Tephra, rock fragments ejected from a volcano during an eruption, are called lapilli when 2 to 64 millimeters in diameter. Small particles like lapilli can travel and be deposited far from the volcano after an eruption.
Tephra consist of pumice, glass, mineral crystals and different types of shattered rock. Volcanic eruptions blast out ash, lapilli and larger tephra called blocks and bombs. The size of particles falling from a volcano is largest near the volcano's source, with particles like lapilli and ash decreasing in size the farther they are from the volcano. Particles more than 1 millimeter in diameter fall to the ground within 30 minutes.