Tephra is the scientific term for the solid fragments that shoot into the air when a volcano erupts.
Tephra, which volcano experts also refer to as pyroclasts, refers to anything solid among the materials that are ejected during a volcanic eruption. In addition to gas and molten lava, tephra spews out in the form of ash, chunks of rock, glass, and cinders. Over time, tephra can accumulate in thick layers that eventually compact into solid rock. The Greek word tephra means "ash."