Lake Elsinore is the largest natural freshwater lake in Southern California and how it formed can be explained in geologic terms. The above coordinates are for a pull off along Ortega Highway, CA Route 74. It can be congested during certain times of the year and parking is limited. Be sure to plan ahead. Oh, did I mention that there is an incredible view too? You will want to bring your camera. The yellow star in the map below denotes where GZ is.
The story of Lake Elsinore begins millions of years ago when the Elsinore Fault was more active than it it today. Before I go into any more details lets first discuss the basic fundamentals of how fault lines (more specifically fault zones) 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 key difference though. One is with water, rather than plastic (silly putty like consistency) rocks and the other is that one is less than a few inches while one is kilometers in depth. Convection currents are continuous cycles in the earth's mantle 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 solid crust. When fractures occur, a fault is created.
Now at this point I'm sure you are asking, "What is a fault line?" In geology, "fault lines" are a misnomer. Instead, faults are made up of a collection of fault lines which create a fault zone. A fault line is a single crack, while a zone is a collection of cracks. Most fault systems that have developed over millions of years are a collection of fault lines, and geologists refer to these as fault zones. Think of fault lines being the microscopic scale and fault zones being the macroscopic. Going back to fault lines, it is where two masses of rock meet and create friction. The place at which they meet is known as a fault line which was created by a fracture. When this friction is released, an earthquake occurs. This friction is formed by these convection currents. When they move in a circular pattern in one direction, they can push rigid rock with them. When tension is released, an earthquake occurs in and creates sesimic waves that propogate in all directions on the X, Y, and Z axises. X is up or down motion, Y is right or left motion, and Z is pivoting side to side. Depending on the amount of potential energy, it can cause a magnitude 1 earthquake on the Richter Scale or a 10.
The Richter Scale, developed by Charles Richter, was the first practicle quantitative scale in measuring earthquakes. It was designed specifically for earthquakes in California. Today, scientists uses the moment scale, and more specificaly use the Moment Magnitude scale which we are all familiar with today. When you hear an earthquake had a magnitude of a 5.0, this is almost always on the Moment Magnitude scale (abbrivated as: Mw 5.0). A Mw 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 occured in Chile on May 22, 1960, along a subduction zone which created a tsunami. You can see my earthcache about that Tsunami here.
At the above coordinates you will be able to view a pond that was created by the Elsinore Fault, known as Lake Elsinore. Sometimes the Elsinore Fault is classified as two different faults. The northern half is sometimes called the Geln Ivy Fault and the southern half is sometimes called Willard and Wildomar Fault. This pond was created by a series of complex geologic forces. One common misconception about fault lines (or zones) 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. In other terms, faults tend to be discontinuous. It is easier to see it on paper, than in words so 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 Elsinore Fault moving side to side in these offset areas, it moves away from each other. This makes these nonmoving areas become stressed and pull the land apart, which creats a depression. When it rains or snows, runoff water collects in these ponds. Depending how big or small they are, the ponds can last year round. Lake Elsinore lasts year round and has lasted for thousands of years.
There are two things that can happen when fault zones 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.
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. The higher the health, the more green plants appear. 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.
Works cited:
http://scec.usc.edu/internships/useit/scec-vdo/animation868
http://www.scec.org/wallacecreek/misc/defs.html#CREE
http://en.wikipedia.org/wiki/Elsinore_Fault_Zone#/media/File:SoCal_Coast.jpg
https://en.wikipedia.org/wiki/Sag_pond
https://www.facebook.com/geologicallyspeaking/posts/2241630662657800
TO LOG A FIND ON THIS CACHE YOU MUST ANSWER THE FOLLOWING QUESTIONS. RESPONSES CAN BE SENT THROUGH MY EMAIL OR THE GEOCACHING MESSAGE CENTER ON MY PROFILE PAGE. ANY INCORRECT ANSWERS WILL RESULT IN A FOLLOW UP MESSAGE FROM ME. ONCE YOU SEND YOUR EMAIL/MESSAGE, YOU ARE FREE TO LOG THIS CACHE.
1. "Elsinore Fault - Lake Elsinore (2.0)" on the first line of your email/message AND list all geocaching names of your party so I can match your answers to them. If you all want to learn something, I would prefer each cacher send me individual emails/messages in the spirt of earthcaching.
2. Take a photo of you (or your signature item if you don't want to show your face) with Lake Elsinore in the background. Please upload these images with your found it log. Do not message me any photos.
3. Do you see signs of any other sag ponds besides Lake Elsinore from this vantage point? If so, state the approximate compass barring of each additional site you see AND estimate its distance. If not, explain why you think this is the case.
4. Describe the (a) similarities and (b) differences in the topography (i.e. rocks, terrain, colors, ect.) between the north side of the lake along the Glen Ivy Fault (to your left) and the south side along the Willard & Wildomar Fault (to your right).
5. Based on your previous answers, do you believe Lake Elsinore is growing, shrinking, or static? Provide justification for your answer.