Geological Surface Mining explained with the help of GIFs
Surface mining is a method which is used for the extraction of metal ores and many types of minerals and geological materials. These naturally occurring sources are usually mined for economic benefits. Mining in a wider sense includes extraction of any non-renewable resource such as petroleum, natural gas, or even water. Surface mining involves the removal of overlying rock above any formation that contains the mineral deposit whereas in the case of underground mining, the minerals and metal ores are extracted by means of tunnels instead of removing the overlying rock layers. The feature covers the surface mining types with their relevant animations.
Types of Surface Mining
Strip MiningImage Courtesy: nroc.mpls.k12.mn.us
Strip mining is a type of surface mining that involves the removal of a whole strip of overlying rocks above a seam of mineral. This type of surface mining is usually carried out for minerals that lie really close to the surface and are usually present in flat terrains. Since strip mining involves the removal of large portions of rock material, it requires the usage of heavy machinery that could carry out a speedy excavation process for the extraction of the mineral. Coal and lignite are most commonly mined by using the strip mining technique.
Open Pit MiningImage Courtesy: sodahead.com
Often confused with strip mining, this surface mining technique mainly involves the removal of earth in the form of a giant burrow or hole for the extraction of minerals and rocks. Open mining is usually carried out to extract the low grade minerals and materials that lie quite close to the surface. Open pit mining is usually used where the extraction of mineral ores is commercially beneficial and where the surface material covering the valuable deposit is quite thin so that it could be easily mined. These mines are enlarged till the time that the excavation of the overlying burden to ore ratio remains economically viable. Open pit mines are turned into landfills upon the desired extraction of the valuable material and are often fenced up since such sites turn into artificial lakes which can turn toxic when they get mixed with remaining materials. Materials usually extracted through open pit mining include coal, copper, uranium, phosphate, diamond and metal ores (gold, iron, silver, molybdenum). The animation shows a controlled explosion done for open pit mining purposes.
Mountaintop Removal MiningImage Courtesy: imgur.com Image Courtesy: treehugger.com
Also referred to as mountain mining, this type of surface mining are mostly done in areas where mountain tops, hills or ridges are overlying the buried coal seams. The area above the coal seams is removed completely and is placed in the side valleys. Usually upon complete extraction of the coals, the overlying material is placed back to maintain the contour of the valley. In mountaintop removal mining, first the overlying waste and material is removed which is placed in the nearby valley. The removal leads to the coal which is extracted using draglines and at the same time regrading process is initiated while the extraction continues. Upon completion of the extraction process, the area is completely regraded and the area is revegetated. The first animation is an explanation of this process. The second animation is that of Hobet mine and its expansion over 25 years. This surface mining technique is mostly used for the extraction of coal seams.
Highwall MiningImage Courtesy: coalzoom.com
A surface mining form which evolved from auger mining, highwall mining is usually done for mining coal. The process involves the coal seam being penetrated by continuous miner. The highwall mining cycle includes sumping i.e launch pushing forward and shearing. Then a conveyor belt mechanism is launched into the centre of the system to carry out the extraction of the coal. The process requires less excavation as compared to mountaintop removal mining but a large amount of capital is required in owning a highwall miner. The capital does pay off since this innovative miner requires only 4 crew members, is environment friendly and doesn’t require the overburden removal. Mapping of the outcrop as well as core-hole data and samples taken during the bench making process are taken into account to best project the panels that the Highwall miner will cut. Obstacles that could be potentially damaged by subsidence and the natural contour of the Highwall are taken into account, and a surveyor points the Highwall miner in a theoretical survey plot line, mostly perpendicular to the Highwall. The animation shows a highwall mining system.
DredgingImage Courtesy: pneuma.it
Dredging is a type of mining technique which is applied in areas where the materials are present underwater. A dredger is used to excavate the material from the bottom of water. This process was mainly used to clear away waterways for boats and ships but since the discovery of minerals underwater, this technique has been applied to recover minerals from underwater with quite efficiency and at a cheaper rate as well. The process of dredging creates excess materials, which are carried away from the dredged area. Dredging can produce materials for land reclamation or other purposes, and has also historically played a significant role in gold mining. Dredging can create disturbance in aquatic ecosystems, often with adverse impacts. The first animation shows how the three piper in a dredger need to be connected to the bottom to start the process whereas the second animation shows the process of dredging by a trailing system.