The term floating island is sometimes used for accumulations of vegetation free-floating within a body of water. Due to the lack of currents and tides, these are more frequently found in lakes than in rivers or the open sea. Peaty masses of vegetable matter from shallow lake floors may rise due to the accumulation of gases during decomposition, and will often float for a considerable time, becoming ephemeral islands until the gas has dissipated enough for the vegetation to return to the lake floor.[1]