Ash is pulverized rock. Falling ash is heavy and can suffocate cattle, cause breathing problems and flatten buildings. Exposure to ash can be deadly to infants and the elderly, who have vulnerable respiratory conditions. Ash is also extremely corrosive and can scratch the eyes.
Lava, which is molten rock or magma, normally flows slowly. But lava mixed with hot gas and ash becomes a pyroclastic flow and can travel quite quickly, engulfing homes and overtaking people. Volcanic eruptions from ash and lava destroy livestock, create forest fires and kill natural wildlife. The lava flow with its high acid content flowing into the ocean can decimate aquatic and marine life.
Volcanoes can have global consequences if the eruption is very large. Large particles of ash thrown high into the atmosphere can trap heat and create a greenhouse effect. Also, ash and smoke can cause major travel and commerce disruption.
What seems bad can turn into something good, as volcanic eruptions can add to the environment. The volcanic ash contains rich minerals that improve the soil. Volcanic slopes from lava provide a haven for rare flowers and animals. Lava paths create amazing scenery, form new islands and add land mass to continents.
