Field trip 3 Columbia River Gorge

Answer as many of the numbered questions as you can. Draw sketches at every field location of any geologic features. Remember to 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. Clean out the vans at the end of this trip. I will give one pop quiz question for every item found in the vans after the trip.

Overview of trip 3: We will leave the Centralia College campus and proceed SOUTH on I-5 toward the Columbia River Gorge. This trip will features discussions geologic processes, history, and hazards revealed in the rocks and deposits of southwest Washington and northern Oregon, specifically in the spectacularly scenic Columbia River Gorge. Although we will have several major stops with field activities (listed below), we will also stop at various scenic viewpoints to observe geologic features, landforms, natural process, and of course scenery! We will be driving along the pathway of the great Missoula Floods, more than a hundred of which roared through the gorge from 12,700 to 15,300 yr. B.P. (Waitt, 1985, p. 1284).


Leave Centralia College

MP 13 rest stop if we need one???

Exit onto I-205 bypass

Cross Columbia River and not long after airport exit go EAST on I-84

Get off at Troutdale –exit 17—rest stop at McDonalds/Burger King

Continue east and turn left (north) toward Troutdale airport—go under I-84 and continue straight past Wendy’s on right and airport on left. After going around a curve to right turn right on E HARLOW PLACE---go 200 m & park on left where the road turns sharply right:











Field trip activities:    (note 1 Ma = 1 mega annum or 1 my; 1 ka = 1 kiloannum or 1,000 years)

MP 69 – 64: Slightly south of Chehalis we ascend what early 19th century pioneers called “mud mountain”. This is the highland that forms the divide between the Newaukum-Chehalis and Cowlitz River valleys. It was called mud mountain because of the muddy soil of the Logan Hill Formation. This geologic unit, whose age has been estimated at about 1 Ma by Dethier (1988), is interpreted mostly as cobble-rich glacial outwash sediments. The soil developed on this geologic unit is thick—tens of meters, and it is well developed. Note the deep red color exposed locally at the northbound entrance ramp to I-5 at Exit 68. Rocks in the upper part of this soil are so weathered you can cut through them like cheese.  You can find information on the geology along State Route 508 and US 12 in Roadside Geology of Mount Rainier National Park and Vicinity (Pringle, 2008)

~MP 63: Near Winlock descend to a lower, younger terrace. Does this terrace have less or more relief than that of the Logan Hill Formation? This terrace is inferred to be only ~0.5 -0.3 Ma and is also interpreted to consist of outwash material from the Cascade highlands. What was the source of the “outwash”?


~MP 60: Descend to another, younger terrace, also very flat. This is interpreted as glacial outwash from the alpine glaciation event named the Evans Creek glaciation, which lasted from about 22 ka to 15 ka. Cross the Cowlitz River, which drains Mount Rainier. Its tributary, the Cispus River, heads on Mount Adams.

Cross the Cowlitz River.

Cross the Toutle River, which heads on Mount St. Helens.

Exit 49: SR 503 to Mount St. Helens. The flat terrace on which the overpass is built is composed of lahars from Mount St. Helens that have been dated at ~20 ka.

Much of the land along the highway here is veneered by sediments deposited by the Missoula Floods. The floods reached as high as 150 ft above sea level (SL) near here.

Exit 39. At Kelso, one of the most destructive landslides in the history of the US took place in 1999 when more than 60 homes were destroyed by the Aldercrest-Banyon Landslide (Wegmann, 2004). Search for information on the landslide in Wegmann (2004), at  or elsewhere on the web or in libraries. What caused the landslide?


Slightly south of the Coweeman River, the highway skirts around the edge of landslide from Davis Terrace, to the east. In this area and to the north as far as Castle Rock, there are Cascade-derived Toutle Formation (sedimentary) and Goble Volcanics on the east side of the highway and, to the west, there are slightly older oceanic-type basalts such as the Grays River volcanics that are interbedded with sediments from the Cowlitz Formation that are inferred to be from nearshore marine as well as nonmarine environments.

There is a very thick exposure of the Goble Volcanics at about MP 31.8 on the West side of the highway called Drays Mound. This may have been a volcanic vent area. Note dikes exposed in the outcrops.

Kalama: the bedrock constriction here (narrowing of the valley) is composed of Columbia River Basalts. This constriction served to hydraulically dam the great Missoula Floods, causing them to backflood as far south as Eugene, Oregon to a depth of as much as 400 ft! The Kalama River heads on Mount St. Helens; tributaries of the Lewis River also head on Mount St. Helens.

Merge onto I-205: From the I-205 south to SR 14 we will be traversing sand and gravel terraces deposited by the late Pleistocene Missoula Floods. As we cross the Columbia River note Rocky Butte, a Pliocene or Pleistocene Boring volcano dead ahead on the horizon. Note the flat Missoula Flood terrace on both sides of it. Note Mount Hood composite volcano and, to its north, Larch Mountain shield volcano.

Head east on I-84 and get off at Exit 17, Troutdale. We will pull into the McDonalds or Jubitz for a break.

Afterwards we’ll head east, turn left toward the Troutdale Airport, and turn right onto E HARLOW PLACE as noted above. We will walk on Port of Portland property about 1/4 mi north to lahar outcrops along the Sandy River. Be careful with your footing here. These lahars were deposited during at least 2 great eruptive episodes at Mount Hood, about 1500 yr B.P. and about 200 yr B.P. (Cameron and Pringle, 1987). The Old Maid lahars commence about AD 1781 (Pringle and others, 2002, 2010; Pierson and others, 2011). Draw sketches of the outcrops and describe the deposits in your notebooks. Describe the characteristics of the sediments (bedding?, sorting, roundness, soils, etc). 







Leave Airport site and go back toward I-84. Turn right at light and drive west on the access road, but turn left at Marine Drive and go back under I-84, then left again past McDonalds. This time TURN RIGHT at the light and go south past outlet stores and up a grade—at light take left into the town of Troutdale (GO THE SPEED LIMIT). We will wind through town and go across the Sandy River; (narrow bridge—careful!) then turn right and continue along the historic Columbia River Scenic Highway. After about 2.3 miles we will round a curve to the left and pull off on the right. Be very careful here getting out of the vans because there is a great deal of traffic. We will all cross at once.

CARFULLY cross the road to the outcrop. Be wary of falling rocks and debris at the outcrop!

STOP 2. OUTCROP OF PLEISTOCENE AND PLIOCENE AGE TROUTDALE FORMATION GRAVELS AND SANDSTONES. The Troutdale sediments are interpreted to have been deposited by the ancestral Columbia River. We will examine the sand and rocks to make some interpretations about what was being transported here and perhaps speculate on the source area(s).  Carefully draw a sketch of the outcrop here, and remember to show approximate scale and label and sketch any sedimentary features. Which directions were currents flowing?






Continue on the highway, going straight past the Oxbow turnoff. There are buried subfossil trees at Dabney Park that were killed by the Old Maid lahar of A.D. 1781, however we will not take time to visit them. Also exposed here is a Columbia River sand possibly deposited by a flood that resulted from breaching of the Bonneville landslide dam between about AD 1440 and AD 1479 (O’Connor and others, 1996). We will ascend a series of terraces that were deposited along the Sandy River. About 1.7 mi past Dabney we will stay right on the Columbia River Hwy at Springfield. Shortly after we will continue on the hwy veering left at Hulbert junction. Note the reddish soil at the top of the terrace!  What does this tell you about the age of the higher terraces?


About 3 miles past Springfield turn left into the Womens Forum Park.

STOP 3. WOMENS FORUM. We will park and walk to the north to the interpretive sign. At the viewpoint, sketch the landscape you see and label it as we discuss the significance and composition of various landforms such as Mount Zion, Crown Point, Beacon Rock, and Rooster Rock. Beeson and Tolan (1987) and Tolan and others (1984) describe the view and features visible from this and nearby locations.





STOP 4. Latourell FALLS. There are rest rooms north of the road and down a path. We will walk to the falls to see the Sentinel Bluffs Member of the Grande Ronde Basalt that forms the falls. Along the trails is platy jointed dacite of the Oligocene age Skamania Volcanics.  Quickly sketch the falls labeling the colonnade and entablature components of the lava flow. Why do columns form in lavas?




STOP 5. MULTNOMAH FALLS.  We will stop here for 20 minutes. You can hike up to the bridge, but please go no farther. Note the many lava flows exposed in the falls! Allen (1979) has a sketch showing the different flows here.



STOP 6: RECENT DEBRIS FLOWS AT DODSON FRONTAGE ROAD INTERSECTION We will stop here to discuss debris flow processes and hazards. There have many episodes of debris flows here over the years. The debris flows originate on the Benson Plateau and are typically triggered by saturation conditions and episodic rainstorms. In 1996 debris flows surrounded the Royse residence slight east of the intersection. The Royses narrowly escaped with their lives. The Tumalt Creek debris flow knocked a train off the tracks in 1996. The debris flow at the onramp to I-84 occurred in 2001 and closed the onramp. GET ON I-84 and proceed east to Eagle Creek exit (if time allows) or to Cascade Locks.


OPTIONAL STOP: EAGLE CREEK We may stop here to see the fragmental deposits of the lower Miocene Eagle Creek Formation, which originated a composite volcano north of here. The deposits include lahars and pyroclastic flows. A buried petrified tree and is visible along the trail. Draw and label a sketch.

=>CAUTION! The trail here is locally a cliff with 15 ft drop to the creek. Be mindful of the edge!



STOP 7. CASCADE LOCKS MARINE PARK, VIEW OF BONNEVILLE LANDSLIDE. Sketch the Bonneville landslide. Label the Table Mountain headscarp, and also show Red Bluffs to the east. The Bonneville landslide dammed the entire Columbia River in the mid 1400s and drowned a forest that had lived along its banks. The forest was described by Lewis and Clark (Lawrence and Lawrence, 1958; Schuster and Pringle, 2002; O’Connor, 2004). The Bonneville landslide is probably the youngest of many major landslides in the Columbia River gorge, although many show continued activity (Palmer, 1977). Much work continues on the Bonneville landslide and its landscape effects (Weaver and Pringle, 2003; Pringle, 2004, 2009).





References (many on hold in Kirk Library)

Allen, J. E., 1979, The magnificent gateway--A layman's guide to the geology of the Columbia River gorge: Timber Press [Forest Grove, Ore.] Scenic Trips to the Northwest's Geologic Past 1, 144 p. [On reserve in Kirk Library]

Allen, John Eliot; Burns, Marjorie; Sargent, Sam C., 1986, Cataclysms on the Columbia--A layman's guide to the features produced by the catastrophic Bretz floods in the Pacific Northwest: Timber Press [Portland, Ore.] Scenic Trips to the Northwest's Geologic Past 2, 211 p.

Beeson, Marvin H.; Tolan, Terry L., 1987, Columbia River gorge--The geologic evolution of the Columbia River in northwestern Oregon and southwestern Washington. IN Hill, M. L., editor, Cordilleran section of the Geological Society of America: Geological Society of America DNAG Centennial Field Guide 1, p. 321-326.

Cameron, Kenneth A.; Pringle, Patrick T., 1986, Post-glacial lahars of the Sandy River basin, Mount Hood, Oregon: Northwest Science, v. 60, no.4, p. 225-237. [accessed on April 16, 2008 at ]

Cameron, Kenneth A.; Pringle, Patrick T., 1987, A detailed chronology of the most recent major eruptive period at Mount Hood, Oregon: Geological Society of America Bulletin, v. 99, no. 6, p. 845-851. [I will make this available via  Angel]

Dethier, David P., 1988, The soil chronosequence along the Cowlitz River, Washington: U.S. Geological Survey Bulletin 1590-F, 47 p.

Lawrence, Donald Buermann; Lawrence, Elizabeth G., 1958, Bridge of the Gods legend--Its origin, history, and dating: Mazama, v. 40, no. 13, p. 33-41. 

O’Connor, J. E, 2004, The Evolving Landscape of the Columbia River Gorge: Lewis and Clark and Cataclysms on the Columbia: Oregon Historical Quarterly, v. 105, No. 3, p. 390-421 [I will make this available via Angel]

O'Connor, J. E.; Pierson, T. C.; Atwater, B.F.; Turner, D.; Pringle, P.T., 1996, An exceptionally large Columbia River Flood between 500 and 600 years ago—Breaching of the Bridge-of-the-Gods landslide?: Geological Society of America Meeting  (Cordilleran), Portland, Oregon, v. 28, no. 5, p. 97.

Palmer, L. A., 1977, Large landslides of the Columbia River gorge, Oregon and Washington. IN Coates, D. R., editor, Landslides: Geological Society of America Reviews in Engineering Geology, v. III, p. 69-83.

Pierson, T.C.; Pringle, P.T.; Cameron, K.A., 2011, Magnitude and timing of downstream channel aggradation and degradation in response to a dome-building eruption at Mount Hood, Oregon. Geological Society of America Bulletin. v. 123, no. 1–2, p. 3–20. [Accessed until January 2013 at: 

Pringle, Patrick T., 2004, Dendrochronology research supported by Murdock Trust, DGER News, v. 1. no. 1., p. 2. [accessed on February 16, 2005 at]

Pringle, 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 3, 2008 at ]

Pringle, Patrick, 2009, The Bonneville slide. Explorations: Columbia Gorge Interpretive Center Museum, Fall–Winter 2009, p. 2–3. [accessed August 12, 2010 via

Pringle, Patrick T.; Pierson, Thomas C.; Cameron, Kenneth A., 2002, A circa A.D. 1781 eruption and lahars at Mount Hood, Oregon—Evidence from tree-ring dating and from observations of Lewis and Clark in 1805-6 [abstract]: Geological Society of America Abstracts with Programs, v. 34, no. 6, p. 511. [accessed on June 3, 2008 at ]

Pringle, P.T.; Pierson, T.C.; Cameron, K.A.; Sheppard, P.R, 2010, Late 18th century Old Maid eruption and lahars at Mount Hood, Oregon (USA) dated with tree rings and historical observations, IN Tree-Ring Analysis in Natural Hazards Research, Stoffel, M., Bollschweiler, M., Butler, D.R., Luckman, B.H. (eds.). Springer, p. 487–491. [I will put this paper on the Angel site]

Schuster, Robert L.; Pringle, Patrick T., 2002, Engineering history and impacts of the Bonneville landslide, Columbia River gorge, Washington-Oregon, USA. IN Rybar, Jan; Stemberk, Joseph; Wagner, Peter, editors, Landslides--Proceedings of the First European Conference on Landslides: A. A. Balkema, p. 689-699.

Tolan, Terry L.; Beeson, Marvin H.; Vogt, Beverly F., 1984, Exploring the Neogene history of the Columbia River--Discussion and geologic field trip guide to the Columbia River gorge; Part II, Road log and comments: Oregon Geology, v. 46, no. 9, p. 103-112. [Accessed on April 30, 2011 at  ]

Waitt, Richard B., Jr., 1985, Case for periodic, colossal jokulhlaups from Pleistocene glacial Lake Missoula: Geological Society of America Bulletin, v. 96, no. 10, p. 1271-1286.

Wang, Yumei; Hofmeister, R. Jon; McConnell, Vicki S.; Burns, Scott F.; Pringle, Patrick T.; Peterson, Gary L., 2002, Columbia River gorge landslides. IN Moore, G. W., editor, Field guide to geologic processes in Cascadia: Oregon Department of Geology and Mineral Industries Special Paper 36, p. 273-287.

Weaver, Russ; Pringle, Patrick T., 2003, Use of dendrochronology to date and better understand the Bonneville landslide, Columbia River Gorge, Washington  [abstract]: Geological Society of America Abstracts with Programs, v. 35, no. 6, p. 80. [accessed on April 1, 2007 at ]

Wegmann, Karl W., 2004, Geologic field trip to the Aldercrest-Banyon Landslide and Mount St. Helens, Washington, Part I—Stevenson to Castle Rock: Washington Division of Geology and Earth Resources, 24 p.