A fault is a break between two blocks of rock along which movement occurs. Along significant faults, there are actually a series of faults that are close to parallel that all allow even larger blocks of rock further away from the faults to move past each other. This grouping of faults is a fault zone. Within a fault zone, earthquakes can result in movement along a single fault or smaller movements spread out among multiple faults but resulting in the same total movement.
However since movement is not exactly parallel, some of the blocks within the fault zone will be pulled apart, creating a depression. Picture pulling apart a warm chocolate bar; as the sides move away, the middle sags down. This depression is called a sag pond (especially if it fills with water).
Of course, in other areas the small blocks can be pushed together forming pressure ridges.
Sometimes each of the faults are names and other times all the faults are close enough together that they are just given the same name. An example of a fault zone that is given a single name is the San Andreas Fault. Portions of the San Andreas Fault are actually a zone of faults ½ mile wide while in other sections, it is just a single fault.
Send me a note with :
- The text "GC5Q65R Nisene Marks Sag Pond" on the first line
- The number of people in your group.
- Estimate the width of the block of rock that sagged down (the part of the chocolate bar that sags) to create this sag pond.
- Which compass direction do you think the sides of the sag pond being pulled apart.
The following sources were used to generate this cache:
- http://decarboni.se/publications/caprock-systems-co2-geological-storage/32-faults-and-fractures
- http://3dparks.wr.usgs.gov/haywardfault/html/glossary.html#geomorph
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