deformed conglomerate

Deformed conglomerate is a metamorphic rock that has been changed by heat and pressure. Its large, round pebbles are igneous rocks that were swept into the layers of sedimentary rock as they were forming. Then, the rock was buried in the Earth's crust. It was heated and squeezed until the pebbles and softer parts flattened into wavy patterns.

Image credits: main image, courtesy of AMNH; Ed Mathez: courtesy of AMNH.