turcotte and schubert geodynamics solutions

The obtained vector maps of the horizontal gradients of the anomalous density of the threedimensional model, built using the parameters of the Earth’s gravity field, are compared with the velocities of the mantle currents of the continental drift model and tangential mass forces. The reason for these geodynamic processes is the heterogeneous mass distribution, which is reflected in horizontal density gradients. If the confining pressure of rock is near the brittle strength of the rock, a transition from brittle to ductile behavior will occur.It is shown and quantitatively substantiated that the source of forces and energy necessary for the movement of continents can be mantle convection and tangential mass forces formed as a result of the Earth’s rotational regime. In determining the transition from brittle to ductile behavior, pressure, temperature, and strain rate are important. The mechanical aspects of faulting are discussed in the next chapter.Īlthough fracture is important in shallow crustal rock at low temperatures and pressures, there are many circumstances in which rock behaves as a ductile material. Faults also occur on all scales examples of faults have already been given in Figures 1–58 and 4–34 b and another example is given in Figure 7–3. Columnar jointing in basaltic lava flows (Figure 7–1) and parallel jointing in granitic rocks (Figure 7–2) are examples.įaults are fractures along which there has been relative displacement. Igneous rocks often develop joints as a result of the thermal stresses associated with cooling and contraction. These processes in turn enhance the visibility of the jointing. The breakdown of surface rocks by erosion and weathering is often controlled by systems of joints along which the rocks are particularly weak and susceptible to disintegration and removal.

Joints are commonly found in sets defining parallel or intersecting patterns of failure related to local stress orientations. They occur on all scales in both sedimentary and igneous rocks. Cracks or fractures in rock along which there has been little or no relative displacement are known as joints. At atmospheric pressure and room temperature most rocks are brittle that is, they behave nearly elastically until they fail by fracture.

Turcotte and schubert geodynamics solutions