Geology Of NW Fishing & Hunting: How A Giant Ice Cube Made Your Trout/Bass Lake

Add in a poopy glacier, a jökulhlaup or two, and shazzam, the fish-filled lowland waters of Pugetropolis (pretty much).

By Andy Walgamott

YELM, Wash.—“Uncle Wes” and I were on Clear Lake in eastern Thurston County one fine day last spring, trolling Woolly Buggers under partly cloudy skies for rainbows. The bite was good, thanks to somewhere around 14,000 stockers up to 4 pounds, but my eyes kept flicking out of the boat to the low rise of hills just to the south.

“That’s where it ended, I’ll bet,” I kept thinking. “That’s where the ol’ berg ground to a halt.”

“Uncle Wes” Malmberg hauls in a rainbow caught at Thurston County’s Clear Lake, the southernmost lowland trout lake in Western Washington created by the continental glacier that completely covered Pugetropolis during the last Ice Age. The Bald Hills are the low rises beyond the lake. (ANDY WALGAMOTT)

According to geologists, from its origins somewhere in British Columbia, a vast ice sheet crept south across the future international border, tipping over forests, smooshing too-slow giant ground sloths and pouring the foundations of what would eventually become the bustling burgs of Bremerton, Bellevue and Buckley.

The glacier T-boned the Olympics and put some knees into the Cascades, but somewhere around 16,000 years ago, a warming climate caught up to the super smoothie. It stopped at its most southerly point of advance, over there, on the Bald Hills, just a couple miles beyond the end of our sinking fly lines that day on Clear Lake.

Clear was not a lake quite yet, but trout and bass anglers owe its existence – and that of hundreds of other waters in Pugetropolis that we will fish this season – to the outsized glacier and the outlandishly large floods of meltwater and debris it spewed as the last Ice Age turned Mild Age.

IT’S A TALE THAT IS overshadowed by the Northwest’s other glacially induced gullywasher, the cataclysmic Missoula Floods, which created a host of basalt-boned fisheries on the other side of Washington’s Cascades.

As that well-known story first pieced together by the geologist J. Harlan Bretz goes, at about the same time that Seattle was sat upon, another fork of the great Canadian ice sheet blocked up the Clark Fork River northeast of Spokane. It filled Western Montana’s valleys with a volume of water that would rival Lakes Erie and Ontario combined.

Eventually the ice dam sprang some leaks, very, very bad news for all the woolly mammoths, dire wolves and any cousins of Kennewick Man who might have had the misfortune to be anywhere from Sandpoint to Spokane to Starbuck to Ephrata to Tri-Cities to Portland in the immediate hours and days after the plug broke.

The resulting floods were so massive at the Idaho-Washington state line they formed river banks that dammed side drainages well back of the valley floor, creating today’s Newman, Liberty, Hayden and Hauser Lakes.

The water raced on and across the Columbia Basin in flows at times 8 miles wide and 200 feet deep, spawning kolks – basically underwater tornadoes that treated bedrock like a Tennessee trailer park – and thundering waterfalls that literally gouged and scoured out some of Eastern Washington’s most well-known fisheries of today.

Lakes like Amber, Williams, Badger, Rock, Coffeepot, Dry Falls, Lenore and the Seeps – all the work of the world’s baddest, most out-of-control flash flood.

Top that, Pineapple Express.

Alkali Lake, in lower Grand Coulee, gouged out during massive flooding during the last ice age. (ANDY WALGAMOTT)

Fast forward 12,000 years, scatter fish in every little depression deeper than a hot tub, and voilà, a fishing paradise for chunky, bugchowing rainbows, craw-killing bass, leechsucking walleye and a host of panfish species.

IF THE EVIDENCE IN THE BASIN is pretty obvious – the ferocity of the Missoula Floods and the dry climate preserved the crime scene – what happened in Pugetropolis is tougher to discern. The region has grown over with cedars, Scotch broom and Starbucks. Then there’s its proclivity for binge raining and mass wasting.

Add in the odd jökulhlaup that came wriggling out of the hills, throw in lahars fired off by volcanoes since the ice melted, and how did the lowlands end up with so many glistening lakes? Why do they come in so many shapes? Why are some so linear? How come some counties have more than others? And what in the hell got into St. Clair, that squirming ball of nightcrawlers of a lake near Olympia?!

We’ll start fishing for answers up north.

For argument’s sake, let us say that a massive swarm of ice worms had so riddled the last continental glacier that it never made it past Bellingham – what would Pugetropolis look like for those of us loading up our canoes and 12-foot aluminums and lawn chairs for this month’s opener?

“It would be a lot more boring,” says Barry Goldstein, a geology instructor at the University of Puget Sound who has studied the region’s glaciation for nearly three decades.

Put another way – and no offense, Oregonians – things would look a lot like the Willamette Valley. Put still another way: We’d all be headed to the Sun Lakes and the wreckage of the Eastside’s little Pleistocene plumbing problem. With like a 100,000-year break between the most recent glaciation and the previous one, the lowlands might have been boggy, but there wouldn’t have been many lakes.

“Those glacial lakes have pretty short life spans,” Goldstein says. “They fill in in 1,000 to 10,000 years. Most have nothing scouring them out.”

Rather, things are either constantly falling into them (trees – think Lake Langlois – and landslides) or growing out from their shores (bog mats, like the one on the lake behind Duvall where a friend involuntarily attempted to become a local version of a sacrificial Danish bogman one winter day while duck hunting).

“Even lakes like Lake Washington would have filled in,” Goldstein says.

Fortunately for anglers, ice worms (which actually eat algae and grit) did not attack the ice sheet and instead it crept south. As it did so, it generated a wee bit of runoff, especially in summer. Where the water couldn’t get around the glacier anymore, some backed into the mountains and did funny things. One of the most interesting backcountry lakes I’ve fished, tiny Twin Falls Lake was actually the spillway for runoff that gathered in the Skagit and Stillaguamish Valleys before it found a low spot 2,400 feet up in the saddle between Mt. Pilchuck and Bald Mountain and poured over.

Elsewhere the water tunneled underneath the ice. That’s what happened on the western end of Mt. Haystack near Sultan. As water raced around the mountain’s shoulder, fierce currents dug out Cedar Ponds, Dagger and Tomtit Lakes. Lakes Washington and Sammamish are much larger versions of this subglacial scouring.

Back on the surface, runoff snaked around the eastern edge of the glacier until somewhere around Eatonville. As the flow rounded the ice lobe’s southeasterly snout, it carved out a series of channels now occupied by some of the South Sound’s better spinyray lakes – Ohop, Tanwax and Kapowsin. The river, by now Columbia sized, passed south of Tenino, picked up a podunk trib that would one day be called the Chehalis, and flowed past the Black Hills.

And that’s how your North Sound steelhead stream once drained through Grays Harbor.

BUT ABOUT THOSE LAKES … let’s hike up Bald Hill for a better view of the processes that would turn Clear Lake and Puget Sound into a trout-fishing mecca. From the top of the 2,000-foot-high bluff we might have heard the dirty glacier growling below, but it was more like a death moan. This was far as she was gonna go – and she was about to give birth.

When glaciers retreat, they don’t pack up their ice and head for Greenland. No, they stick around and slowly began to melt. Thicker parts take longer than thinner ones, and what takes longest of all are the chunks that get buried in sediment. Geologist Goldstein estimates that parts of our ice sheet would have taken thousands of years to defrost. That left an opening for the creation of our many lakes.

The deal with the lobe that invaded Puget Sound at least four different times over the past million years or so is that it wasn’t big on gouging like the glaciers that gnawed granite basins out of the Cascades or created that 50-mile fjord, Lake Chelan. Rather it pooped. And pooped. And pooped. Out of its icehole spewed something like 3,000 vertical feet of grit at Bellingham and a thousand at Seattle.

No glaciers and today we’d have a larger and much deeper Puget Sound to troll around for salmon and jig for halibut – but no Whidbey Island beaches to bomb for pinks and silvers.

But back to our perch on the grassy knoll above Clear Lake. One day 100 to 200 years after the ice quit moving, we would have heard a roar approaching from the northeast. A big ol’ meltwater lake that filled the Carbon River and Wilkeson and Voight Creek Valleys burst through its earthen dam, and the flow, known in Icelandic as a jökulhlaup, spread a layer of schmutz over the ice.

“Lots of glacier was left behind, and it was insulated by the mud flow,” says Goldstein. “As those stagnant ice blocks sat there, covered by the mudflow, they eventually melted and gave rise to lakes from Ohop to Tenino.”

The list includes a pair of Clears – including the one Uncle Wes and I fished, and which this spring will be stocked with 14,705 10- to 11-inchers, 200 1-pounders, 100 2- to 4-pounders and 344 triploids – Silver, Harts, Lawrence, Offut, Deep, Scott and numerous other waters.

Elsewhere in Puget Sound, as the glacier withered, meltwater streams sluiced away massive amounts of sediment which built up around larger blocks of ice the sheet left behind.

Sometimes the torrent filled in the voids, but other times streams shifted as runoff found faster ways to lower elevations. That left bergs stranded on high ground, and over time they melted away and what remained are the typically rounded “kettle” lakes scattered everywhere from Ferndale to Shoreline to Shelton to Maple Valley. But even oddly shaped ones like St. Clair are considered kettles as they were created by ice and sedimentary processes.

Illustrations from the Primer on Lakes in Washington show how many Puget Sound lakes came into being, either by inundating the long, linear “rake” marks the ice sheet left as it ground southeast, south and southwest over loose gravel, sand and grit, or filling holes where giant icebergs broke off the glacier and were surrounded by sediment before melting. (DEPARTMENT OF ECOLOGY)

Then there’s the unusual orientation of other waters. While glaciers are well known for patiently smoothing hard rock – alpine trout anglers, think the granite Lunch Rock at Lake Serene – they aren’t so diligent with gravel, sand and grit. Our ice sheet left behind a surface rife with depressions that filled with water.

“Imagine a giant rake,” says Goldstein.

North of Monroe, Storm and Flowing Lakes show that the ice was headed southeast for a head-on collision with our friend, Mt. Haystack. The grooves in Lake Tapps show a more south-southeasterly heading. In Kitsap County it was moving southwest.

Of course not every lake in Pugetropolis owes its origin to the ol’ berg.

Price – which I wrote about here in May 2009 – Whatcom, Cavanaugh and Cascade are related to faulting.

When Chester Morse Reservoir was created on the Cedar River in the early 1900s, water seeped through the ground and flooded the old town of Moncton and formed Rattlesnake Lake.

And then there are the numerous oxbows courtesy of local rivers.

But for the most part, if you’re launching at a lowland fishery from Whatcom County down to Thurston County, or over on the Kitsap Peninsula and Hood Canal this spring, you’re getting into one cool old lake.

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