Crustal Deformation

The Alps

You may wish to print a copy of the lecture outline (minus the illustrations) and you have two options:

• Microsoft Word if you use that Word Processor or
• A Netscape Document that you can print (use the Left Arrow key to return to this page).
• Or, you may view the Folds and Faults power point presentation shown in class.

Course Objectives

After reading Chapter Fifteen, you should be able to:
1. Define deformation, strain, stress.
2. Explain the differences among compressional stress, tensional stress, and shear.
3. Identify brittle, ductile, elastic, and plastic deformation.
4. Find the orientation of geologic structures using strike and dip.
5. Identify the major features of folds, and list the types of folds.
6. List and describe the types of faults and their features.
7. Explain the difference between a fault and a joint.

Introduction

The San Andreas fault is perhaps the best known active feature of deformation in the United States. In the link given in the chapter title you will take a field trip along the fault in the San Francisco Bay area.

Class Notes

Internet Resources

1. At the Earth's Core

   "IN THE FIRST PLACE PLEASE BEAR IN MIND THAT I do not expect you to believe this story. Nor could you wonder had you witnessed a recent experience of mine when, in the armor of blissful and stupendous ignorance, I gaily narrated the gist of it to a Fellow of the Royal Geological Society on the occasion of my last trip to London. You would surely have thought that I had been detected in no less a heinous crime than the purloining of the Crown Jewels from the Tower, or putting poison in the coffee of His Majesty the King." [Thought you might like to start off with something a little different.]

2. Isostacy

   "The process by which the Lithospheric plates, which are "floating" on the Mantle, adjust vertically to achieve an equilibrium (the crust and upper mantle have a uniform density.) Because Oceanic Crust has a higher density than Continental Crust, it adjusts lower into the Mantle. This condition is augmented by the fact that Oceanic Crust is thinner and therefore has less mass to compensate for through buoyant displacement of the Mantle."

3. Plate Tectonics

   This is a good set of course notes for topics that we will cover by the end of our course.

4. Earth Detective

   Go to Earth Detective and select the Novice section. The animations should help explain structural features you have heard and read about.

A Virtual Field Trip to the Sideling Hill Road Cut

The Sideling Hill Road Cut "lies in the Valley and Ridge Physiographic Province of eastern North America, a region characterized by tightly folded strata. Erosion of these folds has produced a series of subparallel ridges and valleys, in which the ridges are capped by erosion-resistant sandstones, and the intervening valleys are underlain by soluble limestones and easily eroded shales. At first, Sideling Hill may appear to be a somewhat unusual feature, inasmuch as the downfold, or syncline, exposed in the road cut would seem to be more likely to form a valley, rather than a ridge. However, the youngest rocks, or those highest in the stratigraphic section, are the resistant sandstones and conglomerates of the Purslane Formation, which occur in the center of the fold and cap the ridge."

Learning about geology from a computer screen is only half as fun as enjoying it in the field!

Self Quiz

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Copyright by John C. Butler, July 29, 1995