San Miguel Geology
As the northernmost island, and the one least protected by Point
Conception, San Miguel has been subjected to the most severe natural weather forces of all the Channel Islands. That combined with horrible over grazing by excessive sheep population have shaped this windswept isle mercilessly. Primarily sedimentary sandstone, it is vulnerable to ocean erosion, and the carving of Cuyler Harbor is a process continuing today. The highest point on the island is Green mountain at 831 feet. The majority of the island, since it lost its earlier ground cover to sheep grazing during severe droughts, is made up of shifting dunes that reveal and cover fossils, mammoth bones. Tribal artifacts, and World War II weaponry randomly.
The most noteworthy geologic formation on San Miguel is the amazingly
eerie caliche forest - the largest and most intricate on the Channel Islands. A caliche forest is an other worldly appearing mineral formation that has adhered to the lifeless remains of low lying vegetation. The caliche formation are made of rhizoconcretions that form eerie, abstract landscapes of bizarre form. The materials that work together to form a caliche forest are calcium carbonate, sand, gravel, silt and clay. On San Miguel, which has bee stripped of its tress and shrubs by irresponsible ranching practices, these caliche trees offer a testament to the green forests that lived on the island long before man ever arrived.
The Island has seen seismic activity, and in 1895, the leaseholder on
the island reported " There has been quite a commotion on San Miguel Island. The land which formed the high bluff on the west side of the harbor has sunk more than sixty feet and forced itself under the beach, not only raising it, but stones which had lain at water’s edge are now fifteen feet above it … So sudden was the change that fish and crabs were left high and dry and thirty feet above the harbor.