ECHOES IN STONE: WASHINGTON GEOLOGY

Washington State

Two hundred million years ago, what we now call Washington wasn’t Washington at all. 

It was two drifting islands — fragments of a wandering continent slowly inching their way west across the ancient ocean. 

They were vagabonds, carried on tectonic currents until, at last, they collided with the North American continent and made themselves at home.

That restless motion has never stopped. The land still breathes — slow, tectonic breaths that subtly reshape the surface of the Pacific Northwest. Every so often, that breath shudders. 

We feel it in an earthquake, a reminder that the forces that built the land are still at work, deep below our feet. The great plates grind and twist, pushing mountains skyward and sliding California ever so slightly toward the North Pole. Hello, Baja-BC.

It’s this long, dynamic dance — the great continental waltz — that sculpted the ridges, folded valleys, and mountain walls we see today. And it’s also what preserved an ancient world beneath our boots: the subtropical swamps and deltas of the Chuckanut Formation, a geological tapestry stretching some 3,000 metres thick along Chuckanut Drive near Bellingham.

Islands Riding Tectonic Plates

Layer upon layer of sandstone, siltstone, mudstone, and conglomerate record the rhythms of rivers that once coursed through a lush, steaming delta. The lower strata date back roughly 56 million years, at the very end of the Paleocene. 

The upper layers push into the early Eocene, a time when Earth was warmer and wetter than it has been since. Imagine, if you can, not the misty evergreens and glacial peaks of today, but a subtropical floodplain, dense with palms, ferns, and broad-leaved trees. 

Picture the bayou country of the Lower Mississippi, but stretching across what is now the Pacific Northwest.

This was a land of life. Ancient trees towered overhead. Vines tangled in the swamp air. The Chuckanut flora tells us of a greenhouse Earth — plants whose modern cousins thrive in Central America and southern Mexico flourished here, under the same sun that today glints off Mount Baker’s glaciers. 

Every fallen branch, every leaf buried in fine silt became part of the rock record, sealing in the whispers of an ancient climate: its humidity, rainfall, and heat.

But the plants are only part of the story. In rare and beautiful moments, the Chuckanut Formation captures motion — the fleeting steps of animals caught forever in stone. These are the Sumas Eocene trackways, discovered after landslides near Sumas in 2009. 

The Ancient Bayou of Washington State 

Among them are footprints from small shorebirds, the imprints of early equids, and tracks of curious, blunt-footed herbivores belonging to the now-extinct Orders Pantodonta and Dinocerata. 

Together, they sketch a portrait of life 50 million years ago: herds and flocks wandering the muddy margins of rivers, where soft sediment briefly held their weight before drying, hardening, and turning to stone.

One of the most striking finds is that of a delicate shorebird trackway, each print barely larger than a thumbprint, pressed into what was once the bank of a lazy river. 

It’s joined by faint impressions from an early horse-like mammal and, in other sites such as Racehorse Creek, the formidable three-toed stamp of Diatryma — a flightless bird taller than a man, and every bit as formidable as its dinosaurian cousins.

These fossil trackways are precious not just for their rarity but for what they reveal: a moment of life, caught mid-step. Unlike bones, which tell us who lived here, tracks tell us how they lived — where they walked, how they moved, even how they interacted. They are the fossilized choreography of an ancient ecosystem, preserved in mud and time.

These traces are studied and safeguarded by researchers such as George Mustoe and his colleagues, who carefully collected the Sumas trackways and brought them to the Burke Museum in Seattle. There, under controlled light and the quiet reverence of display cases, visitors can stand face-to-face with the footprints of creatures that trod the Pacific Northwest long before the Cascades rose above the horizon.

The landscape along Chuckanut Drive may look serene now — the sandstone cliffs honeycombed by ferns, the sea glittering beyond. But beneath every weathered ledge and outcrop lies a record of turbulence and transformation: continents colliding, mountains rising, rivers changing course, and life adapting in the wake.

To walk here is to walk in two worlds — one of forests and tides, and one of swamps and subtropical rain. The fossils remind us that the ground beneath us has always been moving, always changing, and always keeping its secrets — until the rock, split open by time or by curiosity, whispers them back into the light.