Puget Sound looks simple on a map. A body of water south of the San Juan Islands, wrapped around Seattle, Tacoma, and Olympia. Green shorelines. Ferry routes. City waterfronts.

But look at a depth map and simple disappears fast. Puget Sound is a glacially carved fjord system, not a bay. The bottom drops to 930 feet in places. Underwater sills separate deep basins. Tidal currents rip through narrow passages. The shape beneath the surface is more like a Norwegian fjord than anything you'd expect from a major American metro area.

Over four million people live along its shores. Orcas hunt in its channels. Submarines transit its depths. And most of those four million people have never seen what's underneath.

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The Shape of the Sound

Puget Sound was carved by the Puget Lobe of the Cordilleran Ice Sheet, which advanced south from Canada roughly 17,000 years ago. The glacier was over 3,000 feet thick in places. It ground down into the sediment and bedrock, carving deep troughs that filled with seawater as the ice retreated.

The result is a series of deep basins connected by shallower sills. Think of it like a chain of bathtubs, each separated by a raised lip on the bottom.

The Main Basin, running from the Tacoma Narrows north past Seattle to Admiralty Inlet, reaches about 930 feet at its deepest. The Southern Basin, south of the Tacoma Narrows, is shallower, generally 200 to 400 feet. Hood Canal, the long narrow arm to the west, reaches about 600 feet. The Whidbey Basin to the north connects through Deception Pass and Saratoga Passage.

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Why the Sills Matter

The sills between basins are what make Puget Sound behave the way it does. At Admiralty Inlet, the northern entrance, the bottom rises to about 200 feet. This sill controls how ocean water enters the Sound. Deep Pacific water can't simply flow in freely. It has to clear the sill.

The Tacoma Narrows (yes, where the famous bridge collapsed in 1940) is another sill point. The channel narrows and the bottom rises, creating strong tidal currents that can exceed 8 knots. The water squeezes through. These constrictions drive the tidal flushing of the entire system.

For the ecosystem, this matters enormously. The sills limit how quickly deep water in the Sound exchanges with ocean water. Deep water in the Main Basin can become depleted of oxygen because it's trapped behind the sills for months at a time. Low-oxygen zones form, stressing bottom-dwelling organisms. This is a natural feature of Puget Sound's fjord-like structure, but it's been worsened by nutrient pollution from the surrounding urban area.

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The Life the Depth Supports

Puget Sound's depth and structure support one of the richest marine ecosystems in the temperate Pacific. The Southern Resident orcas are the famous inhabitants, a population of about 75 whales that hunt Chinook salmon through the Sound and the San Juan Islands. Their range follows the deep channels where salmon transit.

Below the surface, the deep basins harbour Pacific octopus, sixgill sharks (ancient, deepwater predators that come shallow in Puget Sound), rockfish, lingcod, Dungeness crab, geoduck clams, and species of coral and sponge that you'd normally associate with deeper ocean environments.

The depth map tells you where these animals live. The steep walls of the Main Basin. The rocky outcrops near the San Juan Islands. The sandy shelves where geoducks bury themselves three feet deep. The deep, cold water where sixgill sharks patrol at night.

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A City on a Fjord

Seattle is one of the few major cities in the world built on a true fjord system. Most people don't think of it that way. It's "Puget Sound." It's "the waterfront." It's where the ferries go. But the water beneath those ferries is deep, cold, and shaped by ice age forces that dwarf anything humans have done to the shoreline.

The depth map reframes Seattle's relationship with its water. The city isn't sitting next to a harbour. It's perched on the edge of a glacially carved trench that drops hundreds of feet below the surface within a mile of downtown.

For anyone who lives on or near Puget Sound, a Pangea Map turns that hidden world into wall art. Nine layers of laser-cut AB-grade baltic birch plywood, each representing a real depth contour. The deep Main Basin. The narrow Tacoma Narrows. Hood Canal stretching west. The complex shoreline of the San Juan Islands. All visible. All tangible.

Each map is designed one-on-one with Tom, the maker, based on the Gold Coast, Australia. For Puget Sound, you can map the whole system or focus on Seattle's waterfront, the San Juans, Hood Canal, Whidbey Island, or wherever your connection lives. The piece you choose depends on which part of the Sound is yours.