GL 107 Earth Systems Science

K. Hannula

Discussion questions for 10/8/07

1.  What is the difference between ductile and brittle deformation?  At what conditions do rocks deform in a brittle manner?

Brittle deformation: rocks crack and break, forming faults.  Brittle deformation occurs at cold temperatures, near Earth's surface.

Ductile deformation:  rocks bend and flow, forming folds and foliations.  Ductile deformation occurs at warm temperatures (but below the melting point of rocks), deeper in the crust and in the mantle.

2.  Define the following terms:

3.  (Specific answer is not in book) Durango lies on the northern edge of the San Juan Basin.  What does that mean about the shape of the local rock layers?

The rock layers in Durango all tilt downwards to the south, and dive underneath younger rocks in the San Juan Basin in southern Colorado and northern New Mexico.

4.  Define the following terms:

5.  In what tectonic setting do normal faults typically form?

Divergent plate boundaries and continental rifts.

6.  In what tectonic setting do thrust faults typically form?

Convergent plate boundaries.