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).
The North Antelope Rochelle coal mine in the Powder River Basin of Wyoming, US, is currently the world's largest coal mine by reserve. The mine was estimated to contain more than 2.3 billion tonnes of recoverable coal as of December 2012. The mine is owned and operated by Peabody Energy.