Ice Age Floods National Geologic Trail
Ice Age Floods National Geologic Trail
6/10/22 Town of Lind Well Handwriten notes Pardee Cursive Notes 8966
6/10/22 Town of Lind Well Handwriten notes Pardee Cursive Notes 8966— Pardee 1910-1940
This is one of more than 1,800 field sites cataloged in the early scabland surveys — the bedrock of the Ice Age Floods scientific record. The Bretz-era researchers walked the ground first; modern cosmogenic dating, LiDAR, and remote sensing have since extended and refined what they mapped.
The Quincy Basin is a broad, shallow structural depression in the western Columbia Plateau, bounded by the Beezley Hills on the north, the Saddle Mountains on the south, the Columbia River canyon on the west, and the basalt uplands toward Moses Lake on the east. The region covered here extends from the Waterville Plateau and Moses Coulee in the northwest, through the Quincy–Ephrata–Soap Lake corridor, the Drumheller Channels south of Moses Lake, the Frenchman Coulee–Potholes–Crater Coulee outlets on the west margin, the West Bar reach of the Columbia River across from Crescent Bar, and the Telford–Crab Creek tract that drains in from the northeast. The Cheney–Palouse tract sits east beyond Moses Lake and is covered separately.
The Quincy Basin is the central pivot of the Channeled Scabland system. Every major Missoula flood pathway across the Columbia Plateau converged into it, every signature flood depositional landform on the plateau is represented inside it, and the basin's evolution through the flood sequence is the cleanest single record of how the routing of water changed as the Cordilleran ice sheet advanced and decayed.
The routing in this region was never static. Before the Okanogan lobe closed the upper Columbia River valley, the Columbia ran its modern course past Wenatchee and through the Sentinel Gap. The 18.2 ± 1.5 ka flood dated by Balbas et al. (2017) using cosmogenic 10Be on boulders along the Wenatchee Pangborn bar is the working anchor for this earliest phase: a flood roughly 335 meters deep down the Columbia past Wenatchee, predating the Okanogan-lobe blockage. As the Okanogan lobe advanced southward across the Waterville Plateau, it progressively shut down the Columbia route. The river was first diverted up and over the Withrow Moraine through Foster Coulee, then through Moses Coulee, and finally through the upper Grand Coulee — each successive route eroded by glacial meltwater plus repeated Missoula-flood overflow from impounded glacial Lake Columbia.
Moses Coulee is the central enigma of the region. It is a 30-mile dry canyon that heads beneath the Withrow Moraine, runs southwest across the Waterville Plateau, and reaches the Columbia near Palisades. Discharges greater than 600,000 m³/s carved it. The Great Gravel Bar at the highway 2 crossing — recognized as the largest and best example of a pendant river bar formed by catastrophic outburst flooding — and the dry cataracts at its head record that scale. But the coulee's mouth was eventually blocked by the same Okanogan ice that fed it, and most workers now agree at least four Missoula floods entered Moses Coulee before the ice closed it off. Whether the coulee was carved primarily by surface Missoula floods, by subglacial floods erupting from the base of the Okanogan lobe (the tunnel-channel interpretation in Waitt et al. 2024), or by some combination is the active debate.
Once the Okanogan lobe closed Moses Coulee, all overflow from glacial Lake Columbia and all Missoula flood discharge that took the eastern routes — the Telford–Crab Creek and Cheney–Palouse tracts — had to find an outlet through the Quincy Basin. The 15.6 ± 1.3 ka mean cosmogenic 10Be age on flood-transported boulders across the Ephrata fan in Balbas et al. (2017) marks the breakout of upper Grand Coulee as the dominant flood route. Once Grand Coulee opened, floodwater from glacial Lake Missoula and overflow from glacial Lake Columbia funneled south through it, dropped over the receding Dry Falls cataract into Lower Grand Coulee, exited at Soap Lake, and spread across the Quincy Basin.
The Quincy Basin then acted as a giant temporary pond. Floodwater backed up against the Saddle Mountains, against the constriction at Sentinel Gap, and ultimately against the downstream choke at Wallula Gap, which raised the entire mid-Columbia into temporary Lake Lewis behind it. Inside the Quincy Basin the floodwater abruptly decelerated as it spread out from the Lower Grand Coulee mouth. That deceleration zone is the Ephrata fan: an expansion bar covering roughly 620 square miles south of Ephrata, up to 130 feet thick, surfaced with house-size basalt and granite erratics including the 25-foot, 1,500-ton "Monster Rock." When the basin pond drained, it found four outlet thresholds across its western and southern rim. To the south, water tore through the basalt uplift between the basin and the Othello sub-basin to cut the Drumheller Channels — a 13–20 kilometer-wide cascade of 150 channels and over 180 rock basins through which water dropped more than 50 meters in 20 kilometers at velocities approaching 30 m/s. To the west, water overtopped Babcock and Evergreen ridges to cut the dual-stepped horseshoe cataracts of Frenchman Coulee, Potholes Coulee, and Crater Coulee, each plunging some 600 feet to the Columbia River canyon below. The fine slackwater portion of the basin pond left graded sand and silt beds — the "Quincy beds" or basin slackwater rhythmites — that are now the agricultural topsoil of the irrigation district.
The post-15.6 ka chronology is the cleanest. Successively younger Missoula floods continued to take the Grand Coulee–Quincy Basin–Drumheller route until the final flood at 14.7 ± 1.2 ka. The youngest floods (14.0–14.4 ka in the Balbas chronology) came back down the northwestern Columbia after the Okanogan lobe thinned and probably represent drainage of residual glacial Lake Columbia rather than Missoula releases. The West Bar giant current ripples — 20 feet high, spaced up to 100 yards apart, on the Columbia River west bank across from Crescent Bar near Trinidad — were laid down by one of these later flows down the Columbia in roughly 650 feet of water moving on the order of 65 mph. Their preservation is a function of the post-flood drop in Columbia base level: nothing has reshaped them in 14,000 years.
The Quincy Basin is where Bretz's career started. In 1909 (before his University of Chicago field years) he stopped at the University of Washington in Seattle to look at the new USGS topographic sheet covering the basin. The map showed an interconnected maze of dry channels, deep rock basins, dry waterfalls on the west rim, and the unmistakable form of a vast gravel apron — features that did not match any uniformitarian landscape he had ever seen in textbook geology. That topographic sheet, more than any field observation, is what set him on the scabland problem.
When Bretz returned with University of Chicago field parties beginning in 1922, the Quincy Basin features were central to his argument. The Ephrata fan, the Drumheller Channels, the Frenchman/Potholes/Crater Coulee outlets, the dry Lower Grand Coulee, and the Dry Falls cataract were all key field stops. His 1923 paper "The Channeled Scablands of the Columbia Plateau" (Journal of Geology 31: 617–649) reproduced his geomorphic map of the entire system; his 1928 paper "The Channeled Scabland of Eastern Washington" (Geographical Review 18: 446–477) named the Telford–Crab Creek tract converging on the Quincy Basin as one of the four major scabland routes. His 1932 USGS Bulletin "The Grand Coulee" (American Geographical Society Special Publication 15) is the densest single field record of the Grand Coulee–Soap Lake–Ephrata–Quincy Basin corridor and remains a working reference. Bretz revisited the basin in 1965 with V. R. Baker and others, leading to the 1969 paper "The Channeled Scabland of Washington: New Data and Interpretations" (GSA Bulletin 80: 1027–1042), which incorporated the Quincy Basin slackwater stratigraphy as supporting evidence for multiple floods rather than a single event.
The Balbas et al. (2017) cosmogenic 10Be chronology is the current absolute framework. Their dataset includes mean ages of 15.6 ± 1.3 ka on Ephrata fan surface boulders (anchoring the post-Grand-Coulee phase) and 18.2 ± 1.5 ka on the Wenatchee Pangborn bar (anchoring the pre-Okanogan-lobe phase down the Columbia). Four flood bars in the upper Columbia Valley dated between 14.0 ± 1.4 ka and 15.4 ± 1.3 ka complete the post-deglaciation sequence. The implication for the Quincy Basin is that nearly all of the post-15.6 ka flood volume — the bulk of the discharge that built the Ephrata fan, scoured Drumheller, and trimmed back the western outlet coulees — passed through this single corridor.
LiDAR coverage has transformed mapping of the basin's surfaces. The Washington Geological Survey, Washington DNR, and the USGS have published bare-earth digital elevation models for the entire Quincy Basin and the Waterville Plateau. The LiDAR exposes the depositional architecture of the Ephrata fan, the unscoured slackwater terraces in the basin interior, the threshold geometry of the outlet coulees, the bar fields at West Bar, and the field-by-field detail of the Sims Corner eskers and kames on the Waterville Plateau. Lehnigk et al. (2022, PNAS) showed that glacial isostatic adjustment — differential crustal rebound under the loading and unloading of the Cordilleran ice sheet — progressively tilted the plateau and changed which divides were lowest at each phase of the flood sequence, directly affecting which outlets the Quincy Basin pond used. Karlstrom and others (2018, Nature, on progressive incision of the Channeled Scabland by outburst floods) used numerical simulations to argue that the canyon-forming discharges may have been substantially smaller than older single-event reconstructions implied, with cumulative incision over many floods doing the work. Waitt and Atwater (2021) revisit the upper Grand Coulee cataract retreat that drove this corridor. The Waitt et al. (2024) Geology paper "Okanogan lobe tunnel channels and subglacial floods into Moses Coulee" reframes Moses Coulee as a tunnel-channel system fed by subglacial floods from beneath the Okanogan lobe, rather than purely a surface flood feature.
Sun Lakes–Dry Falls State Park, at the north end of Lower Grand Coulee just above Soap Lake, contains the Dry Falls cataract — a 3.5-mile-wide, 400-foot-high horseshoe scarp recognized in 2023 by the International Union of Geological Sciences as one of the First 100 IUGS Geological Heritage Sites. The Dry Falls Visitor Center closes in April 2026 for renovation and is expected to reopen in winter 2026. South of Soap Lake, the entire Ephrata fan surface lies along SR 28 and SR 17 — the boulder fields east of Ephrata and the gravel pits along the Crab Creek floor expose the fan stratigraphy. The fan itself is not publicly open (private agricultural land), but the boulder-strewn surface is visible from many road cuts.
Ginkgo Petrified Forest State Park at Vantage, perched on the basalt cliff above Wanapum Lake (the Columbia River reservoir behind Wanapum Dam), is the Sentinel Gap–Saddle Mountains viewpoint and contains its own erratic-boulder hikes. Frenchman Coulee, just north of I-90 at exit 143, is one of the most accessible coulee complexes: free public access, an interpretive parking area, and a network of climbing-bolted basalt columns above the floor. The Drumheller Channels National Natural Landmark is accessible from McManamon Road north of Othello within the Columbia National Wildlife Refuge. The West Bar giant current ripples are visible from the Babcock Bench road across the river from Crescent Bar, or by drone/photograph from the Crescent Bar overlooks. The Sims Corner Eskers and Kames National Natural Landmark and the Withrow Moraine sit on the Waterville Plateau between SR 17 and SR 172. The Great Gravel Bar of Moses Coulee is at the US 2 crossing south of Mansfield.
The Ice Age Floods Institute's Ellensburg Chapter (serving the Quincy Basin, the Telford–Crab Creek tract, Ginkgo, Frenchman Coulee, Drumheller, Sentinel Gap, and the Saddle Mountain and Frenchman Hills anticlines) runs field trips and lectures through the year, with technical support from Karl Lillquist and Nick Zentner at Central Washington University; recent and upcoming offerings include a 2026 Lower Lake Wenatchee field trip and recurring Ginkgo erratics hikes.
Active: ~1909-1956 (USGS career; key Lake Missoula evidence 1910-1942) Affiliation: U.S. Geological Survey Key paper: Pardee, J.T. (1942). "Unusual currents in Glacial Lake Missoula, Montana." Geological Society of America Bulletin 53(11): 1569-1599.
Pardee grew up in a Montana mining family, opened an assay office out of college, and joined the USGS after a self-taught interest in geology became his career. He first proposed an ice-dammed glacial lake in the Missoula valley in 1910, decades before its connection to Bretz's scablands was made. His 1942 paper documented the giant current ripples on Camas Prairie - ridges 15 to 30 feet high with wavelengths around 250 feet - and demonstrated that they could only have formed under catastrophic outburst-flood velocities. That paper supplied the water source Bretz had refused to name and ended the formal Scabland Debate among working geologists, though broader acceptance took another two decades. Pardee died in Philipsburg, Montana in 1960 at age 88.
Source: Joseph Pardee - Wikipedia; GSA Today, Vol. 5 No. 9, 1995; hugefloods.com
Every site along the trail will receive the full Terrain360 capture treatment: ground-level 360° panoramas, drone aerial imagery, and photogrammetry-based 3D models that visitors can spin in their browser. This page reserves the slots; the imagery flows in as field capture completes.
Ground-level 360° panorama, every step along the feature, captured by Terrain360 field crews.
Drone flyovers reveal the geometry of catastrophe — ripple marks, gravel bars, and scour patterns invisible from the ground.
Photogrammetry and Gaussian-splat models let visitors rotate, measure, and inspect features in detail-page WebGL viewers.
Pardee's identification of Glacial Lake Missoula as the source of Bretz's floods was the missing piece that ultimately convinced the geological community. His 1942 paper documenting giant current ripples proved the lake had drained catastrophically, not gradually.