Pacific Star Fault EarthCache
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The discovery of the Pacific Star Fault first came about in 2003 when a team of geologists from Franklin Marshall University in PA were doing fieldwork just south of the Pacific Star Winery, After receiving permission to look from the winery property the team was startled to find visual evidence of a major addition to the San Andreas Fault system. The geologists gave the winery the honor to name this fault and they chose the Pacific Star Fault.
The San Andreas Fault is a rupture on the surface of the earth that marks a separation of two continental plates; the North American and the Pacific. The Northern American Plate is moving about a half-inch per year to the west, while the Pacific Plate is moving about the same speed but to the northwest, towards Japan and the Aleutian Islands. The San Andreas is not a single rupture but many, and the zone is many miles deep. Where the movement shows on the surface we call a fault, and the movement below can show on the surface at more than one place. The San Andreas is therefore a multi-fault system. In No. California it is comprised of the main San Andreas, the Hayward, the Calaveras and several other faults, the Napa and the Pacific Star among them. One cannot track a fault from the surface unless you have visible evidence showing on the surface of the planet. Because Northern California is heavily forested and has inland bodies of water, faults are not readily visible until they have had a recent break. Over time because of erosion, those breaks will be covered by water, or even new sediment, again covering evidence of a fault.
The surface rocks at the winery on which one stands today are 130,00 years old, very young by geologic standards. There is a huge gap in time between that top 6 feet or and the dark, hard rocks beneath them: about 65 million years. The young rocks are part of a recent wave terrace from an earlier, higher sea level when there was less ice at the polar caps than today. What rocks that used to be between them have eroded away by the wave action over millennia. The fault has been moving many millions of years, most of the time covered over by the ocean or newer sediments, like the young sandstone or soil. Where the geologists were able to see the fault was a break between sections of the dark, old sandstone exposed by ocean waves.
The fault has little vertical movement. Each section to the West of a fault break moves northwesterly away from the immediate one on the East side. There are 5 known separate sections of the fault where they have moved. The sea mostly exposes the Westernmost, where geologists first saw the fault here at the winery.
At the coords in the picnic area you can stand and see the fault evidence. The owner has given permission for this earthcache and you need only go through the gate to the picnic area to access it.
UPDATE 10/11/2016
gate is only open
12 noon to 5 pm everyday, but closed Tue & Wed (Nov thru Apr).
That is why it is a harder difficulty since it only can be accessed when the winery is open.
To claim this earthcache you must email answer to these questions and since pictures no longer can be required, they would still be appreciated.
your log will be DELETED in 5 DAYS if answers are not sent.
1. the different color of the rocks on either side of the ocean water.
2. How wide is the crack at it widest spot.
3. How long is the obvious crack
4. what is the weather the day you visit.
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