{"id":4397,"date":"2015-10-01T02:41:34","date_gmt":"2015-10-01T02:41:34","guid":{"rendered":"http:\/\/www.backroadswest.com\/blog\/?p=4397"},"modified":"2022-11-14T00:31:10","modified_gmt":"2022-11-14T00:31:10","slug":"san-andreas-fault-wrightwood","status":"publish","type":"post","link":"https:\/\/www.backroadswest.com\/blog\/san-andreas-fault-wrightwood\/","title":{"rendered":"San Andreas Fault Tour near Wrightwood"},"content":{"rendered":"\n
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We are going to take you on a tour of the San Andreas Fault, starting in the Cajon Pass, through Wrightwood and Big Pines, then along the north side of the San Gabriel Mountains.<\/strong>\u00a0 California is world-famous for many things and one of them is earthquakes. \u00a0This introduction to\u00a0a small section of the infamous San Andreas Fault will show you what the fault looks like and where to go see it.<\/p> <\/div>\n<\/div>\n <\/div>\n

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California\u00a0is covered with earthquake faults.\u00a0 Most people have heard of the dreaded San Andreas Fault yet many of the State\u2019s greatest earthquakes did not happen along the San Andreas.\u00a0 Some of us living in Southern California have heard of other faults like the Helendale, San Jacinto and Elsinore faults but the San Andreas is different.\u00a0 It is a \u201cplate boundary\u201d where the Pacific and North American Plates meet and grind past each other.\u00a0 This grinding action has gone on for millions of years and is what causes earthquakes as well as the features you will see on our tour.<\/p>

During the tour, keep in mind that the fault is just not a crack in the earth.\u00a0 It is more of a fault zone<\/em><\/strong>.\u00a0 This zone can be filled with multiple fractures.\u00a0 In some places, the zone can be just twenty feet wide and other places it can be almost a mile wide.<\/p>

Tectonic Plates<\/h3>

Every\u00a0geology lesson starts out with looking at\u00a0a map of the World showing where all the tectonic plates are located. \u00a0Our tour is no different. \u00a0Many such lessons even start off with a map of the supercontinent\u00a0Pangaea, but we’re not going to subject you to that. \u00a0It is important to note however, that the San Andreas Fault is the division of one of those two huge tectonic plates mentioned earlier.<\/p>

If you watch our YouTube virtual video tour below, you’ll see the map of the World’s tectonic plates. \u00a0You’ll see that\u00a0the next plate boundary to the east of the San Andreas is in the middle of the Atlantic Ocean where the North American Plate meets the Eurasian and African Plates.\u00a0 The next plate boundary to the west is on the other side of the Pacific Ocean. \u00a0Think of that distance. \u00a0During this trip, when you either drive or straddle over the fault line, we hope you feel how significant of a thing you’re passing over.<\/p>

Below is that World map of tectonic plates.<\/p>

\"SanAndreas1Tectonic\"<\/a>
San Andreas Fault in relation to the tectonic plates<\/figcaption><\/figure>

The Tour Begins<\/h3>

We start our tour at the southern end of the Cajon Pass.\u00a0 Use a map or your GPS to get to the intersection of Cajon Blvd (Route 66) and Swarthout Canyon Rd. \u00a0See our map below<\/a> for more geographic detail. \u00a0Reset your odometer to zero and head across Cajon Creek and the railroad tracks.<\/p>

At 0.6 miles, you\u2019ll come to the first San Andreas Fault feature – a sag pond<\/em>.\u00a0 It\u2019s located on the right side, on private property next to a residence, and is difficult to see from the road. \u00a0On this tour, we are going to see a lot of sag ponds, which are all features created by the fault. \u00a0A sag pond is formed when underground water seeping along the fault line comes to some sort of blockage, is forced up to the surface at a low spot along that blockage, creating a pond.\u00a0 This blockage is often a fine earth material, such as clay, that has been created by the fault\u2019s grinding action. \u00a0Watch\u00a0the video to see\u00a0a diagram.<\/p>

At this same point\u00a0but on\u00a0the left side,\u00a0you can see where the San Andreas caused some unique erosion on the hillside next to route 66.\u00a0 This is known as Blue Cut.\u00a0 It got its name when early Route 66 travelers noticed the bluish tint in the soil. \u00a0This form of erosion is called fault gouge<\/em> and sometimes\u00a0known as\u00a0fault flour<\/em>. \u00a0We’ll cover this in more detail at a later stop.<\/p>

Lost Lake<\/h3>

Continue past the second railroad crossing and at 1.3 miles, you\u2019ll reach the parking area for Lost Lake.\u00a0 This is another sag pond and one you can access.\u00a0 Walk the short distance here to take in the views of this unique body of water.\u00a0 Notice that the pond is long and skinny and that it is oriented in the same direction as Lone Pine Canyon, the long skinny valley you\u2019ll soon be driving up. \u00a0That orientation indicates the\u00a0direction of\u00a0the San Andreas Fault. \u00a0This pond is right on top of the fault.<\/p>

Driving on up the dirt road, you\u2019ll pass by a few fault scarps that have been created by numerous earthquakes over the millions of years.\u00a0 A scarp<\/em> is created in the few seconds during an earthquake when the earth is pushed up or moved sideways during the quake\u2019s movement.\u00a0 This surface rupture looks like a small step or offset in the land and can be a few inches or many feet high.\u00a0 Unfortunately, most of the scarps along this trip are hidden by vegetation.<\/p>

Lone Pine Canyon<\/h3>

Continue up the dirt road to a stop sign.\u00a0 Turn left onto the pavement of Lone Pine Canyon Road and notice how long and skinny Lone Pine Canyon is.\u00a0 This particular fault feature is known as a linear valley<\/em> and there are many examples similar to this canyon all along the fault\u2019s trace.<\/p>

Clyde Ranch<\/h3>

Our next stop, which is 8.1 miles from route 66, is Clyde Ranch.\u00a0 This stop has nothing to do with the San Andreas fault, but has some nice\u00a0history to it.<\/p>

This ranch, built in the 1870s, was built by the Clyde family.\u00a0 It\u2019s still owned by the same family today!\u00a0 And even more historically intriguing, is that the Clyde\u2019s were good friends with the Earp brothers, especially Virgil and Wyatt.\u00a0 When Wyatt lived in San Bernardino, he would ride up here on horseback, following the same path you just drove, to visit his friends, the Clyde\u2019s.<\/p>

There is an old photogenic service station that sits along the road on this property. \u00a0Remember however, that the building is on private property. \u00a0If you dare to venture onto the property, just remember who the Clyde’s are friends with ;-)<\/p>

View Point<\/h3>

At about 10.7 miles, the road reaches a summit as it begins descending into another linear valley, which is where Wrightwood is located. \u00a0Before you cross the summit\u00a0however, find a safe place to pull over and look at the view behind you. \u00a0You may have to walk along the guard rail a short distance.<\/p>

On a clear day you can see the fault trace run from under your feet all the way to the mountains near Palm Springs, about 70 miles away. \u00a0The large mountain in the distance on the left is San Gorgonio Mountain and the large mountain on the right is\u00a0San Jacinto Peak. \u00a0The San Andreas passes between the two. \u00a0The three major mountain ranges you see here, the San Jacinto’s, the San Bernardino’s and the San Gabriel’s, the mountains you are in right now, were all created by the forces of the San Andreas Fault. \u00a0The mountains were formed by compression and uplift caused by small bends in the fault. \u00a0To learn more about this process, we recommend reading this article on Wikipedia<\/a>.<\/p>

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Pictures<\/h3>

Below are some pictures of what you will see along the way.<\/p> <\/div>\n<\/div>\n

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