The Sea Lion Caves are a connected system of sea caves and caverns open to the Pacific Ocean on the central Oregon coast. They are located 11 miles (18 km) north of Florence on U.S. Highway 101, about midpoint on the 400 miles (640 km) Oregon Coast.
The caves were discovered in 1880 by Captain William Cox, who first entered through the western channel in a small boat on a calm day. He purchased the land in 1887 from the State of Oregon and his family owned the property until 1926. There were no roads in the area at that time and the slopes above the headlands were used for sheep pasture. In 1930, when it became probable that U.S. Route 101 would be constructed along the coast, a trail was excavated by hand into the face of the cliff. At the bottom, a wooden tower with 250 steps was extended down to the north entrance of the caves. In 1958, an elevator shaft was bored through 208 feet (63 m) of rock that took three years to build.
Sea caves on the Oregon coast have formed where the basalt rock has been weakened by fractures. Broken rock along the fracture zone is quarried by the forces of water under pressure and compressed air and over time is enlarged. Numerous caves are present on the Oregon coast, but the largest ones are at Sea Lion Point. These caves were localized by intersecting fracture zones, one trending roughly north-south and the other in a nearly east-west direction. The largest opening is along the east-west fracture and is the one used by the animals as they move in and out of the cave. A tunnel that passes through the headland was developed along the north-south fracture zone and the fractures are visible in the ceiling of the tunnel. Lateral erosion within the cave and dislodging of rock from the ceiling have shaped it into a large, high-vaulted, amphitheater-like cavern with the height of a 12-story building and stretching the length of a football field. It is the natural home to a colony of sea lions and a diverse array of seabirds and shore creatures. Read more here and here. Explore more of the Sea Lion Caves here: