2 mining

2 mining

• 1.
  MINING
• 2.
  Differences between opencast mining and deep mining Deep mining or underground mining is the extraction of resources from below the ground surface. Underground mining takes place where it is uneconomical to remove the overburden from the seam. Deep mining is very expensive both to set up (initial costs) and also to run the mine (extraction of water and air regulation). Deep mining however has very little effect on any natural habitats and has little surface disruption other than a pit shaft and works(assuming there is no subsidence.) Open cast mining is where the mineral seam is relatively close to the surface, thus it is cost effective to remove overlying rocks to access the coal. The mineral is then extracted. Open cast mining often has higher tonnage, and the overburden may also be of some economical value. Initially they are cheaper that deep mining, although just as expensive to extract the ore. Open cast (surface mining) affects habitats greatly (either by direct destruction, or indirectly such as blasting.
• 3.
  overburden • In mining,overburden (also called waste or spoil) is the material that lies above an area of economic or scientific interest. • In mining, it is most commonly the rock, soil, and ecosystem that lies above a coal seam or ore body. • Overburden is removed during surface mining, but is typically not contaminated with toxic components and may be used to restore an exhausted mining site to a semblance of its appearance before mining began.
• 4.
  Fossil Fuels- coal,oil &natural gas Characteristics: • Formed from the decomposition of the remains of plants and animals • Has taken millions of years to accumulate and form deposits
• 5.
  Formation of coal-coal is a black rock which gives out heat as it burns • Found where dense forests (similar to tropical rain forests)existed millions of years ago- in the Carboniferous • Older trees and plants died • Dead vegetation decomposed on swampy forest floors • In time, this formed a thick layer of peat • Peat was covered by sediments (mud and sand) brought by rivers. • Over millions of years the sediments compressed to form sedimentary rocks • Peat hardened to form coal
• 6.
  FORMATION OF COAL
• 7.
  Formation of oiland natural gas • Formed from the decomposition of microorganisms, sea plants and animals which collected in layers on the sea bed • Layers of sand and mud, and other debris built up over time • Heat and pressure from the earth turned them into oil (petroleum) and natural gas • As the sand compressed to form hard sand stone rock, the oil and gas separated and rose through the sandstone filling in the pores between the particles of rocks • The lighter gas rises to the top
• 9.
  Search and extractionof coal • If coal seams outcrop on the surface, open cast methods of mining are used. • Seams of coal that are too far below the surface, are extracted by deep mining methods • Coal cannot be mined as deep as other minerals because of the risk of combustion (coal seams catching fire)from the high temperature underground.
• 12.
  Extraction of oiland natural gas • Oil companies invest a lot of money and time trying to find oil and natural gas. • These occur in large quantities in favourable geological conditions- such as an upfold in the rock called an anticline • Oil and gas rise to the top of porous sandstone rocks where they are trapped by impervious rock (e.g. shale) • Once geologists figure out the arrangement of rocks below the ground, engineers drill down into the porous rock layer that they believe contain oil • Drilling is the only way to ascertain whether oil and gas are present. • A drilling rig is set up above large deposits on land. • For drilling under the sea a drilling platform is floated to the site • Extraction is highly mechanised • Oil and gas is transported from drilling site by pipelines