Types of disasters

Sudden-onset disasters

According to the International Federation of Red Cross and Red Crescent Societies, sudden-onset disasters, often referred to as natural hazards, are natural physical phenomena caused by rapid or slow onset events that have an immediate impact on human health and secondary effects that cause further death and suffering.

Earthquakes

Earthquakes are sudden shocks or vibrations that occur in the earth’s crust as a result of the collision of tectonic plates or the movement of one plate relative to another. This causes pressure to build up between two plates in the Earth’s crust along what is called a fault line. As the plates move along the fault line, a sudden increase in pressure occurs, causing a strong shaking of the earth’s surface in the form of an earthquake.

Tsunami

A tsunami, which means “harbor wave” in Japanese, is most often the result of an underwater earthquake that creates a very large coastal wave. The world’s largest tsunamis usually occur at the boundaries of converging tectonic plates that collide, causing one plate to sink beneath the other. When this occurs, the leading edge of the upper plate bumps into the lower plate, leading to a build-up of pressure that is eventually released as the most powerful type of earthquake, the so-called interplate earthquake. When these earthquakes occur underwater, large amounts of water are displaced and a tsunami wave is created.

Landslides

A landslide is the movement of a mass of rocks, debris, or earth downhill. Landslides are a type of “mass failure,” which refers to any movement of soil and rocks downhill under the direct influence of gravity. The term “landslide” covers five types of slope movement: falling, overturning, sliding, spreading, and flowing. They are also categorized by the type of geologic material, including rock, debris, or earth. Debris flows, commonly called mudslides or landslides, and rockfalls are the most common types of landslides.

Cyclones

Known as hurricanes, cyclones, and typhoons, depending on where they occur, they are usually seasonal in nature and take several days to occur, although their trajectories can vary, with storms in coastal areas being particularly dangerous. However, preparedness can significantly reduce mortality and morbidity.

Floods

Floods are the most frequent type of natural disaster and occur when excess water floods land, often as a result of heavy rains, rapid snowmelt, or a storm surge from a tropical cyclone or tsunami in coastal areas.

Volcanic activity

A volcano is an opening in the Earth’s crust that allows magma, ash, and gases to erupt from beneath the surface. Most volcanoes occur at the boundaries of tectonic plates. Volcanoes can occur where plates separate and collide. As a result of the collision, the submerged plate melts, which is accompanied by an increase in pressure and leads to the formation of a magma chamber and, in turn, a volcano. An eruption occurs when the rock from the submerged plates melts to form molten magma, which makes its way to the surface, forming a magma chamber. The chamber accumulates gases dissolved in the magma, which expand to cause a significant increase in pressure, lifting the magma and pushing it through cracks/fractures in the volcano. When the magma reaches the surface, the pressure decreases and an eruption occurs, during which volcanic ash, rock particles, dust, gases and lava are ejected.