- Why Bridges Don’t Sink (practical.engineering)
The essence of a bridge is not just that it goes over something, but that there’s clear space underneath for a river, railway, or road. Maybe this is already obvious to you, but bridges present a unique structural challenge. In a regular road, the forces are transferred directly into the ground. On a bridge, all those forces on the span get concentrated into the piers or abutments on either side. Because of that, bridge substructures are among the strongest engineered systems on the planet. And yet, bridge foundations are built in some of the least ideal places for heavy loading. Rivers and oceans have soft, mucky soils that can’t hold much weight. Plus, obviously, a lot of them are underwater.
- Seattle Neighborhoods: Madrona — Thumbnail History (historylink.org)
Seattle’s Madrona neighborhood overlooks Lake Washington from the eastern rim of the city. Madrona’s hilly origins arise from the Vashon Glacier, which melted 40,000 years ago, leaving flood waters and ice to shape Lake Washington and other Pacific Northwest landmarks. Its first life was as a Native American hunting and fishing ground. Seattle was founded (in 1851), and from the 1880s to 1900, Madrona was overrun by loggers, stump farmers, berry pickers, and realtors. The beginning of the Madrona we know today was the introduction of the Union Trunk Line, which ran from the top of the hill at 34th Avenue and Union Street to Madrona Park and beach.
