For this cache you will drive along narrow, twisting Pope Canyon Road west of Lake Berryessa. Park at the gravel turnout at the Parking coordinates and walk about 175 yards west along the narrow shoulder on the side of the road across from the cliff. You will now be facing a rock face of altered pillow basalt.
Pillow basalts form during underwater volcanic eruptions such as those that create seamounts (underwater mountains) or at mid-oceanic ridges where new crust is formed. The chemistry of the basalt here shows evidence that it erupted at a mid-ocean ridge. During eruption, heated seawater intermixed with basalt, hydrothermally altering the original minerals giving the usually black basalt a characteristic color and shape. The shape results from the rapid cooling of the lava as it erupts under seawater.
The steep cliffs for the next 0.3 miles west of here also consist of pillow basalts.
Logging the cache. Send me a message describing the shape of the pillow basalt and its color. Because of the colored minerals in this basalt, geologists have a descriptive name for this rock, -------stone. Can you fill in the blank?
I must receive a message from you with the answers to the questions. Otherwise, your log will be deleted.