A flood is a natural event based on the massive occupation of a place that was dry. The causes can be diverse, including rainfall , river and coastal overflows , climate change , the failure of dams , among others.
This phenomenon is exceptional and the most frequent type is the fluvial one, in which excess rainfall increases the flow of the river, exceeding the capacity of its channel and, finally, overflowing its banks. Examples of this are the famous floods of the Missouri River in the US. in 1993 and the Salado river in Argentina in 2003.
A hurricane is a system of winds of extraordinary force that usually forms whirlwinds turning in large circles, whose diameter expands as it temporarily dilates, reaching 50km.
A hurricane can also be defined as a storm system that circulates around a low pressure center (eye of the hurricane), generating winds and rain. Cloud bands with circulating air rotate clockwise in the southern hemisphere and counterclockwise in the northern hemisphere.
Hurricanes usually occur in tropical or subtropical regions over the ocean. Thus, the formation process begins with the evaporation that occurs in the sea, where it gains strength and begins to move. Depending on the geographical area, there are different terms to refer to this natural phenomenon: typhoon (West Pacific), tanio (Haiti), cordonazo (North or Central America), among others.
Earthquakes are seismic movements, caused by the sudden release of energy accumulated over a long time.
An earthquake always has a point of origin, known as the hypocenter , located inside the earth’s crust and a point on the earth’s surface, called the epicenter , located vertically above the hypocenter. It is at the second point where its maximum intensity is acquired. In almost all situations, after the first tremor, earthquakes of lesser intensity, known as aftershocks , occur.
The magnitude of the force of the seismic movement is usually measured according to the Richter Scale . It is a logarithmic scale that assigns a number to quantify the energy released by the earthquake. This scale measures magnitudes between 2 and 10, although an earthquake of this magnitude has never been recorded in the history of mankind.
A landslide is a type of land mass movement, characterized by a massive and rapid descent along a slope , and caused by the instability of a slope.
This natural disaster occurs when a large mass of land becomes unstable and ends up sliding as a single mass over the stable piece of land. They are usually caused by the absorption of water at a certain depth which changes the density of the underlying layer and thus creates a slip plane.
It is a long process, since the necessary water must be absorbed to allow the upper material to slide. In addition to being caused by the rains that moisten the ground, it can also be due to the effects of earthquakes of a certain intensity.
Two types of landslides can be differentiated: rotational and translational . The former are common in homogeneous terrain and whose failure surface has a curved shape and, as a consequence, the slipped mass accumulates at the foot of the slope. On the other hand, the second type mentioned is generated in soils where the failure occurs through one or several flat failure surfaces oriented in favor of the slope.
A drought is a transient anomaly, characterized by lower than normal rainfall values in a given geographical area over a prolonged period of time.
The initial cause is insufficient rainfall , a fact that leads to a shortage of necessary water resources. The term is relative, since the availability of water depends on the one hand on the supply and on the other on the demand. Therefore, we can speak of drought when the availability of water is below what is necessary to supply the needs of the living beings that inhabit a region in question.
It is important to know how to differentiate the concept of drought and aridity. In this way, although drought is a transitory and sufficiently prolonged natural anomaly, aridity is a natural and permanent situation of a territory. However, this fact does not imply that there is a deficit if there are well-designed exploitation systems and the demand is between moderate limits.