Hills in the Puget Lowland, between the Cascades and the Olympic Mountains, including the entire Seattle metropolitan area, are generally between 350–450 feet (110–140 m) and rarely more than 500 feet (150 m) above sea level. Hills are often notable geologically and for social reasons, such as the seven hills of Seattle.
Formation
The Puget Lowland lies between the Cascades and Olympic Mountains and once contained a plateau of glacial till not usually more than 350–450 feet (110–140 m) above sea level.[1][2][3] The plateau, "the most prominent single landform of the entire region",[4] was dissected by glacial outwash, forming present-day landforms: rivers, creeks and streams; glacial lakes such as Lake Washington; and numerous kettle lakes, and Puget Sound itself. High points on the plateau remain, most of which are a drumlin (rocky glacial debris), or a bedrock intrusion that predated glaciation. Hills above 500 feet are considered exceptional.[a]
Notable lowlands hills
Hills are glacial deposits unless otherwise noted. King, Pierce and Snohomish Counties run up to the crest of the Cascades where their high points reside; therefore, the Cascades and attached foothills are excluded. Likewise for Thurston County in the Mount Rainier area, and Mason County's Olympic Mountains foothills.
North Sound
Landforms north of the Tacoma Narrows (Island, King, Kitsap, Pierce and Snohomish counties)
Argonne Forest hills at Fort Lewis, formed of multiple layers of till deposited during Vashon glaciation; some hills may overlie drumlins from an earlier glacial phase.[14] Hills are designated critical habitat for the Northern Spotted Owl, an endangered species whose forest habitat in the Puget Lowland has been largely destroyed.[15]
The Issaquah Alps Bellevue, Issaquah and Newcastle on the Eastside are considered part of the Cascades foothills by many authors.[b] They are basalt intrusions possibly related to the Blue Hills of the Kitsap Peninsula. Highest point Tiger Mountain summit, 3,004 feet (916 m).
^"The elevation is, with some local exceptions, less than 150 meters (500 feet) above sea level. Much of the landscape consists of rolling hills with a relief of only a few hundred feet."[5]
^"Westernmost encroachment of the Cascades into the lowland contains exposures of preglacial bedrock marked by a series of peaks ... including Tiger and Squak mountains"[5]
Raisz, Erwin (1989), "Washington State landforms map", in Scott, James William (ed.), Washington, a Centennial Atlas, Bellingham, Washington: Center for Pacific Northwest Studies, Western Washington University, p. 4, ISBN0929008243 – 1941 original hand-penned map, 1965 third revision