-and-thrust belt(DahlenF.A,1988) WB: the rate of work on the base and front of the FTB WD: the rate energy is dissipated against friction on the decollement fault WS: the rate energy is dissipated by internal frictional processes within the deforming brittle wedge WG: the rate of work against gravitational body forces

5. Heat Budget Schematic cross section of a steady state FTB and underlying subducting plate(Barr T.D,1989 ) QT: total rate at which heat is conducted out of the top of the Wedge QB: the total rate at which heat is conducted into the base of the wedge from the top of the basal decollement fault QA: the total rate which heat is advected into the wedge across all the boundaries HR: total rate of radiogenic heating HS:thetotal rate of internal strain heatin