North Cascades Ecoregion and Birding Sites Click to see a
detailed map with birding sites. The North Cascades Ecoregion
includes the Cascade Mountains west from the Cascade crest and
north from the South Fork Snoqualmie River drainage (I-90
corridor). Its lower limit is approximately the 1,000-foot
contour, a few miles east of the Puget Trough communities of
Sumas, Sedro-Woolley, Arlington, Granite Falls, Sultan, and
North Bend. It extends northwest into British Columbia. The
North Cascades of Washington compose a highly dissected mountain
terrain created by volcanic activity continuing into recent
times. The two tallest volcanoes, Mount Baker and Glacier Peak,
last erupted as recently as 10,000 - 12,000 years ago. Mountain
peaks over 10,000 feet plunge quickly into valleys as low as 500
feet above sea level, cut out by ancestors of the vast glaciers
that still sprawl in the northern part of the region. Glacially
carved U-shaped valleys and cirques are therefore prominent
features. Some of these have been dam