On Isla San Jos‚ we landed at a beach backed by yellow cliffs of marine sedimentary rock, composed of sediments deposited in shallow seas which predated the Gulf by millions of years. While observing whales and seabirds in the wide channels between the islands and the peninsula, we gazed up at the towering escarpment of the Sierra de la Giganta, 9,000 vertical feet of layers of lava and ash laid down by the action of a tremendous range of volcanoes which once rose where the sea now lies.
And today we explored a beach south of Bah¡a los Angeles, backed by hills of granite, another type of igneous rock. Here and there we found examples of gneiss, a metamorphic rock formed as roof pendants on the great molten masses of granite where the heat was great enough to change the mineral nature of the surrounding rocks.
Of course all of these examples of geologic wonders were appreciated not least for the beauty of the landscapes they created. Nowhere was this more apparent than on our excursion to the Tres V¡rgenes volcanoes, young basaltic mountains near Santa Rosalia which were born as part of the process which tore Baja loose from the Mexican mainland. Here we walked on or along a 700-year-old lava flow to a view of the great cones soaring above. We also encountered Baja elephant trees (Pachycormus discolor), one of the only plants capable of living on the bare lava.
