Sandstone Peak – The top of the Santa Monica Mtns!
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Welcome to the Santa Monica Mountains National Recreation Area EarthCaching Program. This earthcache site is available year round. This cache is on trail. Please do not travel off trail for your safety and preservation of resources.
Located at Circle X Ranch in the Santa Monica Mountains National Recreation Area. Access to this cache is by way of trail from either National Park Service land or State Park land. Mountain bikes are not permitted for travel to this cache.
Information regarding Circle X Ranch and Sandstone Peak.
The two main trails to access this cache are the Mishe Mokwa Trail and the Sandstone Peak Trail. There is free parking at either trail head. Pets are permitted on a leash no longer than 6 feet (2 meters). Bicycles are not recommended on the trails at Circle X Ranch. Horses are not permitted to this cache. Camping is restricted to the Group Campground only. Permits are required for camping.
• Circle X Ranch is open from sunrise to sunset daily.
• All plant material, rocks, animals, and historical features are protected by law and may not be collected or disturbed.
• Poison Oak can be found in this area. It is identified by three leaves ranging in color from green to crimson. The plant is deciduous, so it does lose its leaves in the winter.
•Watch out for mountains lions, rattlesnakes and ticks.
Santa Monica Mountains National Recreation Area Visitor Center Information:
Open daily from 9 AM – 5PM.
Address: 401 West Hillcrest Drive, Thousand Oaks, CA, 91360
Phone number: 805-370-2301
In emergency: dial 911
This former Boy Scout Ranch is home to Sandstone Peak, the highest point in the Santa Monica Mountains with an elevation of 3,111’ (948m). From here a view of Los Angeles, the Oxnard Plain, the Valleys of Southern California, and the Channel Islands can be seen. In 1948, the Boy Scouts acquired the land from a generous donor and named the mountain in his honor. The scouts undoubtedly scrambled up, over, and around this rusty colored ridge. Once the National Park Service acquired Circle X, they changed the name back to the previous name of Sandstone Peak which may seem strange since it is not in fact “sandstone” and there is not any sandstone on the Circle X site.
But why would it be referred to as Sandstone Peak in the first place? It was not formed from ancient riverbeds or fossils or even from sediments from far away. The rock that makes up Sandstone Peak is igneous in origin. The word igneous is from the Latin word, ignis, which means “from fire”. That means that Sandstone Peak was created by a volcano!
First, let us picture what the area was like when Sandstone Peak formed. Imagine yourself 24 million years ago. The dinosaurs are long gone. There are no Santa Monica Mountains, just broad plains that extend from the middle of California to the coast. In fact, much of the land that makes up the Los Angeles area was underwater at the time. Then a short period of time later, geologically speaking, about nine million years, the volcanoes that created the Santa Monica Mountains and the Channel Islands started to erupt, however the lava only oozed underwater at first.
Yet about 15 million years ago the eruptions became explosive. Volcanoes similar to the eruptions of the Cascades in Washington and Oregon or the Andes in South America were a common occurrence. For another 3 million years, the mountains continued to grow to over 10,000 feet high. Three times taller than they are today!
Sandstone Peak is in the Conejo Volcanics Formation (16.1 to 13.1 million years old) and is composed of igneous rocks that include:
• dacitic breccias, andesitic breccias, basaltic breccias
• andesitic flows
• basaltic rocks
Look at the time scale below. About 24 million years ago the Lower Topanga Formation (composed of marine sediment and non-marine sediment) began to develop. There was an interruption in the deposition of the Lower Topanga Formation, such that no geological materials are preserved from this time. This is called an unconformity. The end of the unconformity was marked by the beginning of the Conejo Volcanics and Diabase Intrusions about16.6 million years ago. About 13 million years ago, the Conejo Volcanic eruptions ceased allowing the Upper Topanga Formation to develop. Although the Conejo Volcanics split the Topanaga Formations both physically and in geological time, there is no sandstone at Sandstone Peak!
Geological Time Scale
After 13 million years of erosion the amazing 10,000’ Sandstone Peak is a mere 3111’. The remaining colorful, reddish rock is the heart and core that gives us evidence for a process millions of years in the making!
If you want to explore more about how the mountains formed, then head down the trail to Inspiration Point EarthCache.
To log this EarthCache complete the following:
Sign your name in the register at the cache and put earthcache next to it.
Click the link below to take the quiz and get your EarthCache certificate:
Sandstone Peak Quiz
1. What type of rock is Sandstone Peak? Igneous, Metamorphic, Sedimentary?
2. Look for the monument at Sandstone Peak. Who is the generous donor the mountain was once named after?
3. Why do you think the peak was named Sandstone Peak?
Sources for this cache are:
Dibblee Jr., Thomas W., Ehrenspeck, Helmut E., 1990, Geologic Map of the Point Mugu and Triunfo Pass Quadrangles, Ventura and Los Angeles Counties, California, Dibblee Geological Foundation, Map #DF-29
National Park Service, Santa Monica Mountains National Recreation Area, Thousand Oaks, CA, 91360
Nicholson, Craig, Sorlien, Christopher C., Atwater, Tanya, Crowell, John C., Luyendyk, Bruce P., 1994, Microplate capture, rotation of the western Transverse Ranges, and initiation of the San Andreas transform as a low-angle fault system, Journal of Geology, v. 22, p. 491-495
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