The Mojave Triangle is defined by the Garlock and San Andreas Fault systems. The San Andreas Fault marks the southern boundary, and the Garlock Fault marks the northern boundary. These faults mark the technical end of the Mojave desert to form a valley to the east, surrounded by mountains on all three sides. From satellite images, we can clearly see a triangle at nearly a 60 degree angle. So what causes this to happen?
First, you must understand what a fault line is, and how they work. 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. 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.
So, what makes this place special? Well, for one, there are two separate fault lines, coming together. The San Andreas Fault is the largest fault by far in California. The second, is the Garlock Fault. Each of them are transverse faults meaning they slide past the opposing plate. There are two types of transverse faults. A right-latteral and a left-lateral. You can tell the difference by going on one side of a fault line, and looking at the other. If the other side is moving right relative to you, then it is a right lateral fault. If the other side if moving left relative to you, than it is a left-latteral. You can see on the first picture on this cache page the directions of movement each plate of the Garlock and San Andreas Faults. The San Andreas Fault is a right-latteral fault, and the Garlock fault it a left-lateral fault. When these two faults collide, you get something very cool.
When two transverse opposite lateral faults meet, you get a very low valley on one end, and a sharp mountain range on the other. This is due to the fact that inside the triangle, the land is moving away from the point of contact of these faults. Outside the triangle, the land is moving towards each other creating mountains and ridges. It's very easy to tell when this happens, as you get a low valley, in close proximity to large mountain ranges. At this earth cache, you are standing in the middle of this low valley, created by these two large faults. The land here is sinking, while the mountains are rising, faster than anywhere else along the San Andreas Fault.
Works Cited
http://www.geog.ucsb.edu/~joel/g148_f09/readings/mojave/mojave_desert.html
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1. The Mojave Triangle on the first line of your email.
2. From this vantage point, how far does the Mojave Triangle extend?
3. Take an accurate GPS reading of elevation. Say, you come back to this spot in 1,000 years and take another GPS reading. What would you expect the reading to be? Just give me a ballpark elevation. Doesn't have to be spot on.
4. Using your own observations, do you think the valley is growing or shrinking AND your explanation as to why this might be. If it growing or shrinking (whatever you choose) what would you expect to see eventually?