The Volcanic Peaks of San Luis Obispo County

This is a historial post from Hiking the California Trail, a 1998/2002 book set by Bob Lorentz and Richard Nichols. Where possible an update has been provided.

Morro Rock rises 576 feet like a sentinel above the Coastal Trail and the mouth of Morro Bay, visible for miles on a clear day. In 1542 Cabrillo named the rock “El Moro’ (the Moor) for its dark countenance. But when Portola camped nearby in 1769, he noted the presence of”a rounded morro” (promontory) at the mouth of the estuary. Morro Rock is actually a volcanic plug, the only remnant of a volcanic peak that stood over 20 million years ago. The igneous basalt of Morro Rock was the molten core of the volcano, which in this case never flowed out of the volcano’s crater. Over time the softer outer rock of the volcano eroded away, leaving only the plug in place. Only 120 years ago Morro Rock stood 1000 feet off the mainland shore, with the entrance to Morro Bay on its north side. Then, between 1880 and / 969, more than one million tons of rock were quarried from the inland face of Morro Rock, used to build the breakwaters of Morro Bay and San Luis Bay. Morro Rock was connected to the mainland and a new harbor channel dredged south of the rock and breakwater. Ironically, the quarrying sculpted a more dramatic vertical face for the rock as viewed from shore. In 1969 the rock was preserved in Morro Rock Ecological Preserve to protect the soaring peregrine falcons that nest there.

Morro Rock is the most famous of a chain of nine volcanic peaks highlighting the landscape between Morro Bay and San Luis Obispo. All of them formed beneath the Pacific long before being uplifted onto the expanding continent. From Turri Road you can see Black Hill, Cerro Cabrillo and Hollister Peak. Cerro Romualdo and Chumash Peak are visible from Los Osos Valley Road. The tallest of the plugs, 1546 foot Bishop Peak and nearby Cerro San Luis Obispo can be seen from Foothill Boulevard and most of San Luis Obispo. Islay Hill, the southernmost of the peaks rises east of the San Luis Obispo Airport.

For a grand view from the top of one of the volcanic peaks, head for Morro Bay State Park and make the 3-mile round trip ascent of Black Hill. From the 66 l-foot summit you’ll see several of the volcanic plugs and a breathtaking view of Morro Bay and the surrounding coast.

Originally Published in Hiking the California Coastal Trail: Guide to Walking the Golden State's Beaches and Bluff from Border to Border - Volume Two: Monterey to Mexico by Bob Lorentzen and Richard Nichols
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