OREGON GEOLOGY Oregon Department of Geology and Mineral Industries Volume 66, Number 1, Fall 2004 DOME BUILDING ON MT. ST. HELENS ALSO IN THIS ISSUE: GEOLOGY AND HAZARD RESPONSE PLANS GLACIAL STRATIGRAPHY AND HISTORY OF THE BLUE RIVER DRAINAGE CRYSTAL SPRINGS ZONE OF CONTRIBUTION ALL DEPARTMENT BULLETINS AND OIL & GAS INVESTIGATIONS NOW AVAILABLE ON CD OREGON GEOLOGY VOLUME 66, NUMBER 1 FALL 2004 Contents From the State Geologist Geology and hazard response plans . .3 Mount St. Helens update . .4 Research Article Glacial Stratigraphy and History of the Blue River drainage, Lane County, Oregon: A stratigraphic study of glaciolacustrine sediments detailing reverse drainage glacial ice-margin oscillations and subsequent ice-dam failure similar to a small-scale Missoula Flood event . .5 Crystal Springs Zone of Contribution, Crystal Springs Water District, Odell, Oregon . .15 Publications Bulletins and Oil & Gas Investigations now on CD . .16 New DOGAMI Publications . .21 Thesis/Dissertation Abstract Feeder Dikes to the Columbia River Flood Basalts: Underpinnings of a Large Igneous Province . .23 To Order Publications . .24 OREGON DEPARTMENT OF GEOLOGY AND MINERAL INDUSTRIES Governing Board Grants Pass Field Office: 5375 Monument Drive, Grants Pass 97526, William M. Elliott, Chair . Lake Oswego phone (541) 476-2496, FAX (541) 474-3158. Donald A. Haagensen, Vice Chair . Portland Thomas J. Wiley, Southwest Oregon Section Leader. Steven McNab . Bend Mineral Land Regulation and Reclamation Program: 229 Broadal- Vera E. Simonton . Pendleton bin Street SW, Albany 97321-2246, phone (541) 967-2039, FAX (541) Barbara P. Seymour . Salem 967-2075. Gary W. Lynch, Assistant Director of Regulation. State Geologist . Vicki S. McConnell Nature of the Northwest Information Center: Suite 177, 800 NE Assistant Director . Don Lewis Oregon St. # 5, Portland, OR 97232-2162, phone (503) 872-2750, FAX (503) 731-4066. Internet: http://www.naturenw.org Produced by the Public Education Section of the Department Donald J. Haines, Manager. Main Office: Suite 965, 800 NE Oregon Street # 28, Portland Permission is granted to reprint information contained herein. Credit 97232, phone (503) 731-4100, fax (503) 731-4066. given to the Oregon Department of Geology and Mineral Industries for Internet: http://www.oregongeology.com compiling this information will be appreciated. Baker City Field Office: 1510 Campbell Street, Baker City 97814, Information and conclusions in these articles are the responsibility of the phone (541) 523-3133, FAX (541) 523-5992. author, and are not necessarily shared by the Department and its staff. Mark L. Ferns, Eastern Oregon Section Leader. Coastal Field Office: 313 SW Second Street, Suite D, Newport 97365, phone (541) 574-6642, FAX (541) 265-5241. Jonathan Allan, Coastal Section Leader. On the Cover Mount St. Helens new growth, from the north. USGS Photograph taken on November 29, 2004, by Jim Vallance and Matt Logan. Oregon Geology (ISSN 0164-3304) is published by the Oregon Department of Geology and Mineral Industries on its web site http://oregongeology.com. (Volumes 1 through 40 were entitled The Ore Bin.) OREGON GEOLOGY, VOLUME 66, NUMBER 1, FALL 2004 2 FROM THE STATE GEOLOGIST, DR. VICKI S. McCONNELL Geology and hazard response plans Although the awakening of Mount St. Helens is not A more challenging volcano response plan involves the only geologic activity that has occurred in or near the threat to the communities and resources in the our state in the last year, it certainly created the Central Cascades. From Mount Jefferson to Newber- biggest stir. Why is that? Volcanoes certainly garner ry Volcano there are several volcanoes and volcanic a certain amount of curiosity and infamy in general; centers, with a wide scale of potentially hazardous that attention increases during an eruption. Other types of eruptions and erupted materials. The hazard events like minor earthquakes or the opening or clos- could impact communities on both sides of the Cas- ing of quarries are not considered front page news. cades. A more pragmatic reason for the notice associated We do much more than volcano response plans. We with Mount St. Helens is the immediate impact of are assisting coastal communities with their planning policy decisions made to address the increase in for response to tsunami hazards. We research and risk—closing of visitor centers and restricting access map the extent of past tsunamis and model where to areas and roads. If you want the public to notice we would expect inundation from a future tsunami. something, just tell them they can’t go there! Then we help communities map evacuation routes and develop brochures to explain them to coastal res- The policy decisions made in response to the in- idents and visitors. creased risk of a volcanic eruption from Mount St. Helens were not arbitrary. They resulted from fol- Landslides, particularly fast-moving debris flows, are lowing a decision tree outlined in a coordinated haz- a common winter hazard, and call for a different type ard response plan for Mount St. Helens. Response of response plan. After several fatalities in 1996-98, a plans for geologic hazards are the logical outcome of debris flow warning system has been put in place, in- a basic part of DOGAMI’s mission—to identify and volving the Oregon Department of Forestry, Oregon characterize the geology of the state of Oregon. Emergency Management, and the National Weather Service. Rainfall is monitored, and when pre-estab- To me, the development of geologic hazards re- lished threshholds are reached, a debris-flow warn- sponse plans represents an excellent measure of the ing may be issued. Part of the response plan includes success of both our geologic work and our public ed- highway signs notifying travellers entering potential- ucation programs at DOGAMI. Writing a response ly dangerous areas. plan is done when you have learned of a hazard or threat and you determine there is enough informa- These are only a few of the various types of response tion available to make adequate decisions. plans that DOGAMI has been involved with. Com- munities, businesses, government agencies, and indi- The challenge in preparing any response plan is en- viduals can all benefit from planning their responses suring that proper organizations are involved in the to the many geologic hazards in Oregon. creation of the plan and that everyone has the neces- sary information to aid with decision making. Our work to expand and refine information about Oregon’s geology continues, as does our coordina- Here in Oregon we have our fair share of geologic tion with other agencies and organizations. Response hazards to plan for, including our own volcanoes. plans must be updated periodically to reflect current For example, DOGAMI staff serves as the state geolo- understanding. The more we know about the poten- gy representative to review and revise the Mount tial damage from specific geologic hazards, the more Hood Coordination Plan that is slated to be released we can all use our limited resources more wisely. early in 2005. If you would like to preview the plan, you may do so from our website, oregongeology.com, and click on the “Earthquakes and other natural hazards” page. OREGON GEOLOGY, VOLUME 66, NUMBER 1, FALL 2004 3 MOUNT ST. HELENS UPDATE BY VICKI S. MCCONNELL In late September and early October our most active was indeed migrating. This spurred the decision to volcano in the Cascade Range gave both geologists upgrade to alert level 3, a Volcano Alert. Johnson and emergency response personnel a real wake up Ridge Observatory was evacuated. Tremor blasts and call. Mount St. Helens has entered into a late stage of observable changes in the crater floor increased over dome building activity. Although this is a completely the next several days and on Tuesday, October 5 at normal phase in the life of an active stratovolcano, 9:00 am, a vigorous steam and ash explosion took after several years of negligible activity it seemed place that cleared several small vents. Seismicity quite spectacular. dropped off markedly and scientists assumed that the opening of the vents depressurized the system. Beginning on September 22, 2004 seismologists at the This allowed magma to be extruded to the surface, to US Geologic Survey Cascade Volcano Observatory begin a dome-building episode if enough lava were CVO) noted a marked increase in tiny, shallow earth- available. The volcano alert was downgraded to alert quakes located under the lava dome. By the next day level 2, a Volcano Advisory. hundreds of small (less than magnitude 1) earth- quakes were occurring and the observatory issued an Presently Mount St. Helens continues to extrude lava information statement about it. The earthquakes at the northern edge of the 1980-1986 dome, pushing were so shallow it was not clear if they were actually a spire upwards to over 76 m higher than the dome. occurring at the surface and might be associated with This poses some threat of collapse and formation of Horseshoe glacier that surrounds the dome. By Sep- pyroclastic flows and lahars down drainages. Analy- tember 26 both the frequency and magnitude of sis of bombs collected from the steam and ash emis- earthquake activity had increased enough that the sions indicate the lava is rhyolite. This would be ex- staff at CVO decided to issue a Notice of Volcanic Un- pected if the magma is the cooling product of the rest and the US Forest Service staff closed the flanks 1980-1986 chamber that has been cooling and evolv- of the volcano to hikers and climbers. ing. The volcano was pressurizing beneath the lava dome The volcano alert level remains at level 2, Volcano Ad- in response to fluid migration and there was a good visory; Johnson Ridge Observatory remains closed, chance a phreatic or phreatomagatic eruption could and we watch and wait as the mountain continues to occur.