Methane hydrate, also called methane clathrate, or methane ice, is a compound containing large amounts of the natural gas methane in a water crystal form, rather like ice. It is found on the sea bed, under layers of sediment.

The problems with harvesting it are many.

• Drilling rigs have to be able to reach around 500 metres (1600 feet) to the ocean floor, then usually more than double that depth to reach the clathrate. This is difficult.
• It is mostly found offshore, where the continental shelf starts to slope deeply down. Installing and controlling pipelines here is extremely difficult.
• Sloping seabeds are often unstable, and removing the stabilizing clathrate can lead to landslides. There is evidence of a huge landslide off Norway 8000 years ago which caused a 25 metre tsunami in Norway and Scotland. Scientists believe an unstable clathrate deposit nearby decomposed from temperature and pressure changes at the end of the last ice age.
• The clathrate is under high pressure and low temperature. When it is released it becomes unstable and will leak. Containing it as it rises will be extremely difficult.
• The biggest problem is that methane is a powerful greenhouse gas that, together with carbon dioxide, is the cause of global warming. Scientists fear that the release and escape of methane from methane clathrate harvesting could trigger a massive warming boost to the earth's atmosphere.