Skip to main content
Toggle Menu

Cold Seeps Icon Topic

Cold Seeps

Ocean Fact: What are gas hydrates?

Gas hydrates are ice-like crystalline structures that form when a low-density gas, like methane, ethane, or carbon dioxide, combines but does not chemically bond with water and freezes into a solid under low temperature and moderate pressure conditions. Most gas hydrates are formed from methane (CH4), which has led to the terms “gas hydrate” and “methane hydrate” often being used interchangeably.

On Earth, gas hydrates occur naturally in some marine sediments and within and beneath permafrost. They are also speculated to form on other planets.

For us, hydrate deposits are important for a variety of reasons:

  • Gas hydrate deposits may contain roughly twice the carbon contained in all reserves of coal, oil, and conventional natural gas combined, making them a potentially valuable energy resource.
  • Their decomposition can release large amounts of methane, which is a greenhouse gas that could impact Earth’s climate.
  • Sudden release of pressurized methane gas may cause submarine landslides, which in turn can trigger tsunamis.
  • Gas hydrates in the ocean can be associated with unusual and possibly unique biological communities that use hydrocarbons or hydrogen sulfide for carbon and energy, via a process known as chemosynthesis.
    Ball and stick model of a methane molecule made of one central carbon atom (black) with four covalently bonded hydrogen atoms (white).
    Methane is composed of one carbon atom surrounded by four hydrogen atoms. It is the simplest hydrocarbon. Image courtesy of INSPIRE: Chile Margin 2010.
    Methane hydrate clathrate molecular model. A methane molecule (CH4) surrounded by  a lattice-like structure made of water molecules (blue atoms are oxygen, white atoms are hydrogen).
    A methane hydrate is created when water molecules form a lattice structure around a methane molecule, without actually bonding to it. Image courtesy of NOAA Ocean Exploration.
    The crystalized methane hydrate clathrates appear as "ice" on the seafloor.
    These relatively stable, ice-like substances are created in deep-ocean sediments and conditions of low temperature and high pressure. Image courtesy of NOAA Ocean Exploration, Northeast U.S. Canyons Expedition 2013. 

    Teachers & Educators:

    Did you know you can save educational resources for upcoming classes by creating an Educator Account?

    Get started today

    Already have an account? Sign in here