The Marcellus Shale, the United States’ largest natural gas field and one of the largest in the world, is a huge sedimentary rock thousands of feet below Earth’s surface and is millions of years old. The natural gas was created over those millions of years is a byproduct of the decomposing materials, the mud and organic material that composes the rock. The Marcellus Shale stretches from upstate New York, goes south through Pennsylvania and West Virginia, through a small part of Maryland, then west to parts of Ohio, Kentucky and even Tennessee. Natural gas is harnessed by drilling, and these Marcellus gas wells are drilled by using either vertical or horizontal drilling techniques. Sometimes, they drill vertical wells to gather information
