Premeeting Trips

401. Floods of Water and Lava on the Columbia River Plateau: Analogs for Mars
Tues.–Sat., 13–17 Oct.
Columbia River
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Sorry, this trip has been canceled.
402. The Great Missoula Floods and the Channeled Scabland  — FULL
Mon.–Sat, 12–17 Oct. US$515 (L, R, 5ON).
Cosponsored by GSA’s Sedimentary Geology and Quaternary Geology and Geomorphology Divisions.
Leaders: Richard, B. Waitt, USGS–Cascades Volcano Observatory; Roger Denlinger; Jim O’Connor.
This great circuit of the Channeled Scabland, Columbia valley, the Cordilleran ice sheet margin, and other areas provides a comprehensive view of the erosional and depositional evidence of the Missoula floods. We will explore evidence that there were 90 or more floods during the Late Wisconsinan glaciation and that their peak discharges ranged across two orders of magnitude. We will also explore different routings of floods governed by changing configurations of the Cordilleran-ice margin and see how two-dimensional hydraulic modeling consistent with all field evidence explains that even the greatest floods originated solely from glacial Lake Missoula. Our huge S-route winds from Spokane to the Cheney-Palouse scabland to northern Quincy Basin, Grand Coulee, the ice sheet margin near Chelan, Columbia valley, to immense floodforms near Wenatchee and Moses Coulee, including the site of a Clovis cache, across Quincy basin, to Drumheller and Ephrata scablands, to great scablands and floodbars of Washtucna coulee, and into Snake valley, immense bars in the Snake, to rhythmites near Walla Walla revealing scores of great floods, to the bottleneck of Wallula gap, and down Columbia valley and its gorge through the Cascades past great bars and scabland, ending among the great bars of Portland. Along the way, we will visit many spots familiar to J Harlen Bretz as he was developing the story of one great “Spokane Flood” in the 1920s.
403. Central and Eastern Portions of the Columbia River Flood-Basalt Province—An Overview of Our Current State of Knowledge of Flood-Basalt Stratigraphy, Vent Geometries, Flow Emplacement Mechanisms, and Tectonics
Wed.–Sat., 14–17 Oct. US$365 (L, R, 1D, 3ON).
Leaders: Terry L. Tolan, GSI Water Solutions; John D. Kaufmann; Barton S. Martin; Stephen P. Reidel.
The Columbia River Flood Basalt Province is one of the best exposed and understood Large Igneous Provinces (LIP) in the world. Decades of detailed geologic mapping, stratigraphic studies, petrologic studies on the origin of the basalts, and tectonic studies have provided insight into the evolution of the province. This three-day trip will visit a mix of “classic” and new localities in the central and eastern province that are fundamental to unraveling the geologic and tectonic evolution of this LIP. Participants will be introduced to recent refinements in Columbia River basalt stratigraphy, the nature of dikes and vents, eruptive/flow emplacement histories, as well as new insights into the structural geology of this region and its tectonic evolution. Evidence for and against the Plume Model will be examined and discussed. The first day of the field trip will be in the south-central Columbia Basin and will focus on Columbia River basalt vents/feeder dikes, flow emplacement, intraflow structures, and the structural geology of the Columbia Basin and western Palouse Slope. On the second day, participants will examine features on the eastern margin of the Province where most of the basalt erupted in a complex tectonic environment, and where evidence for and against the Plume Model can be seen. The final day, on the western Columbia Plateau and Columbia River Gorge, will focus on the structural geology of the Yakima Fold Belt, Columbia River basalt intracanyon flows, and the ancestral Columbia River paleodrainage history.
404. Hydrogeology of the Columbia River Basalt Group (CRBG) in the Columbia Plateau
Wed.–Sat., 14–17 Oct.
Drumheller channels
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Sorry, this trip has been canceled.
405. Geology and Geo-Archaeology of Hells Canyon, Oregon and Idaho
Wed.-Sat. 14-17 Oct.
Sorry, this trip has been canceled.
406. Late Triassic to Late Jurassic Petrotectonic History of the Oregon Klamath Mountains
Thurs.–Sat., 15–17 Oct. US$328 (L, 2ON).
Leaders: Doug Yule, California State Univ. at Northridge; Bob Murray; Allan Kays; Tom Wiley.
This field trip to the general vicinity of Grants Pass, Oregon, USA, will visit locales that reveal the multiphase petrotectonic history of the Oregon Klamath Mountains. Here, units strikingly similar to, if not correlative with the Rattlesnake Creek terrane (RCT) in California, occur within two main lithotectonic belts, the western Paleozoic and Triassic (WTrPz) belt and the western Jurassic (WJ) belt. This relationship is a surprise given that a major terrane-bounding fault, the Preston Peak or Orleans (PP/O) thrust, separates the two previously thought to be unrelated belts, and corroborates a tectonic model first introduced by Snoke (1977). Objectives of this trip will be to view (1) the RCT basement in both the active and remnant arc settings; (2) pre-, syn-, and post-rift deformational features; and (3) pre- and post-tectonic plutons that intrude these terranes. Day 1: White Rock pluton and contact aureole with the May Creek terrane. Day 2: The Sexton Mountain ophiolite and sutured contact with the WJ belt; Grants Pass pluton; Western Hayfork terrane and RCT; pillow lavas and cherts of the Onion Camp complex (RCT); and Rogue Formation volcanogenic sediments. Day 3: Mineralized contact between the Rogue and Galice formations; Briggs Creek amphibolite, and deformed gabbros of the Chetco complex.
407. Linking Deep- and Shallow-Crustal Processes in a Continental Arc, North Cascades, Washington
Thurs.–Sat., 15–17 Oct. US$370 (B, L, 2D, R, 2ON).  — FULL
Cosponsored by GSA’s Structural Geology and Tectonics Division.
Leaders: Robert B. Miller, San Jose State University; Stacia Gordon; Noah McLean; Donna L. Whitney; Sam Bowring.
The Cascades core preserves a crustal section (0–40 km) through a thick arc that underwent amphibolite-facies metamorphism, partial melting, arc-parallel extension, and rapid exhumation coeval with subsidence and infilling of thick Eocene non-marine basins during regional transtension and postulated ridge subduction. We will examine the Cretaceous to Eocene structural, metamorphic, magmatic, and sedimentary record of the arc and basins, and responses to transtension at different crustal levels. Topics addressed include (1) strain partitioning between brittle and ductile crust during exhumation, focusing on the Teanaway mafic dike swarm, the steep mid-crustal, dextral Ross Lake fault zone, subhorizontal orogen-parallel, non-coaxial shear and penetrative stretching in 10–12 kb paragneisses (Swakane Gneiss), migmatites, and orthogneisses (Skagit Gneiss Complex); (2) the origin and role of partial melt in mid-crustal flow, emphasizing new field and geochronologic evidence from migmatites for prolonged metamorphism, partial melting, and deformation; (3) the magmatic evolution of the arc, particularly the switch from tonalitic Cretaceous magmatism to compositionally highly diverse Eocene magmatism, and the possible influence of ridge subduction; and (4) non-coaxial flow and constrictional strain during arc-parallel extension, and linkages between deep-crustal domains that underwent Eocene isothermal decompression. The first day, we will examine Eocene basins, dike swarms, Swakane Gneiss, and the Ross Lake fault zone. Day 2 will be in the North Cascades National Park Complex and focus on Eocene plutons and Skagit migmatites. Crystalline rocks will also be examined on the third morning before returning to Portland. Participants should be prepared for cold, wet weather and short hikes.
408. Paleogene Calderas of Central and Eastern Oregon: Sources of Widespread Ash-Flow Tuffs in the John Day and Clarno Formations
Thurs.–Sat., 15–17 Oct. US$350 (L, 2ON).
Cosponsored by the Oregon Dept. of Geology and Mineral Industries and Portland State University.
Leaders: Jason D. McClaughry, Oregon Dept. of Geology and Mineral Industries; Martin J. Streck; Karyn A. Patridge; Caroline L. Gordon; Mark L. Ferns.
Tower Mountain Outflow
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The Paleogene John Day and Clarno Formations of central and eastern Oregon contain a widespread assemblage of ash-flow tuffs previously considered to be the eruptive products of small, isolated volcanic centers coincident with the modern day Cascade volcanic arc. Recent detailed geologic mapping in these Paleogene rocks has identified at least three large-scale rhyolite caldera complexes centered along the northeast trending axis of the Blue Mountains in central and eastern Oregon. These calderas are volcanic vents much larger than the small, isolated eruptive centers envisaged by preceding workers and are comparable in size to some of the largest calderas known worldwide. Over the course of this three-day trip, participants will explore stratigraphic and geochemical aspects of the ca. 29.5 Ma Crooked River caldera at Prineville, the ca. 40 Ma Wildcat Mountain caldera exposed along the crest of the Ochoco Mountains, and the ca. 28.5 Ma Tower Mountain caldera exposed near Ukiah in eastern Oregon. Highlights include examination of spectacular examples of ash-flow tuff deposits exposed at Smith Rock, Steins Pillar, and Dale and associated rhyolite domes and flows.
409. Fire and Water: Volcanology, Geomorphology, and Hydrogeology of the Central Cascades and Adjacent Areas, Oregon
Thurs.–Sat., 15–17 Oct. US$455 (B, L, D, R, 2ON).  — FULL
Cosponsored by GSA’s Hydrogeology Division.
Leaders: Gordon Grant, Marshall Gannett, and Katharine Cashman. Leaders: Gordon Grant, U.S. Forest Service PNW Research Station; Marshall W. Gannett; Katharine Cashman.
This trip will explore the interactions among the geologic evolution, hydrology, and fluvial geomorphology of the central Cascade Range in Oregon. This region offers an unparalleled opportunity to examine over 30 million years of landscape development along a young volcanic arc amidst spectacular natural scenery. Key topics to be examined include the geologic control of hydrologic regimes on both the wet and dry sides of the Cascade crest, groundwater dynamics and interaction between surface and groundwater in volcanic arcs, changing evolution of volcanic styles and products from the Miocene to the Holocene, and interactions between rivers and lava flows. We will also consider the history of and controls on channel incision. Along the way, we will trace the Willamette River back to source springs high in the young volcanic rocks of the Cascades, cross the divide, and then follow the Deschutes River from its source downstream, where its deep canyon has cut through the entire Neogene section, capturing both regional groundwater flow and volcanic flows from the Cascade arc.
410. Newberry Volcano
Thurs.–Sat., 15–17 Oct. US$372 (L, 1D, R, 2ON).
Leaders: Julie M. Donnelly-Nolan, USGS–Menlo Park; Daniele McKay; Robert A. Jensen.
Paulina Peak
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Newberry Volcano is located in central Oregon at the intersection of the Cascade Range and the High Lava Plains. Its lavas range in age from about 0.5 million years to late Holocene. Erupted products range in composition from basalt through rhyolite and cover about 3,000 km2. The most recent caldera-forming eruption occurred about 80,000 years ago. This trip will highlight a revised understanding of the volcano’s history based on new detailed geologic work. Stops will also focus on evidence for ice and flooding on the volcano, as well as new studies of Holocene mafic eruptions. Newberry is one of the most accessible U.S. volcanoes, and this trip will visit a range of lava types and compositions, including tholeiitic and calcalkaline basalt flows, cinder cones, and rhyolitic domes and tuffs. Stops will also include early distal basalts as well as the youngest intra-caldera obsidian flow.
411. A Tectonic Transect through the Salmon River Suture Zone along the Salmon River Canyon in the Riggins Region of West-Central Idaho
Thurs.–Sat., 15–17 Oct. US$345 (L, D, R, 2ON). Trip Begins in Boise, Idaho, and ends in Portland.
Cosponsored by GSA’s Sedimentary Geology Division.
Leaders: David E. Blake, Univ. of North Carolina–Wilmington; Scott Giorgis; Basil Tikoff; Keith Gray.
Field area - trip 411
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This three-day field trip focuses on a west to east cross section through west-central Idaho, from the Seven Devils Mountains into the Salmon River Canyon. Billed as the second deepest gorge in North America, the Salmon River Canyon offers spectacular cross-strike exposures through mid-crustal levels of the Salmon River suture zone (SRSZ) and western Idaho shear zone (WISZ) in the Riggins region. Together, these structures record mid-Mesozoic to Cenozoic accretion of the Blue Mountains island arc with the ancestral western Laurentian margin, transpression in the WISZ, and Basin and Range–style extension. All of these tectonic features are localized along a subvertically oriented, lithospheric-scale, arc-continent boundary. We will view (1) different lithotectonic domains across the SRSZ, including Wallowa terrane arc volcanogenic and Norian carbonate rocks, backarc basin metasedimentary and metavolcanic rocks of the Riggins Group and Pollock Mountain amphibolite, deformed plutonic rocks in the WISZ, and Precambrian metasedimentary rocks of Laurentia; (2) polyphase fold-thrust belt deformation across a greenschist-amphibolite facies metamorphic gradient and the interplay between dextral transpression and partial melting of syn- to post-tectonic granitoid plutons; and (3) ductile-brittle extensional overprint of preexisting rocks and structures, including late Cenozoic Columbia River basalt flows. Quaternary mass wasting and terracing are prevalent along the river. The field trip honors the 40th publication anniversary of the reconnaissance geologic map of the Riggins quadrangle by Warren Hamilton.
412. Freshwater Streams and Wetlands, Artesian Wells, Hot Springs, and Alkali Lakes: High Desert Hydrogeology of Steens Mountain, Southeastern Oregon
Thurs.–Sat., 15–17 Oct.
Sorry, this trip has been canceled.
413. Landslides Along the Winter Rim Fault, Summer Lake, Oregon
Thurs.–Sat., 15–17 Oct.
Sorry, this trip has been canceled.
414. Northwest River Rendezvous: Geomorphology, Whitewater Rafting, and Fly Fishing in the Lower Deschutes Basin
Thurs.–Sat., 15–17 Oct.
Sorry, this trip has been canceled.
415. The Chiwaukum Structural Low, Eastern Cascade Range, Washington
Thurs.–Sat., 15–-17 Oct.
Sorry, this trip has been canceled.
416. Terroir Tour of the Northern Willamette Valley I
Fri., 16 Oct. US$105 (L, R).
Cosponsored by GSA’s Engineering Geology, Hydrogeology, and Quaternary Geology and Geomorphology Divisions; GSA’s Cordilleran Section; the International Association of Hydrogeologists; and Groundwater Resources Association of California.
Leaders: Scott F. Burns, Portland State University.
Terroir is the relationship between geology, soils, hydrology, climate, and wine. The Northern Willamette Valley is one the finest wine regions in North America for cool-climate grapes such as pinot noir, pinot gris, pinot blanc, and chardonnay. Two soils dominate: the Jory Series, which is developed on volcanic bedrock (Columbia River Basalt), and the Willakenzie Series, which is developed on marine sediments of the Oregon Coast Range. This is one of the finest places in the world to taste terroir — to learn how the geology affects the wines. There is a major difference! Join nationally famous terroir specialist, Scott Burns, as he takes you to three wineries: Anne Amie (both soils), Stoller (Jory soil), and Elk Cove (Willakenzie soil).
417. Folds, Floods, and Fine Wine: Geologic Influences on the Terroir of the Columbia River Valley
Fri.–Sat., 16–17 Oct. US$362 (L, D, R, 1ON).
Leader: Kevin R. Pogue, Whitman College.
Blue Mountains above Les Collines Vineyard
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Viticulture in Washington State, the second largest wine producer in the United States, is concentrated in the Columbia River Basin, in the rain shadow of the Cascade Mountains. The bedrock throughout this area is the Columbia River Basalt Group, which has been deformed by east-trending folds of the Yakima fold belt. Anticlines are topographically expressed as long ridges and synclines as valleys in this tectonically active region. At elevations below 365 m, the topography and soils of the Columbia River Basin have been greatly influenced by the Pleistocene Missoula floods, which carved benches, widened canyons, and deposited ice-rafted erratics, gravel bars, and layers of graded turbidite. The physical terroir (French term referring to the physical and cultural environment of viticulture and winemaking) of Columbia River Basin vineyards is affected by Yakima fold belt structures, which influence topography and climate and Missoula flood depositional environments, which affect the composition, texture, and thickness of vineyard soils.
     We will be joined by Paul Gregutt, Seattle Times wine columnist and author of "Washington Wines and Wineries, the Essential Guide" as we examine the geologic influences on terroir and taste wines in the Columbia Basin's seven American Viticultural Areas (AVA's). From Portland, we'll travel west to the Columbia Gorge and Columbia Valley AVAs, then head north over the Horse Heaven Hills to the Yakima Valley, Snipes Mountain, Rattlesnake Hills, and Red Mountain AVAs. We'll spend the night in the Walla Walla AVA, home to over 100 wineries, and then head back to Portland after a visit to the Horse Heaven Hills AVA. Along the way, we'll visit several of the most acclaimed vineyards in the Pacific Northwest, discuss terroir with viticulturists and winemakers, and taste wines that are expressive of their terroir.
418. Archaeology and Geomorphology of the Oregon Coastal Zone
Fri.–Sat., 16–17 Oct. US$225 (L, R, 1ON).
Cosponsored by GSA’s Archaeological Geology Division.
Leaders: Loren Davis, Oregon State University; Steve Jenevein; Jay Noller.
The Pacific Corridor for pan-American transhumanance is focus of this field trip along the central coastal zone of Oregon. Archaeology will be demonstrated and discussed in the context of paleoenvironmental interpretation of several complex sections involving marine terrace cover sediments, coastal eolian dunes, Coast Range debris flows, estuarine and fluvial deposits, ghost forests, and soils. The chronology of events sealing archaeological deposits, including floods, slope failures, and tsunamis will be presented, and evidence supporting the current understanding of the Coastal Corridor will be discussed.
419. Paleo-Landslides in the Tyee Formation and Highway Construction, Central Oregon Coast
Sat., 17 Oct.
Sorry, this trip has been canceled.
420. From Disaster to Recovery: The Hydrogeomorphic, Ecologic, and Biologic Responses to the 1980 Eruption of Mount St. Helens
Sat., 17 Oct. US$75 (L, R).  — FULL
Cosponsored by GSA’s Engineering Geology and Quaternary Geology and Geomorphology Divisions.
Leaders: Jon Major, USGS–Cascades Volcano Observatory; Peter Frenzen; John Bishop.
large debris avalanche deposit at Mount St. Helens
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The major 1980 eruption of Mount St. Helens volcano, Washington State, USA, consisted of an ensemble of volcanic processes that ravaged several watersheds. Within minutes to hours on 18 May 1980, hundreds of square kilometers of landscape were devastated by a massive debris avalanche, a directed volcanic blast, debris flows, pyroclastic flows, and extensive tephra fall. These processes buried 60 km2 of valley to a mean depth of 45 m, ravaged 600  km2 of rugged terrain, blanketed the landscape with up to 1 m of gravel to silt tephra, reamed riparian corridors up to 100 km in length, deposited tens to hundreds of centimeters of gravelly sand on valley floors and floodplains. This field trip travels along the Toutle River valley examining the impacts of, and the hydrogeomorphic, biologic, and ecologic responses to, the 1980 eruption. We will visit engineering works designed to control downstream sediment movement, Johnston Ridge (8 km from the volcano’s crater), which bore the brunt of the directed blast, and hike a 4-km-long trail loop on the massive debris avalanche deposit.
421. Lavatubes of the Mount St. Helen’s Region: Geology, Biology, and More!
Sat., 17 Oct. US$135 (L, D, R).  — FULL —
Cosponsored by the National Cave and Karst Research Institute.
Leaders: Penelope J. Boston, National Cave and Karst Research Institute; Gus Frederick.
Everyone is familiar with the fate of Mount St. Helens on 18 May 1980, but a less-celebrated volcanic treasure is less than an hour’s drive north of Portland, Oregon, USA. Some of the largest lava tube caves in the lower 48 states are located here. Ape Cave (3,904 m in length and 7 m tall in places) is the longest and best known, but Lake, Ole’s, and Little Red River caves also offer textbook examples of multiple lavatube cave styles and other pahoehoe flow-related features, such as lava casts of ancients trees, recent lahars, and “instant rivers” flowing from the sides of hills. The youth of these tubes (~ 2,000 years) is partly the reason that they are so well preserved, as many terrestrial tubes succumb to erosion, seismic activity, or sedimentation. Field trip participants will visit three or four of the excellent and varied lavatube caves in the area, receive overview briefings on the volcanic setting of the region, see conspicuous glittering microbial colonies indigenous to lavatubes around the world, and possibly catch glimpses of larger tube inhabitants. Early human use of the tubes will be discussed and the value of Earth lavatubes as models for volcanic tubes on other planets will be explored. We plan a brown-bag picnic lunch amongst the fir tree casts at the Lava Cast Forest and a dinner stop on the return trip at one of the well-known local eateries. Sturdy footwear and jackets will be essential for comfort.
422. Snowpack Data Collection in the Western U.S. Using SNOTEL and Geologic Hazards and Features Related to Snowmelt
Sat., 17 Oct.
Sorry, this trip has been canceled.
423. The Boring Volcanic Field: Anomalous Volcanism in the Cascadia Forearc
Sat., 17 Oct. US$85 (L, R).
Leaders: Russell C. Evarts, USGS–Menlo Park; Richard M. Conrey.
This one-day trip will examine Plio-Pleistocene volcanic vents of the Boring Volcanic Field in the greater Portland area. The Boring Volcanic Field consists of scattered, largely monogenetic, eruptive centers that occupy a tectonically anomalous position in the forearc of the Cascadia convergent margin. We will visit sites that reflect the diversity of eruptive styles and discuss the geochronology, petrology, tectonic significance, and hazards implications of these curious volcanics.
424. Terroir Tour of the Northern Willamette Valley II
Sat., 17 Oct. US$95 (L, R).
Cosponsored by GSA’s Engineering Geology, Hydrogeology, and Quaternary Geology and Geomorphology Divisions; GSA’s Cordilleran Section; the International Association of Hydrogeologists; and the Groundwater Resources Association of California.
Leader: Scott F. Burns, Portland State University.
Terroir is the relationship between geology, soils, hydrology, climate, and wine. The Northern Willamette Valley is one the finest wine regions in North America for cool-climate grapes such as pinot noir, pinot gris, pinot blanc, and chardonnay. Two soils dominate: the Jory Series, which is developed on volcanic bedrock (Columbia River Basalt), and the Willakenzie Series, which is developed on marine sediments of the Oregon Coast Range. This is one of the finest places in the world to taste terroir — to learn how the geology affects the wines. There is a major difference! Join nationally famous terroir specialist, Scott Burns, as he takes you to the following wineries: Sokol Blosser (Jory soil), Willakenzie (Willakenzie soil), and Oswego Hills (Nekia soil [a shallow Jory]).
425. Dynamic Landscape on the North Flank of Mount St. Helens
Sat., 17 Oct. US$95 (L, R).  — FULL —
Cosponsored by Steven A. Austin, Timothy L. Clarey, Kurt P. Wise, and John Whitmore.
Leader: Steven A. Austin, Austin Research Consulting.
dam breach site
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This six-hour hike follows a 13-kilometer-round-trip route to an extraordinary geologic location called “Breached Dam Overlook” just seven kilometers north of the crater of Mount St. Helens. The trail leads us from the Johnston Ridge Observatory onto the largest landslide deposit to have accumulated during human history. This debris avalanche deposit of May 18, 1980, forms one of the earth’s newest landscapes of 45 square kilometers area within the headwaters of the North Fork of the Toutle River. The objectives of the field trip are (1) to identify, classify and name individual landforms within the upper North Fork Toutle River landscape, (2) to relate the landforms to the sequence of events and processes that have occurred next to the volcano, and (3) to ponder questions about how the landscape at a volcano changes through time. Landforms on the debris avalanche landscape are relicts that have been impacted significantly by geomorphic processes that exceed a certain minimum energy threshold. Following the debris avalanche of May 18, 1980, the most significant event was the mudflow of March 19, 1982. That mudflow event breached the natural debris dam, caused adjustment within the drainage basin, and derived the present landscape. Now that the power of geomorphic processes has diminished, finer sediment is what is being moved. Channels are incised and armored with coarser clasts, and valleys are now plugging with sediment. Hikers can observe the new landscape from two selected overlooks. Johnston Ridge Observatory on the west side of Mount St. Helens Volcano National Monument is the staging area this roundtrip hike of 13.6 kilometers (8.4 mi).


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