The North Cascades features some of the most rugged topography in the
Cascade Range with craggy peaks, ridges, and deep
glacial valleys. Geological events occurring many years ago created the diverse topography and drastic elevation changes over the Cascade Range leading to the various climate differences. These climate differences lead to vegetation variety defining the
ecoregions in this area. The history of the formation of the Cascade Mountains dates back millions of years ago to the late
Eocene Epoch. With the
North American Plate overriding the
Pacific Plate, episodes of
volcanic igneous activity persisted. In addition, small fragments of the
oceanic and
continental lithosphere called
terranes created the
North Cascades about 50 million years ago. During the
Pleistocene period dating back over two million years ago, glaciation advancing and retreating repeatedly scoured the landscape leaving deposits of rock debris. The U-shaped cross section of the river valleys is a result of recent glaciation.
Uplift and
faulting in combination with glaciation have been the dominant processes which have created the tall peaks and deep valleys of the North Cascades area. ==See also==