Welcome to Joe's Valley, a 75-mile long, north-south trending depression graben, what's a graben you ask?
Horsts and Grabens
A graben is a depressed block of land bordered by parallel faults. Graben is German for ditch.
A graben is the result of a block of land being downthrown producing a valley with a distinct scarp on each side. Grabens often occur side-by-side with horsts. Horst and graben structures are indicative of tensional forces and crustal stretching.
Graben are produced from parallel normal faults, where the hanging wall is downthrown and the footwall is upthrown. The faults typically dip toward the center of the graben from both sides. Horsts are parallel blocks that remain between grabens, the bounding faults of a horst typically dip away from the center line of the horst.
A single graben or multiple grabens can produce a rift valley.
Block Diagram
(Horsts are up thrown blocks bounded on either side by parallel normal faults.)
(Grabens are downthrown blocks bounded on either side by parallel normal faults.)
Half-Graben
Half-grabens develop when parallel faults on either side of a block develop, but the block becomes tilted instead of dropping down as in a graben.
Logging Requirements:
(answers can be found at the coordinates)
- In the diagram, what do the green bands represent?
- How far has Joe's Valley dropped in it's becoming a graben?
- Which nearby graben is most prominent? did you know it was a graben? do you know of any other grabens?
- (optional) Include a photo in your online log of you at the cache site with your GPS.
