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Elephant Rock

From Oregon Hikers Field Guide

Elephant Rock, Seal Rock State Recreation Site (bobcat)


Elephant Rock, part of the Oregon Islands National Wildlife Refuge and the Oregon Islands Wilderness, is composed of columnar basalt, technically the Gingko flow of the Frenchman Springs Basalt, Wanapum Member (15.6 million years ago). This is the farthest south remnant of the Columbia River Basalts, which originated from vents about 300 miles farther east and flowed towards the ocean down existing river valleys. The basalt flows do not, in fact, end at the shoreline, and may extend ten miles out under the ocean. Elephant Rock squats on a layer of softer sandstone from the Yaquina Formation, an indentation clearly visible at its base. Gulls, cormorants, and other seabirds nest on top of the rock.

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