The forest covers 3.9 million acres (6,093 mi² - 15,782 km²), and has over 445,000 acres of water (695 mi² - 1,800 km²) in over 2,000 lakes. There are more than 1,300 miles (2,092 km) of cold water streams and 950 miles (1,528 km) of warm streams. The lakes were formed by the action of glaciers during the last ice age. The forest is boreal forest or taiga located on part of the Canadian Shield. The Boundary Waters Canoe Area Wilderness (BWCAW) is located within the Superior National Forest. The BWCAW is directly south across the border from Quetico Provincial Park in Ontario, while Voyageurs National Park (USA) lies to the west of both parks.