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West Sulphur Mountain Oil Spring

Hidden : 03/13/2008
1 out of 5
1.5 out of 5

Size: Size:   not chosen (not chosen)

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Geocache Description:

On the west side of Sulphur Mountain oil, water, and gas seep out of natural fractures in the hillside. The gas released by the seep give the mountain its name.

The seep is located a short walk along Sulphur Mountain Trail, an unpaved fire road. Parking is off the pavement at the end of the road (watch the fire access). Bikes, horses, leashed dogs, and hikers use the popular trail.

You should smell the seep before reaching it, so you likely will not need the gps once you get close. The oil and water also run a fair way down the side of the trail, so it will also lead you to it.

This oil and water likely rises up from the Monterey Formation that is likely a short distance under the soil. The Monterey Formation is common along the coast of California. In fact, similar rocks were deposited throughout the Pacific Rim during the Miocene (17.5 to 6 million years ago). All of these rocks share similar characteristics. They are

  • Diatomaceous (made up of the shells of microscopic plankton called diatoms)
  • Phosphatic (containing phosphate)
  • Dolomitic (containing dolomine); and
  • Rich in organic matter (oil and gas).
This last characteristic, being rich in organic matter, makes these rocks economically important because they often are reservoirs for oil and gas. Most of the off-shore oil rigs along the California coast are pulling oil from this formation. Across the Pacific, Japan has similar rocks and oil reserves.

Pure oil does not occur in the rock. It often has other compounds mixed in. One common impurity is water. At this location both oil and water are coming to the surface.

As you might expect, the oil flowing out across the landscape and the gasses escaping into the atmosphere have their detrimental effects upon the environment. The plants and animals are exposed to the toxins in oils and the gasses that escape are greenhouse gasses. You will also likely find some plants and animals stuck in the oil.

However, you will also notice that the area around the seep has some of the most robust plantlife, especially in the dry months of the year. The plants that grow on the edge of the seep must obviously develop some immunity to the toxins, but more important in this dry climate, the seep also produces a constant water source.

Logging requirements:
Send me a note with :

  1. The text "GC1A5E2 West Sulphur Mountain Oil Spring" on the first line
  2. The number of people in your group.
  3. your evaluation of the plants adjacent to the seep and some another 100 feet or so up the trail.
  4. Take a close look at the liquid flowing along the trail and estimate the relative percentage of water and oil.
  5. How would your answer to #4 relate to your answer in #3

The above information was compiled from the following sources:

  • Sorlien, Gratier, Luyendyk, Hornafius, Hopps, 2000, Map restoration of folded and faulted late Cenozoic strata across the Oak Ridge fault, onshore and offshore Ventura basin, California, GSA Bulletin; July 2000; v. 112; no. 7; p. 1080–1090; 7 figures.
  • Siang S. Tan and Terry A. Jones 2006 GEOLOGIC MAP OF THE MATILIJA 7.5' QUADRANGLE VENTURA COUNTY, CALIFORNIA: A DIGITAL DATABASE , CALIFORNIA GEOLOGICAL SURVEY, Prepared in cooperation with the U.S. Geological Survey, Southern California Areal Mapping Project

Placement approved by Ventura County Parks

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