What a graben is is hinted at from the etymology of the word. In German, Graben as a verb means to dig, as a noun graben means ditch or trench[1].
The posted coordinates are at a scenic lookout on the shoulder of the road, with room for a couple of cars to park. There you will find a sign describing the geological processes which created the valley you see before you. Consult the sign to help answer the following questions, send me the answers via the geocache messenger:
1. How do grabens form?
2. What is the name of this graben? Why did the graben begin to form? What ancient continent did this area belong to?
3. What are the names of the faults that run through the area, forming the boundary of the graben?
4. Why do you suppose the graben stopped forming?
Include in your log a photo of yourself, or your GPSr, or a trackable, or something unique that shows you were there.
In geology a graben refers to a type of valley formation. The earth's crust is not one solid mass floating on top of the mantle. Rather, the crust is broken into several pieces called plates. These plates float around and move, and this movement causes intense stress on the plates. This stress manifests itself as faults. Smaller faults exist all through plates, larger faults form the boundaries of the plates. Those larger, plate defining faults usually have fancier names such as "transform faults" (which refer to plates moving horizontally against each other[2]). The process of two plates moving away from each other can cause valleys to form as the land between the plates sinks. "Graben" is the term for the chunk of land that sinks in between two plates that are moving apart[3].
References
- Cambridge Dictionary. "Graben", translate German to English. 2018. https://dictionary.cambridge.org/dictionary/german-english/graben
- Moores, E.M., and R.J. Twiss. "Transform Faults, Strike-Slip Faults, and Related Fracture Zones." In Tectonics, 130. Long Grove: Waveland Press, 1995.
- USGS. "graben", Earthquake Glossary. Accessed 17 September 2019. https://earthquake.usgs.gov/learn/glossary/?term=graben