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Geology of the National Parks

GEOLOGY OF OLYMPIC NATIONAL PARK: PART Il NOTES ON THE GEOLOGY

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Hurricane Ridge Road

STOP 10: Hurricane Hill Trail

The old roadcut along the Hurricane Hill Nature Trail reveals alternating layers of gray sandstone and shale. These rocks have been strongly folded, and in the outcrop along the trail, the careful observer can trace sandstone beds around the bend of the fold (fig. FT 21).

Folded sandstone and shale
Fig. FT 21. Folded thin-bedded sandstone and shale.

At the last climb of the Hurricane Hill Nature Trail, where the trail begins to zigzag, the mountain stroller reaches the first thin beds of volcanic rock (of the Crescent Formation) that spilled out across the ocean floor about 55 million years ago. To the left, these lavas make small, rugged cliffs. Rubble weathered from alternating layers of dark volcanic and sedimentary rocks is found all the way up to the gentle meadow on top of Hurricane Hill. Much of the volcanic rock here is sprinkled with white dots which are small cavities filled with white minerals, mostly calcite and zeolites. The cavities were formed by gas bubbles escaping from the once-molten rock. Later the zeolite and calcite precipitated from mineral solutions in the rock and filled these fossil bubbles At the very summit, where the old fire lookout used to be, is a ledge of pillow basalt, much like that described along the Dungeness River (Field trip stop 1).

The main mass of the submarine volcanic field, now tilted on end, can be seen on Mount Angeles across the valley to the east.

Cross section of Klahhane Ridge
Fig. FT 22. Cross Section of Klahhane Rige area showing tipped up volcanic field (the Crescent Formation) and other rock units. For a key to the colors see the geologic map.

Material in this site has been adapted from Guide to the Geology of Olympic National Park by Rowland W. Tabor, of the USGS. It is published by The Northwest Interpretive Association, Seattle.

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