Ore Bin / Oregon Geology Magazine / Journal
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State of Oregan The ORE BIN Department of Geology Vol. 29, No.5 and Mineral Indu,t rie ~ Moy 1967 1069 Stole Office Building Portlond, Oregon 97201 GEOLOGY OF CAPE LOOKOUT STATE PARK. NEAR TILLAMOOK. OREGON By Doris Mangum" Introduction to t he Pork Cope l ookout is probably the most striking ond scenic headland on the Pacific Coast. The two - mile- Iong cope is a narrow wedge of basaltic lovo with vertical sec cliffs 800 feet high . Extending north from it is Netarts Spit, a six - mile- long, dune covered ridge of sa,!d that separates Netarts Boy from the open ocean. North of Ne tarts Bay is Cope Meores, another basalt headland. Cope l ookout State Pork provides excellent recreation faci li ties on the fine beaches of Netarts Spit adjoining Cope lookout. The pork is situated on the north ern Oregon coost off U.S. Highway 101 southwest of Ti Ilamook. It moy be reached from Tillamook by woy of Netarts and Whiskey Creek roods, a total distance of 12 mi les (figure 1). Overnight camping facilities include 53 trailer sites, with hookups for water, sewage, and e lectricity, and 196 tent sites. fresh woter, firewood, laundry, and showers are available near campsites. Sheltered electric stoves are prov ided in the day-use areo at nominal charges . Group camping by reservation will accommodate 100 people, thus permitting organized groups to convene aport from the main-use area. Pork facilities are generally availoble to the pub li c year-round according to publ,c demand and weather conditions. Other parks (including federal, state, and county) with overnight camping facilities are available in the proximity o f Ti llamook; their general locations are shown on figure I. There ore mony interesting and scenic places for the pork visitor to see at Cope Lookout and in the surrounding areas. Four trips, including both hikes and drives, to points of interest ore outlined in this report. Their locations are shown on figure 1. But first, a review of the geographic setting and the geology of the region should help make these excursions more enjoyable. * Doris Mangum is doing grock.rate work in soil science and geology at Oregan State Uni versity. Her report on Cope Lookout State Park is the result of a cooperative ar rangement between the Stale af Oregon Department of Geology and Minerallnck.rstries and the State Parks and Recreation Division of the Highwoy Department to present the geology of the oreain a way thaI is interesting and understandable to park visitOfS. 85 N Oth. , comptrMll .i,,, (S'ot., Fed.rol 8 County) Htk" or drh'u to points of Int.,•• 1. Figure 1. Index mop of the Til lamook region, Voowing location of Cope l ookout Slate Pork and o ther geographic features. Numbers 1 through 4 refe r to hikes and dr ives described in text. 86 Geographic Setting Historians claim that in 1788 John Meare~, an English sea captain, applied the name "Lookout" to the present Cope Meares 10 miles to the north. Then, through some misunderstonding, the Coast Survey odopted the nome Cope lookout on its charts of 1850-53 for a point 10 miles south of Meares' original locolion ond the name still stands (ArmsITong, 1965) . Til[omook, which means "land of Mony Waters," was the name of a large tribe of Salish Indians who lived in the oreo south of Tillamook Head. Early explorers writing in their journals spelled the nome Killomook, Col lemex, and vorious other woys, but finoll y the presenl spelling was odopted. In 1853 Tillomook County was created by territoriol legislature, and in 1866 a post office named Tillamook was es tablished. The first 20 years were difficult ones for the settlers, especiolly since they had to pock 01 1 oftheir supplies in from the north over the treacherous NeahkohnieMoun toin. Several shipping ottempts foiled. Thirty- two shipwrecks (Orcutt, 1951) be tween Neahkohnie Mountain and the Nestucca bar attest to a dangerous Pacific Coost. ( I ,mote and vegetation The Tillamook area is located in a marine climate typical of the wes t coo~h of continents between 40" ond 50" latitude. The average January and July air tem peratures ore 42" and 59" respectively. Tillamook records about 90 inches of rain a year, with the months November through March receiving more thon 10 inches, while July ond August each overage less thon 2 inches. The worm Japanese current passes the Al eutian Is lands and continues south along the Pacific Coast. Ir provides mois tvre 0$ clouds and fog whi ch are channe led upward by the Coast Range, where they cool to produce rain. The prevailing winds are from the southwest during the winter and the northwest dud ng the summer. A humid tronsition vegetation zone extends from the Pacific Ocean to the mid dle slopes of the Cascades . Major trees are the western hemlock (Tsugo he terophyllo), western red c edar (Thujo plicoto), Douglas fir (Pseudotsugo menziesii), and Sitko spruce (Picea sitche ns is). Species of maple, older, Pacific yew, salol, red elder berry, huckleberry, $Olmonberry, thimbleberry, and trailing blackberry form a dense understory. Many fern species abound in the cool, moist shade. Physiographic features The Tillamook area lies in the Coost Range physiographic province, which ex tends from the Columbia River on the north 10 the Coquille River and the Klomath Mountains on the south ond to the Willomelle Volley on the east (Highsmith, 19Sn. The averoge elevOlion of the Coost Range is about 1,500 feet, but peaks such as Mount Hebo south of Tillamook rise about 3,000 feel. The norrow coastal plain is interrupted by headlands mainly of basalt, which is more resistant to erosion than sedimentary rocks such as sandstones and sh oles. Cape lookout and Cope Meares are fine examples of bosoltic headlands surrounded by $Ofter, more easily eroded rock. The work done by oceon waves is well illustrated in the Cope lookout-Cape Meares orea. Waves have a tendency to straighten out 'he coost line by eroding B7 88 headlands and building sand ~pit5, such as N etarh Spi t. Thes e long ridges of sand are connected at one end with the rr.ainlond. They form when waves meet the shore at on angle and move sand a long it. Wind accentuates the hei ght of the sp its by blowing the dri ed sand inta dunes . Waves are constantly eating away any rock that iuts into the ocean at Cape lookout and Cape Meares. Erosion;s accompl ished in several ways. When a wove washes over a rock, a ir becomes trapped and compressed in cracks and ioints; when the water leaves, the air expands explosively and acts like a wedge to break the rock. When waves hur l sand, grovel, and bo..., lders against the rock they chip it owdy. The force of t.he waves is tremendous. Pieces of rock have been thrown as much as 200 feet up the cl iffs at Cope Meares and have domoged the lighthouse. Wh en the lower part o f the sea cliff is undermined by the waves, the upper portion loses its support and breaks off. Du ring th is process, coves some ti mes develop where the rock is weak . Re treat of the sea cliff forms a wove- cut bench. The end of Cape l ookoot has both a cove and a bench (figure 2). When a portion of a headland is cu t off from the mainla nd, sea stacks, like those at Cope Meares, are created (fig..., re 3) . G e ologic H i story Most of the rocks that underlie the Til la mook area were laid down in seas dur ing Eocene, O ligocene, ond Miocene epochs (see geologic map on plate I -A). These rocks consist of lava flows and sediments, some of which contain marine fossils. At various times in the geologic history of the area the slrolo were upl ifted from the sea , gently folded, faulted, ond eroded. The old marine beds and lavas are now overlain in places by terrace deposits, dunes, ond ri ver si lts of Pl iocene, Pl eistocene, and Recent age. Eocene epoch About 60 million years ago (see geologic time chart). during the earl y port of the Eocene efX'ch, a huge trough- like basin or geosyncline occupied Ihe site of the present Olympic Mountains, Coast Range, and Puget-Wil lamette low land. It ex tended from Vancouver Island in the north to the Klamath Mountains in the sovth. Sediments were eroded from the adiacent land and accumulated in the bas in. At the same time, lava erupted from vents on the sea floor. At places the lava pi led up to form volcanic islands, perhaps like the Hawai ian Is lands today. Tillamook Volcanics: In the north ern Coast Ra nge these roc ks are known as th e Till amook Volcanics. They are the oldest rocks exposed in the Tillamook orea and ore, in port, equivalent to the Siletz River Volca nics in the centra l ond southern portions of the Coost Range (Bo ld,yin, 1959). The Tillamook Volcanics may be seen east of Ti llamook in the Wilson, Trask, Neha lem, and N estucca drai nages (see geo logic mop, plate 1). They are dark greenish a nd gray, fine- grained to porphyri ti c (contain visible crystals) bosalt~ with pil lows, breccia , and related structures . Cir cu lating chemical solutions have altered the boso lts a nd have precipi ta ted zeolites, quartz, and calcite in cavities.