In the late 1990s, American oil and gas companies used new technologies to advance into previously unexplored layers of the earth. They drill up to 4,000 meters (13,123 feet) into the shale, then make a sharp turn and continue to drill horizontally. Then they inject a mixture of water, chemicals and sand into the drilled well at high pressure. This creates small fractures in the surrounding rock, allowing gas and oil to be released and rise to the surface through pipes.

And it’s geo-political implications:

The gas revolution is changing the political balance of power all over the world. Americans and Russians have waged wars, and they have propped up or toppled regimes, over oil and gas. When the flows of energy change, the strategic and military calculations of the major powers do as well.