These effects are caused by the blast wave produced by large air burst explosions. The Halifax Explosion was one of the largest artificial non-nuclear explosions. There were two explosions in taxis caused by timer bombs. They are caused by earthquakes, landslides, volcanic explosions, glacier calvings, and bolides. Numerous small explosions and dome-building eruptions occurred. Security sources said all three explosions were suicide bombings. There were additional reports of grenade explosions. Both battleships proved resistant to nuclear air burst but vulnerable to underwater nuclear explosions. Radionuclides are produced as an unavoidable result of nuclear fission and thermonuclear explosions. Natural sources include the sun, lightning and supernova explosions. The eruptions of this period were likely phreatic (steam explosions). Smoke trails are often seen in photographs of nuclear explosions. Welding caused the tank to ignite resulting in several explosions. Its combat tires are capable of enduring anti-personnel mine explosions and small arms fire. Cosmic rays are generated by stars and certain celestial events such as supernova explosions.