A bushfire is a wildfire that burns out of control spreading across vegetated regions of bushland. Most bushfires happen in times of high temperatures, in summer, conditions must be dry. Areas with dense undergrowth, as can be found in south-eastern Australia, are the most vulnerable to bushfire. Bushfires often start when dry winds blow inland from central Australia. While the winds bring dry weather, they also provide ventilation for the flames. Trees such as eucalypts are especially prone to fire because their leaves have a highly-flammable oil. Dry leaves and bark are especially flammable.
A drought is a prolonged, abnormally dry period when there is not enough water for users' normal needs. Drought is not simply low rainfall; if it was, much of inland Australia would be in almost perpetual drought. Because people use water in so many different ways, there is no universal definition of drought.
Earthquakes are a sudden shaking of the ground caused by the movement of tectonic plates. Many people think that Australia never has earthquakes. There have, however, been a number of earthquakes on the Australian continent in recorded history. In fact, Australia's level of earthquake activity is moderate to high compared with other intraplate regions, or regions in the centre of a tectonic plate.
Floods occur when water covers land that is usually dry. Floods are fairly commonplace in Australia. Floods can be deadly, but deaths due to flood are preventable. Most flood deaths occur when people underestimate the depth and current of flood waters and try to cross on foot, by car or by swimming. Flooding, unlike some other natural disasters, is usually fairly localised. Sometimes, however, many floods can take place over a large area.
Thunderstorms develop when warm, humid air near the ground receives an initial upward push from converging surface winds and rises rapidly in an unstable atmosphere. Thunderstorms can become severe when the atmosphere is particularly unstable and/or additional energy is drawn in from surrounding winds.
Tropical cyclones are strong winds and rain, tropical cyclones are capable of generating high waves, damaging storm surges, and tornadoes. They typically weaken rapidly over land where they are cut off from their primary energy source. For this reason, coastal regions are particularly vulnerable to damage from a tropical cyclone as compared to inland regions.