Flood is an overflow of water that soaks or covers land. Floods are the most frequent type of natural disaster worldwide. It can be caused by several things, naturally and form the effect of human behavior. The most common cause is because of the over capacity of the body of water, e.g. river or lake. As a result some of the water flows outside of the body of water. It can also occur in rivers, when the strength of the river is so high that it flows right out of the river channel. A flood from sea may be caused by a heavy storm, a high tide, a tsunami, or a combination the three.
Soil and vegetation absorbs most of the surface water, floods happen when there are lack of trees and the soil alone cannot absorb all the water. The water then runs off the land in quantities that cannot be carried in stream channels or kept in natural ponds or man-made reservoirs. A flood can also be caused by blocked sewage pipes and waterways, such as the Jakarta flood.
There are several types of flood. Periodic floods occur naturally on many rivers, forming an area known as the flood plain. These river floods usually result from heavy rain, sometimes combined with melting snow, which causes the rivers to overflow their banks. A flood that rises and falls rapidly with little or no advance warning is called a flash flood.
Earthquake is a sudden shaking of the earth’s surface that often causes a lot of damage. It is the result of a sudden release of stored energy in the Earth’s crust that creates seismic waves. Earthquakes may happen naturally or as a result of human activities. Smaller earthquakes can also be caused by volcanic activity, landslides, mine blasts, and nuclear experiments.
At the Earth’s surface, earthquakes can be seen from the shaking or displacement of the ground. Sometimes, they cause tsunamis, which may lead to loss of life and damage of property. There are two types of earthquake that occurs naturally, they are tectonic and volcanic earthquakes. Tectonic earthquakes are earthquakes that are caused by tectonic plates getting stuck and putting a strain on the ground. The strain becomes so great that rocks give way by breaking and sliding along fault planes.
Volcanic earthquakes are earthquakes which are caused by themovement of magma in volcanoes. In volcanic regions earthquakes may be caused both by tectonic faults and by the movement of magma in volcanoes. Such earthquakes can be an early warning of volcanic eruptions
The size of an earthquake is usually reported using the Richter scale or a related Moment scale. Earthquakes which are 3 on the Richter scale or lower are hard to notice. Whereas, those which are 7 on the Richter scale causes serious damage over large areas.
A tornado is a violently rotating column of air which is in contact with both a cumulonimbus cloud or, in rare cases, a cumulus cloud base and the surface of the earth. Tornadoes come in many sizes but are typically in the form of a visible condensation funnel, whose narrow end touches the earth and is often encircled by a cloud of debris.
Most tornadoes have wind speeds of 110 mph (177 km/h) or less, are about 250 feet (75 m) across, and travel a few miles (several kilometers) before disappears. Some reach wind speeds of more than 300 mph (480 km/h), stretch more than a mile (1.6 km) across, and stay on the ground for dozens of miles (more than 100 km).
Although tornadoes have been observed on every continent except Antarctica, most occur in the United States. They also commonly occur in southern Canada, southcentral and eastern Asia, east-central South America, Southern Africa, north-western and central Europe, Italy, western and south-eastern Australia, and New Zealand.