Term: Clathrates

• A. Methane trapped in frozen water within sediments on the ocean floor
• B. A form of methane hydrate found in freshwater
• C. A type of gas that traps carbon dioxide
• D. A solid form of methane on land

Answer: (A)

Clathrates are methane hydrates, where methane gas molecules are trapped inside a lattice of water ice. This structure forms as a solid, ice-like compound under low temperatures and sufficient pressure, which is exactly what happens in sediments on the continental margins of the ocean floor. That environment allows the water molecules to arrange into cages that hold methane, creating a stable, solid hydrate.

So, describing the methane as trapped in frozen water within sediments on the ocean floor matches the real nature of methane clathrates: a solid, ice-like composite where gas is encased by water ice, typically found in deep-sea sediments and sometimes in permafrost regions. The other options misstate either the environment (freshwater rather than ocean sediment), the gas involved (carbon dioxide rather than methane), or the form/location (implying methane is simply a solid on land, rather than a methane-water ice clathrate in specific high-pressure, low-temperature settings).