|
Clerical:
Reminder: Exam #1 is next Tuesday (2/8/11). The Exam #1 Study Guide is posted.
Quizzes 1-4 are due by 3:00pm on Tuesday (2/8/11).
Themes of the Day:
Stress & Strain
- Stress - force applied per unit area - Three Types
- compressive
- tensional
- shear
- Strain - deformation of a material as a result of applied stress
- elastic - completely recoverable when stress is removed
- yield point - boundary between elastic and plastic behavior
- plastic - permanent (ductile) deformation imparted
- fracture - brittle failure - permanent and unrecoverable
- Type of behavior is influened by:
- Rock Composition (e.g., calcite in limestone and marble deforms in a ductile manner under the same conditions that quartz and feldspar in a granite deform in a brittle manner)
- Temperature and Pressure - High T, P favor ductile behavior (e.g., earthquakes - brittle behavior - are most common in the shallow crust - < 15 km deep)
- Strain Rate - faster fosters brittle behavior, slower fosters ductile behavior
Folds
- Plastic deformation - more common deep in the crust or as a result
of low strain rates
- Best seen in stratified rocks
- Parts of a Fold:
- Axial Plane
- Limbs
- Axis
- Fold Nose or Hinge
- Basic Types of Folds:
|
