Small Scale Mining of Surface Deposits Dates Back Thousands of Years. for Example, in Roman

Coal Mining Small scale mining of surface deposits dates back thousands of years. For example, in Roman Britain, the Romans were exploiting all major coalfields (save those of North and South Staffordshire) by the late 2nd century AD. While much of its use remained local, a lively trade developed along the North Sea coast supplying coal to Yorkshire and London. The Industrial Revolution, which began in Britain in the 18th century, and later spread to continental Europe and North America, was based on the availability of coal to power steam engines. International trade expanded exponentially when coal-fed steam engines were built for the railways and steamships. Coal-cutting machines were invented in the 1880s. Before this invention, coal was mined from underground with a pick and shovel. By 1912, surface mining was conducted with steam shovels designed for coal mining. Methods of Extraction The most economical method of coal extraction from coal seams depends on the depth and quality of the seams, and the geology and environmental factors. Coal mining processes are differentiated by whether they operate on the surface or underground. Many coals extracted from both surface and underground mines require washing in a coal preparation plant. Surface mining and deep underground mining are the two basic methods of mining. The choice of mining method depends primarily on depth of burial and thickness of the coal seam. Seams relatively close to the surface, at depths less than approximately 180 ft (50 m), are usually surface mined. Coal that occurs at depths of 180 to 300 ft are usually deep mined, but in some cases surface mining techniques can be used. For example, some western U.S. coal that occur at depths in excess of 200 ft are mined by the open pit methods, due to thickness of the seam 60–90 feet. Coals occurring below 300 ft (100 m) are usually deep mined.