The Sinks - Irvine Ranch Wildlands EarthCache
Hidden : 10/1/2009
Difficulty:
1 out of 5
Terrain:
3 out of 5

Size: Size: not chosen (not chosen)

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Geocache Description:


The Irvine Ranch Conservancy was established in 2005. It is a non-profit, non-advocacy organization, created to help care for the 50,000 acres of permanently protected wildlands and parks on the historic Irvine Ranch. The organization works with its partners to enhance the public’s appreciation, understanding and connection to the land, while helping other land owners and managers with all aspects of stewardship. The Conservancy contributes its resources, expertise and energy to achieve the best possible balance of preservation and public participation.

Nearly 40,000 acres of the 50,000 acres indicated above of open space on the historic Irvine Ranch have been designated a Natural Landmark by both the State of California and the U.S. Department of Interior. This honor recognizes the exceptional value of these lands to California and the entire nation.

Beautiful geological formations - including "the Sinks", “Dripping Springs” and the rock formations located at Black Star Canyon - plus a rich diversity of flora and fauna make the The Irvine Ranch a favorite among hikers, mountain bikers and naturalists.
This cache is placed with the permission from and in cooperation with the Irvine Ranch Conservancy. Access is limited; reservations for docent-led outings are required due to the area's sensitive habitat. Pre-registration is required for all programs. No walk-up registration is allowed, no exceptions. Registration for weekday programs closes at 4 p.m. on the day prior to the event and registration for weekend programs closes at 4 p.m. on the Friday prior to the event. A calendar of scheduled hikes can be found at www.irvineranchconservancy.org or irlandmarks.org.
Additionally, they can be reached at (714) 508-4757 to coordinate small or large group hikes for these Earthcaches and other hikes within the Conservancy boundaries.

The Sinks - Irvine Ranch Wildlands
The destination for this approximate 3 miles round trip hike with approximately 200 feet elevation gain is The Sinks within the Irvine Ranch Conservancy protected area. The Sinks is located in the Loma Ridge portion of the Irvine Conservancy protected area. Much of Loma Ridge immediately southwest of the ridge crest is marked by steep cliffs, commonly 20 to 60 m in height.

The Sinks area is separated from the southeast end of Loma Ridge by the fault , with The Sinks being on the relative up side. Rejuvenated drainage likely carved this more landslide-and erosion-prone area. The Sinks are part of the upper Sespe Formation dated back to the Palogene System, Oligocen Series representing formations dating back 24-65 Million years ago.

Sandstone is a sedimentary rock composed mainly of sand-size mineral or rock grains. Most sandstone is composed of either quartz and/or feldspar because these are the most common minerals in the Earth's crust. Sand and the sandstone it creates can be an color (the sandstone would be reflective of the color of the base sand in its formation, but the most common colors are tan, brown, yellow, red, gray and white. Since sandstone beds often form highly visible cliffs and other topographic features, certain colors of sandstone have been strongly identified with certain regions. A predominant additional colorant in the southwestern United States is iron oxide, which imparts reddish tints ranging from pink to dark red (terracotta).

The formation of sandstone involves two principal stages. First, a layer or layers of sand accumulates as the result of sand particles settling and stopping movement either from water (as in a river, lake, or sea) or from air (as in a desert). Finally, once it has accumulated, the sand becomes sandstone when the pressure of additional layers of deposits compact the sand layer, and the sand is then cemented by the precipitation of minerals within the pore spaces between the individual sand grains. The most common cementing materials are silica and calcium carbonate, which are often derived either from dissolution or from alteration of the sand after it was buried.

Rock formations that are primarily sandstone usually allow percolation of water and are porous enough to store large quantities, making them valuable aquifers.
Sandstone has been a main building material dating back into most of history.

The sandstone located in the foundation of The Sinks had apparently dissolved over time based upon acid rainwater that would have drained into fissures in the rock. According to sources through the Irvine Ranch Conservancy, the shaking from an earthquake likely caused a failure in the internal structure of the sandstone. This caused some of the surrounding formation to collapse and large amounts of debris were then carried downstream over time. Further weathering of the exposed sandstone has caused the formation seen today when facing south from the coordinates.

In order to log this cache, please:

1. Post a picture with you, your group and your GPS at The Sinks from the coordinates.
2. When facing The Sinks, look approximately 225 degrees. There is an earthquake fault. Email me (logs that provide the answer will be deleted) what direction (vertically, horizontally or diagonally) the fault appears to be in relation to where you are standing.
3. Additionally, please email me (logs that provide the answer will be deleted) the color of the rocks at 225 degrees and 190 degrees when facing The Sinks and provide a guesstimate as to why the difference.

References:

Cooper, John D., and Michael G. Sawlan, 2008, Evaluation of the Irvine
Ranch National Natural Landmark: in: Fritsche, A. Eugene and Richard J. Behl (editors), Geology of Orange County, California and the Irvine
Ranch National Natural Landmark: Pacific Section, SEPM (Society for
Sedimentary Geology) Book 106.

Irvine Ranch Wildlands and Parks (visit link)
Wikipedia: http:/en.wikipidia.org/wiki/Sandstone
U.S. Geological Survey: (visit link)

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