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Geology and Earth Resources Division Bulletin No. 72

Washington Coastal Geology between the Hoh and Quillayute Rivers



Rock formations, from which oil-men, since 1913, have attempted to remove petroleum (see Historical Notes), are exposed in the high sea cliffs and low-tide outcrops between the Hoh River and Hoh Head. All three major sedimentary rock types, siltstone, sandstone, and conglomerate, are present and are part of SEDIMENTARY ROCK SEQUENCES of the HOH ROCK ASSEMBLAGE (see Part I).

Poorly exposed outcrops of sandstone can be seen along the trail that leads from the parking area to the beach, on the north side of the Hoh River. Landslides are common along the bluff in the vicinity of the mouth of the river (fig. 20). Aside from the obvious slumping of rock debris at the base of the bluff, the extent of this landslide area is marked by a "DRUNKEN FOREST" where trees are standing at various angles and many have developed bent trunks in an attempt to grow vertical once again. The slumped material is a jumbled assortment of sandstone and siltstone blocks set in a relatively soft matrix of clay and siltstone fragments. The chaotic nature of these rock materials may appear to be caused by the landslide itself. However, the landslide has only superficially rearranged rocks that have already been intensely deformed and intermixed by the earth's crustal forces (see Part I, Tectonic Melange Rocks). A landslide occurred here because these tectonically jumbled rocks are much less competent than most other rock formations of the area. Landslides, such as this one, and in places even larger ones, are a common sight along much of the coast to the north.

From the mouth of the river northwestward for about a quarter of a mile, no bedrock is exposed because the low bluffs are heavily vegetated and the beach area is blanketed with relatively young deposits of sand and gravel and much driftwood. Beyond this area, bedrock is exposed almost continuously along the beach and in high cliffs that form the headlands south of Jefferson Cove. Rocks of the headlands are also a sequence of Hoh sedimentary rocks and consist of massive to thick-bedded sandstone and small to very large irregularly formed lenses of conglomerate. Several landslide areas are present in small coves between the Hoh River and Jefferson Cove.

JEFFERSON COVE beach from Hoh Head trail (fig. 23).

Structural relations of the Hoh rocks in these headlands are not clearly apparent, mainly because they are massive and are locally folded and faulted. The available data of today suggest that the regional trend or strike of these beds is in a northwest direction, somewhat parallel to the coast; they are tilted or dipping northeastward about 40° from horizontal. Furthermore, evidence indicates that these beds are overturned with their tops facing downward and to the southwest (fig. 24).

ROUTE MAP—Hoh River to Toleak Point (fig. 24). (click on image for an enlargement in a new window)

Rocks that form the headland area between the Hoh River and Jefferson Cove are mapped as the west limb of a large ANTICLINAL structure (upward fold). Most of it lies inland from the coast and occupies about 10 square miles of area (fig. 25). The structural trend of the rock strata along the coast gradually swings inland north of Hoh Head. Hoh sedimentary rock sequences are relatively resistant to erosion and so form headlands and wave-cut terraces. Hence, wave-cut platforms, at approximately low-tide level, extend seaward from the headlands (fig. 14). Resistant erosional remnants of sandstone and conglomerate of this rock sequence are seen in the two major offshore rocks: Middle Rock, with its bifurcated top about three-quarters of a mile immediately west of the mouth of the Hoh River (fig. 26), and the sharply pointed North Rock, nearly 2 miles offshore (fig. 28). Both of these rocks are sandstone. Bedding on North Rock is oriented similar to the regional structure.

GENERALIZED GEOLOGIC MAP of the area between the Hoh, Quillayute, and Bogachiel Rivers (fig. 25). (click on image for an enlargement in a new window)

MIDDLE ROCK, viewed from the air and offshore, is one of the more prominent rocks near the mouth of the Hoh River. It is an erosional remnant of Hoh sandstone (fig. 26).

LOOKING NORTHWARD from the first headland south of Mosquito Creek (fig. 27).

NORTH ROCK, another prominent offshore rock of Hoh sandstone near the Hoh River (fig. 28).



The trail begins at the end of the road on the north side of the Hoh River where, in 1917, Fred Fletcher owned and operated a fish cannery. Along the river a short trail leads to the ocean beach and from there northward for approximately half a mile the beach route is unobstructed. Headlands immediately south of Jefferson Cove are best rounded at low tide, when much of the sandy beach is exposed. In any event, attempts to traverse this area should be restricted to the lower half of any tide. Once around these headlands, the sandy beach of Jefferson Cove provides a pleasant change of pace for half a mile (fig. 23).

The beach ends abruptly at the north end of Jefferson Cove where nearly vertical cliffs of massive sandstone and conglomerate form the prominent headland between the cove and Boulder Bay (fig. 24). For a distance of three-quarters of a mile, the surf pounds directly on the cliffs even at low tide. The route northward is therefore over, rather than around, this major headland. The trail rises steeply and in places over bare outcrops of massive sandstone. In the steepest area, ropes are available to assist in the climb. At the top, the trail continues for 2-1/2 miles through the woods over Hoh Head and along sea cliffs nearly to the mouth of Mosquito Creek.

For the more adventurous, a number of side challenges to the beach could be attempted but without the aid of trails. Among these excursions are Boulder Bay immediately south of Hoh Head, the top of Hoh Head itself, Secret Cove immediately north of Hoh Head, and several small coves farther north (fig. 24). However, the headlands between these small coves can be rounded only during low tide. A trail from the main inland route extends to the beach in the vicinity of the northernmost of these headlands. Northward beyond these headlands for about a mile, a sandy beach stretches unobstructed. Another headland at the north end of the beach can be rounded only at low tide. Unless this headland is reached at a definitely low tide, the inland trail should be used. Several additional small headlands must be rounded or easily climbed before reaching Mosquito Creek (fig. 27).

Because the rock strata of this area are hard, massive sandstone and conglomerate, they tend to erode into relative large blocks. Thus, the beaches immediately below the cliffs of this area are strewn with exceptionally large boulders. The conglomerate of many of these large boulders is composed of grit- to cobble-size pebbles of various rock types (fig. 29). Sandstone, chert, and siltstone, together with metamorphic and granitic rocks, are the most common. These materials were previously eroded from a mountainous land area, some 25 million years ago. From there they were rapidly transported by streams and thus became well-rounded pebbles to be eventually deposited in a sea. Further transport took place down the slope of the ocean floor where they came to rest in channel-like deposits and in association with massive deposits of sand and some silt.

CONGLOMERATE, south of Jefferson Cove, is composed of sandstone, chert, siltstone, and metamorphic and granitic pebbles (fig. 29).



The first petroleum test well to be drilled in the Hoh River country was located a short distance inland from Jefferson Cove. During July of 1913, machinery and other equipment were brought in by barge and landed through the surf. A buoy attached to large anchors 2,000 feet offshore served as a point from which landing operations took place. From there the equipment-laden skow was beached and a steam donkey engine fired up. By means of a steel cable attached to a large stump onshore, the donkey engine dragged itself from the barge, onto the beach. From there it and all other materials were skidded up the cliff and several hundred yards farther inland to the drilling site. The donkey engine was to be used as the major source of power during drilling operations (Aberdeen World, 1913).

Two test wells, Hoh Head Nos. 1 and 2, were both drilled with cable tool equipment to depths of about 1,000 feet. Although substantial amounts of oil and gas were encountered in these wells, they did not prove to be sufficient for commercial us (Washington Division of Geology and Earth Resources unpublished files). However, these findings encouraged the drilling of a number of wells in the 1930's a quarter of a mile to the north of the original Hoh Head wells.

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Last Updated: 28-Mar-2006