The Cascade Mountains, in southeastern corner of the map area, consist mainly of metamorphosed sedimentary and volcanic rocks. Thick Ice Age and modern sediments underlie the larger valleys in these mountains.

Photo #22	Rugged, high peaks of the Cascade Mountains stood above the surface of the ancient ice sheet that covered British Columbia and therefore have retained their craggy shape. In contrast, the lower, rounded ridge in the foreground was overridden and eroded by the flowing ice.
Photo #27	Landslides are common along the banks of the Chilliwack River. Most of the landslides involve unstable Ice Age sediments and occur during heavy rains. Landslides contribute large amounts of sediment to the river, filling its channels and increasing the risk of downstream flooding.
Photo #28	Aerial view of a steep logged slope in the Cascade Mountains near Wahleach Lake. Several landslides moved down this slope during a heavy rainstorm. The landslides were caused by the failure of logging road embankment materials. Landslides are common in our coastal mountains both on logged and unlogged slopes.
Photo #29	Chilliwack River at Vedder Crossing. Chilliwack River transports large amounts of sediment, including gravel which forms the river bars at Vedder Crossing. The river has a history of damaging floods, most of which occur during heavy autumn rainstorms.