Field trip to Mount St. Helens

What this field trip is about:

During this field trip we will see a remarkable amount of geology including evidence of past volcanism from both Mount St. Helens and from volcanoes that have erupted over the past 30+ million years. We will evidence that glaciers have modified the landscape over the past ~1.6 million years, see geologic structures such as folded and faulted rocks, dikes, and sills; rocks cooked by intrusions of magma or sheared along a fault zone, and observe several types of landslides as well as modern stream processes, landslide-dammed lakes, and primary and secondary successional landscapes.

What to do during this field trip (observe, ask questions, take notes, sketch):

Make comments and descriptions and ask questions as you go—ON THE BACK OF THIS PAGE OR ANOTHER PIECE OF PAPER (or in field notebooks). Draw and label sketches at every field location of any geologic features or landscapes. 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 multi page word-processed summary. Consult web references and any of the references listed at the end of this guide (many on hold or on reserve in the library). FIELD TRIP WRITE UP DUE JUNE 2.

Overview of trip: We will leave the Centralia College campus and proceed SOUTH on I-5 Exit 49 where we will head east on SR 504 into the Cascade Range toward Mount St. Helens. This trip will features discussions about geologic processes, history, and hazards revealed in the pre- and post- Mount St. Helens rocks and deposits, specifically in the scenic Toutle River valley. 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!

Itinerary:

Leave Centralia College South on I-5.

EXIT 49: Go east on SR 504. See Pringle (2002), particularly “Leg A”

OPTIONAL STOP AT SILVER LAKE VISITOR CENTER (Restrooms & water; free admission, exhibits, bookstore)

STOP 1. HARRY GARDNER PARK—Mount St. Helens lahars (near Toutle WA). See detailed write up in Doukas (1990) for info en route and Mullineaux (1996) for ages of tephra.

OPTIONAL STOPS. HOFFSTADT BLUFFS VISITOR CENTER OR FOREST LEARNING CENTER. Restrooms.  At FLC views of spectacular dikes cutting Oligocene volcanics.

STOP 2. ELK ROCK VIEWPOINT.

STOP 3 (Depending On The Weather) JRO –JOHNSTON RIDGE OBSERVATORY

STOP 4: HUMMOCKS TRAIL: We will see blocks and pieces of the mountain as we walk through the deposit of the great debris avalanche of 1980.

 

FIELD TRIP ACTIVITIES

Exit 49: SR 504 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.

STOP 1: HARRY GARDNER PARK—LAHAR DEPOSITS.  Take notes here and sketch outcrop—the older “Pine Creek age” lahar deposits and the 1980 deposits to show the relative scale. See Doukas, 1990.

FOREST LEARNING CENTER (optional): Greenish color is low grade metamorphism. Note dikes! Sketch these. 

ELK ROCK VIEW POINT: Sketch and label landscape—note blown down trees.  Take notes on metamorphism of the bedrock—blackish rock is hornfels, a recrystallized volcanic rock. 

JOHNSTON RIDGE OBSERVATORY: Mount St. Helens is the main attraction, but also note the layering and dip of the exposed bedrock..

HUMMOCKS TRAIL: We will see blocks and pieces of the mountain as we walk through the deposit of the great debris avalanche of 1980.

Assignment: Pick an aspect of the eruption or its effects or the deposits of previous eruptions and write a one or two page short paper (extended abstract) using some of the references below and/or others. Perhaps make some interpretations on the significance of the 1980 eruption to geology in general and to how we perceive stratovolcanoes. Be sure to cite all you references properly! In addition to the sketches, descriptions, and notes you are taking, you must do this assignment to get credit for this field trip. At the end of your assignment, add a section in which you share any feelings, observations, and new perceptions about the eruption and the landscape that you may have derived from this trip and/or from your encounters with this disturbed landscape. Does knowing more about this landscape and about the scale, nature, and history of volcanic processes make you think differently about some of the other Cascade volcanoes or about volcanism and humans in general? Please explain this. Is this important to Pacific Northwesterners? NOTE: Check the online rubric mentioned on the class syllabus for guidelines on writing papers.

References (some on hold or in the collection in Kirk Library=*    …or available online)

Clynne, Michael A.; Ramsey, David W.; Wolfe, Edward W., 2005, Pre-1980 eruptive history of Mount St. Helens, Washington: U.S. Geological Survey Fact Sheet 2005-3045, 4 p. [accessed Jul. 7, 2005 at http://pubs.usgs.gov/fs/2005/3045]

Crandell, D. R., 1987, Deposits of pre‑1980 pyroclastic flows and lahars from Mount St. Helens volcano, Washington: U.S. Geological Survey Professional Paper 1444, 91 p., 1 plate.

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

Doukas, Michael P., 1990, Road guide to volcanic deposits of Mount St. Helens and vicinity, Washington: U.S. Geological Survey Bulletin 1859, 53 p. [accessed Jan. 19, 2001 at  http://vulcan.wr.usgs.gov/Volcanoes/MSH/Publications/Bulletin1859/  (see “report” link for doc text and “view as a series of images”; pp. 41–48 is SR 504 Spirit Lake Highway area; p. 44 is the Harry Gardner Park)]

Mullineaux, Donal R., 1996, Pre-1980 tephra-fall deposits erupted from Mount St. Helens, Washington: U.S. Geological Survey Professional Paper 1563, 99 p. [accessed Feb. 12, 2002 at http://greenwood.cr.usgs.gov/pub/ppapers/p1563/]

*Pringle, Patrick T., 2002, Roadside geology of Mount St. Helens National Volcanic Monument and vicinity; rev. ed.: Washington Division of Geology and Earth Resources Information Circular 88, 122 p.

*Pringle, P.T.; Cameron, K. A., 1999, Eruption-triggered lahar of May 14, 1984, In Pierson, T. C. ed., Hydrologic consequences of hot-rock/snowpack interactions at Mount St. Helens Volcano, Washington, 1982-1984: U.S. Geological Survey Professional Paper 1586, p. 81-103.

*Scott, Kevin M., 1988, Origin, behavior, and sedimentology of prehistoric catastrophic lahars at Mount St. Helens, Washington. IN Clifton, H. E., editor, Sedimentologic consequences of convulsive geologic events: Geological Society of America Special Paper 229, p. 23-36.

Tilling, Robert I., 1983, Monitoring active volcanoes: U.S. Geological Survey, 13 p. [accessed Feb. 12, 2002 at http://pubs.usgs.gov/gip/monitor/contents.html]

Tilling, Robert I.; Topinka, Lyn J.; Swanson, Donald A., 1984, rev. 1990, Eruptions of Mount St. Helens--Past, present, and future: U.S. Geological Survey, 56 p. [accessed Feb. 12, 2002 at http://pubs.usgs.gov/publications/msh/]

Wolfe, Edward W.; Pierson, Thomas C., 1995, Volcanic-hazard zonation for Mount St. Helens, Washington, 1995: U.S. Geological Survey Open-File Report 95-497, 12 p., 1 plate. [accessed Feb. 12, 2002 at http://vulcan.wr.usgs.gov/Volcanoes/MSH/Hazards/OFR95-497/framework.html]

 

Selected Web References

http://vulcan.wr.usgs.gov                                                        CVO, Cascades Volcano Observatory

http://www.geophys.washington.edu/SEIS/PNSN/               Pacific NW Seismic Network

http://www.pnsn.org/HELENS/welcome.html                       PNSN Mount St. Helens (MSH) and webcam link

http://volcano.und.edu/vwdocs/msh/                                      Volcano World Mount St. Helens

http://geoweb.tamu.edu/misc/Trixie.html                               Trixie Anders’ site for Jim Fitzgerald

http://www.dnr.wa.gov/Publications/ger_washington_geology_1980_v8_no3.pdf               Washington Geology Mount St. Helens issue, July 1980

http://www.fs.fed.us/gpnf/mshnvm/index.shtml                    MSH National Volcanic Monument

http://www.agiweb.org/geotimes/may00/featurestory.html   MSH 20 years later by Bob Tilling

http://mshinstitute.org/                                                           MSH Institute

http://www.dnr.wa.gov/AboutDNR/Divisions/GER/Pages/home.aspx                  Division of Geology and Earth Resources

http://www2.wadnr.gov/dbtw-wpd/washbib.htm                  Search the online bibliography of the geology of Washington State

http://home.comcast.net/~wa_geology/                                  Chris Heg’s WA Geology maps

http://www.dnr.wa.gov/ResearchScience/Topics/GeosciencesData/Pages/geology_portal.aspx   Washington Div. of Geology info Portal---geologic maps and other info

http://www.centralia.edu/academics/earthscience/resources/resources.htm           Student resources and tools at Centralia College Earth Sciences page