Natural disasters are major changes in the Earth that can cause damage through volcanic eruptions, earthquakes, cyclones, avalanches, floods, droughts, and fires. The document defines each type of natural disaster, explaining that volcanic eruptions occur when gas and lava burst through the Earth's crust due to underground pressure. Earthquakes are caused by the movement of tectonic plates, while cyclones involve fierce circulating winds. Avalanches happen when snow, ice, and rock slide down mountains rapidly. Floods result from overflowing rivers and coastal flooding. Drought is a prolonged lack of rain, and fires can burn out of control in forests or bushlands.