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Rocky Shores

Aerial image of Gregory Point on Cape Arago
Gregory Point on Cape Arago, just south of the mouth of Coos Bay, Oregon, composed of upturned, resistant sedimentary strata. Sunset Bay, a popular sheltered recreation area, is the small cove near the top of the image.
Oregon's rocky shores are artifacts of dynamic geologic processes; for thousands of years the Pacific Ocean has worked against the rocks of the land, exploiting variations of hardness and orientation in the rocks, seeking out the zones of weakness caused by fractures and faults, eroding deeper into the coastal mountains.

Volcanic basalt, a resistant rock forms the cliffs and rocks along the north coast at Cape Lookout, Seal Rocks, Haystack Rocks [there is one at Cannon Beach and one at Pacific City], and Otter Rock. South of Coos Bay, the reefs and rocks of Cape Arago are tilted layers of hardened sedimentary rocks that once formed on the ocean floor. Further south, remnants of ancient metamorphic rocks form the cliffs, offshore rocks and reefs such as Coquille Point, Cape Blanco, Cape Sebastian, and Cape Ferrelo.
The rise of sea level after Earth's most recent ice age accelerated erosion against the land and drowned remnant rocks and islands before they could be completely worn away. Rogue, Orford, and Blanco reefs are the largest of these drowned remnant rocky landscapes covering thousands of acres with only the tips of rocky spires now visible above water.
Because of this variety of geologic origins and processes, Oregon's rocky shores are mixtures of kinds, types and conditions. While there are some similarities among sites, each is unique.

Rocks and Islands
More than 1400 rocks and islands are sprinkled along nearshore zone of the Oregon coast, usually in association with cliffs and other resistant rocky features of the shoreline. These rocky remnants are dramatic and picturesque, but the are also valuable habitat that supports a diverse coastal ocean ecosystem. Most of these rocks and islands are in the Oregon Islands National Wildlife Refuge and are home to major colonies of seabirds, such as the common murre and marine mammals, including the threatened Steller sea lion.

Picture of Steller sea lionsThese Stellers sea lions are resting on a rock in Rogue River Reef, on the southern Oregon coast. The Rogue River Reef is an important breeding, pupping, and rearing site for the Steller sea lion. Photo courtesy of Robin Brown, Oregon Dept. of Fish and Wildlife.

Submerged Reefs
Submerged rocky reefs are also scattered along the coast. These areas are critical habitat for a wide variety of marine species, from encrusting corals and sponges to invertebrates, fish, and marine mammals and seabirds. In waters less than 80 feet deep, Bull kelp [Nereocystis luetkeana], a large marine algae, is associated with these rocky reef structures. The presence of kelp adds a third dimension to the reef and creates additional habitat. Over the past several years the Oregon Department of Fish and Wildlife has conducted a research program to map and inventory reef areas to understand how they contribute to fish populations and overall ecosystem structure on the continental shelf.


Picture of two people looking into a tidepool
Rocky intertidal areas, or tidepools, are unique marine environments that offer a glimpse into the marine realm. These areas are biologically rich and have evolved to take advantage of, as well as withstand, the environmental rigors of the edge of the sea. Tidepools are also vulnerable to human overuse and degradation. Oregon has developed a management strategy for protecting rocky shores while allowing for appropriate use. This Rocky Shore Strategy is a cornerstone of the state's Ocean Resources Management Program and is described in Part Three of the Oregon Territorial Sea Plan.