B Tephra Tephra, or pyroclastic material, is made of rock fragments formed by explosive shattering of sticky magma. Tephra refers to any airborne pyroclastic material regardless of size or shape. The best-known tephra materials include pumice , cinders, and volcanic ash. These fragments are exploded when gases build up inside a volcano and produce an explosion. The pieces of magma are shot into the air during the explosion.
Some bombs can be the size of a small car.
C Gases Gases, primarily in the form of steam, are released from volcanoes during eruptions. All eruptions, explosive or nonexplosive, are accompanied by the release of volcanic gas. The sudden escape of high-pressure volcanic gas from magma is the driving force for eruptions. Gases come from the magma itself or from the hot magma coming into contact with water in the ground. Volcanic plumes can appear dark during an eruption because the gases are mixed with dark-colored materials such as tephra.