Temple of god Khenoum -Esna - Egypt By Montyshot.
These ice bubbles are mostly filled with methane and are the product of plant matter decomposing on the lake bed. Ice bubbles tend to group because bodies of water freeze from the top down, so bubbles cluster along the frozen ceiling until they themselves freeze. As spring sets in and the lake thaws, the bubbles break free and rise to the top. And when the ice cracks, the bubbles escape and vanish into the atmosphere.
Photo credit: Jim Brekke