Three Arch Rocks, Oceanside

Three Arch Rocks, Oceanside

by | Sep 10, 2021

Three Arch Rocks are massive arched basalt sea stacks located south of Cape Meares and 0.5 miles (0.9 km) offshore from Maxwell Point at the community of Oceanside, about 8 miles (13 km) south-southwest of Garibaldi and 2.7 miles (4 km) northwest of Netarts, Oregon. The sea stacks are part of Three Arch Rocks National Wildlife Refuge that consists of three large and six small rocks within an area of only 15 acres (6 ha). The largest rocks were once called the Three Brothers, but are now called Finley, Middle, and Shag Rocks. Shag Rock is the farthest from shore, and Finley Rock is the highest with an elevation of over 300 feet (91 m). Other named rocks include Seal Rock and Storm Rock. The refuge is the smallest designated wilderness area in the U.S. and is one of six refuges within the Oregon Coast National Wildlife Refuge Complex. This complex provides wilderness protection for thousands of small islands, rocks, reefs, headlands, marshes, and bays totaling 371 acres (150 ha) and spanning 320 miles (515 km) of Oregon’s coastline. The refuges are all managed by the U.S. Fish and Wildlife Service. Three Arch Rocks National Wildlife Refuge protects the largest seabird nesting colony on the Oregon coast and includes 30 percent of Oregon’s common murres and 60 percent of the tufted puffins. It is also the only pupping site for the Steller sea lion in northern Oregon. 

Cape Meares and the islands adjacent to it are formed of a relatively thin layer of middle Miocene basalt flows, breccia, and associated feeder dikes. These Grande Ronde basalts erupted from volcanic fissures in southeastern Washington and northeastern Oregon 15.6 to 16.8 million years ago and flowed over large parts of Washington and Oregon, down what is now the Columbia River drainage, and all the way to the coast. Similar basalts form the headlands at Yaquina Head, Cape Foulweather, Cape Lookout, and Tillamook Head. These middle Miocene basalts are the youngest Tertiary rocks exposed along the northern coast of Oregon. The basaltic rocks of the Cape Meares area extend seaward to form Three Arch Rocks and other rocks and sea stacks. Three Arch Rocks were once part of Maxwell Point before wave erosion separated them into individual sea stacks. They consist of low dipping pillow lava, subaerial flows, and breccias, together with associated feeder dikes and sills and small pluglike bodies. The middle Miocene basalts that form the surface rocks at Cape Meares and Three Arch Rocks overlie a thick sequence of Tertiary marine sedimentary rocks that were deposited in a structural feature known as the Tillamook embayment, which extends along the coast from Tillamook Bay to Sand Lake. These sedimentary rocks are more than 8,000 feet (2,438 m) thick and range in age from middle Eocene to middle Miocene. The Tertiary sedimentary sequence rests on more than 10,000 feet (3,048 m) of lower to middle Eocene basaltic pillow lavas and breccias that contain interbeds of marine tuffaceous siltstone and basaltic sandstone. These basalts and interlayered sediments are known as the Tillamook Volcanic Series and are the oldest rocks exposed in the northern part of the Oregon Coast Range.

Three Arch Rocks is the oldest National Wildlife Refuge west of the Mississippi River and was established largely as a result of the efforts of William Finley and Herman Bohlman, two early wildlife photographers and conservationists. William Finley was born in Santa Clara, California in 1876, and Herman Theodore Bohlman was born in Portland, Oregon in 1872, and the two became fast friends when the Finley family moved to Portland in 1887. In high school, Finley and Bohlman became interested in ornithology, and collecting inspired them to start a side business selling biological specimens, including bird skins and eggs, to scientists and private collectors. By the late 1890s, however, the impact of over-collecting on bird populations led to a shift in public sentiment on the practice. The pair traded their collecting kit for a camera and embarked on a decade-long partnership of artistic and scientific works. Between 1899 and 1908, Finley and Bohlman photographed and wrote about thousands of birds on expeditions throughout Oregon and California. Concerned about egg gathering and the wildlife devastation brought about by marine mammal hunting and the killing of seabirds by local sport shooters, Finley and Bohlman began to study and photograph Three Arch Rocks in 1901 to support the establishment of a wildlife sanctuary. During the summer of 1903, after several failed attempts, they rowed a dory to Shag Rock where they camped for fourteen days, photographing birds. Later that year, Finley took the photographs to Washington and personally showed them to President Theodore Roosevelt, lobbying for the protection of the birds. The Three Arch Wildlife Refuge was established by Roosevelt on October 14, 1907. Read more here and here. Explore more of Three Arch Rocks and Oceanside here:

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