Fracking comes from the term hydraulic fracturing and is a process used to extract natural gas from the ground. This video explains the process and was produced by Cuadrilla Resources, the company that drilled the sites in Blackpool that caused two earthquakes in April and May last year.
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Transport Secretary Chris Grayling believes Network Rail should share the responsibility with private train operating companies.
Two vehicles were swallowed up by the sinkhole on Sunday night, killing Dora Linda Nishihara and injuring one man.
Elliott Livingstone, aged three, spent most of his life in hospital before the operation in April.