Blue Mountains (Australia)

Blue Mountains (Australia), rugged plateau region on the eastern side of the Great Dividing Range, in the state of New South Wales, Australia, about 60 km (about 37 mi) west of Sydney. The name refers to the striking bluish color of the mountains when viewed from a distance.

The Blue Mountains extend from Lake Burragorang in the south to the Colo and Wolgan rivers in the north. The plateau reaches its maximum height of about 1,100 m (about 3,600 ft) in the west and then slopes gently toward the east. It consists of hard sandstone from the Triassic period, from about 225 to 195 million years ago, overlying a softer layer of coal dating from the Permian period, about 280 million to 225 million years ago. In the west, rivers such as the Grose, Coxs, and Nepean have cut through the sandstone to the underlying rock, creating spectacular cliffs, canyons, and waterfalls. The Blue Mountains have been a popular tourist spot for Sydney residents since the 19th century, favored for the cooler summer temperatures and picturesque scenery. In recent years the region has experienced great population growth. The Blue Mountains contain a number of designated wilderness areas. Katoomba is an important resort town.