Field trip to
updated May 31, 2013
Make comments and descriptions and ask questions as you go. Draw sketches at every field location of any geologic features or landscapes. Use a scale. Ask your instructor if you don’t understand what to do. Also, elaborate on at least two of the field sites in a one page word-processed summary on a separate piece of paper. Consult web references and any of the references listed at the end of this guide. They can be found on hold in the library. THIS FIELD TRIP WRITE UP IS DUE ON MONDAY JUNE 11.
a field trip report as requested. At the end of your report don’t
forget to include a summary section in which you share any feelings,
observations, and new perceptions about what you saw and learned about
the geology. DOES LEARNING ABOUT THE GEOLOGIC HISTORY CHANGE THE WAY
YOU LOOK AT THINGS? Explain. Check the online rubric for help.
PART I: Interstate 5 to State Route 123 via
approach, the western segment of the White Pass Scenic Byway generally follows
This 71 mi (115 km) route along U.S. Highway (US) 12
begins on the Jackson Prairie (underlain by the Pleistocene Logan Hill Formation) and descends a series of
progressively younger glacial terraces in stair-step fashion:
About 4 mi (6.4 km) west of Morton, the road crosses a
divide into the
At Randle, this route accesses SR 131 and Forest Roads
(FRs) 25 and 23, which lead to the east side of the Mount St. Helens area, as
well as to the Cispus River drainage and the north side of Mount Adams (see
Pringle, 2002). Hummocky glacial deposits (end moraine and ice-marginal
deposits) of Evans Creek age (~22,000–15,000 yr B.P.) near here suggest this is
the terminal position of the large valley glacier that occupied the
0.0 0.0 Mileage
starts on US 12 at its junction with Interstate 5 (I-5). The road passes east
over Jackson Prairie, a gently rolling terrace of the lower(?)
Pleistocene Logan Hill Formation. This surface, which
may be about a million years old, displays as much as 40 ft (12 m) of relief.
Here, the Logan Hill Formation consists mainly of a compacted mixture of
cobbles and pebbles in a sandy clay matrix. The sediment is outwash from an
ancient glacier whose source was in the southern Washington Cascade mountains near
3.2 5.1 Roadcuts expose the clayey, reddish, deeply weathered top of the Logan Hill Formation. Weathering reaches depths > 50 ft (15 m).
4.5 7.2 We descend from Jackson Prairie to Lacamas Prairie, the surface of an outwash plain of the middle(?) Pleistocene Wingate Hill Drift. Notice that Lacamas Prairie is flatter than the older Jackson Prairie—it displays relief of only a few feet. Colman and Pierce (1981) estimated the age of the Wingate Hill Drift to be about 600 to 300 ka.
11.4 18.2 Near Salkum, the road descends to a terrace underlain by outwash deposits of Hayden Creek age (~170 to 130 ka?) and then crosses Mill Creek. This terrace is an equivalent of Cowlitz Prairie to the southwest. Till of Wingate Hill age is visible to the right just after we pass Mill Creek. The Wingate Hill terminal moraine is about a mile (1.6 km) west of here, whereas the maximum extent of the Hayden Creek glacier was about a mile (1.6 km) to the east.
15.2 24.3 Cross Mayfield
16.6 26.6 The first outcrops of dark
23.3 37.3 STOP.
OPTIONAL STOP: Riffe_Lake_viewpoint. DRAW A SKETCH IF WE STOP HERE. WHAT IS THE EVIDENCE FOR GLACIATION?
28.2 45.1 As the road descends into Morton, a zone of reddish altered rocks is exposed on the left. Slickensides are common on these rocks. The smooth southwest-facing hillslope visible northwest of Morton is the dip slope of a limb of a northwest-trending anticline. Folding near
31.0 49.6 Junction of US 12 with SR 7 at Morton. We will continue east on US 12.
33.3 53.3 Slightly east of MP 100 sedimentary rocks of the Puget Group crop out on the south side of the highway. These rocks for the most part predate the Cascades, but they do interfinger with the earliest Cascade volcanic rocks. Clevinger (1968, 1969) provided details about the fossils and minerals associated with rocks in this area in two useful guidebooks.
55.7 Junction of
Cathy Whitlock (Barnosky,
1981) developed an extensive record of paleoclimate and environmental change
using pollen and plant fossils she obtained by coring at Davis Lake and at
other sites in this region, including Mineral Lake, 12.7 mi (20 km) to the
north-northeast. Her radiocarbon dates for the
36.4 58.2 Light tan to brown volcaniclastic rocks of Tertiary age crop out in the cliff on the left (northeast) side of the highway about 260 yards (240 m) east of the Kosmos Road.
37.9 60.6 Glenoma.
The south valley wall along Rainey Creek (the elongated ridge south of Glenoma)
is composed of upper Oligocene basaltic rocks, mostly lava flows. These rocks
were derived from a volcanic center south of
Although not readily visible from the
highway, deposits of yellowish tephra are common in roadcuts and stream banks
near where the road crosses Rainey Creek. This pebble-size pumice is the Yn
tephra layer from
43.0 68.8 Cliffs on the north side of road are Oligocene andesite flows.
44.6 71.4 Here we cross the drainage divide between Rainey and Kiona Creeks, located on coalescing alluvial fans from those two creeks. LOOK IN THE STREAM CHANNELS--DO YOU SEE ANY EVIDENCE FOR RECENT DEPOSITION?
Slightly east of here
the highway passes through a terminal moraine constructed by the large valley
glacier that occupied the
MP 114. A significant landslide more than 197 ft (60 m) wide blocked
the highway here at about 6:00 p.m. on
50.0 80.5 The broad flood
plain of the
48.3 77.3 Randle and intersection of US 12
with SR 131..SR 131 accesses the east side of the
51.2 81.9 MP 118. Cliffs to the left (north) are Miocene diorite and granodiorite intrusions.
54.0 86.4 Pullout to the right (south). The outcrop on the left is granodiorite with inclusions of andesite.
55.1 88.7 MP 121. The road curves to the left. Note the big scarp visible in the distance to the southeast on the face of Castle Butte. Strata of upper Oligocene volcaniclastic rocks are visible in the scarp.
58.8 94.1 Near MP 125 we notice some large boulders near the mouth of the canyon to the south. They were carried down to the flood plain by debris flows.
59.1 94.6 MP 126. Rest area.
The hummocky terrain and large, angular to subangular boulders are typical of a
landslide deposit, although Swanson and his USGS colleagues Norm Banks and
Richard Moore (1997) have mapped this area as “alluvial fan”. The source area
of the debris is Goat Dike, a rock promontory to the south composed of volcaniclastic
rocks. Light-gray granules of Mount St. Helens Wn tephra (A.D. 1479) lie atop
the debris; however, there is no trace of the 3,500 yr B.P. Yn tephra from
Cross sections of the geology in this area as
interpreted by Swanson and his colleagues are shown in Figure [packwoodxsec].
Their studies revealed that the area is underlain by bedded volcaniclastic
rocks of late Eocene and Oligocene age, mostly laharic units, that interbed with andesite and basaltic andesite lava flows on
the south side of the
64.1 102.6 MP 131, downtown Packwood. This small
town may be located closer to more volcanoes than any other town in
heading east. Note landslides visible ahead and slightly to the left, on the
south face of Tatoosh peak (the local name for the exposed rocky face to the
north that is the southernmost peak of the
64.9 103.8 The black sedimentary rocks that crop out on north side of road are lake deposits. On the south side of road is an andesite sill.
67.2 107.5 Thin shale laminae under the sill are lake deposits that contain some leaf fossils.
68.7 109.9 The small outcrop of tuffaceous sedimentary rock on the right contains fossil wood.
69.6 111.4 Green to light-gray tuffs crop out to the right (southeast) of the road.
71.5 115.0 SKETCH AND LABEL THE VOLCANIC DEPOSITS HERE. Intersection of US 12 with SR 123. We can continue east on US 12 via Leg H or turn left here and follow Leg G (in reverse order) toward Chinook Pass (16.3 mi or 26.2 km). Alternatively, we can intersect the end of Leg B and the Ohanapecosh Entrance to Mount Rainier National Park by going north on SR 123 5.4 mi (8.6 km).
PART II: Ohanapecosh (State Route 123) to Naches (State Route 410) via U.S. Highway 12 (from a draft by P. T. Pringle, P. E. Hammond, N. P. Campbell, and W. J. Gerstel)
This route is the eastern segment of the White Pass
Scenic Byway and was featured in Newell Campbell’s geologic road guide (1975).
The byway passes through one of the most scenic and geologically interesting
0.0 0.0 Junction of SR 123 and US 12. Sills and pyroclastic flows here in Ohanapecosh rocks.
Fiske and others (1963) measured a stratigraphic section of the Ohanapecosh
Formation volcaniclastic rocks from
0.6 1.0 A poorly sorted deposit of till of Evans Creek age, 22 to 15 cal. yr B.P. Evans Creek is the youngest major episode of alpine glaciation in this area
1.9 3.1 Ohanapecosh sedimentary rocks dip about 30 degrees to the southwest several hundred yards (meters) west of MP 141. The sill is a plagioclase-phyric olivine basalt. Note the gentle 10- to 13-ft- (3–4 m) wavelength folds in the rocks above the sill. The deformation likely occurred during emplacement of the sill.
2.3 3.7 STOP Palisades rest area. Here are some spectacular columns in the Clear Fork andesite, an intracanyon lava flow of Pleistocene age from a vent near Goat Rocks (Fig. [clear_fk_andesite_col]). Clayton (1983) dated the Clear Fork flow at 0.65 Ma.
4.2 6.7 MP 143. Here we see hydrothermally altered volcanoclastic
rocks of the Ohanopecosh Formation. At the east end
of the outcrop a small amount of coal is exposed. Also visible in the outcrop
are the vesicular olivine basalt flow of
4.6 7.4 The pullout to the right offers an excellent view of Lava Creek Falls as the stream goes over the Palisades columns and plunges into the Clear Fork River. The river incised its course along the contact between the valley dacite flow and the older Ohanopecosh Formation. Lava Creek was not able to erode the valley dacite flow at the same rate as the river, and as a result the waterfall was formed.
6.0 9.7 We enter a stretch of the road that passes through colluvium as we approach the margin of the pre-Tertiary rocks.
7.0 11.2 The inferred fault contact between the Russell Ranch Formation and Ohanopecosh Formation is near here. Although the fault itself is not visible, the east block is up relative to the west block, which places black carbonaceous shale of the Russell Ranch (east) against light-colored andesites of the Ohanopecosh on the west. This faulting causes chronic landslide problems here.
7.1 11.4 MP 146 area. Hammond (1980) described the steeply west dipping beds
of Summit Creek sandstone here that overlie shattered and sheared argillite rocks of the Russell Ranch
Formation. The Summit Creek deposits are arkosic sandstone that underlie the
Ohanapecosh Formation in this part of the
8.9 14.2 The pullout to the right has a good exposure of the Russell Ranch Formation. DESCRIBE THESE ROCKS!
9.1 14.6 Scenic
vista points near here (MP 148) offer views of Goat Rocks to the
10.6 17.1 Note the hummocky landslide surface in the forest south
of the road between here and
10.7 17.2 Knuppenburg
Ridge is the source of the
13.2 21.1 This roadcut is in Spiral Butte dacite.
13.7 22.0 Spiral
14.8 23. STOP. The turnout on the south side of the road has a scenic view of Clear Creek falls, a view down Clear Creek valley to the southeast, and restrooms (except in winter). Clayton (1983) mapped the silicic andesite lava flow that forms the falls. It was erupted from a vent area about 3 mi (5 km) farther west. The flow overlies a basalt flow that Clayton dated at 0.65 Ma.
17.6 28.3 At this curve on the left, the contact between Indian Creek Gneiss (to the east), about 154 Ma, and the sheared rocks of the Russell Ranch Formation (>144–146 Ma) is exposed (Clayton, 1983; Miller, 1989). Till deposits of alpine glaciers are extensive in this area.
17.9 28.6 Indian Creek Gneiss and amphibolite crop out in this roadcut. The rocks are highly sheared and deformed by high temperature metamorphism. Pegmatite dikes intrude the outcrop.
18.9 30.4 An outcrop of greenstone of the Russell Ranch Formation is on the south side of road slightly east of MP 158.
20.3 32.5 Indian Creek. MP 159. The type locality of the Indian Creek Gneiss, a unit in the Indian Creek complex, lies about 4 mi (~6.5 km) to the northwest.
22.7 36.3 Rest area south of road (not marked). Chert beds north of the highway.
23.2 37.1 MP 162. Sheared sedimentary rocks north of the highway include turbidites of siltstone, sandstone. and shale. Faulted greenstone and cherts are below the turbidites. Radiolarian cherts in the Russell Ranch Formation were found near here by Miller and others (1993). They noted that the Radiolaria in the cherts are compatible with a Late Jurassic to Early Cretaceous age. For the next 1.5 mi (2.4 km) we are in sheared metasedimentary rockss and basalts of the Russell Ranch.
23.3 37.3 An outcrop of sheared shale and greenstone with slickensides is north of the highway. The greenstones include remnants of pillow basalts.
26.3 42.1 MP 165. Swanson and others (1989) pointed out that there is a dark margin of hornfelsed Oligocene Wildcat Creek lapilli tuff in contact with the Pliocene/Oligocene Westfall Rocks here. They described the Westfall Rocks as a ‘micro’ diorite because of its small crystals. The heat of the Westfall Rocks intrusion along this contact has largely recrystallized the tuff along the dark margin.
26.6 42.6 Exit Tunnel. Tieton Dam was constructed between the
masses of shallow intrusive diorite of Tertiary age (about 22 Ma) at Goose Egg
Mountain (east) and Westfall Rocks (west) (Fig. [kloochman2]). The dam was
built between 1917 and 1925, chiefly for irrigation purposes. In the next 0.1
mi (0.1 km), there are exposures of the Westfall Rocks diorite. Straight ahead
in the distance is a Pleistocene lava flow of olivine basalt. This flow
originated from a vent to the northwest and moved down Wildcat Creek (
27.2 43.5 Rimrock Grocery store on our right. Gabbroic rock crops out on the left side of road, then we cross Wildcat Creek.
28.0 43.2 Light greenish,
mostly fine grained volcanic sedimentary beds that crop out north of the road
near here are the Wildcat Creek tuffs. Vance and others (1987) obtained dates
on these rocks that range from about 34 to 30 Ma;
Bethel Ridge may be cored by a fault. A ridge-top trench several meters in depth and evidence of recent landslide movement including tilted trees on its north and south slopes could be sackung. Not that the road to the top is rough, and four-wheel drive vehicles are advisable.
36.1 57.8 Diamict with angular rocks on the north side of the road likely is the toe of a large landslide from Bethel Ridge. Large landslides are mapped on both sides of the road near here, yet they go almost unnoticed by the casual viewer. Many radial dikes of the Tieton volcano have intruded the rocks of this area. The dikes crop out on both sides of the valley here. Rounded river cobbles and gravels of Quaternary age sit atop the volcanoclastic rocks of the volcano.
37.0 59.2 Pillow basalts and basalt columns.
42.7 68.3 Stone stripes, a type of patterned ground, are draped on the hillside here. (See also Leg F, p. ??.)
43.3 69.3 About 0.4 mi (0.6 km) east of MP 182 there is a good view of the valley-filling Tieton Andesite lava flow overlying the Columbia River basalt.
SPECULATE ON HOW COLUMNAR JOINTS FORM?
46.6 74.6 Junction of SR 410 and US 12. From here we can drive east or west on Leg F. We join this leg about 16 mi (26 km) west of where it begins. Reset odometers if proceeding on Leg F.