This earthcache will place you between Tuttle Creek Dam and the Spillway System. You will need to cross the earthworks dam coming from the west or the Spillway System coming from the east. There has been construction to reinforce the dam for several years and the information sign you are looking for has been inaccessible during that time. It is along Highway 13 so watch for traffic.
The Spillway Fault System at Tuttle Creek Dam is a geological feature that can be seen in the east side of the spillway cut. Rock layers are offset along diagonal lines that can be traced along the face of the cut. Signs in the northwest spillway parking lot identify the faults visible on the opposite wall. These faults were discovered during investigations prior to construction of the dam. The faults actually extend across the lake and have been traced in the hills on the west side of the lake.
These features have also been traced for several miles to the east of the spillway. The faults do not extend below any part of the dam or spillway gates. No earthquakes in historic times have been associated with these faults. Microseismic studies have been conducted by the Kansas Geological Survey with funding from the U.S. Army Corps of Engineers. These studies used very sensitive instruments to detect earthquakes that cannot be felt and did not show any recent activity related to this fault system. Additional investigations also show that there are no disturbances in the surface soils above the fault that indicate any recent activity.
These faults are not considered active, and do not pose a danger to Tuttle Creek Dam.
OK now some educational stuff about faults.
Geologists can categorize faults into three groups based on the sense of slip:
1. a fault where the relative movement (or slip) on the fault plane is approximately vertical is known as a dip-slip fault
2. where the slip is approximately horizontal, the fault is known as a transcurrent or strike-slip fault
3. an oblique-slip fault has non-zero components of both strike and dip slip.
For all naming distinctions, it is the orientation of the net dip and sense of slip of the fault which must be considered, not the present-day orientation, which may have been altered by local or regional folding or tilting.
Dip-slip faults can be sub-classified into the types "reverse" and "normal". A normal fault occurs when the crust is extended. Alternatively such a fault can be called an extensional fault. The hanging wall moves downward, relative to the footwall. A downthrown block between two normal faults dipping towards each other is called a graben. An upthrown block between two normal faults dipping away from each other is called a horst. Low-angle normal faults with regional tectonic significance may be designated detachment faults.
A reverse fault is the opposite of a normal fault — the hanging wall moves up relative to the footwall. Reverse faults indicate shortening of the crust. The dip of a reverse fault is relatively steep, greater than 45°.
A thrust fault has the same sense of motion as a reverse fault, but with the dip of the fault plane at less than 45°. Thrust faults typically form ramps, flats and fault-bend (hanging wall and foot wall) folds. Thrust faults form nappes and klippen in the large thrust belts.
The fault plane is the plane that represents the fracture surface of a fault. Flat segments of thrust fault planes are known as flats, and inclined sections of the thrust are known as ramps. Typically, thrust faults move within formations by forming flats, and climb up section with ramps.
Fault-bend folds are formed by movement of the hanging wall over a non-planar fault surface and are found associated with both extensional and thrust faults.
Faults may be reactivated at a later time with the movement in the opposite direction to the original movement (fault inversion). A normal fault may therefore become a reverse fault and vice versa.
The fault surface is usually near vertical and the footwall moves either left or right or laterally with very little vertical motion. Strike-slip faults with left-lateral motion are also known as sinistral faults. Those with right-lateral motion are also known as dextral faults.
A special class of strike-slip faults is the transform fault, where such faults form a plate boundary. These are found related to offsets in spreading centers, such as mid-ocean ridges, and less commonly within continental lithosphere, such as the Alpine Fault, New Zealand. Transform faults are also referred to as conservative plate boundaries, as lithosphere is neither created nor destroyed.
A fault which has a component of dip-slip and a component of strike-slip is termed an oblique-slip fault. Nearly all faults will have some component of both dip-slip and strike-slip, so defining a fault as oblique requires both dip and strike components to be measurable and significant. Some oblique faults occur within transtensional and transpressional regimes, others occur where the direction of extension or shortening changes during the deformation but the earlier formed faults remain active.
The hade angle is defined as the complement of the dip angle; it is the angle between the fault plane and a vertical plane that strikes parallel to the fault.
A listric fault is a type of normal fault in which fault plane is curved. The dip of the fault plane becomes shallower with depth.
Ring faults are faults that occur within collapsed volcanic calderas. Ring faults may be filled by ring dikes.
Now for the logging requirements:
Email me with the answers to these questions.
1. Tell me what type of fault you think the Spillway Fault System is.
2. From the information board: Tell me what scale is used in the map in the upper right corner of the information board.
3. From the coordnates you can see the spillway to the east. Look at the end closest to you and find the numbers on the spillway. Tell me the top most number and the largest number you can see.
4. You can also post a picture of yourself at the location.
Thanks and I hope you enjoy my Earthcache!
Congratulations to JJTally on the FTF.