As was noted in the previous post, we attempted our trip during the Bombogenesis storm that wreaked havoc across Southern California. This kind of storm can often result in disaster as highways get closed or damaged by landslides, but we were lucky and were able cross the Inyo Mountains and Darwin Plateau without problems. But we did get the opportunity to see some great geology, and even were able to add a new stop to our itinerary (because we missed a different one, but I'm not complaining).
Our first sight as we approached the mountains was the snow covering the desert peaks (first picture above), a hint to the seriousness of the storm we were challenging. The tilted rocks are Paleozoic-aged (300-550 million years) limestone layers. They recall a time when California was very different, completely submerged under a shallow tropical sea. We would be seeing more of these fascinating rocks later on. The road crossed the flat uplands of the Darwin Plateau, and then plunged down a steep incline towards the Panamint Valley.
We actually had fog in this arid environment, since the clouds were crowding against the edge of the steep mountains. As we passed the Father Crowley Vista Point, the clouds briefly parted and we had a view into the deep gorge of Rainbow Canyon. At this point, the slopes and flats are covered with basaltic lava flows ranging in age from 8 to 4 million years old. The immediate question becomes, why volcanoes? Why right here?
In a sense, volcanism is possible almost anywhere on the planet. It's not that there is magma everywhere, but that a hundred miles beneath our feet there is a zone, the asthenosphere, where the rock is almost molten, but not quite (perhaps 5-10% liquid). To melt this rock and create volcanic activity would require raising the temperature (as happens at hot spots like Hawai'i), or releasing pressure (pressure keeps the rocks from melting in the same way that pressure cookers prevent water from boiling). There aren't any hot spots in the immediate vicinity, but the crust across the Basin and Range Province has been stretched and thinned, allowing pockets of basaltic magma to form and rise into the rocks above, often following fault zones to the surface.
|Looking across the Panamint Valley towards Hunter Mountain. The dark rocks on the left summit area are identical to the rocks at Father Crowley Vista Point.|