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Gas hydrate, also called flammable ice or fire ice, is an icelike substance with natural gas locked inside under high-pressure and low-temperature conditions.

If gas hydrate is warmed or decompressed, it can quickly expand to 164 times its volume, breaking up into water and natural gas.

Gas hydrate exists in sea sediments at about 900 to 1,200 meters below sea level and in permafrost at 200 to 2,000 meters underground.