Cuillin range. Cracks and fissures in the rock provided pathways for later magma intrusions, leading to dykes of basalt which are commonly seen across Skye. The Red Cuillin also have volcanic origins, being formed from a later intrusion of acidic, granitic rock. This granite was more uniformly eroded by wind and water than the gabbro and basalt, causing the red hills to have smoother outlines. The Cuillin provide classic examples of glacial topography and were the subject of an early published account by James Forbes in 1846 (who had become a fellow of the Royal Society of Edinburgh aged only nineteen).
Hills in the Puget Lowland contain several peaks over high, including the Fidalgo Island high point, Mount Erie. Mason County's Olympic Mountains foothills are called the Satsop Hills. Hills in the Puget Lowland Hills in the Puget Lowland, between the Cascades and the Olympic Mountains, including the entire Seattle metropolitan area, are generally between and rarely more than above sea level. Hills are often notable geologically and for social reasons, such as the seven hills of Seattle. The Puget Lowland lies between the Cascades and Olympic Mountains and once contained a plateau of glacial till not usually more than above sea level. The plateau, "the