Road Log

0.0 (0.0)       Refer to Map 2B.1.  Intersection of the Crescent Cutoff Rd and FS Rd46.  Head west on the Crescent Cutoff Rd.

3.0 (3.0)       Refer to Map 2B.2.  Road cuts in Mazama Ash.  Notice how much thicker the pyroclastic deposit is here relative to locations progressively further north and east; the air-fall pumice lapilli are also coarser.  Mt. Mazama, the source for this ash, erupted roughly 36 miles southwest of here about 7,700 years ago.

3.1 (0.1)       Intersection of Crescent Cutoff Rd and Oregon Hwy 58.  Turn right (west) onto Hwy 58  toward Willamette Pass.

5.6 (2.5)       Refer to Map 2B.3.  Road cuts in Mazama Ash overlying basaltic lava flows.

6.1 (0.5)       Passing through Crescent Lake Junction.  A good view of Maiden Peak shield volcano lies just ahead at about 1:00.  Maklaks Butte is the large cinder cone lower and to the east on about the same line of sight.

6.4 (0.3)       Intersection of Oregon Hwy 58 and FS Rd 60 to Crescent Lake.  Remain on Hwy 58.  Crescent Lake is dammed by an end moraine complex associated with the late Pleistocene Suttle Lake (LGM) advance of the Cabot Creek glaciation.

6.9 (0.5)       The road cuts here and for about the next half mile expose till of the late Pleistocene Suttle Lake glacial advance forming an end moraine complex that encircles the southeast shore of Odell Lake.  Notice the relatively thin brownish-orange soils developed in the moraine surface (the original gray-colored till is exposed beneath).

8.3 (1.4)       Entrance road to the left (southwest) for the Odell Lake Resort and lake shore access.  Notice that the forest is dramatically changing composition from domination by lodgepole pine to Douglas fir.  This is mainly due to a transition from drier, rainshadow-dominated moisture conditions on the east side of the Cascade Crest, to wetter, west-side, orographic-dominated moisture conditions.  The abruptness of the change may in part be related to the better moisture retaining properties of older soils developed in glacial till versus the young soils developed in porous Mazama Ash.

10.1 (1.8)     Scenic Viewpoint pullout on the left side of the road.  The view across Odell Lake prominently reveals the glaciated composite volcano of Diamond Peak with Lakeview Mountain’s older, smaller, more highly eroded shield volcano summit further to the east (Figure 2B.1).

Figure 2B.1.  Scenic pullouts on Hwy 58 along the north shore of Odell Lake offer nice views of Diamond Peak.

13.9 (3.8)     Refer to Map 2B.4.  Willamette Pass on the Cascade Crest.

14.6 (0.7)     Another pullout on the left-hand side of the road here offers superb views of Diamond Peak and Mt. Yoran on its northeast flank.  These mountains form a Pleistocene, composite volcano complex that has been subjected to multiple episodes of glacial sculpting.

17.0 (2.4)     Intersection of Oregon Hwy 58 and FS Rd 5897 (Waldo Lake Rd).  You will return to this road junction shortly, but first continue straight ahead on OR Hwy 58 to take in a visit to one of Oregon’s tallest waterfalls.

18.0 (1.0)     Road cuts near here and for the next three-quarters of a mile expose basaltic andesite lavas overlying mafic pyroclastic material.  This interlayering of dense mafic lavas and weaker, porous volcaniclastics is common in this area as you shall see.

18.8 (0.6)     FS Rd 5893, the entrance road to Salt Creek Falls Scenic Area on the left.  Turn in here.

19.3 (0.5)     Refer to Map 2B.5.  Parking area for Salt Creek Falls Scenic Area.  Park here and hike the short trail that takes you to both the falls overlook, and to the base of the falls.  When you reach the scenic overlook, take a few moments to observe the lay of the land; examine the canyon of Salt Creek and the rocks exposed in the canyon walls near the falls.  Now reflect on the formation of what you have seen.

Streams erode the valleys in which they flow (although valleys such as this one may be modified by other factors including the passage of glaciers), and Salt Creek is no exception. Salt Creek Falls and its environs make an excellent example of the dynamic characteristics associated with the development of waterfalls.  If the earth’s crust were composed of homogenous material, a stream’s erosive ability would depend primarily on the channel gradient and the stream’s average discharge.  Where stream gradients are relatively steep, channels tend to incise into the material underlying the bed, forming a fairly straight pattern in a generally narrow, V-shaped valley.  Where stream gradients are gentle, channels tend to wonder laterally, alternatively cutting into their bank on one side while simultaneously depositing sediment on their opposite bank, and forming a meandering pattern on a floodplain in a generally wide, flat valley.  Over time, the stream’s valley would broaden and its channel gradient would decrease at the downstream end, while maintaining a narrow, V-shaped valley and steeper gradient upstream.  The stream’s channel would lengthen in the upstream direction by a process called headward erosion because the maximum erosive ability would remain concentrated higher in the watershed.

However, the earth’s crust is rarely uniform, especially over the distance of a gradually deepening and lengthening stream valley.  Instead, the stream would encounter multiple rock and/or sediment types with variable resistance to erosion by running water.  Eventually, at some location along the stream’s channel, flowing water may begin to incise into a relatively resistant material.  Where the channel first succeeds in eroding through the resistant bed material and into a weaker substance below, erosion would continue more slowly upstream (where the resistant material still exists) and more rapidly downstream (where the resistant material has been removed).  This process creates a short steep segment of stream channel, what a geologist calls a “nick point”.  Over time, the downstream segment of the stream overlying the weaker material would erode more deeply and begin to undercut the resistant material upstream, generating a waterfall.  Waterfalls are self-perpetuating, once started, they may back-waste upstream at the nick point by differential erosion for considerable distances.  This basic process has been observed and discussed at Tumalo Falls on Field Trip 1E.  Nick points and waterfalls can be generated in other ways as well, such as where faulting has steepened a segment of the stream channel, or as seen in Field Trip 1A, where a stream channel has been steepened by blockage from a lava flow or other natural obstruction.  These latter types of waterfall formation are usually quite temporary in a geologic sense.

Now examine the environs of Salt Creek Falls (Figure 2B.2).  Notice that about a third of the way up the canyon walls from the plunge pool, an indentation occurs where the cliffs have been excessively weathered.  This marks a contact between overlying basaltic andesite lava flows, and underlying mafic tuff, a weaker layer of rock and a likely place where running water preferentially erodes, undercutting the more resistant unit above.  The weaker tuffaceous material is also experiencing frost action and mass wasting due to the cool, moist conditions prevailing in the area, processes that enhance backwasting into the lower cliff.  Perhaps, as you gaze on Salt Creek Falls, you’ll witness its further development as the next slab of undermined rock peals away from the upper cliff?

Figure 2B.2.  Fantastic Salt Creek Falls, on Oregon Highway 58 near Willamette Pass.

After taking in the upper viewpoint, climb the stairs to your right and hike the trail to the lower overlooks at the midpoint and close to the plunge pool of the falls.  At the stair, examine the smooth basaltic andesite lava outcropping to your right.  This outcrop has been sculpted by glacial erosion and still exhibits polish and striations formed during the late Pleistocene (Figure 2B.3).  As you descend the switchbacks in the trail, note the exposures of mafic pyroclastic material along its lower part.  This is the weak tuff prone to water erosion which underlies more resistant basaltic andesite lavas, the true culprit behind the formation of Salt Creek Falls.  Once you reach the lower viewpoint, notice the columnar jointing in the lava flows exposed in the upper cliff behind and to either side of the falls.  From this vantage point, you can also more clearly see the backwasting lower portion of the cliff comprised of tuffaceous material.  Please do not climb down to the base of the falls from this location, it damages the vegetation and enhances soil erosion on these steep slopes.

Figure 2B.3.  Glacially sculpted basaltic-andesite outcrop at the top of Salt Creek Falls; note the polygonal jointing of the igneous rock.

After experiencing the thunderous roar of Oregon’s second highest waterfall, make your way back to the parking area and your vehicle.

20.1 (0.8)     Return to the junction of the Salt Creek Falls Scenic Area entrance road and Oregon Hwy 58.

This is the turn-around point for Field Trip 2B.  Turn right (east) onto Hwy 58.

21.9 (1.8)     Back to the junction of Oregon Hwy 58 and FS Rd 5897 (Waldo Lake Rd).  Turn left (north) onto FS Rd 5897.

24.0 (2.1)     The pullout on the right side of the road is for the Fuji Mountain Trailhead.  Park here and walk across the road to examine the road cut to the left.  The exposure reveals till of the late Pleistocene Suttle Lake advance of the Cabot Creek glaciation.  Notice the characteristics of the till; it is comprised of a heterogeneous mixture of clay, silt, sand, gravel and coarser material.  The till is capped by a fairly well-developed soil; greater moisture and biological productivity have enhanced soil development here relative to glacial deposits of the same age observed to the east of the Cascade Crest near Odell Lake.  Multiple road cuts further up the road display similar features.

28.1 (4.1)     Trailhead parking area on the right for The Twins Trail.  This trail climbs The Twins, a Pleistocene shield volcano with a glacially dissected summit cone that now forms dual high points (see The Twins Trail under the Optional Hiking Trails section at the end of this road log for a complete description of this hike).  The view of Waldo Lake, Oregon’s second largest, is phenomenal from the top; and it is an easy stroll when compared to summiting Maiden Peak or Fuji Mountain, other possible day-hiking destinations nearby.

28.5 (0.4)     FS Rd 5896 on the left, the entrance road to Shadow Bay Campground and Boat Launch area.

A short round-trip drive of about four miles takes you to the shore of Waldo Lake.  Although natural, the lake is maintained at an artificially high level of 5412 feet by a small dam at the western edge of Klovdahl Bay, almost directly across from the campground.  Waldo Lake is a rather large tarn, an origin quite different from Crescent and Odell Lakes which are impounded by moraines. It’s basin was scoured by the passage of flowing ice from part of the broad, volcanic plateau that makes up the Cascade Crest in this area.

Waldo Lake’s elevation is over a mile high.  It is located in a heavy snow zone just west of the Cascade Crest, so be aware that snow often lingers well into the summer (Figure 2B.4).  The lake has no permanent inlets to bring nutrients into the lake for plant growth, so the water is very pure and is crystal clear; with the added bonus of pristinely forested shores, canoeing and kayaking are quite enjoyable.

Figure 2B.4.  The snowpack can linger at Waldo Lake well past Independence Day.

30.2 (1.7)     The entrance to Shadow Bay Campground on the right, a nice layover destination if you have the time.  Sunsets from this campground are superb (Figure 2B.5); but watch out for mosquitoes if you stay earlier than about August 1st.

Figure 2B.5.  A stunning Waldo Lake sunset.

30.6 (0.4)     The Shadow Bay Boat Launch area.  A nice, family-friendly, shoreline trail can be accessed from the left edge of the large parking area at the Shadow Bay boat ramp.  The first one and three- tenths miles of the trail follows the lake edge around Shadow Bay to the south end of Waldo Lake.  At this point, you’ll find a comfortable sandy beach sheltered by a small, wooded island, a good location for swimming.  Turn around here or explore further at your leisure.

32.7 (2.1)    Back to the junction of the Shadow Bay Rd (FS Rd 5896) and FS Rd5897.  Turn right (south) onto FS Rd 5897.  Taking FS Rd 5897 to the left (north) brings you to additional campgrounds and boat access points on Waldo Lake’s northeast shore.

39.3 (6.6)     Back to the junction of Oregon Hwy 58 and FS Rd 5897 (Waldo Lake Rd).  Turn left (north) onto FS Rd 5897.

53.2 (13.9)     Intersection of Oregon Hwy 58 and Crescent Cutoff Rd.  Turn left (west) onto Crescent Cutoff Rd.

56.3 (3.1)     Junction of Crescent Cutoff Rd and FS Rd 46 (Cascade Lakes Highway).  This ends Field Trip 2B.

Road Route Maps

Map 2B.1.  Color shaded-relief map of the Odell Butte 7.5” Quadrangle containing a segments of Field Trip 2A and Field Trip 2B.

Map 2B.2.  Color shaded-relief map of the Crescent Lake 7.5” Quadrangle containing a segment of Field Trip 2B.

Map 2B.3.  Color shaded-relief map of the Odell Lake 7.5” Quadrangle containing a segment of Field Trip 2B.

Map 2B.4.  Color shaded-relief map of the Willamette Pass 7.5” Quadrangle containing a segment of Field Trip 2B.

Map 2B.5.  Color shaded-relief map of the Diamond Peak 7.5” Quadrangle containing a segment of Field Trip 2B.

Map 2B.6.  Color shaded-relief map of the Waldo Lake 7.5” Quadrangle containing a segment of Field Trip 2B.

Optional Hiking Trails

The Twins Trail (Tr 2B.1)

This hike offers spectacular views of nearby Waldo Lake, several peaks along the Cascade Crest, and the upper watershed of the Deschutes River.  The Twins Trail first ascends gradually up the southwest slope of The Twins, a dual- summitted, middle to late Pleistocene shield volcano comprised of basaltic andesite lava flows and an eroded cone exposing abundant lava bombs and blocks, lapilli, and volcanic ash (Map 2B.1.1).  In about one and a half miles, the trail crosses the Pacific Crest Trail and then begins to climb more steeply.  The ascent is rather unremarkable, with a few small ponds scattered among an initially dry, lodgepole-dominated forest that changes over to a wetter, Western hemlock and Douglas fir dominant forest as you climb.

At about three miles, views begin to open up southward to Diamond Peak.  The trail begins crossing porous, reddish cinders on the upper slopes of the mountain which retain little water for tree growth.  Follow the trail clockwise as it climbs a scoria-covered ridge to the highpoint on the northern “twin” summit.  From here, an amazing view emerges of seven-mile-long Waldo Lake, Oregon’s second largest, covering 10 square miles and reaching a depth of 417 feet (Figure 2B.1.1).  Bushwacking along the northern rim of the summit cone leads to cliffs at the headwall of a northeast facing cirque carved into The Twins upper slopes.  The position of the cirque suggests that the glacier coalesced with the ice cap that covered much of the Cascade Crest to the north, and flowed down the valley of Charlton Creek eastward and around the western flanks of Ketchketch Butte.  This vantage point affords superb views along the spine of the Cascade Range; north and northeast toward the Three Sisters, Broken Top, and Mt. Bachelor volcanoes, east into the lake- and reservoir-dotted upper Deschutes basin, and west and northwest into the U-shaped, glaciated troughs of the Middle Fork of the Willamette River and South Fork of the McKenzie River that head at Waldo Lake.

Figure 2B.1.1.  Waldo Lake from the north summit of The Twins; North Twin’s glaciated northeast slope is at the right edge of and below the photo.

Now cross the open saddle to the southern rim of The Twins summit cone.  Maiden Peak and Diamond Peak can be seen to the southeast and south, respectively.  Maiden Peak is a similarly aged, shield volcano comprised of basaltic andesite lava flows, also notched on its northeast flank by glaciers.  Diamond Peak is a taller, older, stratovolcano of intermediate composition that was situated more directly under the Quaternary ice caps covering the Cascades, and is thus much more heavily dissected.  Once you have absorbed the views, feel free to hike back to the trailhead and your vehicle.  If time permits, a short dip in Waldo Lake might be your reward.

Hiking Trail Map

Map 2B.1.1.  Color shaded-relief map of the northwest quarter of the The Twins7.5” Quadrangle showing The Twins Trail (Tr 2B.1).