Jacobson Preserve
Field trip description
This is a day of up-valley exploration of the Wenatchee River from the Wenatchee Foothills to the Lower Icicle River, led by guest geologist, Brent Cunderla and Wenatchee Naturalist Susan Ballinger.
We start with a foothills shrub-steppe walk on the Chelan-Douglas Land Trust Jacobson Preserve and to the Balsamroot Trailhead in the north Foothills that experienced wildfire in 2015, learning about CDTL’s post-fire plant monitoring Citizen Science project.
Weather permitting, we drive 3 miles up to higher elevation viewpoint walk on the Trust’s Horse Lake Reserve for a panoramic geologic view tour.
The next stop is Peshastin Pinnacles State Park to view rock formations up-close. Lunch is at Wenatchee River Institute’s (WRI) sustainably certified building, the Barn and learn about WRI’s mission, programming, and volunteer opportunities.
After lunch, we drive to Chelan-Douglas Land Trust’s Mountain Home Preserve to walk a 2-mile loop, focusing on native trees and shrubs, and at overlook of the lower Icicle River Valley we explore its geologic formation. Our final stop is at the USFS Snow Creek Trail head, located in a glacier-carved valley beneath cliffs. Leavenworth Bird Fest is the featured education program
View NW from Horse Lake of Lower Wenatchee River
Logistics
Field Trip 3 Lower Wenatchee Exploration
Guest scientist leader
Brent Cundera, retired BLM geologist
Featured Organization
Community Science Project
Resources
Drive and Discuss Geology Guide
CDLT Jacobson Plant Species List
CDLT Mountain Home Plant Species List
Photos
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- Our day begins in the Wenatchee Foothills, at the base of Horse Lake Mountain. Geologist Kelsay Stanton points out the many layers of lake-desposited sediments (varves), evidence of temporary lakes backed up-valley, during repeated episodes of the Bretz Floods, 18.000-15,000 years ago.
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- Pat, Jeanie, Liz, Cindelia, and Matt talk with Kelsay about the Bretz Floods. Excavated nest cavities (now empty) are used in summertime by neotropical migrant swallows. A belted kingfisher has been observed here using an excavated nest cavity. The surrounding shrub-steppe plants include big sagebrush, bitterbrush and bunchgrasses.
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- The view of lower Sunnyslope, looking up the Wenatchee River. Black cottonwoods flank the riparian corridor, ablaze in gold on this late Autumn morning.
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- Barbee snaps a photo as Kelsay Stanton pointed out the flat terraces (often orchards) on either side of the current Wenatchee River floodplain, evidence of past river deposits.
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- Views to the east toward the Confluence of the Wenatchee and the Columbia Rivers. Badger Mountain outlines the sunrise skyline. In the foreground long-lived perennial plants, like balsamroot and buckwheats, have lost their above ground leaves, but remain alive underground, awaiting next spring.
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- The railroad bed constricts the energy of the river’s south bank, yet the broad swatch of riparian vegetation on the north bank serves as a buffer to slow floodwaters during peak flows.
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- View of Enchantments from Horse Lake
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- Bird’s eye view of Icicle Valley from the ridge
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- Eagle Rock (center, back) formed 25 million ago, a result of active small volcanos during the Miocene. Birch Mountain (right, back) is composed of Swakane biotite gneiss, a metamorphic rock formation, now uplifted along the Entiat fault.
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- Wenatchee Naturalist Class Fall Field Trip #3: Geology of the lower Wenatchee River
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- Kelsay Stanton jokes with our class that she could talk forever from this single viewpoint!
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- Beyond Cordi, the folded uplifted hills of the Horse Lake Mountain tell a story of sedimentary rocks, laid down by wind and water in horizontal layers, and later uplifted and tilted 90 degrees. Each layer erodes differently, created the pleated formation that artist Jan Cook Mack describes as a folded rainbow robe.
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- At the Peshastin Pinacles State Park, we are up-close to the Chumstick formation, tilted layers of sandstone, siltstone, and conglomerate sedimentary rocks. Geologists name a formation for the geographic landmark where the rock was first described. A formation can cover a large geographic area and include many rock types.
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- Kelsay pointed the black-and-white chunk of rock as evidence of mountain-building that occurred nearby. During the time these sediments were being deposited by an ancient river, the proto-Cascades were being pushed up to the west, and this piece of igneous Chiwaukum schist, part of the massive Mt. Stuart Batholith, were subject to erosion, carried by water, and deposited as a sediment.
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- Kelsay has us captivated! (From left to right: Barbee, Liz, Cindelia, Mark, Matt, Krista, Cordi, and Pat)
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- Kelsay points out cavities (this one with evidence of use by birds), that are the result of wind and water weathering, often triggered by a pebble dislodging from an exposed rock layer.
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- Kelsay points out some cross-bedded layers intermixed within horizonally parallel layers of sedimentary rocks. Within the Eocene Era Chumstick Formation, sandstone dominates, along with layers of siltstone, conglomerate, and some organic-rich coal layers. The Chumstick Formation is explosed along the Wenatchee River valley in many places.
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- Wenatchee Naturalists begin their geology field sketches, making close up diagrams of rock layers.
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- Wenatchee Naturalists at work, creating geology field notes with labled rock layers and features.
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- Here it is- the piece of the Mt. Stuart Batholith!
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- After lunch, we traveled to the CDLT Mountain Home Preserve ridgetop, overlooking the town of Leavenworth.
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- Kelsay directs our attention to the “U” shaped valley below, evidence that an alpine glacier filled the valley to the brim with a moving, frozen bulldozer of ice.
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- Standing here on the ridgetop, we are on top of the jumble of rocks washed off the edge of the glacier, plastering it with “till.”
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- Above us, the mound is a lateral morraine, formed at the meltwater edge of the retreating alpine glacier.
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- Looking north, the “U” valley of the Icicle River cradles Leavenworth, and in the center back is the “V” shaped Chumstick Creek drainage, carved by flowing water, not by glacial ice.
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- From Mountain Home Preserve, looking south down the Icicle Creek valley.
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- The view of Leavenworth, and the confluence of Icicle Creek with the Wenatchee River. A towering Ponderosa pine stands as a sentinel.
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- Our last stop: the Snow Creek trailhead parking lot, with a view of the “Sleeping Lady” ridge line. The 1994 wildfires swept the east slope of the Icicle valley.
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- Our eyes follow the Snow Creek trail, with the “Backside” of the Snow Creek Wall (center of photo). At an elevation of 1317 feet in the parking lot, the elevation gain to the top of Mt. Stuart (9415 ft) is greater than the Grand Canyon rim-to-river elevation difference.
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- Looking up the Icicle, slow post-glaciation continued uplift and continual down-cutting of the river, result in a “V” pattern superimposed on the glacially -carved “U” shaped valley.
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- Barbee, Lisi, and Mark think about doing a walk-through the Enchantments before dinner.
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- The boulder-moving power of the Icicle River roars below the bridge. We watch an Ameican Dipper flail a small fish, and dowstream, a great blue heron lands on a water-spashed boulder.