Most often when we think about exercise we think aerobic. That is in part because of the high energy classes available at most gyms. Aerobic exercise is not confined to those classes, however. For most people, low to moderate exercise or exertion is generally aerobic.
The biggest iron mine. The worlds biggest open pit iron mine can be found near Hibbing, Minnesota. At its maximum, the area covered by the Hull Rust open pit mine is five miles (8km) long, 2 miles (3,2km) wide and 535 feet (180m) deep. It looks like a man-made Grand Canyon of over 2,000 acres (8,1kmÂ²).
Uranium resources can be extracted from the ground in three ways: open pit, underground, and in-situ leach (ISL). Open pit mining, also known as strip mining, is the removal of surficial soils and uneconomic rock to get at the ore below. Ore grades are normally less than 0.5%.