Methane hydrates, which are natural gas molecules trapped in ice, offer a potentially abundant source of natural gas widely distributed across the globe. Methane hydrates form at a specific range of low temperatures and high pressures. They occur in the Arctic permafrost and along continental slopes, typically at water depths greater than 500 meters (1,640 feet). Once considered only a hindrance to conventional extraction, emerging technologies to tap methane hydrates mean they now have the potential to alter the global energy outlook. Estimates for total methane hydrate gas in place are rough, but range anywhere from 3,000 trillion cubic meters to more than 140,000 trillion cubic meters, the large range illustrating the uncertainty of the estimate. By comparison, combined global technically recoverable conventional natural and shale gas reserves total roughly 640 trillion cubic meters. (In 2011, global natural gas consumption stood at approximately 3.4 trillion cubic meters.) Despite the promise of methane hydrates, the technology for their extraction is still under development, and potential risks have not been neutralized. These include the uncontrolled release of natural gas formerly trapped in ice, which could result in large amounts of the greenhouse gas methane entering the atmosphere. They also include the possibility of destabilizing the ocean floor, leading to underwater landslides and subsequently the possible sinking of drilling rigs.