A fissure or vent on the Earth's surface connected by a conduit to the Earth's interior, from which lava, gas, and pyroclastic material are erupted. Each volcanic eruption has its own characteristics, but they can be classified generally as: 1. Hawaiian Fairly quiet eruptions in which fluid lava is erupted from fissures or pits, with gas being liberated freely. When the eruption is accompanied by spurting gases, incandescent spray is thrown into the air.