Road Log

0.0 (0.0)       Refer to Map 1F.1.  Intersection of Franklin Avenue and U.S. Hwy 97(3rd Street) in Bend, OR.  Drive north and remain on Hwy 97 (3rd Street) through town.

0.3 (0.3)       Intersection of U.S. Highway 97 (3rd Street) and U.S. Hwy 20 (Greenwood Avenue). Continue north on Hwy 97.

2.6 (2.3)       Highway interchange between U.S. Highway 97 (3rd Street) and U.S. Highway 20.  Remain in the right-hand lane and head for Hwy 97 and Redmond, OR.

4.1 (1.5)       Leaving Bend, OR city limits.  The road here lies on the Basalt of Bend, widespread lavas originating on the lower north flank of Newberry Volcano.

7.5 (3.4)       Refer to Map 1F.2.  Junction of Hwy 97 and the Tumalo – Deschutes Market Rd.  Long Butte lies to the left at 10:00, a small, older Pliocene shield volcano probably associated with Deschutes Formation lavas that is surrounded by Pleistocene age Basalt of Bend.

13.1 (5.6)     Refer to Map 1F.3.  U.S. Hwy 97 passes beneath high-tension power transmission lines at this location.  Forked Horn Butte lies to the left at 10:00, another small, older Pliocene shield volcano.  It has probable affinity to nearby  Pliocene lava flows of the Basalt of Redmond erupted about 3.6 million years ago (Sherrod et al., 2004).  The road here is still on Basalt of Bend which nudges against Forked Horn Butte on its southeast side.

16.2 (3.1)     Refer to Map 1F.4.  Intersection of U.S. Hwy 97 and Oregon Hwy 126 West (SW Glacier Avenue) in Redmond, OR.   This intersection also provides access to downtown Redmond and old Hwy 97 (5th Street northbound).  Continue to follow Hwy 97 north toward Madras, OR.  The town of Redmond is built on Pliocene lava flows of the Basalt of Redmond erupted about 3.6 million years ago (Sherrod et al., 2004).

16.4 (0.2)      Intersection of U.S. Hwy 97 and Oregon Hwy 126 East (SE Evergreen Avenue).  Remain on Hwy 97 heading north.

18.3 (1.9)     The exit 119 northbound off-ramp from U.S. Hwy 97 here provides access to downtown Redmond and old Hwy 97 (6th Street southbound).  Remain on Hwy 97 heading north toward Madras, OR.

19.4 (1.1)     Hwy 97 skirts the eastern flank of the southernmost series of cinder cones and spatter cones that comprise Tethrow Butte.  The composition of cinders and other ejecta from Tethrow Butte is very similar to lava flows of the Agency Plains basalt member of the Deschutes Formation, a widespread unit forming much of the cap rock in the Deschutes basin.  Tethrow Butte lavas are dated at about 5.3 m.y., and are the most extensive intrabasinal volcanic rocks erupted contemporaneously with collapse of the early High Cascades and formation of the central Oregon High Cascades graben (Smith et al., 1987; Smith, 1991; and Sherrod et al., 2004).

22.0 (2.6)     Intersection of U.S. Hwy 97 and B Avenue and in Terrebonne, Oregon.  Turn right (east) onto B Avenue for Smith Rock State Park.  B Avenue becomes Smith Rock Way on the outskirts of town.  Terrebonne sits on the Pliocene Basalt of Redmond (Sherrod et al., 2004).

22.4 (0.4)     The road descends onto the Pleistocene Basalt of Bend which is inset into the older Basalt of Redmond here (Sherrod et al., 2004).  The volcanic rocks of Smith Rock State Park are to your left at about 10:00.

22.6 (0.2)     Intersection of Smith Rock Way and NE 1st Street.  Turn left (north) onto NE 1st Street.

23.1 (0.5)     NE 1st Street bends sharply right to become NE Wilcox Avenue; continue on NE Wilcox Avenue.

24.6 (1.5)     Intersection of NE Wilcox Avenue and Crooked River Drive.  Turn left (north) onto Crooked River Drive.

25.1 (0.5)     Smith Rock State Park Sign.  Parking requires an annual Oregon State Parks Pass, or a Day Use Permit.  An overflow parking area and automated, self-pay, Day Use Permit kiosk can be found to the left here, but more parking and another kiosk lie ahead, closer to the park’s main trailhead.

25.4 (0.3)     Proceed past the park’s entrance and park in the observation parking area.  Take the short walk to the viewing platform, and let’s consider the geology of the area.

The spectacular cliffs and spires of Smith Rock State Park have a long established reputation as Oregon’s foremost climbing Mecca.  Combined with the twists and turns of the Crooked River and sprinkled with a few hardy Ponderosa pine, these rock formations provide amazing scenery (especially accented by the light of a sunrise or sunset), as well as an interesting geologic story.  Smith Rock State Park exposes tuff and rhyolite that is correlated with the regionally extensive ash-flow tuffs, lava flows and domes, and debris flow deposits of the John Day Formation.  The Gray Butte Rhyolite and Smith Rock Tuff have been correlated to the 29.6 m.y. old welded-ash-flow tuff of member G of the John Day Formation (Smith et al., 1998).  John Day rocks, combined with the older Clarno Formation, represent the Paleogene basement of the Deschutes basin to the west, cropping out in the highlands of the Mutton and Ochoco Mountains north and east of the basin (Bishop and Smith, 1990).

Bishop (1989) provides a detailed description of the rock units comprising the Gray Butte – Smith Rock volcanic complex, not all of which are readily observable from Smith Rock State Park.  The Gray Butte Rhyolite is an ash-flow tuff exhibiting flow banding and folding (Bishop, 1989), and is poorly exposed within the park.  The Smith Rock Tuff forms much of the spectacularly weathered cliffs and hoodoos north of the Crooked River (Figure 1F.1), pocked and pitted and ready-made for climbing.  The tuff  is a complex, buff colored unit composed of air-fall tuff, ash-flow tuff and muddy tuffaceous sediment dated at about 29 m.y. B.P. (Bishop, 1989; McClaughry and Ferns, 2006).  The tuff has been devitrified, meaning that the glassy ash and pumice has been altered over time into clay minerals.  Angular rhyolite and tuffaceous rock fragments are common, although graded bedding is absent, suggesting the volcanic material was not transported far from its source vent.

Figure 1F.1.  View to the northeast from the observation platform at Smith Rock State Park.  The jaggedly weathered, buff-colored rock on the north side of the Crooked River in Smith Rock Tuff; in the immediate foreground and on the south side of the river are younger basaltic lava flows from Newberry Volcano.

The Smith Rock Tuff was penetrated by small rhyolitic intrusions following caldera collapse.  A distinctive reddish, hard, brittle, finely crystalline rhyolite dike intrudes the tuff north of the Crooked River, at the first meander bend, easily observed from the parking/overlook area and the feature most visitors readily identify as “Smith Rock” (Figure 1F.2); Smith Rock itself is actually the promontory visible beyond the next bend in the river.  The dike exhibits vertical flow banding and has a chilled margin against the Smith Rock Tuff.  Emplacement of the silicic dike shortly following deposition of the tuff and prior to its solidification and dehydration is indicated by pronounced vesicles in the tuff near the baked zone and co- mingling of the rhyolite and tuff, suggesting feathering of the magma into the weak unconsolidated tuff during intrusion (Bishop, 1989).

Figure 1F.2.  View to the northwest from the observation platform at Smith Rock State Park.  The jaggedly weathered, buff-colored rock on the north side of the Crooked River is Smith Rock Tuff; the tuff is intruded by a distinctive, reddish rhyolitic dike (right side of image).  Younger basaltic lava flows from Newberry Volcano occupy the south side of the river.

Younger, Pleistocene basalt lava flows from the north flank of Newberry Volcano form the low cliff and  terrace along the south side of the Crooked River (Figure 1F.1 and Figure 1F.2) and directly underlie the observation area (Sherrod et al., 2004).  The S-shaped contact between the older silicic Smith Rock Tuff and its intrusives and the younger basaltic lavas from Newberry forms a natural zone of weakness along which the Crooked River has carved its course; however, it is probable that the Crooked River had already carved a valley into the older rocks similar to the one seen today by middle Pleistocene times and then was inundated by the younger lava flows, only to carve another valley at the boundary between the two rock types.

Recent research indicates that the silicic volcanic rocks exposed at Smith Rock State Park form the northwest margin of a caldera formed in the late Oligocene, named the Crooked River Caldera by McClaughry and Ferns (2006).  The Gray Butte Rhyolite probably represents the outflow tuff facies generated during caldera formation, while the lithic tuff of Smith Rock fills a portion of the eroded core of this caldera and corresponds with a closed gravity flow flanked by large fields of late Oligocene rhyolite lava flows and domes to the northeast, northwest, and southeast.  The caldera margin is elsewhere defined by smaller rhyolitic domes, lava flows and ash-flow tuffs, and small rhyolitic domes and intrusions penetrate the caldera-filling tuff at Barnes Butte and Smith Rock.

The Crooked River Caldera may represent one of several source vents for the voluminous ash-flow tuffs composing much of the John Day Formation (McClaughry and Ferns, 2006).   The age of the caldera forming event is constrained to approximately 29 m.y. ago by a number of sources: Robinson et al. (1990) report a 30.8 Ma K-Ar date for the Smith Rock Tuff; Brown et al. (1980) report a 30.1 Ma date on a basalt flow shown to be offset by the caldera margin (McClaughry and Ferns, 2006); and radiometric dates on post-collapse rhyolite domes and flows at Gray Butte, Barns Butte, Powell Buttes, and Ochoco Reservoir range from 28.8 to 25.8 Ma.

A relatively short hike of several miles in length provides excellent opportunities to observe the Gray Butte Rhyolite, the Smith Rock Tuff, vertically oriented rhyolite intrusives within the tuff, the younger basaltic lava flows from Newberry Volcano, and entrenched meanders of the Crooked River.  From this location, hike the loop trail that climbs to the ridge crest overlooking Smith Rock State Park and then back along the river trail (see Smith Rock Trail under Optional Hiking Trails at the end of this road log for a complete description of this hike).

From the parking area, turn around, and return to Hwy 97 in Terrebonne, OR.

28.7 (3.3)     Intersection of B Avenue (Smith Rock Way) and U.S. Hwy 97.  Turn right (north) onto Hwy 97 and proceed toward Madras, OR for a short side trip to Peter Skene Ogden State Park and a marvelous view of the deep gorge carved by the Crooked River beyond Smith Rock State Park.

31.7 (3.0)     Refer to Map 1F.5.  The entrance to the Peter Skene Ogden State Park is on the left; turn in here and drive to the parking area.

This wayside provides excellent views of the 330-foot-deep Crooked River gorge (Figure 1F.3).  The vertical cliff observable under the highway bridge is the 5.3 m.y. old Agency Plains basalt member of the Deschutes Formation, a lava flow erupted from the Tethrow Buttes about 4 miles to the south that nearly filled the ancestral Crooked River canyon (Smith, 1998; McClaughry and Ferns, 2006).  By about one million years ago, the Crooked River had recut its gorge to nearly its present-day depth, and Miocene to Pliocene basalt lava flows of the Deschutes Formation formed the canyon walls.  About 780,000 years ago, a voluminous series of lava flows from the north flank of Newberry volcano, some 40 miles to the south, refilled the canyon to overflowing at this location (Sherrod et al., 2004).  The Crooked River again incised its gorge to the present depth.  Spectacular cliffs of the Newberry volcano intracanyon lava flow can be seen in the dark cliffs along both sides of the river, extending from the highway bridge to the bend in the river downstream of the old railroad bridge.  This record of channelized lava flows is in distinct contrast to gradually thickening blanket of equivalent rocks within the central and western Deschutes basin that extends to the High Cascades.

Figure 1F.3.  Looking westward down the Crooked River Gorge (at Peter Skene Ogden State Park near Terrebonne, OR).

Turn your vehicle around here and return to Bend, OR.

32.1 (0.4)     Intersection of the Peter Skene Ogden State Park entrance road and U.S. Hwy 97.  Turn right    (southeast) onto Hwy 97 and remain on the highway all the way back to Bend, OR.

57.1 (25.0)     Refer to Map 1F.1.  Intersection of U.S. Hwy 97 (3rd Street) and Franklin Avenue in Bend, OR.  This ends Field Trip 1F.

Road Route Maps

Map 1F.1.  Color shaded-relief map of the Bend 7.5” Quadrangle containing segments of Field Trip 1A-F and Field Trip 2.

Map 1F.2.  Color shaded-relief map of the Tumalo 7.5” Quadrangle containing segments of Field Trip 1D and 1F.

Map 1F.3.  Color shaded-relief map of the Tumalo 7.5” Quadrangle containing segments of Field Trip 1F.

Map 1F.4.  Color shaded-relief map of the Redmond 7.5” Quadrangle containing segments of Field Trip 1F.

Map 1F.5.  Color shaded-relief map of the Opal City 7.5” Quadrangle containing a segment of Field Trip 1F.

Optional Hiking Trail

Smith Rock Trail (Tr 1F.1)

This hike highlights the geology of the spectacular cliffs and hoodoos north of the Crooked River formed of the Smith Rock Tuff.  This tuff was deposited during an eruption about 29 m.y. B.P. during formation of the Crooked River caldera and subsequently penetrated by small, distinctive rhyolitic dikes.  Younger, Pleistocene basaltic lava flows from the north flank of Newberry volcano that form the low cliff and  terrace along the south side of the Crooked River are also explored.

Begin at the trailhead sign at the observation parking area (Map 1F.1.1).  A paved, wheelchair-accessible ramp leads to a wonderful overlook on the Crooked River.  The overlook provides superb views of the Smith Rock Tuff and its intrusives directly across the Crooked River, as well as the adjacent Newberry Volcano lavas on the observation platform side of the river (Figure 1F.1 and Figure 1F.2).  The reddish spire which protrudes upward through the tuff at the first bend in the river downstream is a rhyolite dike, a slightly younger silicic volcanic intrusive rock that cross-cuts the previously formed ash-flow tuff.  The overlook is built on basaltic lava flows Newberry volcano basalts which immediately overlie the Gray Butte Rhyolite at this location.

The trail plunges from the overlook down to the Crooked River, crossing a bridge over the river in about two-tenths of a mile (Map 1F.1.1).  After crossing the bridge, follow the trail upslope to your right (marked the Misery Ridge Trail on a sign).  Take time to walk up to the cliff face to examine the Smith Rock Tuff up close.  Note the fine-grained, buff-colored ashy matrix containing coarser pumice lapilli and rock fragments.  The tuff is pocked with large and small semicircular holes called taffoni (holes which make for great climbing holds).  Taffoni is a byproduct of weathering pits developed in porous rock that often occur along bedding planes or around rock fragments and lapilli. Continue on the trail, taking it diagonally upslope and angling away from the river.  The darker reddish bands striking through the tuff are veins of rhyolitic intrusive.  Looking across the river to the southeast, you can easily observe the dark, flat-lying basaltic lavas from Newberry Volcano.  About four-tenths of a mile from the river crossing, the Misery Ridge Trail begins climbing in earnest, passing upward through several tight switchbacks.  Shortly, look to your right, the wall of tuff exhibits layers, attesting to its deposition as sheets of pyroclastic material.

The trail tops out on Misery Ridge at about eight-tenths of a mile from the Smith Rock overlook, and in a few hundred feet you’ll reach a small sign indicating that you are on the official park trail (Map 1F.1.1).  From here, take the fainter spur trail to the left and out onto a promontory at the end of the ridge overlooking the Crooked River valley (its two-tenths of a mile round trip).  The views are marvelous.  Immediately below your perch, the dark, rhyolitic “Smith Rock” dike you first observed from the overlook juts skyward.  To the southeast, the actual Smith Rock forms a classic gooseneck meander bend on the Crooked River (Figure 1F.1.1).  This vantage offers a particularly good view of the several dark, rhyolitic dikes intruding the resistant fin of tuff.  As you broaden your views, notice that the tuffaceous beds dip outward and away from your general location (especially if your look to the cliffs to the east and north-northwest).  Notice that the Newberry lavas on the south side of the river flow right up against the Smith Rock Tuff and the contact between the two rock units is the meandering course of the Crooked River, indicating that the river was essentially located in its present position when the lavas arrived from the south.  On the skyline to the south is Newberry Volcano’s dimpled form and to the west is the Cascade Crest, dotted with snowcapped stratovolcanoes from Mount Bachelor in the south to Mount Adams in the north.

Figure 1F.1.1.  Smith Rock forms a prominent “gooseneck” on the Crooked River; as viewed from a promontory on Misery Ridge on the north side of the Crooked River.

Return to the main trail and head left, in a few hundred feet another trail sign points to the right.  Before heading that way, take a few moments to walk downslope to the left to a rocky promontory near the Monkey’s Face, a pinnacle of Smith Rock Tuff separated from the cliff (probably along cooling joints) and a popular rock climbing route for the technically skilled (Figure 1F.1.2).  Carefully examine the sides of the pinnacle to see color banding and layering in the tuff.  To the north and east, you can see layering in the tuff dipping away from you.; while to the south, you cannow see the east side of Smith Rock’s fin and its associated gooseneck meander. Now climb back to the main trail and head downslope to your left.  The trail takes you down the west bank of the Crooked River, passing directly below the Monkey’s Face.

Figure 1F.1.2.  The Monkey’s Face, a pinnacle of Smith Rock Tuff protruding from the main east-facing cliff at Smith Rock State Park exhibits color banding and layering related to deposition of the tuff (note the human figure hanging from the sunny southern side of the pinnacle for scale).

Remain on the trail signed as “River Trail” after passing Spiderman’s Buttress, another popular climbing spot, about one and seven-tenths of a mile into the hike (Map 1F.6).  The base of the cliffs here exhibit many nice examples of taffoni weathered into the tuff.  Across the river, the contact between the Smith Rock Tuff and overlying Newberry lavas is occasionally exposed.  In another seven- tenths of a mile, the trail crosses a dark, rhyolitic dike several feet thick; on the opposite side of the river, the resistant dike is easily observed protruding from the river bank, the weaker tuff having been stripped away.  The distinctive reddish hue of the rhyolite can now be seen as an oxidized coating, unweathered rhyolite appears only slightly darker gray than the Smith Rock Tuff.  As you round the nose of the Smith Rock fin, you’ll pass several more dikes exposed near the trail and in the cliff face, as well as across the river.  Roughly a quarter mile from the first dike crossing, another dike appears on your left exhibiting fault slickensides (Figure 1F.1.3).  These appear as small, parallel groves on a surface polished by the grinding of rock passing side-by-side along the fault.  In this case, the faulting probably occurred long after the intrusion of the dike, related to localized settling and collapse of the tuff within the caldera.

Figure 1F.1.3.  Slickensides, probably a collapse feature, formed along a fault plane at the contact between a rhyolite dike and the Smith Rock Tuff.

Continue your streamside stroll along the River Trail, but be sure to look back downstream and up at the cliffs on this side of the river.  A dark, reddish rhyolite dike cuts upward through Smith Rock Tuff paralleling the cliff face, this dike is likely the same one that crossed the river on the far side of the river on the far side of the gooseneck.  Half a mile from the slickensided fault (Map 1F.6), the trail bends south around a meander and offers a great view straight upriver at vertical cooling joints exposed in a cliff of Smith Rock Tuff (Figure 1F.1.4a).  Spur trails afford access below “Smith Rock” to the base of the cliff where you can examine the tuff in detail (Figure 1F.1.4b).  In a little over four-tenths of a mile further, you round another meander bend back the north, the trail passing directly below the prominent dark, reddish “Smith Rock” dike first observed at the overlook starting point of this hike.  From here, its two-tenths of a mile back to the bridge over the Crooked River and an equal distance upslope to the overlook at the trail’s beginning.

Figure 1F.1.4.  The Smith Rock Tuff; (A) columnar jointing in the Smith Rock Tuff as viewed looking upstream from the hiking trail along the Crooked River; and (B) a close up of the tuff, note the buff-colored groundmass and coarse rhyolitic rock fragments and pumice lapilli.

Hiking Trail Map

Map 1F.1.1.  Color shaded-relief map of the Gray Butte, O’Neil, Opal City, and Redmond 7.5” Quadrangle showing the Smith Rock Trail (Tr 1F.1).