Saturday, April 6, 2019
Tales from the Semi-Super-Bloom Tour, Part 1: The Mojave Desert and El Paso Mountains
Although the fault motion is primarily lateral, some warping and deformation has lifted a mountain range on the north side of the fault, the El Paso Mountains. The mountains are composed largely of older Paleozoic metamorphic rocks. The rocks had been quite deep in the crust, but were brought to the surface and eroded, and by around 12-15 million years ago had been eroded to a fairly flat surface. This surface was eventually covered by terrestrial sediments deposited in alluvial fans, grassy plains and ephemeral lakes that would remind a person of the African savannah. The comparison is apt, because the sediments contain fossils of a diverse fauna that included ancient camels, horses, antelope, elephants, and a number of predators including to the forerunners to our modern cats and canines.
Our highway turned north, crossed the Garlock fault, and entered Red Rock Canyon State Park, which preserves the Neogene sediments containing the fossils mentioned above. Millions of people have seen Red Rock Canyon, but not necessarily in person. The brightly colored cliffs have been used as the backdrop for hundreds of Hollywood movies (they were the cliffs of 'Snakewater', Montana in the opening scenes of the original Jurassic Park).
We found that many of the Joshua Trees were blooming. The trees are a defining characteristic of the Mojave Desert and are found primarily in east California and portions of Arizona and Nevada. The trees are a potential victim of global warming. Their seeds once were spread in the scat of giant ground sloths during the last ice age, but the sloths are gone, and with the increasing heat, the trees (actually lilies) are unable to propagate up slopes where they can thrive. Ironically, the trees may disappear entirely in the national park that is named after them.