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 10.
east on US-12 to Packwood and then up over
Assignment: Write 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.
I: Interstate 5 to
This approach, the western segment of the
White Pass Scenic Byway generally follows the
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:
4 mi (6.4 km) west of Morton, the road crosses a divide into the
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
Distances along the route are given in miles, followed by kilometers in italics. If we take any of the optional trips or sidetrips along the way, we'll have to keep track of, and add those miles to all remaining miles listed in each log. Having a pencil and paper handy, and even a calculator will be helpful.
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
Milepost (MP) 67.
Roadcuts expose the clayey, reddish, deeply weathered top of the Logan Hill Formation. Weathering reaches depths greater than 50 ft (15 m).
Good exposures of red soils of the Logan Hill Formation are in a roadcut here.
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.
On a fine day, there is a good view
Wingate Hill outwash is exposed in a roadcut about 300 ft (90 m) west of MP 76. The reddish-brown weathering of this deposit extends to depths that range from 16 to 32 ft (5–10 m) and does not have the deep red hue of the older Logan Hill deposits.
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. The hills and mountains of the Cascades come into view as we continue farther east.
16.6 26.6 font?
The first outcrops of dark
There is an outcrop of amygdaloidal basaltic andesite on the right (south) side of the highway, but no place to safely pull over and view it.
On our left is another outcrop of basaltic andesite.
The cliffs on the left (north of the highway) are more Oligocene-Eocene basaltic andesite.
Landslide with riprap to prevent its moving onto the roadway.
South-southeast of Riffe Lake, Mount Margaret and other peaks in the Mount Margaret Wilderness north of Mount St. Helens are composed of granodiorite and granite of the Spirit Lake pluton, whose age has been estimated at 22 to 20 Ma by Evarts and others (1987)(Fig. [riffe_lake_view_new]).
DRAW A SKETCH OF THE THIS AREA IF WE STOP HERE. WHAT IS THE EVIDENCE FOR GLACIATION?
There is a good exposure of hyaloclastite beds on the left (north), but no safe place to get out and examine them.
road climbs past glacial drift, out of the Cowlitz drainage, and then crosses a
drainage divide into the
Remember to adjust the odometer to compensate for mileage along the side trip.
As the road descends into Morton, a zone of reddish altered rocks is exposed on the left. Slickensides are common on these rocks. Although no trace of a fault is visible, this may be a shear zone.
smooth southwest-facing hillslope visible northwest of Morton is the dip
slope of a limb of a northwest-trending anticline. Folding
near Morton is more complex and tightly spaced than the gentle folding
typically found in the region. Whereas the crest spacing (wavelength) of the
folds in the younger rocks south of Rainey Creek ranges from about 6 to 18 mi
(18–30 km), the spacing in the older rocks north of Rainey Creek ranges from
about 2 to 6 mi (3–10 km). Because of this more intense folding, the rocks are
generally more shattered and altered, and erosion has cut a window through the
volcanic rocks into the older sedimentary rocks of the Eocene Puget Group.
Landslides abound in this area, which lies between two active,
north-northwest-trending seismic zones, the St. Helens zone and the
Junction of US 12 with SR 7 at Morton. We will continue east on US 12.
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 (Fig. [clev-morton-xsec]).
There is an outcrop of volcaniclastic rocks of Tertiary age on the right (southwest), but no pulloff.
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
About 4.2 mi (6.7 km) past the SR 7 junction, the road crosses a northeast-trending normal fault, and we are back in the Goble Volcanics. The fault is not visible in outcrop. Although the fault motion has been interpreted as down-to-the-southeast, the topography appears inverted because the down-dropped rocks now stand higher than those rocks across the fault. If the interpretation of the fault is correct, this situation resulted perhaps because the Goble Volcanics are more resistant to erosion than the sedimentary rocks of the Puget Group.
highway starts to climb once it reaches the volcanic rocks, passes again into
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.
A lava flow of Tertiary age crops out on the inside of a curve on the left (north) side of the road.
Basalt flows of Tertiary age are exposed here.
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
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
Cliffs on the north side of road are Oligocene andesite flows.
MP 111. Junction of US 12 with
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?
Glacial drift of Hayden Creek age is exposed on the left (north) side of the highway.
Slightly east of here the highway
passes through a terminal moraine constructed by the large valley glacier that
A significant landslide more than 197 ft (60 m) wide blocked the highway here
at about 6:00 p.m. on
The broad flood plain of the
Randle and intersection of US 12
with SR 131. Note: If heading south from here to visit the Mount St.
Helens area, there are no service stations between here and the town of
accesses the east side of the
on-snow event and inundated the valley floor from wall to wall, left the uppermost layer.
MP 118. Cliffs to the left (north) are Miocene diorite and granodiorite intrusions.
Pullout to the right (south). The outcrop on the left is granodiorite with inclusions of andesite.
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.
Near MP 125 we notice some large boulders near the mouth of the canyon to the south. They might have been carried down to the flood plain by debris flows.
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
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
FR 20. More large rocks south of the highway may also be part of the same landslide noted at the rest area.
More large rocks, these at the mouth of Dry Creek, were probably deposited by debris flows.
The terrace or bench on the south
side of the highway near the curve, slightly after Hall and Johnson Creeks, is
supported in part by southwest-trending andesitic dikes. Hager Creek is a “disappearing stream” that drains into the
coarse rocky debris of a large alluvial fan. What could be the source of all
this rocky debris?
Swanson (1995) found no significant evidence of active faulting in this area, although he did identify many small, mostly north-northwest-trending shear zones that cut Tertiary rocks. He constrained the age of most folding in this area to “between 18 Ma (possibly 15.6 Ma) and 12 Ma” based on paleomagnetic data, several K-Ar ages, and field observations.
MP 131, downtown Packwood. This
small town may be located closer to more volcanoes than any other town in
Glacial grooves and striations on rocks locally offer further evidence of the huge glaciers that have carved this broad valley during past ice ages.
We depart Packwood 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
The outcrop on left is a Miocene intrusive andesite sill.
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.
Cross Lake Creek, which drains
MP 134. Columnar-jointed rock exposed south of the road is an andesitic sill of the Packwood complex of Oligocene or Miocene age (Swanson and others, 1997).
Thin shale laminae under the sill are lake deposits that contain some leaf fossils (Figs. [pack_laptuff_shale839] and [leaf_fossil_cu_mosaic]).
Grizzly Road. The highway is cut through an andesite sill.
Gray, intrusive andesite of Miocene or Oligocene age.
Coal Creek and
The small outcrop of tuffaceous sedimentary rock on the right contains fossil wood.
Near MP 136, FR 46 is on the southeast side of the road, and slightly past here, FR 1270 goes to Backbone Lake Trail #164.
Gray tuff on the right (southeast) that overlies a resistant andesitic sill is probably the Purcell Creek tuff of Miocene age, identified by Swanson (1996) in this area.
Green to light-gray tuffs crop out to the right (southeast) of the road.
At a curve to the right slightly before MP 137, note a large cliff of greenish-brown volcaniclastic rocks, possibly Purcell Creek tuff.
Fine-grained tuffs on the right here contain lapilli and larger clasts.
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)
The highway is sometimes closed in winter, so it is wise to check on road conditions before traveling. Road status can be checked at Washington State Dept. of Transportation via their web site or by phone. (See Web Links and Phone Numbers, p. ?).
Distances along the route are given in miles, followed by kilometers in italics. If we take any of the optional trips or side trips along the way, we'll have to keep track of, and add those miles to all remaining miles listed in each log. Having a pencil and paper handy, and even a calculator, will be helpful.
Junction of SR 123 and US 12. Sills
and pyroclastic flows are visible here in Ohanapecosh rocks. Fiske and
others (1963) measured a stratigraphic section of the Ohanapecosh Formation
volcaniclastic rocks from
Milepost (MP) 139.
A poorly sorted deposit or diamicton here is 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.
Near MP 140, Forest Roads (FRs) 45 and 4510 lead to Soda Springs Campground. The historic Cowlitz Trail heads at the campground. This route linked local tribes east and west of the Cascade crest, a distance of more than 40 mi (64 km) between settlements. Outcrops of Ohanopecosh Formation volcaniclastics are visible before and after FR 45.
Ohanapecosh sedimentary rocks dip about 30 degrees to the southwest several hundred yards (meters) west of MP 141 (Fig. [us12ohan_dipswavemp140p6-38]). 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.
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.
the columns here wider at the top? The columns develop at different rates as
cooling progresses both upward from the base and from the top down. (See Fig. [flow
anatomy/structure] in Leg F). The flow-top rubble at this site has been
removed by subsequent glaciation.
West dipping water-laid beds of the Ohanopecosh Formation crop out here.
.Note that the beds of the sedimentary rocks here dip at least 10 degrees more steeply to the southwest than the rocks 2 mi (3 km) to the west; beds become steeper over the next several miles (kilometers) and are nearly vertical as we approach the rocks of the pre-Tertiary Rimrock Lake inlier.
MP 143. Here we
see an outcrop of 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
The pullout to the right offers an
excellent view of
The contact between the Ohanopecosh
Formation and the overlying
The Ohanopecosh Formation is
exposed for about 0.8 mi (1.2 km).
Higher up, in cliffs above the roadway
Intrusive rocks are exposed on the left near where the road curves to the right (if eastbound). At the turnout slightly past this curve, note the valley slightly east of the high exposure of intrusive rocks, as well as the yellowish alteration in volcanic rocks adjacent to the intrusive body. The intrusion evidently altered and weakened the surrounding rocks.
We enter a stretch of the road that passes through colluvium as we approach the margin of the pre-Tertiary rocks.
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.
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
Intrusive andesite with large hornblende and biotite crystals crops out here.
Here we see out first good outcroppings of the Russell Ranch Formation. DESCRIBE THESE ROCKS!
The pullout to the right has a good exposure of the Russell Ranch Formation.
Scenic vista points near here (MP
148) offer views of Goat Rocks to the south-southwest (Fig. [goatrxfr_sliW_mp149wide]),
The Russell Ranch Formation is exposed for next 0.4 mi (0.6 km).
Note the hummocky landslide surface
in the forest south of the road between here and
Hogback Ridge is the source of the
FR 1284 and entrance to a Department of Transportation maintenance facility.
Boundary between Gifford Pinchot
Pacific Crest Trail crosses our route here
This roadcut is in Spiral Butte dacite.
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.
A broad turnout on the south side
of US 12 at a pronounced curve about 0.5 mi (0.8 km) offers a panoramic view of
the local terrain (Fig. [morapan154pan]):
We’ll see platy andesite outcrops for the next 1.5 mi (2.4 km).
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.
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.
An outcrop of greenstone of the Russell Ranch Formation is on the south side of road slightly east of MP 158.
More greenstone of the Russell Ranch Formation.
Indian Creek. MP 159. The type locality of the Indian Creek Gneiss, one of the units in the Indian Creek complex, lies about 4 mi (~6.5 km) to the northwest. Those who want to further explore the rocks of the Indian Creek complex via foot trails and nearby roads can find information in Miller (1985) and Northwest Geological Society (1991).
Indian Creek Campground .
Heritage Marker for the Russell Ranch that was flooded by the reservoir.
Steeply-dipping beds of the Russell Ranch Formation are exposed north of the highway.
Rest area south of road (not marked). Chert beds north of the highway.
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 Formation.
An outcrop of sheared shale and greenstone with slickensides is north of the highway. The greenstones include remnants of pillow basalts.
The sheared intrusive rock exposed
along the highway here is mapped as the “trondhjemite” of the Indian Creek pluton
of Jurassic age (Swanson and others, 1989). The name for this type of
low-potassium granitoid rock originated at
Rounded boulders of probable glacial till can be seen north of the road at MP 164. Note the slickensides in an area of sheared intrusive rocks near here.
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 R?ocks 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.
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 (
Rimrock Grocery store on our right. Gabbroic rock crops out on the left side of road, then we cross Wildcat Creek.
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;
Junction of US 12 with
the ridge are outcrops of the Tieton volcano (Oligocene-Miocene). We will see
many outcrops of volcaniclastic deposits
and lava flows related to Tieton volcano as we proceed on Highway 12. Swanson described the Tieton volcano as a
large stratovolcano having a basal shield more than 200 m (656 ft) thick
and overlain by 1500 m (4922 ft) of tuff and breccia (Swanson, 1964).
Many of the layers of fragmental debris have the steep dips that overall
describe a composite volcano; Swanson and others (1989) described at least 300
m (984 ft) of gently dipping volcanic debris flow deposits, lava flows,
and pyroclastic flow deposits “that can be traced nearly continuously into the
cone.” These deposits likely formed the part of an apron at the foot of the
volcano. The center of the Tieton volcano lies about 4 to 6 mi (6.5–10 km) east
of the summit of Bethel Ridge. Shultz (1989) obtained an age of 26 to 25 Ma for
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.
Outcrop of flow breccias of the Tieton volcano. Blocks of andesite as much as 30 in. (0.9 m) in diameter crop out in a buff-colored pumice matrix.
An overhanging rock outcrop of flow breccia and andesite is slighty west of the Wildrose picnic area.
Enter Rimrock Retreat (elev. 2250
ft or 386 m). This is a popular put-in site for rafters on the
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.
Pillow basalts and basalt columns.
Another of the andesite or basaltic-andesite dikes of the Tieton volcano.
MP 177. We cross the
Windy Point Campground. Near here Swanson (1978) mapped 12 distinct flows of the Grande Ronde Basalt of the Columbia River Basalt Group. The lower three flows belong to magnetostratigraphic unit R2 and the upper nine flows are N1. (See the sidebar “Paleomagnetism—volcanoes as tape recorders” in Leg F in Pringle, 2002)
On the south side of the highway is
a viaduct taking irrigation water from a diversion dam west of Rimrock Retreat
to agricultural lands in the
Eastern boundary of
Landslide deposit near MP 180. Exceptionally well developed jointing in the Tieton Andesite is visible at on the right (Fig. [tieton-andesite-columns]).
Stone stripes, a type of patterned ground, are draped on the hillside here. (See also Leg F, p. ??.)
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
A micaceous sandstone and
siltstone layer between two N2 flows of Grand Ronde Basalt (Swanson
and others, 1989). Swanson (1967) suggested that the metamorphic and plutonic
minerals in these interbeds here indicate a northern source area for the stream
that deposited them in Grande Ronde time. The mica in these sedimentary rocks,
therefore, could be interpreted to be from the ancestral
On the left at a tight (dangerous)
curve to the left, upper entabulature and well-developed lower colonnade (columns) of Tieton Andesite sit on rubbly, cobble-rich fluvial
deposits of the ancestral
SPECULATE ON HOW COLUNMNAR JOINTS FORM?
We can see well-developed columns of Tieton Andesite to the south.
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.
References (some on hold or in the collection in Kirk Library=* …or available online)
N. P., 1975, A geologic road log over Chinook, White Pass, and Ellensburg to
Dethier, David P., 1988, The soil chronosequence along the Cowlitz River, Washington: U.S. Geological Survey Bulletin 1590-F, 47 p
P. E.; Pringle, P.
T., 2008, June 18th field
trip guide: Selected geologic sites along US 12 between Yakima and the
River valley: NAGT 2008 fieldtrip: IN 2008 Annual meeting Pacific
Section of the National Association of Geoscience Teachers, p. 31-38. [Accessed May 31, 2013 at http://www.centralia.edu/academics/earthscience/pubs/hammond_pringle_nagt2008.pdf ]
Hoblitt, R. P.; Walder, J. S.; Driedger, C. L.; Scott, K. M.; Pringle, P. T.; Vallance, J. W., 1998, Volcano hazards from Mount Rainier, Washington, revised 1998: U.S. Geological Survey Open-File Report 98-428, 11 p., 2 plates. [Accessed Feb. 11, 2002 at ]
Mullineaux, Donal R., 1996, Pre-1980 tephra-fall
deposits erupted from
Patrick T., 2002, Roadside geology of
Patrick T., 2008, Roadside geology of Mount Rainier National Park and
vicinity: Washington Division of Geology and Earth Resources
Information Circular 107, 191 p. [Accessed on June 22, 2008 at http://www.dnr.wa.gov/ResearchScience/Topics/GeologyPublicationsLibrary/Pages/pub_ic107.aspx ]
K. M.; Vallance, J. W.; Pringle, P. T., 1995, Sedimentology, behavior, and
hazards of debris flows at Mount Rainier,
Walsh, Timothy J.; Korosec, Michael A.; Phillips, William M.; Logan, Robert L.; Schasse, Henry W., compilers; Meagher, Karen L.; Haugerud, Ralph A., digitizers, 1999, Geologic map of Washington--Southwest quadrant (digital edition): U.S. Geological Survey Open-File Report 99-382, 15 p. [accessed Sept. 7, 2000 at http://geopubs.wr.usgs.gov/open-file/of99-382/]
OPTIONAL TRIP TO SEE ELLENSBURG FORMATION DEPOSITS AT NACHES
The distant rounded hills on the north side of the valley near Naches are composed of the Ellensburg Formation; the type section is exposed there. Note the color and shape of hills determined by the softer, lighter-colored sediments. The Ellensburg Formation is made up of coarse lahar runouts, conglomerates, and interbedded pumiceous and ashy, stream‑worked deposits that occurred between approximately 7 and 13 Ma. Smith (1988a) reported ages of 7.4 to 13.3 Ma. These deposits are the distal or downvalley facies of the lahars produced by Miocene volcanoes. Although the volcanoes themselves have since been eroded away, these deposits have provided important evidence of the past eruptions.
If we have time, we’ll take the