There is adequate parking along the riverside of the highway. Winter snows will cover the exposures and spring runoff in the river may get high enough to put the exposures underwater.
At Savage Rapids the Klamath River flows over an exposed section of what appears to be the Rattlesnake Terrain. It is primarily serpentine, but there are veins of quartz (
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These various rocks were added to the North American Plate during an accretionary episode in the Late Jurrasic (
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Often this rock is referred to as serpentine. However, it is actually called serpentinite (
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Up close, serpentinite looks either platy or fibrous depending upon which of the three most common serpentine minerals (
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Serpentinite is a metamorphic rock. But unlike the majority of metamorphic rocks that form from increased heat and pressure, serpentinite forms most commonly when peridotite (
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Mafic (
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As the peridotite is pushed up into the crust at a mid-ocean spreading center and moves away, the temperature and pressure on the minerals is reduced. Fractures from plate movement and cooling rock create conduits for sea water to come into contact with the peridotite. Another major location where fractures are created is at subduction zones where the oceanic plate full of peridotite bends, forming additional cracks, and descends back into the mantle.
It is at subduction zones where serpentinite gets sheared off the subducting plate and attached to the continental plate. A subduction zone was present off the coast of California relatively recently. That is why serpentinite is common in California.
Now that the minerals that make up the peridotite are no longer in the high pressure and temperature conditions under which they are stable, they begin to metamorphose. Water is incorporated into the minerals and they become serpentine minerals turning the peridotite into serpentinite. The minerals brucite and magnetite are also formed with the magnesium and iron ions that are left over along with the release of hydrogen ions. Methane is formed as a by product of the formation of magnetite. This methamorphic process is called serpentization.
Serpentization increases the volume of the crystals by about 30%, thus decreasing the density of the rock. This further enlarges any cracks in the rock allowing more water to come into contact with unmetamorphosed peridotite, continuing the process deeper into the rock. This less dense rock begins to work its way up through more dense material above it, partially explaining how serpentintie is exposed at the earth’s surface.
Serpentization also creates heat in exothermic chemical reactions. The chemical reactions are capable increasing the temperature of the surrounding water by about 260 deg C (550 deg F). This creates deep undersea thermal vents as hot water is forced out of sea floor cracks pulling in cooler water. Entire undersea ecosystems have developed around these vents that are completely independent of the sun as the heat and food source (methane) is all derived from the chemical reactions of serpentization. It is thought that such ecosystems may have been important in the formation of early life.
Serpentization is also a major factor in the “deep” water cycle. That is discussed in a The Deep Water Cycle and Serpentinite.
Later volcanic activity introduced the quartz veins into the Rattlesnake Terrain