Surface mining, including strip mining, open-pit mining and mountaintop removal mining, is a broad category of mining in which soil and rock overlying the mineral deposit (the overburden) are removed, in contrast to underground mining, in which the overlying rock is left in place, and the mineral is removed through shafts or tunnels. In North America, where the majority of surface coal mining occurs, this method began to be used in the mid-16th century and is practiced throughout the world in the mining of many different minerals. In North America, surface mining gained popularity throughout the 20th century, and surface mines now produce most of the coal mined in the United States. In most forms of surface mining, heavy equipment, such as earthmovers, first remove the overburden. Next, large machines, such as dragline excavators or bucket-wheel excavators, extract the mineral. The pros of surface mining are that it has a lower financial cost and is a lot safer than underground mining because all mining operations take place above the surface. The cons are the hazards it presents to human health and the environment. Humans face a variety of health risks caused by mining such as different cardiovascular diseases, food, and water contamination. Habitat destruction, alongside air, noise, and water pollution, are all significant negative environmental impacts caused by the side effects of surface mining. Types There are five main types of surface mining as detailed below. Strip mining Strip mining is the practice of mining a seam of mineral, by first removing a long strip of overlying soil and rock (the overburden); this activity is also referred to as overburden removal. It is most commonly used to mine coal and lignite (brown coal). Strip mining is only practical when the ore body to be excavated is relatively near the surface and/or is mostly horizontal. This type of mining uses some of the largest machines on earth, including bucket-wheel excavators which can move as much as 12,000 cubic metres of earth per hour. There are two forms of strip mining. The more common method is area stripping, which is used on fairly flat terrain, to extract deposits over a large area. As each long strip is excavated, the overburden is placed in the excavation produced by the previous strip. Contour mining involves removing the overburden above the mineral seam near an outcrop in hilly terrain, where the mineral outcrop usually follows