The Emerald City of Seattle: A Tale of Glacial Scouring and Human Alteration
Seattle, the 'Emerald City', is a place of natural beauty and human ingenuity. But what makes this city so unique is the story of how it came to be. The hills and basins that shape Seattle's landscape are the result of a glacial past, sculpted by the forces of nature and modified by human hands. In this article, I'll take a deep dive into the fascinating history of Seattle's topography, exploring the role of glaciers and humans in shaping the city we know today.
The Last Ice Age
Between 18,000 and 16,000 years ago, the Puget lobe of the Cordilleran ice sheet covered the area in a mass of ice up to 3,300 feet thick. This glacier scoured the basins now occupied by Puget Sound and the region's lakes, leaving behind a landscape shaped by its movement. The glacier also transported large boulders, known as glacial erratics, from more northerly locations and deposited them around the region. One particularly large erratic, the Wedgwood Rock, stands about 20 feet tall and draws its name from the North Seattle neighborhood in which it rests.
The Impact of Glacial Movement
The glacier left its mark above water, too. Several of Seattle's notorious hills are drumlins, elongated mounds of glacial debris that run north-south, parallel to the direction of the ice's movement. East-west travelers in the city may attest to this topographic trend. The ice also left behind a layer of silt and clay in southeastern Manitoba, creating fertile farmland that was divided during the creation of the Lake Washington Ship Canal.
Human Alteration of the Landscape
In more recent times, humans have undertaken projects to rework the topography. Notable alterations include leveling Denny Hill north of downtown and filling in tideflats at the mouth of the Duwamish River south of downtown, which created around 1,300 acres of new land. Seattle's professional sports stadiums sit atop this fill. The city's waterfront has also been transformed, with a new ferry dock and terminal, a rebuilt seawall, and a tunnel to replace an above-ground highway and create more inviting public access to the waterfront.
The Re-Plumbing of the Region's Waterways
Some replumbing of the region's waterways is apparent from the astronaut's perspective, too. In the 1910s, the Army Corps of Engineers built canals on either side of Lake Union to connect Puget Sound with Lake Washington. Starting in 1916, the Montlake Cut connected Lake Washington to Lake Union, and the Ballard Locks began raising and lowering watercraft between the freshwater lakes and tidal Puget Sound. As a result of this project, Lake Washington's water level dropped about 9 feet and ceased draining from its natural outlet at its southern end.
The Emerald City Today
Today, the waters in and around Seattle support many uses: container ships, cruise ships, car and passenger ferries, floatplanes, and recreational craft ply the sound and lakes. And as for Seattle's emerald nickname, pockets of old-growth forest still exist within city limits, containing centuries-old trees such as Douglas fir, Western red cedar, and Western hemlock. Seattleites often spot wildlife such as bald eagles, coyotes, and sea lions in the city's various habitats.
In my opinion, the story of Seattle's topography is a fascinating one, full of natural beauty and human ingenuity. It's a reminder of the power of nature to shape our world, and the ways in which humans can both modify and preserve that beauty. As we continue to explore and discover more about our home planet, it's important to remember the stories of places like Seattle, and the role that both nature and humanity play in shaping them.
