What is really interesting here is how these mountains came to be. Everyone knows about the San Andreas Fault and how it's famous, but what many people don't realize is that it lies right under the town of Palmdale. The the fault line crosses Highway 14 once near Avenue S. At this particular site, there is a sag pond, just one of many along the San Andreas Fault.
Before I go into any more details lets first discuss the basic fundamentals of how fault lines are created and now they work. The answer can be found in your kitchen, literally. When boiling pasta on the stove, the hotter pasta floats to the surface then when it cools it sinks. This effect has a name. Convection currents in your pot at home and in the earth are nearly identical. There are a few difference though. One is with water, rather than boiling rocks and the other is that one is less a few inches while one is miles deep. Convection currents are continues cycles in the earth's mantel that make hotter rock rise, and cooler rock fall and the cycle begins over and over again. When this happens, it causes fractures in the earth's crust. When fractures occur, a fault line is created.
Now at this point I'm sure you are asking, "What is a fault line?" Well, it is place where two tectonic plates meet and create friction. When this friction is released, an earthquake is formed. This friction is formed by these convection currents. When they move in a circular pattern in one direction, they can push rock with them. When tension is released you get an earthquake in an that moves in waves on the X, Y, and Z axises. X is up or down, Y is right or left, and Z is pivoting side to side. Depending on the pressure, it can create a magnitude 1 earthquake on the Richter Scale or a 10. A 10 has never happened in recorded history, but is believed to have only occur when large meteors hit the earth. The largest earthquake ever recorded happened in Chile on May 22, 1960. It happened in open waters, just off the coast in the Pacific where it created a Tsunami. You can see my earthcache about that Tsunami here. A Richter Scale works like this. Say there was a 5.0 earthquake, which are common, and a 7.0, a little less. A 7.0 on the Richter scale is 100 times greater of that of a 5.0 on the same scale. Each decimal point in-between is twice as as bad as the preceding one.
Now, at this site you will view a pond that was created by the San Andreas Fault. This pond was created by a series of complex geologic forces. One common misconception about fault lines is that they are perfectly connected in a line. This is not necessarily true. In some areas, there are breaks in the fault itself. For example there are areas of the fault that are missing, that have no fault activity whatsoever. It is easier to see it on paper, than in words so please refer to the diagram below.
You can clearly see that the fault itself is offset in some areas. When this happens, many times a sag pond is created. Instead of the San Andreas moving side to side in these offset areas, it moves away from each other. This is because the fault offset areas are already moving and these nonmoving areas are not. These makes these nonmoving areas become stressed and pull the land apart, which creates a depression. When it rains or snow, runoff water collects in these ponds. Depending how big or small they are, the ponds can last year round. This one lasts year round.
There are two things that can happen when fault lines become jagged such as the Elsinore Fault. One thing is a sag pond, which I've discussed in the paragraph above. This happens at a divergent step when the fault creates a basin as the land in-between the fault moves away and stretches, relative to the other side of the fault. The other option is for a fault to create hills in a convergent step. Just like when you push to sides of the same piece of paper together and you get a ridge in the paper, the same happens here. The only difference is the size and scale.
The water clarity inside the sag pond can also give us clues of the geology occurring here. Clear water suggests that the bottom is mainly hard rock. Harder materials tends to hold water more and not let it leak into the soil. Hard rock, dense rock also moves earthquake waves much easier and much faster than loose rock. If the water is murky this can mean one of two things. Either that there is algae living here or that there is loose sediment at the bottom. Looser materials tend to leak out more water into nearby soils. Loose rock may also be an indicator that the water source is not just coming from runoff. It may be an underground water source that comes to the surface.
Indicators of a possible sag pond presence are denser vegetation relative to its surroundings. This is due to the fact that when plants grow near sag ponds, they are better off. More water means better productivity and higher health. Higher health and more green. If you see any areas that are more lush than its surroundings, this may indicate that a sag pond is present. Another indicator are small ridges. These ridges are tension areas where the land next to the fault literally rolls like sheets of paper. You will be standing on one of these ridges at the above coordinates.
Works Cited
http://www.scec.org/wallacecreek/misc/defs.html#CREE
https://en.wikipedia.org/wiki/Sag_pond
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1. San Andreas Fault - Una Lake on the first line of your email.
2. From this vantage point, do you see any other indications of sag ponds nearby, besides this one? If so, what do you see and how far away do you see them?
3. Estimated the size of the extent of this sag pond. How many feet does the extent of the sagging occur? Do not estimate for the water only spots, this is for the entire extent of the sagging of the land due to the fault.
4. In the sag pond, describe the water clarity AND what does this suggest?
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